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Publication numberUS2669679 A
Publication typeGrant
Publication dateFeb 16, 1954
Filing dateNov 28, 1952
Priority dateNov 28, 1952
Publication numberUS 2669679 A, US 2669679A, US-A-2669679, US2669679 A, US2669679A
InventorsGeorge R Purifoy
Original AssigneeWestinghouse Electric Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Dynamic-braking motor-protection
US 2669679 A
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Description  (OCR text may contain errors)

1954 G. R. PURIFOY DYNAMIC-BRAKING MOTOR-PROTECTION 2 Sheets-Sheet 1 Filed May 28, 1952 .ll lll INVENTOR George R. Purifoy. BY

PROGRESS ATTORN EY Feb. 16, 1954 R. PURIFOY 2,669,679

DYNAMIC-BRAKING MOTOR-PROTECTION Filed May 28, 1952 2 Sheets-Sheet 2 I Fig. 5. INVENTOR ATTORN EY RC BRAKE E 3 202 5 BR George R. Purifoy.

Patented Feb. 16, 1954 UNITED STATES DYNAMIC-BRAKING MOTOR-PROTECTION George R. Purifoy, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 28, 1952, Serial No. 323,046

23 Claims.

My invention relates to direct-current electrically propelled railway-vehicles, and it has particular relation to electrical control-systems therefor, in which provision is made for dynamic braking. The principal object of my invention is to provide a new means or instrumentality for reducing the high buildup-rate and overshooting of the motor-current and the motor-voltage when the dynamic-braking circuits are established while the motors are being operated at high speeds. Excessive motor-current and excessive motor-voltage result not only in a rough brakeapplication, but also in motor-flashing. My invention is an improvement over the controlequipment which is shown in an application of William L. Barclay, Jr. and myself, Serial No. 295,794, filed June 26, 1952, in which other means were provided in order to mitigate overshooting when dynamic braking is applied.

I have provided a novel means, responsive to the establishment of dynamic braking during a short-field condition of the traction motor, for reducing overshooting during the initial second of the dynamic-braking operation. I am showing several forms of embodiment of my invention, all of them having the general effect of preventing a too-rapid restoration of full-field operating-conditions in the traction motors, during the initial period of the dynamic-braking operation.

In what is perhaps the least expensive, and therefore preferred, form of embodiment of my invention, a choke-valve is interposed in the connection between the pneumatically operated dynamic-brake actuator and the so-called "straight-air pipe of the air-brake system, so that, when the brake-handle of the brake-valve is moved to any adjusted braking-position, the resulting air -pressure adjustment in the straight-air pipe will not be communicated too rapidly to the dynamic-brake actuator, so that the dynamic-brake actuator will not instantly adjust itself to its full-brake position, even though a full-brake application is called for, by the brake valve, while the train is running fast with a shunted condition of the field-windings of the traction motors. As is common in railway control systems to which my present invention is applicable, the brake-actuator controls a brakin rheostat which is included in series with the ratecoil of the overcurrent limit-relay when dynamicbraking conditions are established, so that, according to the amount of braking which is called for by the brake-valve, more and more resistance will be inserted by this rheostat, thereby decreasing the energization of the rate-coil, and thus increasing the current-setting of the limit relay. In accordance with my present invention, this current-settin of the limit-relay is momentarily held at is minimum value, when a full-brake application is called for during a short-field opcrating-condition, and this causes the limit relay to open its back-contact and thus prevent a rapid or uninterrupted adjustment of the field-controlling means from its short-field condition to its full-field condition. In thi way, I prevent the too-rapid building-up, and overshooting, of the dynamic-braking current of the traction motors.

In an alternative form of embodiment of my invention, an auxiliary contactor is energized whenever the dynamic-braking circuits are established during a short-field operating-condition, and this contactor is used to immediately reinsert some of the previously cutout resistance of the field-shunting circuit, thus quickly strengthening the motor-fields, thereby producing an immediate surge of braking-current suificient to pick up the limit relay and thus interrupt the movement or adjustment of the field-controlling means from its short-field condition to its full-field condition. This is enough to prevent the immediate fullscale adjustment of the field-shunting circuit. Hence, the field-shunting circuit is not completely out out during the first second, more or less, of the dynamic-braking operation, even though a full brake application is called for, while the train is running fast with a short-field condition of its motors.

A second alternative form of embodiment of my invention uses a short-field condition of the fieldcontrolling apparatus to by-pass the previously mentioned braking rheostat which is in series with the rate-coil of the limit-relay, so that, even though this bralring-rheostat should be too quickly adjusted to its maximum-resistance condition, as a result of high air-pressure in the dynamic-brake actuator, the resistance cannot be inserted in the rate-coil circuit because of the presence of the shunting or lay-passing circuit which I thus provide.

A third alternative form of embodiment of my invention utilizes a short-field condition of the field-controlling apparatus to by-pass a resistance which is in series with the commonly employed brake-coil of the limit relay, thu increasing the energization of this brake-coil, which results in reducing the current-setting of the limit relay, with the results which I have already described. Since this brake-coil, as it has been known, for som time, is energized across a resistance which i included in the dynamic-braking circuit, this shunting or by-passing of the resistance, which is included in the brake-coil circuit in response to a short-field condition of the field-controller, becomes effective, in controlling the rerating of the limit relay, only when the dynamic-braking motor-circuit is established.

A fourth alternative form of embodiment of my invention uses the previously described auxiliary contactor, or one like it, to delay the adjustment or movement of the field-controlling means from its short-field condition toward its full-field condition, as by reducing the speed of the field-controller motive-means, or by sligh ly delaying the actuation of the means which moves the field-controller in the direction toward its full-field position or otherwise delaying this movement.

With the foregoing and other objects in view, my invention consists in the circuits, systems, apparatus, combinations, parts, and methods of design and operation, hereinafter described and illustrated in the accompanying drawing, wherein:

Figure 1 is a simplified circuit-diagram of the parts or" one car, which are necessary to illustrate my present invention, omitting many parts which are known to be needed in a successful railway-control equipment or" the type to which my invention is applied, but which are not necessary to be discussed in setting forth the nature and operation of my present improvement, and

Figs. 2 to 5 are simplified diagrammatic views of parts of the equipment which is shown in Fig. "1, illustratin the previously described four alternative forms of embodiment of my invention, respectively. v

Fig. 1 represents some of the equipment which is carried by a single electrically propelled railway-car embodying my invention. Directcurrent power is supplied to the car from a third rail 55:5, or a trolley ,wire, which is engaged by 'a third-rail shoe 2%,01' a trolley pole, pantog'r'a'ph, or other current colleoting equipment, carried by the car. I 'gize's a line is? which constitutes a supply-circuit for the car.

