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Publication numberUS3737736 A
Publication typeGrant
Publication dateJun 5, 1973
Filing dateApr 4, 1972
Priority dateApr 23, 1971
Also published asCA954931A1, DE2128651A1, DE2128651C2
Publication numberUS 3737736 A, US 3737736A, US-A-3737736, US3737736 A, US3737736A
InventorsH Stampfli
Original AssigneeLucifer Sa
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electromagnet-controlling system
US 3737736 A
Abstract
An arrangement for feeding the power winding of an electromagnet with rectified A.C. by means of a thyristor or triac. The latter is inserted in parallel with a transistor the conducting condition of which is provided by a condenser fed by the rectified A.C. and discharging into the base of the transistor which latter acts then on the electrode controlling the thyristor, to allow the latter to return into its non-conductive condition at the end of an alternation. A maintenance or holding current is provided either through an auxiliary electromagnet winding or through a chopped current feeding the power winding and produced by a pulse generator.
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United States Patent 91 Stampfli [54] ELECTROMAGNET-CONTROLLING SYSTEM [75] Inventor: Harald Stampfli,

Geneva, Switzerland Petit-Saconex,

[73] Assignee: Lucifer S. A., Carouge-Geneva,

Switzerland [22] Filed: Apr. 4, 1972 [21] Appl. No.: 240,354

[30] 7 Foreign Application Priority Data Apr. 23, 1971 Switzerland ..'.....59()9/71 June 4,1971 Germany ..P 21 28 651.1

[5 6] References Cited UNITED STATES PATENTS Gieffers ..3 l 7/DIG. 4 Lancles ..3l7/l48.5 B

[111 3,737,736 51 June 5,1973

Primary ExaminerWilliam H. Beha, Jr. Att0rneyEmory L. Groff et a1.

57 ABSTRACT An arrangement for feeding the power winding of an electromagnet with rectified A.C. by means of a thyristor or triac. The latter is inserted in parallel with a transistor the conducting condition of which is pro vided by a condenser fed by the rectified A.C. and discharging into the base of the transistor which latter acts then on the electrode controlling the thyristor, to allow the latter to return into its non-conductive condition at the end of an alternation. A maintenance or holding current is provided either through an auxiliary electromagnet winding or through a chopped current feeding the power winding and produced by a pulse generator.

5 Claims, 2 Drawing Figures ELECTROMAGNET-CONTROLLING SYSTEM The present invention covers an arrangement controlling an electromagnet and adapted to supply upon energization a strong initial current, followed by a weaker maintenance current. Such an arrangement allows in particular the electromagnet to exert a larger initial attraction without exaggeratedly heating its winding, since the maintenance current following the initial current is comparatively weak.

The control arrangement comprises, according to the invention, a Graetz rectifier connected with a supply of AC. and feeding an electromagnet winding in series with a thyristor, the control electrode and the cathode of which are connected with each other through delaying means which become conductive at a predetermined moment following the closing of a control switch.

In the accompanying drawings:

FIGS. 1 and 2 illustrate diagrammatically and by way of example two embodiments of the arrangement forming the object of the invention.

As illustrated in FIG. 1, a rectifier 1 operating on both alternations is connected through a switch S with the terminals a and b fed by a supply of A.C., e.g. the

mains.

The controlled electromagnet includes two windings B, and B the maintenance winding B being fed directly across the terminals and d of the rectifier l. The power winding B, is connected across said output terminals of the rectifier, in series with a resistance R and a transistor T,. Said winding B, is also connected with the negative output terminal d of the rectifier through a thyristor T in series with two diodes D, and D The base of the transistor T, is connected with a condenser C through a Zener diode Z. This condenser C forms with the resistance R, and RC element. The base of the transistor T, is connected with its emitter through a leak resistance R The power winding B, is shunted by a diode D The operation of the arrangement is as follows:

The closing of the switch S obviously energizes the winding B The winding B, is also subjected to a positive voltage since the transistor T, is non-conductive at the start; in fact the control electrode of the thyristor T is practically subjected to the voltage of the positive terminal c of the rectifier, whereas the cathode of said thyristor is substantially at the voltage of the terminal d. The thyristor T is therefore conductive, so that the power winding B, is fed.

The condenser C is loaded gradually through the resistance R, and when itsvoltage reaches the threshold voltage of the Zener diode, said voltage is applied on the base of the transistor T, which becomes conductive.

The control electrode of the thyristor T returns then to the voltage of the terminal b and is therefore negative with reference to the cathode of the thyristor by reason of the drop in voltage by about 2 volts across the diodes D, and D Since the drop in voltage across the transistor T, is about 0.5 V,.the control electrode is biased negatively by about 1.5 V with reference to the cathode of the thyristor T The thyristor is therefore under conditions which make its extinction an easy matter during the next passage through zero of the rectified current fed by the rectifier l.

