Patent GB-370122-A (GB)
Title: Improvements in or relating to voltage failure protection devices
IPC: H02H3/13
Filed: 1931-02-19
Abstract: 370,122. Protective cut-out arrangements ; electromagnetic switches. IGRANIC ELECTRIC CO., Ltd., 147, Queen Victoria Street, London, and WRIGHT, S. R., 113, London Road, Bedford. Feb. 19, 1931, No. 5270. [Class 38 (v).] Retarding devices; switches, locking and unlocking ; contacts.-A voltage failure protection device for polyphase circuits comprises a circuitinterrupter, armatures respectively associated with windings in the several phases and mechanically correlated with the interrupter such that the latter opens on voltage-failure in only one phase but not on failure of all phases simultaneously. There may also be provided an overload armature common to all the phases. Fig. 1 shows diagrammatically a form in which a main contactor coil 23 is energized by closing a manual switch 26a to energize coils 1 in the respective phases of a motor, whereby the plungers 2 rise and engage the closed switches 21, having pivots x, y, to raise them, without, however, separating them. If voltage-failure occurs on all phases, all the plungers fall and the switches 21 drop but still remain closed, but if voltage-failure occurs on only one phase, only the lower contact of the switch 21 corresponding to that phase drops and opens the circuit, the remainder being prevented from moving by the interlocks shown. The opened switch 21 is held open, Fig. 3, by a gravity latch 28 until reset by a member 30. An overload armature 19 is also arranged to open one of the switches 21, the overload causing the armature 19 to rise, in a time dependent on its severity, against the action of a dashpot 4a of the nature described in Specification 355,738. If the overload is severe, the part 24a is separated from the part 24b against the action of the spring 25 so as to secure instant opening of the switch 21. In another form, Figs. 4 and 5 (not shown), some of the arms of the switches 21 are spring-controlled and act as latches to keep the switches 21 open. In Figs. 7 and 9, a V-shaped member 34, pivoted at the axis X-X, is urged by a spring so that contacts on its ends engage contacts at one end of the arms 36 pivoted intermediate their ends, the other ends resting under collars 35 on the ends of two of the plungers 2. The third collar 35 rests on an arm 36 engaging the apex of the member 34. This switch is in series with a coil 23 and contacts 39 of a relay 40 which is in series with the manual switch 26a. When the contactor 23 closes its contacts 23a and energizes the coils 1. the collars 35 are lifted, thereby causing the arms 36 to be rotated by the member 34, without however breaking contact. Voltage-failure in a line causes the corresponding collar 35 to drop, thereby acting on its arm 36 to move the member 34 from either or both contacts and break the circuit of coil 23. An overload device similar to that of Fig. 1 is provided and acts also on the member 34, which is held displaced by a hand-freed latch on overload. With the circuit arrangements shown, it is impossible to re-energize the contactor until the fault is remedied. In a modification of Fig. 9, the contactor is controlled from a starting-button which is shorted by an extra contact on the contactor when the latter closes. In Figs. 11 and 12, a plate 34a is pivoted at X and urged downwards by a spring to bridge contacts 38. The collars 35 in their lower positions engage a lever 42 which lifts the plate 34a. In its upper position, a plate 44 is engaged by the collars 35 to lift a plate 34b from bridging across parallel contacts 38. A spring-latch 45, pivoted at 46, normally bears on the collar 35 associated with the line L<1> and on plate 44, as shown, so that when the collar is down and the plate up, the latch can come between them. When the coils 1 are energized, the plungers 2 rise and allow the plate 34a to fall and, later, cause the plate 34b to rise. Voltage-failure in line L<2> or L3 causes the appropriate plunger to fall and raise the plate 34a which breaks the circuit of coil 23 whereby the other plungers fall. The plate 34b also recloses its contacts, as the plate 44 engages the latch 45 before the collar 35 of line L<1> releases it. If line L<1> fails, however, the collar 35 of that line falls and allows the latch to function, as the plate 44 is held by the other collars until the coil 23 is de-energized. The latch is removed by a button 48 which also serves to release a catch Z when the latter has come into operation as the result of an overload having lifted the plate 34a.