The traction-motors for the car are series motors, which are indicated, by way of showing a simple example in Fig. 1, as comprising two motor-armatures Al and A2, each being associated with its own series field winding SF! and SP2, respectively, the ordinary reversing-switches being omitted for the sake of simplicity. Two serie's-rnotor means, or circuits, are shown. The first series motor means comprises, in series, an armature-terminal ATl', a motorarmature or armatures Al, an intermediate connection-point AXE, a series field winding or windings SW, for

supplying the field-excitation for said armature or armatures, and a field-terminal FM. The corresponding parts for the second series-motor means are indicated at AT2, A2, AXZ, SP2, and

A series-parallel motor-control arrangement is shown in the drawing, in which a line-switch or relay L'Si and a ground-switch Gl are used as power-switch means for establishing a powercircuit for energizing the motors, by connecting the first armature-terminal A'Ii to the supply-circuit 591, and connecting the second armature-terminal ATE to ground. For completing the series-circuit connections, a switch JR is closed in addition to the power-switches LS! and G5. switchesl/l and G are'closed n addition to the power-switches 'LSi and G5. The parallel-motor switch M provides a circuit' connection be tween the armature-terminal ATl of one seriesmotor means and the field terminal FT of the other series-motor means; while the other parallel-motor switch G provides a circuit-connection between the other armature-terminal ATE and the other field-terminal?! l. Duringan intermediate transition-period, a switch '3 is "closed.

The third-rail shoe 96 ener- For parallel-motor operation, two- :2 These motor-controlling connections are all in accordance with a well-known switching-system. Dynamic-braking circuits are established by opening the two power-switches LS! and Gi and closing a braking-switch Bl in addition to the two parallel-connection switches M and G, also in accordance with a well-known system or arrangement. The braking-switch Bi provides a common dynamic-braking circuit-connection H38 between the respective intermediate connectionpoints AX! and AX2 of the two series-motor means, thus'providing two dynamic-braking circuits wherein the motor-armature or armatures of each of said series-motor means are loaded by the field winding or windings of the other one of said series r'notor means, respectively.

A suitable number of series-connected tC celerating resistances are used, as indicated at RE, R2, R3 and Ed. The resistanc'e ltl disposed between the supplydine l9? andthe first armature-terminal A'Ii, and is shorted out by means of a second line switch LS2. The resistance R2 is in series with the first field terminal F! I, andis progressively shorted outby means or" switch-contacts Si, S3 and S9. The resist"- ance- R3'is in series with the second fieId-termi rial FT, and is progressively shorted out by 'switch contact's S2, S and SW. The resistance Rd is the series niotor connection which is made by the switch JR, and this resistance is finally shorted out by the transition-switch J, for obtaining the full-series power-circuit con nection of the motors.

During parallel motor operation, the switch"- contacts S3, S13 and S9, S10 are succ'essively'or progressively closed, during the aceele'ifationof the motor, and after all or the acceleratingresistances R2 and R3 have been cut out, the field-strengths of the motors are progressively reduced, to provide shortfield operating co'nditions.

In accordance with a usual arrangement, the motor-fields are reduced by equipping each or the series field windings SF! and'SFE with a field-shunt, comprising an inductive reactor X4 or X2, as the case'may bejand a variable-resistor RSi "or RS2, respectively. The field sHun-t's XL-RSI mem -RS2 are first connec-tedin parallel relation to their respectivefieId-wihdings SP5 and 'SFZ, by means of contact-terminal's it and #2, respectively, of a progressively or sequentiallyoperating field-controlling means, which is herein illustrated as -an electricallyiop erated drum-type field-controller FC. After the respective field-shunts-have been connected: into operation, the field shunt resistances RSI- and RS2 are then progressively shorted ou'thby Successive controller-points i3, i5, IT and it, for RSI, and'i i, i6, i3 and 26, for RS2, as "the field-controller FO-is moved from its initial dullfield position through its intermediate Eiposi tions'Fi, F2, F3 and F3 to its short field'vpositio'n at which point the field winding :currents'are reduced to about. fiftyper centxcf their 'unslmnted values.

During dynamic braking, the two motor'sar-e connected by the common dynamic-'brakingicircuit-connection l 98, which contain's the brakingsw-itch BI and a braking-resistanceRi. Thisare sistance-RE is used, in addition to the previously mentioned accelerating-resistances R2 andnRBJ, in establishing the complete. dynamic-braking circuit. The braking-resistance R5 is progressively shorted out by means ofbraliing-switches B2, B5 and B6, during dynamidhrakingeopera a aaezo.

tions, after which the acceleration resistances R2 and R3, or portions thereof, are progressively shorted out, as by the switch-contacts S3, S4, and S9, SW. (The switch contacts SI and S2 are permanently closed during the dynamic-braking operations, in the illustrated system.)

The progressive operation of the various resistance-shorting switches, during both motoring operation and dynamic braking, is under the automatic control of a suitable limit-relay or relays, which are energized to be responsive to conditions which accompany excessive torque in the motors. Such a limit-relay is illustrated in the form of a current-relay CR, having an actuating-coil CR which is connected in series-circuit relation between the terminal AXI and the series field winding SFI. This current-relay CR also has a back-contact I99 (also marked CR), which is normally closed, that is, which is closed in the non-actuated or low-current position of the relay.

The current-relay CR is also provided with certain recalibrating-neans. In accordance with previous practice, this relay is provided with a. cumulatively operating rate-coil RC, which is energized through a weight-responsive rheostat 200, during accelerating operations, and which is energized through a braking-responsive rheostat 20I during dynamic-braking conditions. The weight-responsive rheostat 260 is automatically adjusted according to the variable weight or live load carried by the car,'so that-the rate-coil RC is the most strongly excited during light-load conditions, thus reducing the minimum-current setting at which the limit-relay CR picks up and opens its back-contact 199. The braking-responsive rheostat 23! is automatically changed in response to the position of a brake-valve BV, which will be subsequently described, so that the rate-coil RC has its maximum excitation when a low braking-rate is called for, thus providing a low minimum-current setting at which the limit-relay CR picks up and opens its back contact I99, and also providing limit-relay calibration which is different for braking and poweroperating conditions. The brake-valve BV carries a contact 202 which will be subsequently referred to.

