US2196868A - Alternating current circuit breaker - Google Patents

Description

April 9, 1940. w. KRAMER I -ALTBRNATING CURRENT CIRCUIT BREAKER Find lay 2a, 1938 2 Sheets-Sheet 1 I I l A I W I l I II InveI cor-z Werner- Kramer,

b9 WW6.

I His Attor-nes.

-I 9, 1940. w., KRAMER ALTWQING CUM!!!" CIRCUIT BREAKER Filed lay 28, 1938 2 Sheets-Sheet 2 m o m v .m.

Wer-ner- Kramer. bH 1 4 5 K/waAM His Attorney.

Patented Apr. 9, 1940 Y um'rsn STATES PATENT OFF-ICE 2,196,868 I aumamrmc mm cmcnrr panama Application V In May 28,,1938, serum. ziasai Germany July 15, 19:1 1

12 Claims. (01. 175 294) the synchronous type for eifecting separation of I the coacting breaker contacts only at or near a It current zero.

v Synchronous circuit breakers for interrupting" alternating current power arcs have been proposed wherein the opening impulse initiates simultaneous movement of the engaged coacting contacts until a current zero is reached, where- 7 The devices heretofore proposed, however, have a number of inherent disadvantages such as, for

example, excessive timelag due to too complicated control means or too great inertia. Also imperfect mechanical operation has. been encountered due to rebound when the retarding device en-' gages theseparating contact structure that is already moving at high speed. The principal object of my invention-is the provision of an improved synchronous circuit 30 breaker of the aforesaid type that is eife'ctive to apply within a very short and constant specific l time after the opening impulse a positive retarding force to one of the contacts tocause high speed separation of the breaker contacts at or near a 86 current zero. e

My invention will be more fully set forth in the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with 40 particularity in the claims annexed to andforming a part of this specification.

"Referring to the drawings, Fig. 1 is a partly diagrammatic illustration of a synchronous electric circuit breaker embodying my invention 46 showing'the contacts thereof in an intermediate position, and Fig, 2 is an enlarged detailed'view partly in section showing a part of the retarding mechanism shown in Fig. 1. o

The circuit breaker illustrated by way of ex- 50 ample comprises a pair of relatively movable contacts I and 2, the socket contact I being designated as the fixed contact and the coacting rod contact 2 as the movable contact that is recipro cally operable along a rectilinear path with respect to the contact I. For the purpose of aimplicity no special I arc-extinguishing .means, is shown,'it being'understood that the presentinyention can be applied to various types of circuit V breakers such as-the well-known gas blast and oil blast types, The external circuit connections can be connected tothe contact terminals as diagrammatically indicated at 'r," p

The so-called fixed contact I is mounted 'for limited following movementwith-respectto the contact 2 by means of a compression spring 3 that is stressed in the closed circuit position. when the rod contact '2 is lowered to cause opening of the circuit theco'a'cting fixed contact I remains in following engagement under the influence of the biasingspring 3 until the synchronous control embodying my invention arrests the movementof the contact I at or near a current zero. I

The synchronous. control means comprises ess'entially anelectromagnet generally indicated at- 4, having a coacting armature 5 that is connected P to a detent 6. The detent is adapted tocoact with a brake device I for controlling, in a mannerpresently described, the contact I. 'l In general, the arrangement is such that the detent 6, which. is spring biased toward the brake device 1, is 8| released so as immediately to stop the movement of contact I through the brake device when the magnet-flux at the armature 5 indicates a current zero;

energized from a suitable synchronous control source, such as a current transformer 8 that is related to the circuit to be interrupted. The armatureicoacts with the magnet pole pieces 5' that are spaced by acomparatively short air gap as illustrated so that the holding force acting on. the armature when the magnetic circuitis', closed is large, and the attracting'force after initial movement of the armature from the'poie pieces is comparatively small. The detent its 40 directly connected torthe armature 5 through a connecting rod 9 and is biased by, a spring I0 (Fig. 2) that is mounted within a fixed housing I I in a direction opposing the holding force of the The magnet and -toward the brake device I.

