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Publication numberUS2646205 A
Publication typeGrant
Publication dateJul 21, 1953
Filing dateAug 6, 1947
Priority dateFeb 3, 1942
Publication numberUS 2646205 A, US 2646205A, US-A-2646205, US2646205 A, US2646205A
InventorsRosenschold John Rutger Mun Af
Original AssigneeAtlas Diesel Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Compressor plant
US 2646205 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

July 21, 1953 R. MUNCK AF ROSENSCHGLD 2,646,205

COMPRESSOR PLANT 3 Sheets-Sheet 1 Filed Aug. 6, 194'? :3: m :33 us;

F VA Jum July 21, 1953 J. R. MUNCK AF ROSENSCHOLD 2,646,205

COMPRESSOR PLANT 5 Sheets-Sheet 2 Filed Aug. 6, 1947 E mm JwO USE.

July 21, 1953 J. R MUNCK AF ROSE NSCHOLD 2,646,205

COMPRESSOR PLANT Filed Aug. 6. 1947 5 SheetsSheet 5 I J M g Y:

RELAY 1, 29

TIME DELAY Patented July 21, 19 53 5 1 UNITED, STATE s PATENT OFFICE,

COMPRESSOR/PLANT John Rutger Munck af Rosenschiild, Saltsjobaden, Sweden, assignor to Aktiebolaget Atlas Diesel, Sickla, near Stockholm, Sweden, a corporation of Sweden 1 Application August 6, 1947, Serial No.1766,511

In Sweden February. 3, 1942 Section 1, Public Law 690; August 8, 1946 Patent expires February 3, 1962 1 asynchronous or auto-sychronous motors which between full load and idle speed operate at a constant or nearly constant number of revolutions. I

The regulation of the air quantity delivered by such compressors is usually obtained by unloading the compressor in one or more stages. For this purpose several known methods may be applied, such as throttling of the suction conduit, adding auxiliary clearance spaces to the com.- pression chambers, keeping the suction valves open, and so on. All these methods have the disadvantage that the compression is carried out with reduced efiiciency when the compressor is unloaded. This'is usually expressedby'stating that the specific power consumption of the compressor increases the more the compressor is un-" loaded. v I

, One object of this invention is to providea compressor plant which 'op'erates with increased efliciency at'reduced load.

7 Claims. (01.230-44) "Fig. 1 -is a, diagrammatic view showing an electrically" driven compressor plant and a control circuit therefore constructed in accordance with this invention;

"Fig. 2, a view similar to Fig. 1 showing a modiiied compressor drive and "Fig. 3; a view similar to Fig. 1 showing a still further 'modified compressor drive utilizing a change speed-transmission.

. In Fig; 1 a three-phase'short-circuit'motor M ISCOll-l'lBGllGd directly to an air compressor K,

which delivers compressed airthrough a conduit I8 to a receiver -B forming part of a compressed The present invention consists of a compres-' sor plant comprising in combination a compressor, an electromotor for driving said compressor at different numbers of revolutions and at d1ffer-- ent loads, means for varying the number of revolutions at which the compressor is driven, a mechanism for unloading the compressor, a regulating the compressor. The means for varying the num-.

ber of revolutions of the compressor may be me- {40 -whi'ch'inay be a two speed pole change asynchanical speed shift gears and/or means for elec- 'trically changing the connections of the motor for driving the compressor with different numbers of revolutions. The regulating device may be-responsive to changes in pressure or temperature of the plant. 7 I

In a preferred embodiment the motor, may be connected foroperation with different pole numbers under the influence of the regulating device.

These embodiments of the invention which of the compressed medium produced by the plant or any other medium responsive to the operation be closed by energization of a solenoid 23. -main"switch 'Oi'isconnected to a pole changing air distribution system. The receiver is connected with a control means comprising two electric pressure switches 'Ti and T2 by-pipes l, 8. 'Thepressure switch T1, breaks its contact at a pressure P in the receiver B and T at a lowerv pressure p. Furthermore, the receiver B is connected-to a compressed air relay S by a pipe 9. Said relay consists of a valvemember H which by a return force such asa spring not shown' 'is normally kept in the lower one of two positions.