All of the electrically controlled relays and switches which are shown in the drawing are diagrammatically indicated as having vertical switch-stems (indicated by dotted lines), which are biased by gravity toward their lowermost positions, and all of these switches and relays are shown in their deenergized or non-actuated positions. All of the relays and switches are electri cally controlled, and they are illustrated as being electrically or magnetically operated; by means of an appropriately numbered or lettered coil or solenoid, represented by a circle, acting magnetically to lift an armature which is represented' diagrammatically by a small circle inside of the coil-circle. In general, the same switchdesignation is applied to any particular switch, its coil, and its contacts, by way of identification of the parts belonging to a given switch or relay. The various electrical control-circuits for a train are under the control of a numberof trainline wires, which-extend from car to car, through out the entire lengthof the train (not shown). In the simplified circuit-diagram ofthe drawing, eight of these train-line wires are used, being given their usual designations, namely 3, 4', 5, 6,1, [2 and GS.

Energy: for the various relay-circuits or 6 switch-circuits is provided by means of a battery B on each car. The negative terminal of each battery is permanently grounded, while the positive terminal of each battery is connected, through a switch 203, to the positive train-line wire Each end of each car is provided with a motormans master controller MC, only one of which is indicated in the drawing. The illustrated master controller MC is indicated as being an accelerating-controller having an oiI-position and three on-positions l, 2 and 3. In each of the three onpositions of the master-controller, MC, the positive control-wire is connected to the trainline wires 12', GS and 6. The train-line wire [2' is the energizing-wire for the operating-coil LSI of the line-switch LS1; while the train-line wire GS is the energizing-wire for the operating-coil GI of the ground-switch GI, as will be subsequently described.

In the second and third on-positions of the accelerating-drum of the master controller MC, the train line wire 4 is energized from the positive bus while in the third on-position of this controller, the train-line wire 1 is energized from the positive bus (I) In the off-position of the accelerating drum or master controller MC, a connection is made from the positive control-Wire to the trainline wire 3. In the master controller MC, in ac-.. cordance with a known practice, there is an overlap between the off-position contact which energ'izes this conductor 3, and the on-position contacts which energize the conductors l2 and GS, so that, during the notching-oflf of the mastercontroller MC, the contact at 3 is made before the contacts at H and GS are broken. This overlapping construction is particularly necessary in properly controlling a braking-operation protective-relay BP which will be subsequently described, and which also constitutes the subject matter of a Riley Patent 2,597,183, May 20. 1952.

The first on-position of the accelerating-controller MC, in Fig. 1, is a switching position, in which the control-wires 12', GS, and 6 are all energized. The control-wire l2 energizes a control-circuit wire l0, through interlocks which are provided, by the braking-switches BI and B5, in the form of back-contacts 2M and 205, respectively; and the control-circuit wire 10 is used to energize the operating-coil LSI of the line-switch LSI.

In accordance with a usual practice, the exciting-circuit for the line-switch operating-coil LSI also contains a make-contact 205 of a linerelay LR, which is a voltage-responsive relay which drops out upon a voltage-failure of the sup-.' ply-line [91. This line-relay LR is shown as an undervoltage relay which has an operating-coil LR which is connected between the supply-line I91 and ground, through a back-contact 201 of the line-switch LS2, said back-contact 201 being paralleled by a make-contact 208 of the linerelay LR.

As set forth in an application of R. E. Burkhart and myself, Serial No. 269,752, filed February 4, 1952,. the control-wire l9 energizes a control-wire 12 through a back-contact 20-9 of the line-relay LR. This line-relay back-contact 209 thus closes in the event of a power-line voltage-failure, which mightresult from either a third-rail gap or from any other cause; and if the master-controller MO is, at the time, on any on-position, the conductors l2 and 10 will be energized, and hence the line- 9 switch J, thus dropping out the initial seriesconnection switch JR, and the third and fourth accelerating-switches 3-4 and 9-H).

The next step in the acceleration of the traction-motors is accomplished by a movement of the master-controller MC to its No. 3 position, which is a parallel-motor running-position. This position 3 of the master-contro1ler energizes the train-line wire 7, which is connected, through a back-contact 249 of the fourth accelerating or resistance-shorting switch 9-46, and a makecontact 250 of the transition-switch J, so as to energize a control-circuit 3!, which is in turn connected, through a JR back-contact 25i, to a control-circuit 66 which energizes the operatingcoils M and G of the parallel-motor-connection switches M and G. These switches M and G thereupon connect the traction-motors in parallel, between the supply-circuit I91 and ground,

with only the first two 0. the resistance-shorting switches energized, in the illustrated form of embodiment of my invention, namely the second line-switch (or first progression-switch) LS2, and the second progression-switch i--2 which carries the main switching-contacts SI and S2. The energization of the parallel-connection switch G opens the previously described backcontact 246, which drops out the transitionswitch J. The energization of the parallel-com nection switch M closes a make-contact 252, which establishes a holding-circuit for the conductor 66 from the line 60.

Responsive to the dropping-out of the transition-switch J, the back-contact 238 of this switch recloses, and re-initiates the switchprogression of the resistance-shorting contacts 53 to S10, under the control of the switches 3- 3 and 9-40, through the circuits which have been previously described. This establishes the maximum armature-voltage conditions on the motors, and it completes the connections for the full-field parallel-connection operation of the tractionmotors.

As soon as the resistance-shorting switch 9-4 closes, it closes an additional contact 254, which energizes a field-controller actuating-circuit from the progress-wire 41, said circuit extending from the wire 41 through the previously mentioned make-contact 254 of the resistanceshorting switch B-JD, a back-contact 256 of the third progression-switch 34, a make-contact 2510f the parallel-connection switch M, and a sive operation of the field-controller, and it may be brought about in any one of several ways. In the illustrated form of embodiment, since the power for the short-field wire 39 is obtained from the progress-wire 4?, which is under the control of the limit-relay CR, the field weakening progression of the field-controller FC progrosses under the control of the limit-relay CR,

until the short-field position SF is reached. This completes the connections for the short-neld parallel-connection operation of the traction motors, thus completing the accelerationprogression.

