Patent GB-992546-A (GB)
Title: Improvements in devices for testing the carrying out of switching operations in synchronised relay groups
Inventor: HOPPE WALTER
IPC: H04Q1/20
Filed: 1961-06-02
Abstract: 992, 546. Fault testing. EL-RE-MA S.A. PER LO SPRUTTAMENTO DI BREVETTI. June 2, 1961, No. 19996/61. Heading G1U. Apparatus for testing the completion of switching operations in synchronized groups of relays energized by an impulse generator, and for correcting defective switching operations, wherein each relay group has testing means sensitive to a valve of electric current or voltage consequential on correct completion of the switching operation; the circuit connections being such that switching-on can only occur at fixed values of the electrical variable, while if the current or voltage values depart from such values the testing means initiates a correcting cycle operative to maintain the contact position of a non-faulty group, to reverse the contact position of the faulty group, to re-operate the relay from whose operation the faulty contact position has arisen, and to re-test the value or presence of the electrical variable. Fig. 1a shows a basic known relay arrangement of e.g. a denomination row of a binary computing machine comprising groups A, B each of two relays respectively registering one of two alternative conditions of the group. Relays A have control windings A1, A2 and contacts a 1 , a 2  while relays B have control windings B1, B2 and contacts b 1 , b 2  respectively; with holding windings MA, MB. The contacts a 1 , a 2  are connected to windings B1, B2 over a reversing switch C and the relays are excited by an impulse generator Ig with trains of control and holding pulses (Fig.1b) over branches I, II, III, IV; a pulse over branch I operating A1 if b 1  is closed or A2 if b 2  is closed, whereby a 1  or a 2  is closed and held over MA by holding impulses through branch II, and control impulses through branch III energize either B 1  or B2 to operate contacts b 1  or b 2  and hold over MB by impulses over branch IV; the impulses being interspaced in time so that one relay group completes operation before the next group is switched in. Fig. 2a shows a known contact pyramid of a binary relay register in which there are three positional contact groups GP1, GP2, GP3; each group being operated by a relay B1 controlled by contacts of relays A, in arrangements as shown in Fig. 1a, and imperfect contact may be detected by increased resistance in the series circuit containing the contact, but since both make and break contacts may be imperfect, testing is facilitated by rearranging as shown in Fig. 2b to the equivalent contact pyramid utilising only make contacts; it being necessary that the contacts in the upper part or in the lower part of each group are together held closed, so that both contact errors in inoperation of a relay may be detected by an increase of normal resistance of the appropriate series circuit. The contacts of the relay pyramid are contacts of respective groups B (Fig.1a) and control corresponding relay groups A in a binary relay register, and the normal parallel energization of the relay windings (Fig. 3 not shown) is rearranged as in Fig. 4 by utilizing changeover contacts b 1 , b 2 , b 3 , b 4  &c. to series energize relay A, or equal resistance R 1 ; relay A 2  or equal resistance R 2 ; relay A 3  or equal resistance R 3 ; relay A 5  or relay A 4  of equal resistance thereto, so that the energization circuit is symmetrical and the series resistance is independent of the number of actuated relays but increases on faulty contact closure. Auxiliary series windings are provided to reverse the relay contacts. Fig. 5 shows an application of the invention to the circuit of Fig. 1 comprising relay groups A and B, wherein two impulse generators IgI and IgIII comprising e.g. halfwave rectifiers in series with an AC supply generator control impulses to branches I and III, which respectively pass through changeover contacts b 1  and a 1  and thence through contact b 1  and relay A or resistance R<SP>1</SP> a; contact a and relay B or resistance R<SP>1</SP>b. On correct closure of all contacts, current traverses b 1  A or a 1 B since the windings of the corresponding relays B 1 , B<SP>11</SP>1, or A 1 , A<SP>11</SP> 1  are always traversed by control or holding impulses. Holding currents in B<SP>11</SP> 1  or A<SP>11</SP> 1  are