In said normal position, which is illustrated in thedrawing,-pipe 9 is'closed while there'is an open-communication between a passage [I leading-to the atmosphere and a pipe 12 leadingto an unloading mechanism 13 on the compressor.

ThereIay Sis operated electromagnetically by' means ofthe s'olenoid'lllwhich when energized causes the valve memberluto move to the upper position in which the communication from the pipe IZ-tothe passage. I l is closed and a communication between the pipes 9 and I2 opened; I Three-phase current is supplied to the plant from a line 20 and control current from an auxiliary line 2 I. a

, An electrically operated main switch 01 of standard design is provided through which the three-phasecurrent is supplied to the motor M,

ch'ronous motor; as soon as a control circuit for the switch'is closed. For this purpose the switch 01 'mayinclude three phase switch means 22 which is urged toward the off position by the force of gravity'or others'uitable'means and which may The switchOz through leads 24, switch 02 including switch means 25 which by the force of gravity or 7 other suitablemeans is urged towardlowposition andwhich may be moved to high position should only be considered as examples are'described hereinafter with reference to the accompanying diagrammatic drawings-in which:

by. energization of a solenoid 26. In low position switch means 25 connects leads 24 through leads 21 totne low speed'windingof the motor M and in high position connects leads 24 through leads 28 to the high speed windings of motor M. This change of connections takes place according to principles known per se, the stator winding of the motor consisting either of one single winding capable of being connected in dififerent ways or of two 01 more diirerent windings. In the illustrated embodiment it is assumedthat the change of connections may be carried out so that two difierent pole numbersare obtained, of which one is twice the other. Furthermore, it'is assumed that the pole changing switch 02 normally takes the low position corresponding to the high pole number when the pertaining control circuit is broken and the high position corresponding to the low pole number when said circuit is closed.

The pressure switch T1 controls a circuit containing the solenoid 29 of a relay R1 and the control circuit of the main switch 01 which runs from the line 2i through switch 03, leads 30 and 3|, solenoid 29 of relay R1, lead32, solenoid 23 of switch 01 and lead 33 and 34 to switch 03 'cuit is closed the switch is assumed to take its on position. The relay R1 normally closes two contacts I, 2 and when the solenoid 23 is energized the contacts are broken with atime delay sufficient to allow motor M to accelerate the compressor K from rest to low speed. This time delay is of the order of approximately ten seconds.

The contacts l, 2 form a part of the control circuit of the compressed air relay S. This control circuit runs from line 2! through switch 03, leads and 3|, resistance 35, contacts I and 2 of relay R1, solenoid l9 and leads 33 and 34 to switch 03 and line 2 I The pressure switch T2 controls a circuit from line 2| through switch 03 and leads 3|] and 36 to solenoid 3"! of a relay R2, lead 38 and solenoid is of the electrically operated valve S and leads 33 and 34 to switchOs and line 2|. Normally the relay R2 in deenergized state keeps two contacts 3, 4 open and closes them with a time delay when the solenoid 31 is energized. The contacts 3, 4 control a circuit from line 2| through switch 03 and leads 34 and 39 to solenoid 4B of relay R3, solenoid 2 5 of switch 02 and leads 3!; and so to switch 03 and line 2!. The contacts 5, 8 of relay R3 are normally open but close with time delay when the solenoid 4B is energized.