If, now, the master-controller MC is returned to its oiT-position, the car or train being now running at some considerable speed, th mastercontroller will energize the train-line wire 3, which may be described as the brake-wire 3, because it is used to set up the dynamic-braking circuits for the motors during the coasting operation. When the braking-protectiv relay Bl? is used, as shown, the brake-wire 3 is used to directly energize a hold-coil BP-i-icld of the braking-protective relay BP, and this hold-coil may be regarded as representative of any holding-means which is effective only after the protective relay 23? has previously been moved to its actuated position. When a separate holding-coil, BP-i-Ioid, is used as such a holding-means for the BP relay, said coil will be made so as to be too weak to pick up the BP relay if the relay is in its non-actuated position when the hold-coil is energized, but the hold-coil BP-Hold has enough energy to hold the relay actuated or closed, once it has been actuated.

As set forth in the previously mentioned application of Burkhart and myself, th BP-Hold coil is also provided with a second energizing-circuit, which is independent of the brake-wire 3, and thus operative in any of the three on-positions of the master-controller MC. This second holdcoil energizing-circuit includes a make-contact 259 of this brake-protectiverelay BP, and this make-contact 259 is used to energize the brakewire 3 from the previously described control-circuit I20, which is under the control of the linerelay LP -so that the control-circuit I29 is energized whenever there is a failure of the linevoltage, at a time when the train-line wire I 2' is energized, that is, at a time when the mastercontroller is on any one of its three on-positions, as previously described. In this way, I not only maintain the energization of the BP-I-Iold coil under the no-voltage conditions just described,{thus making sure that the brake-protective relay Bl? remains in its actuated condition, but I also immediately energize th brake-line 3, without waiting for the master-controller MC to be returned to its off-position, which establishes the coasting braking-circuit connections, as will now be described.

The brake-wire 3 is connected, through an LSI back-contact 260 and at BP make-contact 25!, to a control-circuit SIB. This control-circuit 31B is connected'through a GI back-contact 252, to the previously described control-circuit wir 3!, which energizes the previously described parallel-motoring switches M and G through the JR back-contact 25! and the control-wire 65. The control-conductor 3 IB is also connected, through a. GI back-contact 253, to a control-wire 31C, and thence to the positive terminal of the braking-switch coil Bl, the negative terminal of which is connected in a circuit which includes a B5 back-contact 2B5, a conductor Hi2, another B5 back-contact 256, a conductor Hi4, and a JR back-"contact 251, and thence to the grounded negative battery-terminal The closure of the switches M, G and B! completes the establishment of a weak coasting-operation dynamicbraliing circuit-connection for the tractionr'notors, with all of the available dynamic-braking resistances R5, R2 and R3 in circuit, this dynamic-braking resistance being large enough so that the braking tractive-efiort is usually quite weak, at moderate motor-speeds, thus permitting the train to coast, with little or no sensibl or perceptible braking-effect, as long as the field-controller FC remains in its short-field position.

before the spears-c9 reconnection is also providecl, for controlling the-field-controller F duringv the coasting-operation. In accordance with almown practice- I provide a circuit extending from the control wireJ'iiC, through a back-contact 268 of a brake relay BR, to a control-circuit 32, and. thence through the back-contactziifi of a spotting-relay SE, to. the full-field wire 33 of. th field-controller EC. The brake-relay BR was shown and described. in a Riley-Purifoy Patent 2,523,143, granted September 19; 1950. The spotting relay SR is a previously used re1ay,. having an operate ing-coil SB which is includecl inthe common brake-circuit connection 98, as by being-connected in shunt across a portion R of the braking-resistance R5, in the dynamic-braking oir wit-connection Hi8. Thus, the; spotting relay SR is responsive to the braking-circuit current. This spotting-relay SR is adjusted to have a-low current pickup-value, so that it can hold the braking-circuit current to a small value suitable for spotting purposes, during the coasting operation of the traction-motors, as is well understood in the art. I

'Thefull-field wire 33' of the field-controller energizes a full-field coil. FC- FF, or other meansfor causing the field controller FC to move or progress from its short-field position SF to its full-field; position FF. This energization of the full-field coil PFC-FF under the control of the spotting relay SR thus progressively adjusts the fields-controlling meansV' FC toward its fullefielcl position; as spotting-conditions may require.

Inaccordance with: aknown control-method, the'spotting-relay SR has a make-contactilil which connects the circui-t 3-2:. to a circuit '36, which goes to a field-controllercontact-segment 2H,. which is closed onlyduring certain early points in the-progressive movement of theifield controller PC from itsiu-ll-field positionFF toward its short-field position SF. This field-com troller segment 21.! is preferably opened at a certain-poi-nt near the short-field position SF, pref.- erably before'the field-controller reachesathis short-field position shown, I prefer to have this field-controller segment 2-1! closedat the positions FF through F3 of thefield-controller PC: This field-controller segment 2-1! is used: to connect the wire 36 to theshort-fielcl wire 39 of the field-controller Inthis way, when the spotting-current is too large, that is large enough to pick up the spottingqelay SR, the spotting current is reduced by adjusting the motor-fields towarcla weaker condition,- by maining the field-controller iG-progress in; the direction towards its short-field: position, but -,th-is progression is usually arrested before-the fieldcontrollerreturns alleof. the way back to its: original short-field position. SF, which it occupied spottingcontr.ol commenced to operate.- I v e i A service braking-application is-xnade by the closureof the brake-valve contact 202,, which energizes" the full-brake wire 5 from the brakewire 3. full-brake wire is connected-directly to the coil BR of the brakarelay BR; The

brake-relay BR has a .mahe-contact; 212,. which oonnectsthefull brake line 5 to the conductor .45 which leads up to the limit-relay progressioncircuit 46, thus putting the. braking progression under the control of the back-contact I59 of the limit-relay or current-relay CR',as well as under the control. of. the B1". make-contact 23!}, both of which are in circuitbetween the conductor to and the limit-relay progression-circuit 46. At the 12 sametime, the. opening, of. the. back-contact 26.8 of the now-actuated. brake-relay BR takes, the braking progression out of the control of the spotting relay SR.

. Whenever a braking-application is called for, the energization of the brake-relay ,BR. closes a BR. make-contact 273-, which is'used in the 1111? tiation of the dynamic-braking progression. Thus, the BR make-contact 213 is usedto makeza connection from the limit-relay progression-icincuit it to the full-fieldwire 33 of the fieldeconwtroller FCl This causes a progression ofithefieldcontroller FCjuntil' it reaches its full-field position FE. under the control of the. limit-relay CE.