detent 6' is also guided for reciprocal rectilinear movement within a bushing I2 that is mountedin the frame of the magnet.

v When an overload or short circuit occurs the movable contact 2 is moved downward towardslo the open circuit-position at high speed by conventional operating means (not shown), the contact I during the initial openingmovement tend ing to tollow the rod contactunder bias of spring,

' 3. For the purpose of arresting the movement of u The coils l'of the electromagnet normally the contact I in the manner above described, the brake device I is connected through an endless belt or cable I3 to the contact I at II as illustrated. The belt is also adapted to carry the brake device I so that stopping of the brake device necessarily results in stopping of the contact I. The belt I3 in the present instance is mounted on a fixed pulley I4 and a brake roller I5, an idler roller I6 being provided for adjustment of belt tension and for positioning the belt portions carrying the brake device and contact respectively.

Referring more particularly to Fig. 2, the brake device I comprises a longitudinal housing II that is connected at its opposite ends at I! and I! to the belt I3. The housing I! is slotted at opposite sides thereof for permitting entries at one side of the detent 6 and at the opposite side for a fixed guide and positioning member 20. Mounted within the housing I is a stack of individual steel plates 2I. As illustrated, the width of the plates is uniform and appreciably less than the corresponding dimension of the housing I! so that the fixed member 20, which extends within a slotted wall of the housing, can realine the plates opposite thereto in abutting relation to the opposite wall. The plates 2|, as previously indicated, are individually movable and are held in a given position simply by friction except when otherwise restrained. In the normal closed circuit position of the apparatus, a cam plate 22 secured to the housing I1 at the upper part thereof is opposite the detent 6 in abutting relation thereto so as to hold the detent and armature retracted against the bias of spring I0.

Accordingly, in response to the circuit opening impulse above referred to, the contact I starts to move downward with the rod contact 2 and the brake device I carried by the belt II simultaneously moves upward to a position such as shown in Fig. 1 wherein the cam plate 22 has cleared the detent i. In this position the arma ture 5 is held only by the flux of the magnet l. When, now, the current in the main line, apprOaches or reachesthe zero value, the detent 6 is released through the armature 5 so that the biasing spring I0 is immediately effective to project the detent 6 through the slotted wall. of the housing I1 to displace certain of the plate members 2|. As shown in Fig. 2, the detent in this position overlaps one of the undisturbed lower plates, thereby latching and blocking immediately further upward movement of the housing I! and belt I3.

The movement of the contact I is therefore promptly arrested at a current zero by the detent 6 and by the brake roller I 5 which can function in a manner similar to a band brake. Preferably, the speed of the contacts at the instant of contact separation is of the order of magnitude of 3 to 4 meters per second. The speed of the braking operation can be furthermore increased by designing the movable parts including the detent 6 of comparatively small hardened steel parts, so that the inertia is small, and also by relating the cam 22 and detent so that the stroke thereof is very short. Notwithstanding practically instantaneous stopping of the movable structure, the stresses on the braking device are not large by reason of the belt and brake roll arrangement.

The circuit-closing operation is effected by lifting the contact 2 in the usual manner so as to engage the contact I and force the same against the bias of spring 3 to its upper initial position. During this movement the belt II is moved a corresponding distance carrying downward with it the brake device I, so that the fixed guide member 20, by reason of its rounded camming surface 20', progressively moves the steel plates 2| to their original alined positions abutting the left wall of housing I1. At the end of the stroke the cam member if engages the coacting cam surface 6' of the detent 0 to force the same and the armature 5 to the reset position shown in Fig. 1. Since the plate members II and the detent 8 are now reset, the apparatus is in readiness for another circuit-opening operation as above described.

For the purpose of mounting the magnet I so that the armature 5 is not loosened by vibration,

the armature frame can be resiliently mounted at 23 to a fixed supporting plate 24. The detent spring I0 which is mounted within the housing II is, however, mounted in flxed relation to a support 25.

In order to overcome the initial inertia of the movable structure, a biasing spring 20 acting on the brake device 1 is provided for accelerating the circuit-opening movement of the mechanism.