The contacts 5, 8 of relay R3 are connected in parallel with the solenoid IQ of the valve S and short-circuit said solenoid l9 when the sole- 7 a The unloading mechanism l3 may in a manner known per se consist of a piston which under the influence of the compressed air in the pipe I! and against a spring action lifts the, suction .Yalve or valves from their seats so that said valve cannot close during the pressure stroke of the compressor piston and the air in the compressor cylinder flows out again through the suction valve. Thus during the operation of the compressor the air alternately flows out and in through the suction valve and no compression work is carried out. In other Words the compressor is unloaded as soon as compressed air is admitted to the pipe [2. On the other hand, if compressed air is conducted away from the pipe 12, the piston of the mechanism It will be returned by the spring action so that the suction valve again takes its normal position and the compressor is rendered operative.

The compressor plant works in the following manner: If the compressor is at rest and the receiver B contains air of a pressure lower than the pressure at which the pressure switches T1 and T2 break their contacts the compressor may be started by closing the switch 03. The circuits of the pressure switches T1 and T are immediately closed so that the main switch 01 is immediately turned on. The motor starts and increases its speed to the low number of revolutions corresponding to the highpole number which is normally connected by the switch 02 in the low position shown in Fig. 1. It will be obvious that the motor lvi is at this time supplied with full line voltage. The solenoid iii of the valve S was immediately energized via the contacts 5,2 and the valve was thereby moved to. a position in which the unloading pipe 12 is connected with the receiver B through the pipe 9 so that the compressor is unloaded. After a time sufficient to accelerate motor M-to low speed and corresponding to the abovementioned time delay the relay R1 breaks its contacts I, 2 whereupon, however, the solenoid IQ of the valve S is kept energized since current is supplied via the switch T2 and the solenoid 31- of relay R2. The relay R2 closes its contacts 3, il after the time delay period so that the pole changing switch 02 is switched over from the high to the low polenumber or high speed connections to the motor which'oonsequently immediately starts to increase its speed. It will be obvious that the motor M is likewise at this time supplied with full line voltage. The solenoid 2d of relay R3 is energized upon closure of contacts 3 and s of relay R2 and after the time delay period, durin which the acceleration of motor M takes place, closes contacts 5 and 6 causing the solenoid E9 of the valve Sto be short-circuited'and the valve S to return to'it's normal position in which the air in the unloading pipe i2 is exhausted so that thecompressor is loaded. The motor and compressor now have reached full speed and the compressor starts to pump air into the receiver B in which the pressure rises.

When the pressure has reached the first pressure limit p the pressure switch T2 is turned off. The solenoid 3'! of relay R2 becomes deenergized and breaks the control circuit of the pole changing switch 02 so that the switch means 25 moves to low position and the motor M is connected to a high pole number or low speed winding. Also'the solenoid lii oi'the relay R3 is deenergized so that the short-circuit of the solenoid IS-of the valvesbythe contacts 5, 3 is removed. .The solenoid i9 of the valve S, however, remains deenergizedsince thepressure switch T2 is open. The compressor then operates at about half speed and pumps air into the receiver at a slower rate.

Now, if the pressure rises tothe upper pressure limit? the pressure switch T1 also breaks its contacts and the-solenoid 23 1s. deenerg'i'zedso that the main switch 01 controlled therebytdisconnects the motor and stops the compressor, the-contacts I, 2are'c1osed and theysolenoid' l9 of the valve Sis energized and the compressor unloaded. I

was assumed that'this condition lasts until th'e pressure in' the receiver has fallen belowthe upper pressure limit P, at which time the. pressure switch T1 is again turned on. -The--control-circuit of the main switchOiisclosed and: the motor is started and runs up to the-low. number of revolutions since the switch 02 is in low position.

At first the contacts I, 2 are closedandthe solenoid' H) of the valve, S energized' so that the compressorremainsunloaded via-t-he-pipe} l2. After the time delay period of the relay R1 the itingdevices may: consist of constructions that jduringthe beginning of anew running period of the motor connect'the statorwinding inistar connection and only after some time change it'over to'mesh connection. *Further the voltage on the motor at the moment when the connectionis changed: may be reduced by changing the-connectiorr of" variable tapping. points .at: a transformer; said tapping points-being then connected for .normal voltage in: one. or: more steps. Also current limiting 'impedances or. resistances --m'ay beused for this purposeas shown at 4 lin Fig. 1.