The closure of the brake-relay BR also closes a make-contact 234 which makes a connection from the control-wire 3 l0 to a brakingmperation hold-wire ii, in readiness for use in th subsequent brake-progression operations.

When the braking-controlling progression has proceeded. to the point: at which full-field conditions are. restored in the. traction-motors, the field-controller EC. closes a full-field. contact;- member 21%, which closesa circuit from the full"- field wire 33' to a conductor 38', and thence througha BR make contact 2-37 to a brakingprogression circuit 48. a

. The energization of. the braking-circuit: pro.- gression-wire 58 immediately serves, through a Bi make-contact 218, which is already closed, to energize a circuit ?2, which is connected, through a B2 back-contact 2'ifi;ito a circuit 82 which is connected to the positive terminal of the? B2 actuating-coil, the negative terminalof which is connected to thepreviousI-y described" conductor I82. The 132 switch thus picks up and closesits main contact- B2 which shorts" out apart of the braking resistance R5 in the common: dynamicbraking circuit has of the traction motors. The

' actuation of the B2 switch also closes a makecontact 283 which establishes a holding-circuit for the wire 82 from the hold-wire "H".

A circuit is next established from the lower end of the progression-wire 48, through a B6 back contactzfil, to a conductor and thence through a B2 make-contact 282, which has just been closed, to a conductor to which is connected to the positive terminal of the B5 actuating-coil, the negative terminal of which is connected to :the previously mentioned wire [64; The- B5 switch closes its main-circuit contact B5, which shorts out more of the braking 'esistance R5 in the common dynamic-braking circuit 1980f the traction-motors. At the sometime, the B5- switch closes a make-contact 283 which establishes" a holding-circuit from the conductor back to the hold wire- 1 I.

j The energi'zation of the braking-progression switch B5 opens its previously mentioned back ccntacts 265 and 256, thus dropping out the switches BI and B2, the main contacts of which are both short-circuited, now, by the main contact B5. The dropping out of the B! switch closes its lowermost back-contact 28 i,v which completes a circuit from they conductor 15 to a B5 make-contact 285, and thence to a wire 86, which is connected to the positive terminal of the B5 coil, the-negative terminal of which is connected to the wire 194. The BB switch thus closes, and closes its main contact B6 which further shorts out some of the braking resistor R5, thus still further reducing the efiective brakingresistance in the dynamic-braking circuits. At the same time, theactuation of the B6 switch closes its make-contact 28%, which establishes a holding-circuit for the wire 88 from the wire H.

The actuation of the B6 switch also closes-.9. make-contact 281, which connects the progression-wire 48 to the previously described conductor 12, thereby reenergizing the B2 switch, the negative circuit of which is now completed from the wire I02, through a B6 make-contact 288, to the wire I04.

It will be understood that all of these brakingprogression operations are under the control of the limit-relay progression-circuit 46, which interrupts the progression whenever an excessive motor-current causes an opening of the currentrelay back-contact I99, which is connected in the energizing circuit for said wire 46, thus interrupting the progression until the motor-current subsides to a desirable value.

The braking-circuit progression-wire 48 is also connected, through a out-contact or backcontact 289, to the accelerating-resistance progression wire 41.

After the second closure or actuation of the B2 switch, so that the B2 and BB switches are now both closed, a circuit is made, from the accelerating resistance progression-wire 41, through a B2 make-contact 290 and a B6 make contact 29!, to the previously described conductor '59, thus re-initiating the progression of the switches 1-2, 3-4, and 9-10, which progressively close the accelerating-resistor switches SI to Sill, thereby cutting out the accelerating resistors R2 and R3 which are in the individual portions of the respective dynamic-braking circuits of the traction-motors, this progression being also under the same limit-relay control.

Ever since the actuation of the B5 switch, a B5 make-contact 292 has been energizing the accelerating-resistance hold-circuit 67 from the braking-operation hold-wire 71, in readiness for this progression of the accelerating-resistor switches SI to 810. The braking-progression thus continues until substantially all of the braking-resistance is removed from the dynamicbraking circuit, thus resulting in the completion of the dynamic-braking operation, during which the speed of the car or train has been reduced from the initial speed at which the dynamic brake was applied, down to a low speed at which the dynamic brake fades out.

If a braking-operation is to be discontinued, after once having been started, the braking-circuit switches are released by an opening of the brake-contact 202, without requiring the establishment of a (perhaps momentary) power-circuit (or MC (in-position), in order to deenergize the braking hold-wire N. This is accomplished the BR-contact 214, which is in series with the hold-wire H. The opening of the brakecontact 292 deenergiaes the brake-relay BR and opens its contact 214, without requiring an onposition of the master controller MC to release the brake-wire 3, in order to deenergize the concluctor 31C and hence the hold-wire II.

It has long been customary to automatically adjust the calibration or setting of the limitrelay GR, in order to cause this relay to drop out in response to various accurately controlled desirable minimum motor-current values, during both the acceleration-progression and the dynamic-bralring progression. This is conveniently done by various controls for the energization oi a brake-coil BC and a rate-coil RC, both of which act cumulatively with respect to the main over-current-coil CR of the limit-relay CR.

In Fig. 1, I have shown that the brake-coil BC is energized in shunt across the previously mentioned resistance-portion R5 which is a part of the dynamic-braking circuit 198. This is the same resistance-portion R5 across which the spotting-relay coil SR, is energized. In the case of the brake-coil, it is customary toinclude a brake-coil resistance RBC in series with said brake-coil BC.

In Fig. 1, I have shown two previously known circuits for the rate-coil control or calibration. One such rate-coil circuit involves the weight,- responsive rheostat 209, and is traceable from the positive control-power line through an LS2 make-contact 293, a conductor 58, the aforesaid weight-responsive rheostat 200, a resistance 294, a conductor 92, a resistance 295, and the rate-coil wire 95. A second old or known rate-coil energizing-circuit involves the braking-responsive resistance 2M, and is traceable from the positive bus through a BB make-contact 296, a cone ductor 9!, and the aforesaid braking-responsive rheostat 201 to the conductor 92. In accordance with a known form of construction, the rate-coil rheostats 200 and 291 are both pneumatically actuated.