The inertia of the movable structure including the detent C necessarily introduces a slight delay in arresting the contact structure I and, for this reason, it may be desirable to provide means for displacing the phase of the magnet current with respect to the main line current so that the armature 5 is actually released slightly before the current zero in the main circuit. This phase displacement provides sumcient time for the necessary mechanical operation of separating the contacts I and 2 or even slightly before a current zero in the main circuit.

A current transformer such as shown is particularly adapted for this use since in any current transformer the primary ampere turns are equal to the secondary ampere turns plus the magnetizing ampere turns. Therefore, if the secondary circuit has a higher power factor than that of the magnetizing current, the secondary current will lead the primary current and the respective current zeros will be advanced accordingly in the secondary circuit. Since the magnetizing current is generally lagging to a considerable extent, and since the secondary circuit can readily be given a much higher power factor by inserting resistance, for example, the degree of lead of the secondary current can readily be adjusted as desired.

Another expedient is the use of an air gap in the current transformer core which increases the amount of the magnetizing current and. accordingly, tends to increase the lead in the secondary circuit. It may be noted that as the primary current is increased the ma netizing current is also increased so that the proportional amount of lagging current'will be greater thereby increasing the lead of the secondary current. l'br example, a degree lead in the secondary circuit can readily be secured under heavy current conditions when the interrupting duty is more severe. This 45 degree lead allows 0.002 second for the latch to function in a cycle system, or 0.005 second on a '25 cycle system. Accordingly, the time constant of the latch or detent can readily be compensated so that separation of the contacts takes place as near the current zero in the main line as desired.

.In case a series coil instead of a transformer as illustrated is used, the magnet poles can be encircled with so-called 188 rings for del ying 7s said electromagnet to the circuit controlled by in a well-known manner the release of the armature until after a current zero in'the magnet coil. -This or course would be in the opposite direction to the lead that is desired but it, for example, the magnet were lagged degrees the following current zero would then be anticipated by 180-80 degrees or degrees. This would provide 0.0045 second in a 00 cycle system which in the case of slightly sluggish operation or the detent would insure separation of the contacts I and 2 substantially at or before the following current zero. 7

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A synchronous electric circuit breaker comprising. relatively movable contacts, said contacts arranged initially to move in following relation, means coacting with one of said contacts for arresting vit to cause contact separation at a current zero including an electromagnetic device having means for restraining said one of said ocntacts with respect to continued following movement, and means relatiing said electromagneticdevice to the circuit controlled by said breaker for shifting the phase of the energizing current of said device with respect to the current in said circuit.

2. A synchronous electric circuit breaker comprising relatively movabie contacts, said contacts arranged initially to move in following relation, means for arresting the movement of one of said contacts to cause contact separation at a current zero including an electromagnet having a restraining member coacting with said one of said contacts, and a current transformer related to the circuit controlled by said breaker for energizing said electromagnet to cause actuationof said restraining member, the secondary circuit of said current transformer having a higher power factor than that of the mangetizing current whereby the phase of the magnet current is advanced with respect to the current in said circuit.

3. A synchronous electric circuit breaker comprising relatively movable contacts, means for controlling one of said contacts to cause contact separation at a current zero including an electromagnet having restraining means coacting with said one of said contacts, and means for energizing said electromagnet from the circuit controlled by said breaker, said means having such circuit characteristics that the phase of the magnet energizing current is advanced with respect to the current phase of said circuit for compensating the inertia of said restraining means.

4. A synchronous electric circuit breaker comprising relatively movable contacts, means coacting with one of said contacts to cause contact separation at a currentzero including an electromagnet having a movable armature, a latching member connected to said armature, a spring for biasing said member in opposition to the magnet holding force at said armature in a direction to latch said one of said contacts, means controlled by the position of said contacts for holding said memberretracted against the bias of said spring, said last-named means releasing said member after predetermined initial contact movement, and an energizing circuit for relating said breaker.