The unloading mechanism 1 3 described-hereinabove may 'be replacedby' athrottle valvein the contacts 1, 2 are broken and-the valve S moved so that the unloading pipe 12 is connected with the outlet passage ll and the compressor starts to work. y- I If, however, more compressed air is drawn from the, receiver B then the supply. from the slowrunning compressorthe'pressure will fall further and finally passes the low limit value 10'. The pressure switch T2 then closes its contacts, the solenoid 37 of relay R2 and solenoid l9 of valve S become energized, the unloading-pipe I2 is connectedto the pipe 9, andthe compressorsis-unloaded. After the time delay periodof the relay R2 the contacts 3 and 4 close so that thepole changing switch Q2 is switched over to highposition and the motor runs with lowpole number and increases its speed. After-the time delay period of relay R3 this relay also closes its contacts and short-circuits the solenoid 19 of 'the valve S so that the compressor is again loaded.

The motor now runs at fullspeed and the compressor works with maximum capacity.

A plant according to the invention has several important advantages. Firstly, instead of a reduced efiiciency an imp-roved e'fiiciency is obtainedat' half-load at the low' speed. A low specific power consumption is obtained since the air velocities in the valves and passages for the compressor. at the low speed are reduced to about than in conventional ,plants having devices for reduction of the capacity, 'of' the compressor. A

great advantage ist-hatthe starting current of:

the motor also in 'automatic'plants is reduced causingth'e 'motor 'to start at a? lowsp'eed where its maximum output is less than'half'the output at the high speed. Sincethe'value of the startairinlet passage of the compressor which 'chokes .sa'id passage when the compressor is to be unloaded.

. In: order not to wear the switches. Or and. O2 unnecessarily by frequent changes of the con-nections it-:maybe suitable =to' design :the pressure switches. Tr and-Tawith-a certain .inertia or hysteresis. Thismeans for-instance that a rising pressure causes a change-of the connections inthe direction towards'reduc'ed speed only when the: pressure has: risen. to 'P+D andp-l-d, re-

spectively; where D and dare certain small: pressure differences while: a falling pressure causes a change of'the connections 'in' the direction towards increased speed, only-when the pressure has fallen to P-D and p d, respectively.

Thepressure switches '-I1= and T2 may be replaced .byanother regulating deviceswithman equivalentfunction which upon actuationunder half the velocities at full speed and a more isothermic compression is obtained'due to better. cooling; The wear of'the moving parts" and the consumption of lubricant is also more favorable ing current often prevents 'the'use of the economical "arrangement with automatidstart and stop; the invention now makes it possible to use.

large compressors'in such an arrangement. I

, The embodiment of the invention hereinabove described and illustrated in Fig. lis only an' example and may be modified in manyways within v the scope of'the claims.

When a change from stop to runningand from running at low speed to running'atlhigh speed-=is made i. e. generally speaking,-upon increase of 'speed,- a"heavy current flow takes place. The

'main switch 01- aswell ,as' the pole changing switch 02 may therefore be provided with current limiting devices known per 'se' which are 'automatically connected during, apcerta'in. period.

This period shouldbe suitably relatedztothe time 'nelay of the relays R1 .and R3. wi-The current-limdating purposes. works togetherrwith a refrigerating plant-the reduction in the temperature, for instance in :the refrigeratingspace, below a'certaifi limit may the influence of the compressed airme'chanic'ally or through fluid pressure "means actuates the switches 01 and Oz.

sage immediately after the compressor-the device .may be suchthat when'the temperature of the compressed ail" exceeds a certain valueor certain values, respectively, the change in the connections previouslymentioned is effected.