The weight-responsive rheostat 200 is actuated to adjustable positions in accordance with the weight or passenger-load on the car, by well- KiiOV/Il means (not shown), which are not necesto an understanding of my present inven- The inching-respcnsive rheostat 20l is commonly actuated by means of a dynamic-brake actuator BA which is energized from the socalled straight-air pipe SA of the air-brake equipment. This straight-air pipe containsair at a variable pressure, which is under the control of the brake-valve BV, according to the degree of brake-application which is called for by the on-position adjustment of the brake-handle of this brake-valve. When a heavy braking-operation is called for, the brake-handle is moved to its full-on service-position, thus applying a maxin'ium air-pressure in the straight-air pipe SA. At intermediate on-positions or braking-positions of the brake-handle of the brake-valve BV, the air-pressure is less. During all on-positions, or brake-application positions of the brake-valve BV, the previously mentioned brake-valve contact 202 is closed, which connects the train-line wire 5 to the train-line wire 3.

In accordance with the form of embodiment of my invention which is shown in Fig. l, I inter-'- pose, in the straight-air connection to the brakeactuator BA, a choke-valve CV, which admits air only slowly from the straight-air pipe SA. If a mild brake-application is called for by the brakevalve BV, the air-pressure in the straight-air pipe SA is small enough so that the brakingrheostat 29! is operated at a reasonably slow rate,

by the brake-actuator BA, thus only gradually I increasing the recalibrating resistance of the rheostat MI in the energizing-circuit of the ratecoil RC.

When, however, a full-brake or a heavy-brake application is called for by the brake-valve BV, the air-pressure in the straight-air pipe SA is high enough so that, previous to my incorporation of the choke-vaive CV, the brake-actuator BA would be moved very rapidly to its full limit of operation, thus inserting all of the resistance of the braking-rheostat 2B! in the energizing-circuit of the rate-coil RC, and doing this in a matter of a second, or less. Thus, before the limit relay CR had a chance to pick up its back-com tacti as inthe-circuit t/A, the decreased excita+ ltionof' the rate-coil RC would so far increase the cu-rr(ant-. set-ting or re limitmelay CR, that this relay would. not pick up at all, until the field- 'co-ntrolier was adjusted to its full-field position FF, as a result-of the continued energization of'the circuit l5A-23fi6-1273--33, and thence to the full-field operating-coil FC-'FF of the field-controller FC. This resulted in setting up a full-field condition in the motors very rapidly, at the very beginning of the dynamic-braking operation. 7 V

' This condition would occur during the highspeed operation of the train, and hence during ahigh-spe'ed operation of the motors, which are now operating as generators for supplying the dynamic-braking current. The speed is high, because the field-controller PC is never adjusted, in the first place, to its short-field position, until the last stages of the acceleration-notching of the motor-control during the motor-operation. If-the motorman had coasted for a considerable time, in the off position of his master controh 'ler'MC', after having reached the full-parallel shunted-field power-circuit motoring-condition, on a level or an uphill track, the train would coast down to a suificiently low speed, so that the spotting-relay SR would gradually notch back the field-controller from its short-field position SF until it finally reached its full-field position FF. But if the field-controller F0 i in or near its short-field position SF, the train will be opcrating at a fast speed.

With the traction-motors operating as generators at a fast speed, under spotting-conditions, if a 'full brake application is called for by the 'l or'akewalve BV, and if the brake-actuator BA is permitted to practically instantly operate the hiaking-rheostat 293! to its full-resistance positi'on, then the calibration of the limit-relay CB will he so high that this limit-relay cannot pick up and deenergize the full-field coil FCFF of the field-controller, with the result that the fieldcontroller moves very quickly to its full-field position, thus causing overshooting of the dynamicbraking control.

In accordance with my invention, as shown in Fig. 1', the added choke-valve- CV, in the air-inlet of the brake-actuator BA, prevents this brakeactuator from moving too fast, in response to a high-pressure condition inthe straight-air pipe SA, as a result of a full-brai e application of the Brake-valve BV. In this way, the limit-relay CR is left at its minimum setting long enough to enable this relay to pick up, in response to the V dynamic-braking current, thereby opening the limit relay back-contact I93 which deenergizes the circuit tea-3s, which immediately 'deenerglass the full-field coil FC-F.F' of the field controller FC. This arrests the movement of the field-controller in the direction toward its fullfield'position FF. After that, this field-controllelr movement is resumed, in a step-by-step fashion, under the control of the limit-relay CR, thus making the field-controller FC reach its full-field tus; inxwhich there has never been any trouble clue to over -shooting. Any added delay, due to the presence of the choke-valve CV, during a milcl-brake application, would not be noticed at all inthe operation of the train.

' In the alternative form of embodiment of my invention which is shown in Fig. 2, instead of working on the brakin rheostat 2539, to prevent itirom upwardly calibrating the current-setting of the limit-relay CR too rapisly, I have provided an auxiliary contactor C, which I use to give the motor-fields a kick, or a sudden increment in excitation, enough to cause the motcr-currentto practically instantly rise to a value which corresponds to the current-setting of the limit=relay CR, even though this current-setting is recalibrated to its maximum value by the speedy oporation oi the hrake heostat 26%. This auxiliary contact-or C, in Fig. 2, is provided with an operating-coil C, and two back-contacts C, which are normally closed, as by gravity, being opened when the operating-coil C is energized.

The operating-coil C is energized from the re lay-circuit 9!, in series with a field-controller contact-segment see, which energizes the. coil C whenever the circuit ti is energized, and whenever, at the same time, the field-controller FC is on or near its short-field position SF, as, for example, when the field-controller is on either one of its positions F4 or SF. It will he recalled that the control-circuit Si is energized from the positive bus in series with the make-contact 28% of the brake relay BR. It will also be recalled that this brake-relay ER is energized in response to the traindine wire 5, which is. energized through the brake-valve contact 2B2, the train-line wire 3, and the off position of the master controller MC, as indicated at MCI-OFF in 2.

The two back-contacts C of the auxiliary contactor C in Fig 2, are connected in series with two field-controller segments 35 3 and 35 i, respectively, which are respectively connected between the circuits H and i3, and between the circuits i2 and Hi. These contact segments Bis and Bi l of the field-controller E C eiieot a circuit-closure in the field-controller positions between F2 and SF. Thus, even though the field-controller F0 is in one of these positions, from F2 to SF, during which the. field-shrmtins; resistances RS! and RS2 would normally be partially short-circuited, between the circuits ii and i3, and between the circuits 5% and it, respectively, if the auxiliary contactor C is energized, these portions. ofithe field-shuntingresistors RS! and RS2 will be cut back again into circuit, thus increasing the resistance of the field-shunts, and increasing the current through the iZiGtOr=fi61GS SFi and SP2.