After extinction of the thyristor T the winding B, is no longer fed and only the maintenance winding B remains operative. It should be remarked that the diode D cuts out all overvoltages in the winding B, during said extinction of the thyristor T Of course, many modifications may be brought to the circuit described and in particular it is possible to re place the Zener diode Z by any other component provided with a threshold voltage beyond which it becomes conductive.

The embodiment illustrated in FIG. 2 distinguishes from the first embodiment through the absence of an auxiliary maintenance winding B for the electromagnet. The circuit feeding the winding B, is identical with that of FIG. 1 except for a resistance R inserted be tween the collector of the transistor T, and the control electrode of the thyristor T In this second embodiment, a pulse generator 2 provides the application to the control electrode of the thyristor T of pulses synchronized with the frequency of the mains and phase-shifted with reference to the latter. Thus, when the transistor T, becomes conductive and prevents consequently the automatic ignition of the thyristor T the latter is rendered conductive during each alternation by the pulses supplied by the generator 2. Thus, there is obtained a chopped current, the average value of which is lower than that of the current obtained at the start. Said chopped current forms the maintenance current for the electromagnet.

The pulse generator comprises, as well-known per se, a single-junction transistor T fed through a resistance R, and across a Zener diode Z The voltage across the terminals of said diode Z is applied to the base of the transistor T through a resistance R which loads a condenser C Each time the voltage across the terminals of said condenser reaches the threshold value of the transistor T the latter becomes conductive and allows the passage through a resistance R, of a current which produces a voltage pulse which is applied to the control electrode of the thyristor T An important advantage of the circuits described resides in the fact that, whatever the voltage of the mains may be, the voltage to which the transistor T, is subjected never rises above a few volts, since fora voltage of this magnitude, the thyristor T becomes immediately conductive.

It is of course possible to bring numerous modifications to the wiring diagrams described and, in particular, the thyristor T may be replaced by a triac. In such a case, the pulse generator 2 may be provided so as to supply pulses of a negative polarity while the diodes B,v I"

and D may be omitted.

I claim:

1. An electromagnet-controlling system adapted to produce a strong starting current for an electromagnet power winding followed by a weaker holding current comprising a Graetz rectifier, adapted to be fed with A.C., a thyristor circuit including an anode and a cathode inserted in series between the rectifier and the electromagnet power winding and a controlling electrode, and delaying means inserted between said cathode and controlling electrode and adapted to become conductive at a predetermined moment after energization of the rectifier to allow the thyristor circuit to return to its inoperative condition and means feeding a weaker holding current to the electromagnet.

2. A system as claimed in claim 1, wherein the delaying means include a transistor, the emitter-collector circuit of which is inserted in parallel with the thyristor circuit and is connected with the controlling resistance of the latter, a resistance and condenser circuit fed by the rectifier and an element provided with a threshold voltage and operatively connecting said condenser with the transistor base as soon as the condenser voltage has reached a predetermined voltage.

3. A system as claimed in claim 1, wherein the delaying means include a transistor, the emitter-collector circuit of which is inserted in parallel with the thyristor circuit and is connected with the controlling resistance of the latter, a resistance and condenser circuit fed by the rectifier and an element provided with a threshold voltage and operatively connecting said condenser with the transistor base as soon as the condenser voltage has reached a predetermined voltage, and at least one diode inserted between the negative terminal of the rectifier and the cathode of the thyristor circuit and leading the current passing out of the latter towards voltage and operatively connecting said condenser with the transistor base as soon as the condenser voltage has reached a predetermined voltage and wherein the means feeding the holding current include a generator of pulses synchronized with the frequency of the AC. fed to the rectifier and phase-shifted with reference thereto and means for applying said pulses to the thyristor circuit.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3864608 *May 21, 1973Feb 4, 1975Mkc Electronics CorpCombination monostable and astable inductor driver
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US4214290 *Mar 18, 1977Jul 22, 1980Sevcon LimitedControl circuit for electromagnetically operated contactor
US4227231 *Sep 5, 1978Oct 7, 1980Eaton CorporationIntegral relay low voltage retentive means
US4274122 *Jun 20, 1979Jun 16, 1981Eaton CorporationEnergizing and quick deenergizing circuit for electromagnetic contactors or the like
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Classifications
U.S. Classification361/154, 361/194, 361/205
International ClassificationH03K17/64, H01F7/18, H03K17/72, H03K17/73
Cooperative ClassificationF02D2041/2079, H03K17/72, H01F7/1833, H03K17/64, H03K17/73
European ClassificationH03K17/73, H03K17/64, H01F7/18B4, H03K17/72
Legal Events
DateCodeEventDescription
Sep 13, 1984ASAssignment
Owner name: HONEYWELL LICIFER SA, 16, CHEMIN DU FAUBOURG DE CR
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SPERRY VICKERS LUCIFER SA;REEL/FRAME:004300/0237
Effective date: 19840827