Furthermore, sincethe compressor consumes more andmore power when the. pressure rises this circumstance,- which is indirectly dependent on the pressure, may be utilized instead of the air. pressure itself. Consequently, a relay responsive to the output of the motor and provided in the supply circuit of the motor may be utilized to actuate the switches 01 and 02 so that an increase of the output of the motor beyond a certain limit causes a change to'the low speed, whereas a. reduction of'the output below a certain other value m'aycause a change'to the high speed. In similar manner a device may act which is actuated when the turning moment transmitted from the motor to the-compressor which is indirectly dependent on the air pressure exceeds or falls below a certain value.

Still-further secondary conditions responsive to'the compressor work may be utilized for regu- For-instance, if the compressor I-Iereinabove, it has been assumed that one electric motor capable of being connected 'for different speeds is used. However, there is nothing to prevent that, for instance, two motors are directly coupled to the compressor and that each motoris designed for a single speed difiering from the speed of the other motor. Both motors may then be of standard design and are connected alternately by a switch while the motor which is not connected is carried along idle.

This gives great liberty with regard to the speed relation and also with regard to the number. of speeds, which may be more than two if several motors are used. The motors may also be arranged for alternating separate operation and operation'in cascade connection providing great liberty with regard to speed.

Furthermore, different-motors M1 and M2 with the same or different normal speeds may be used and arranged to drive the compressor over gear transmissions, as illustrated in Fig. 2, in which gears l4, [5 with different diameters engage a gear wheel 16 fixed n the driven shaft of the compressor K. These motors may be connected alternately by the switch 04 over a suitable coupling mechanism II. The switch 04 and coupling mechanism [1 then replaces the switch 02 of Fig. 1 whereas the other details of Fig. 2 may be the same and are similarly designated as in Fig. l and are consequently not described again. The change speed switch 04 includes a switch means .42 which normally connects the lead 24 to leads 43 and the motor M1 which through gears l4 and I6 drives the compressor K at low speed. The switch 04 also includes a solenoid M in series with solenoid M] of relay R3 and a solenoid 45 which upon energization shifts mechanism H to a position uncoupling motor M1 and coupling motor M2 through gears l and Hi to drive compressor K at high speed. Upon energization. of solenoids 40, 44' and 45 the switch means 42 operates to connect the leads M to the leads 46 of motor M2 to drive the compressor K at high speed. Fig. 3 illustrates a plant of the same general arrangement as in Fig. 1 but having the pole changing switch 02 and the motor M replaced by'a speed change. gear 47 and a conventional motor M3 adapted to run at one speed only. In

this case the leads 24 from the main switch 01 are connected directly to' the motor Ms. A solenoid 48 is connected in series with solenoid 40 of relay R3 andupon energization shifts the mech-' anism 49 of speed change gear 41 to drive the compressor K at high speed. V

In certain installations it is often desirable to provide means for limiting the current flow through the driving motor at the start gradually increasing this current as the speed increases from zero to some predetermined running speed.

One method for providing such a current limiting control is illustrated diagrammatically in Fig. l

in which the main switch 01 is provided with a variable resistance disposed in each power lead 24, the switch arm 22 gradually reducing the resistance in the line as the speed of the driving motor increases. Various devices of this nature are commercially available and any desired type may be utilizedin the compressor plant of this invention, the showing and description being by way of illustration only.

What I claim is:

1; A compressor plant comprising in combination a compressor electric motor driving means coupled to said compressor for selectively driving the same at diiferent work producing speeds,

said compressor for loading or unloading said compressor and control means operatively associated with the-output of said compressor and'electrically' connected with said speed changing means and with said unloading mechanism in such a manner that the speed of said compressor is changed in response to a change of a condition resulting from the compression work of said compressor and that said unloading mechanism is actuated to unload said compressor while the speed thereof is being increased from one of said speeds to another.