The. operation of this apparatus, as shown in Fig. 2, will therefore be obvious. Whenever a dynamic-braking operation is called for during a short-field operating-condition, the brake-relay contact 295 will be closed, and a contact will he completed at the contact-segment 395 of the field-controller FC, thus energizing the auxiliary contactor C, and increasing the current-strength in the motor-fields SIM and SP2. This increases the braking-current enough to pick up the limitrelay SR, thus instantly interrupting the adjustment of the field-controller FC toward its full-field position, in the manner which was described in connection with Fig. 1. In Fig. 2, as the field-controller is moving from its short-field position SF toward its full-field position FF, in a 'step-by-step fashion as "controlled by the limit-relay CR, when the field-controller FC leaves its F4 position and moves to its F3 position, the auxiliary contactor C will become deenergized at 306, thereby increasing the shunting current and decreasing the field-current, causing the fieldcontroller to pause, at this position, long enough to prevent the previously described overshooting difliculties.

In the form of my invention which is shown in Fig. 3, the field-controller contact-segment 306 is retained, but the contact-segments 3I3 and 3I4 of Fig. 2 are not used. In Fig. 3, the contact-segment 306 of the field-controller FC is used to connect the control-wires 9! and 92. This has the effect of using field-controller segment 306 to by-pass the braking-rheostat 20! whenever the field-controller PC is in either its position F4 or SF, or otherwise in a position at or close to its shunt-field position SF. In this manner, the field-controller segment 305, during short-field operation, shorts out, or nullifies, the braking-rheostat 20I, so that it does not matter if a full-brake application of the brakevalve BV causes a too-rapid actuation of this braking-rheostat ZIII. In this manner, the limit-relay CF. is left at its minimum-current adiustment, during the first second (more or less) of a dynamic-braking operation which is instituted while the field-controller F is at or near its short-field position SF. This prevents overshooting in the manner which has already been described.

In the form of my invention which is shown in Fig. 4, the field-contactor segment 356 of Fig. 3 is replaced by a segment 3I6, which is shown as making a closed circuit whenever the fieldcontroller F0 is in any one of its positions F3, F4 or SF, although this is intended to be representative of any field-controller adjustment which is at or close to its short-field position SF. In Fig. 4, this contact-segment 3IS of the fieldcontroller F0 is used to connect a parallel resistance 31'! in shunt across the brake-coil resistor BBC, so as to give the brake-coil a stronger response to the braking-current which flows through the braking-circuit resistor R5.

In Fig. 4, the brake-coil resistor BBC is shown as being connected between the intermediate connection-point AXI of the motor circuit, and a conductor B'C', from which a circuit continues through the brake-coil BC to the braking circuit I98, so that the brake-coil BC, with its serially connected resistance BBC, is connected across the braking-circuit resistance R5. The circuits AXI and BC are connected to the fieldcontroller contacts for the segment 3I6, preferably through the previously mentioned resistance 3", by which the degree of strengthening of the brake-oil response can be predetermined at whatever value is necessary to increase the current-setting of the limit-relay CR to the point where it is able to pick up on the first inrush of the braking current, when dynamicbraking conditions are established during a short-field operating-condition.

Since the brake-coil BC is energized in response to the current in the braking-circuit I98, and since this braking-circuit is not energized except when dynamic-braking conditions are established by the closure of the contactor BI, the field-controller contact-segment 3I6 of Fig. 4 has no effect upon the operation of my motorcontrol system except when the dynamic-braking circuit. I98-BI is established, and also ex- 18 cept when, at the same time, the field-controller F0 is on or near its short-field position SF.

In Fig. 4, I also show a modification of the limit-relay CR so as to make the field-controller FC vibrate, as avoltage-regulator, under the control of this limit-relay CR. This same operation could be provided for in any of the other forms of embodiment of my invention, although it is shown only in Fig. 4. In accordance with this feature of my invention, the limit-relay OR, in addition to having the previously described back-contact I99, which is connected between the circuits 45 and 45A, is provided with a makecontact I99A, which is connected between the circuits 25 and 39. This circuit 39 is the circuit which energizes the short-field coil FCSF of the field-controller FC, whereas the circuit 45A, as shown in Fig. 1, is the circuit which energizes the circuit 33 of the full-field coil FCFF of the field-controller FC, as was explained in connection with Fig. 1.

Thus, when the limit-relay CR, picks up, in Fig. 4, it energizes the short-field coil FC-SF and starts moving the field-controller FC further toward its short-field position SF. This weakens the motor-fields and thus reduces the braking-current, causing the limit-relay CR to drop out and close its back-contact I93, which energizes the circuit 46A33, which energizes the fullfield coil FCFF, thus starting the field-controller FC moving further toward its full-field position FF. In this Way, the field-controller FC oscillates back and forth, after the manner of a voltage-regulator, resulting in a gradual reduction of the shunting-current until the fieldshunts are entirely out out, which happens in the full-field position FF of the field-controller FC. It may happen, under certain adjustments of the apparatus, that the field-controller FC of Fig. 4 will not reverse its movement toward the full-field position FF, and start back toward its short-field position SF until the recalibrating circuit-contact is broken at the contact-segment 3I6 of the field-controller, so that the field-controller FC will oscillate between the positions F2 and F3 under this voltage-regulator operation, under the control of the make and brake-com tacts IBM. and I99 of the limit-relay CR.

In the form of embodiment of my invention which is shown in Fig. 5, instead of using the limit-relay CR to prevent the too-rapid movement or progression of the field-controller FC to its full-field position FF, when dynamic braking is called for during short-field conditions, I provide a means which may be broadly defined as a means for changing the rate of movement of the field-controller F0, or slightly delaying the time of that movement. Any means to that end is contemplated, within the broad purview of Fig. 5. I use an auxiliary oontactor CI, which is similar to the contactor O of Fig. 2, except that it has only one back-contact 32I, which is somewhat differently used. The operating-coil CI in Fig. 5 is energized, as in Fig. 2, from the circuit BI and the field-controller contact 306 which has already been described. The backcontact 32I of the auxiliary contactor CI is used, in Fig. 5, to delay the starting or the rate of the field-controller movement in the direction toward its full-field position FC.