5. A synchronous electric circuit breaker comprising relatively movable contacts, means for maintaining said contacts in engagement for simultaneous movement thereof at the initiation of the contact opening operation, means for positively arresting the movement of one of said contacts to cause contact separation at a current zero comprising an electromagnet having a movable armature, a latching member connected to said armature, a spring for biasing said armature in opposition to the magnet holding force for moving said member to a latching position with respect to said one of said contacts, said spring being adapted to actuate said latching member after initiation of the contact-opening movement when the magnet energizing current drops to zero, and means relating said electromagnet to the circuit controlled by said breaker for energizing said magnet, said last-named means having a phase-shifting characteristic for relating the time constant of said spring biased member and the phase of the manget-energizing current for causing application of said-latching member at or near a current zero of said circuit.

6. A synchronous electric circuit breaker comprising relatively movable contacts, means coacting with one of said contacts to cause contact separation at a current zero including an electrothe bias of said spring only in the closed circuit position of said contacts, and means relating said magnet to the circuit controlled by said breaker for energizing said manget, said last-named means having a phase-shifting characteristic for relating the time constant of said spring biased detent and the phase of the magnet-energizing current for causing application of said detent after initiation of the contact opening operation .at or, near a current zero of said circuit.

'7. A synchronous electric circuit breaker comprising relatively movable contacts, means for maintaining said contacts in engagement for simultaneous movement thereof at the initiation of the contact-opening operation, means for positively arresting the movement of one of said contacts to cause-contact separation at a current zero comprising an electromagnet "related to the circuit controlled by said breaker, a brake device including a flexible member operatively connected to and movable with said one 01' said contacts, and a latching member coacting with said brake device controlled by said electromagnet.

8. A synchronous electric circuit breaker comprising relatively movable contacts, means main taining said contacts in engagement ior simultaneous movement at the initiation of the contact-opening operation, means for positively arresting the movement of one of said contacts to cause contact separation at a current zero .comprising an electromagnet related to the circuit controlled by said breaker, a latching device controlled by said electromagnet, means adapted to means.

9. A synchronous electric circuit breaker comprising relatively movable contacts, resilient means for biasing one of said contacts into 101- lowing engagement with a coacting contact at the initiation of the contact-opening operation, means for positively arresting the movement of said resiliently biased contact to cause contact separation at a current zero comprising an endless belt connected to said resiliently biased contact, an electromagnet related to the circuit controlled by said breaker, a latching member "controlled by said electromagnet, and means meeting with said latching member likewise carried by said belt arranged so that latching thereof arrests movement of said resiliently biased contacts.

10. A synchronous electric circuit breaker comprising relatively movable contacts, resilient means for biasing one of said contacts into following engagement with a coacting contact at the initiation of the contact-opening operation, means for p'o'sitively arresting the movement of said resiliently biased contact to cause contact separation at a current zero comprising an electromagnet energized from thecircuit controlled by said breaker having a movable armature, a latching member connected to said armature, a spring for biasing said armature in opposition to the magnet holding force for moving said latching member toward a latching position, a cam member movable in accordance with movement of said resiliently biased contact for holding said latching member in retracted position against the bias of said spring whereby said armature is in the closed magnetic circuit position, and means operatively connected to said resiliently biased contact adapted to be engaged by said latching member when said armature is released at a current zero following movement of said cam to an unobstructing position.

11. A synchronous electric circuit breaker comprising relatively movable contacts and means for restraining one of said contacts to cause conture closed, and means connected to and movable with said one of said contacts adapted to be engaged and restrained by said latch when said armature is released at a current zero following movement oi. said cam to an unobstructlng position.

12. A synchronous electric circuit breaker comprising relatively movable contacts and means for restraining one of said contacts to cause contact'separation at a current zero including an electromagnet energized from the circuit controlled by said breaker having a movable armature, a latch connected to said armature, a spring forv biasing said armature in opposition to the magnet holding i'orce, a cam member movable in accordance with predetermined movement of said contacts for restraining. said latch against the bias of said spring and for holding said armature closed, and a latch receiving structure connected to and movable with said one or said contacts having a plurality of individually movable members adapted to be displaced by said latch when said armature is released at a current zero following movement of said cam to an unobstructing position, the undisplaced members blocking further movement or said structure, and means for restoring said members to reset position in accordance with the circuit-closing operation.

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