2. A compressor plant comprising in combination a compressor, multi-speed electric motor driving means coupled to said compressor for selectively driving the same at different work producing speeds, means supplying substantially constant voltage to said motor driving means at all work producing speeds, switch means for selecting any one of said speeds for operating said compressor to produce compression work while said voltage remains substantially constant, switch actuating means for operating said switch, unloading mechanism operatively associated with said compressor for loading or unloading said compressor and control means operatively associated with the output of said compressor and connected with said switch actuating means and with said unloading mechanism in such a manner that the speed of said motor is changed in "response to a change of a condition resulting from the compression work of said compressor and that said unloading mechanism is actuated to unload said compressor while the speed thereof is being increased from one of said speeds to another.

3. A compressor plant comprising in com-bination a compressor, multi-speed electric motor driving means coupled to said compressor for selectively driving the same at difierent work producing speeds, said driving means including an electric motor having a plurality of groups of poles with a different number of poles in each group which may be selectively energized to operate said motor at different speeds, means for supplying substantially constant voltage to said motor driving means at all work producing speeds, switch means for selecting any one of said pole groups to thereby change the driving speed for operating said compressor to produce compression work while said voltage remains sub stantially constant, switch actuating'means for operating said switch, unloading mechanism operatively associated with said compressor for loading or unloading said compressor and control means operatively associated with the output of said compressor and connected with said switch actuating means and with said unloading mechanism in such a manner that the speed of said motor is changed in response to a change of a condition resulting from the compression work of said compressor and that said unloading mech- U anism is actuated to unload said compressor while the speed thereof is being increased one of said speeds to another.

4. A compressor plant as defined in claim 1 in which said speed changing means comprises a change speed transmission coupling said motor to said compressorfor selectively driving the same at difierent work produ-cingspeeds and transmission actuating. means for changing the speed in which said control means includes pressure responsive means connected to the output of said compressor, and electrically connected with said speed changing means and with said unloading mechanism in such a manner that the speed of said compressor is reduced upon an increase in 6. A compressor plant as defined in claim 1 in which said electric motor driving means includes an electric driving motor operable at one speed,,a second eleotricdriving motor operable at a different speed, coupling means for selectively coupling said first or second motor to said compressor to drive thesame and actuating means for said couplin means, said control means being electrically connected to said actuating means.

7. A compressor plant as defined in claim 6 in which said'coupling means comprises clutches.

1 JOHN RUTGER MUNCKAF RbSENSCHLD.

pressure above a predetermined value and that I thereof is being increased fromone of said speeds to another.

References Cited in the file of this'patent UNITED STATES PATENTS

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2986617 *Mar 16, 1959May 30, 1961Westinghouse Air Brake CoFluid compressor motor control apparatus
US3186630 *Sep 5, 1963Jun 1, 1965Jaeger Machine CoRotary compressor
US4068980 *Oct 1, 1976Jan 17, 1978Gardner-Denver CompanyCompressor startup control
US4401412 *Jun 1, 1981Aug 30, 1983Ga Industries Inc.Heavy duty electric pump control unit
US4549400 *Apr 13, 1984Oct 29, 1985King Alex CElectro-hydraulic engine throttle control
US4702083 *Oct 30, 1985Oct 27, 1987Toyota Jidosha Kabushiki KaishaControl system and method for controllable output type hydraulic fluid pump of automatic transmission providing decreased pump output in association with the engine starting condition
US5167491 *Sep 23, 1991Dec 1, 1992Carrier CorporationHigh to low side bypass to prevent reverse rotation
US6457306 *Nov 13, 2000Oct 1, 2002Lockheed Martin CorporationElectrical drive system for rocket engine propellant pumps
Classifications
U.S. Classification417/12, 417/28, 417/16
International ClassificationF04B49/24, F04B49/20, F04B49/02, F04B49/06
Cooperative ClassificationF04B49/243, F04B49/20, F04B49/06, F04B49/022
European ClassificationF04B49/06, F04B49/20, F04B49/02C, F04B49/24B