Any means, which will accomplish this purpose, may be used, in Fig. 5. The particular means which is chosen for illustration in Fig. 5 includes a field-controller FC which is actuated by an electric pilot-motor PM, as distinguished ply-circuit for the series-motor means; (b) a power-switch means, for establishing a powercircuit for energizing the series-motor means from the supply-circuit; (c) a braking-switch means, for establishing a dynamic-braking circuit for the series-motor means; (d) a brakingcontrolling limit-relay means, having an operating-coil which is energized to be responsive to conditions which accompany a lower-than-desired braking-current in the dynamic-brakin circuit; (e) a variable field-controlling means, for progressively adjusting said series field winding toward a full-field condition and'toward a short-field condition, respectively; (1) an acceleration-controlling means, for controlling the closure of said power-switch means, and, contingent upon such closure, progressively controlling the acceleration of said series-motor means during power-circuit operating-conditions, said acceleration-controlling means including a finally-operating means for causing said field-controlling means to progressively adjust said series field winding toward its short-field condition; (y) a braking-controlling means, for controlling the closure of said braking-switch means, and operative progressively, only whenever a low-current condition exists in said limit-relay means,

to progressively control the braking-adjustment of the dynamic-braking circuit during dynamicbraking conditions, said braking-controlling means including a first-operating means for causing said field-controlling means to adjust said series field winding toward its full-field condition; (it) a dynamic-braking recalibratingmeans, responsive only in a closed condition of said braking-switch means and also responsive to the degree of brake-application of said braking-controlling means, for increasing the current-setting of the limit-relay means, as the degree of brake-application is increased; and (i) an overshooting-preventive means, for limiting the rate of response of the dynamic-braking recalibrating-means to a heavy-brake application of said braking-controlling means.

12. The invention as defined in claim 11, characterized by said braking-controlling means (g) also including a retrogressively operative means, operative only whenever a high-current condition exists in said limit-relay means (d), for causing the field-controlling means (e) to adjust said series field winding toward its shortfield condition.

13. The invention as defined in claim 11, characterized by said braking-controlling means (g) being a part of an air-brake equipment and including a brake-valve which provides a supply of air at a variable pressure dependent upon the degree of brake-application; said recalibratingmeans (h) including a dynamic-brake actuator and a variable-pressure air-pipe connection between said brake-valve and said actuator; and said overshooting-preventing means (i) including a choke-valve in said variable-pressure airpipe connection.

14. A railway-motor control-assembly, including the combination; with two series-motor traction-means, each series-motor traction-means including a motor-armature or armatures, and a series field winding or windings connected in series therewith; of: (a) a supply-circuit for the two series-motor traction-means; (b) a powerswitch means, for establishing a power-circuit for energizing the two series-motor tractionmeans from the supply-circuit; (c) a brakingswitch means, for establishing two dynamicbraking circuits wherein the armature or armatures of each of said series-motor traction-means are loaded by the field winding or windings of the other one of said series-motor tractionmeans, respectively, said two dynamic-braking circuits having a common dynamic-braking circuit-portion which is not a part of a power-circuit; (d) a limit-relay means having an operating-coil circuit which is energized to be responsive to current flowing in a power-circuit for a series-motor traction-means; (e) a dynamicbraking recalibrating-means, responsive only to dynamic-braking conditions, for changing the current-setting of said limit-relay means; (I) a variable field-controlling means, for progressively adjusting said series field windings toward a fullfield condition and toward a short-field condition, respectively; (9) an acceleration-controlling means, for controlling the closure of said power-switch means, said acceleration-controlling means having a first-operating means, operative only whenever a low-current condition exists in said limit-relay means, for progressively controlling the acceleration of said series-motor traction-means during power-circuit operatingconditions, said acceleration-controlling means further having a finally-operating means for causing said field-controlling means to progressively adjust said series field windings toward their short-field conditions; (It) a braking-controlling means, for controlling the closure of said braking-switch means, and operative progressively, only whenever a low-current condition exists in said limit-relay means, to progressively control the braking-adjustment of the dynamicbraking circuits during dynamic-braking conditions, said braking-controlling means including a first-operating means for causing said fieldcontrolling means to adjust said series field windings toward their full-field conditions; and (i) an overshooting-preventive means, operative only whenever said field-controlling means is in a shortened-field condition, for modifying the action of said dynamic-braking recalibratingmeans in such a direction as to reduce the current-setting of the limit-relay means below what it would be without said overshooting-preventive means.

15. The invention as defined in claim 14, characterized by said braking-controlling means (It) also including a retrogressively operating means, operative only whenever a high-current condition exists in said limit-relay means (d), for causing the field-controlling means (I) to adjust said series field windings toward their shortfield conditions.

16. The invention as defined in claim 14, characterized by said recalibrating-means (e) comprising an operating-coil circuit of said limitrelay means (d) which is energized to be responsive to current flowing in said common dynamicbraking circuit-portion, and said recalibratingmeans (e) also comprising an operating-coil circuit of said limit-relay means (d), which is energized independently of the braking current but only whenever the braking-switch means is closed.

17. The invention as defined in claim 16, characterized by said overshooting-preventive means (i) being operative upon said operating-coil circuit which is energized to be responsive to ourrent-flowing in said common dynamic braking circuit-portion.

18. The invention as defined in claim 16, characterized by said overshooting-preventive means

Non-Patent Citations
Reference
1 *None
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2965825 *Feb 27, 1957Dec 20, 1960Westinghouse Electric CorpTraction-motor control
US2980036 *Jul 2, 1957Apr 18, 1961Westinghouse Electric CorpTraction-motor acceleration and dynamic-braking control
US3353075 *Dec 16, 1963Nov 14, 1967Tokyo Shibaura Electric CoSafety device for dynamic braking of electric vehicles
US5091680 *Apr 23, 1991Feb 25, 1992Seagate Technology, Inc.Motor brake circuit for magnetic disk drive system
Classifications
U.S. Classification318/56, 318/383, 318/381, 318/380, 318/363
International ClassificationB60L7/04
Cooperative ClassificationB60L2200/26, B60L7/003, B60L7/04
European ClassificationB60L7/00B, B60L7/04