derived from an impulse circuit independent of the flow of a control impulse through resistance Ra, operating from impulse generator IgI<SP>1</SP> in parallel with IgI and delivering similar impulses through resistances R<SP>11</SP>a and R<SP>111</SP>a and diode Da<SP>1</SP> to so control the direct current flow from source BaII that current impulses of the same form as in the holding windings A 1 <SP>11</SP> or B 1 <SP>11</SP> flow in the holding circuits MA or MB of the relay groups. The working contacts b 3  and a 3  are permanently closed during the normal switching cycle, since the corresponding windings A 3  and A<SP>1</SP>1 or B 3  and B<SP>1</SP> 1  are continuously traversed by controlling or holding pulses, while contacts b 1  and a 1  are switched to conduct control impulses to closed contacts b 3  or a 3  when the circuit is correctly operating. These contacts are arranged in series with the relay group circuits to be tested, and are operated by relays having a very short time constant by comparison with the group switching relays; these relays having windings A 3 , A<SP>1</SP> 3  or B 3 , B<SP>1</SP> 3  in the appropriate relay groups and allowing operation on interruption of the control impulse circuit or on interruption of the holding impulse circuit allowing interruption of the control impulse due to absence of holding, so as to introduce a correcting switch cycle. E.g. if holding circuit MB is interrupted, B 3  releases due to interruption of current in B<SP>1</SP> 3  at the beginning of the succeeding current impulse of IgI, and the arrangements operate as if the control impulse circuit had been broken through MA, so that the correct contact position of a is maintained by the holding current in MA, and the correcting cycle can commence. A contact disconnection is b, A arising as opening of b 3  or non-closure of a control contact b interrupts control pulses from IgI so that relay winding A 1  carries no current, and the holding winding A 1 <SP>11</SP> is energized from DC source BaII over holding pulse generator IgI<SP>1</SP> supplying impulses to branch II (Fig. 6a). Changeover contact a 1  releases to rest position, but the holding current in MA continues to flow, diode Da receives no inverse voltage, and the correct position of contacts a is maintained. Since a 1  has released, the rest control impulse of generator IgIII traverses resistance R<SP>1</SP>b equal to the relay circuit resistance and also relay winding B2. The consequent drop across Rb is applied inversely to diode Db, so that a holding impulse pause occurs in MB to allow all the b contacts to release and since contact a 1  is at rest the b contacts cannot be reoperated and are effectively closed; all the operative b contacts as well as the defective contact having reversed their positions. The operated relay B is held during the next control impulse of IgI (Fig. 6a) over b<SP>1</SP> 2 , B<SP>1</SP> 2  which as shown is in parallel with MB but may alternatively be in parallel with b 1 <SP>1</SP>, B<SP>11</SP> 1  as shown in broken lines. This control impulse cannot flow through Ba since the operative contacts have been operated, but the closed contact b 2  allows it to flow in relay winding A<SP>1</SP> 1  which operates. The impulse does not traverse R a  so that diode Da is not biased and the positions of the contacts MA are maintained. Holding current over contact a 1  and winding A<SP>11</SP> 1  maintains contact a 1  in operating position during the next impulse of IgIII (Fig. 6a) so that the impulse current now flows through contacts a into B and the sequence of relay operation in which a broken contact position has arisen is repeated. All the make contacts are closed, including that previously broken, and the rest impulse of IgI is applied to the circuit including b 1  A. If the fault clears, the switch operation cycle continues normally; if it remains the foregoing cycle is indefinitely repeated; Fig. 6b showing the consequent cycle of impulses, wherein two control impulses fail in branch I and a holding impulse in branch II is prolonged to hold the non faulty relay switching group during the correcting switch cycle, which is superimposed on the switch programme of the relay groups. The occurrence of faults may be recorded or counted, as may the number of correction cycles necessary to clear a fault. The circuit may be arranged to switch in a reserve relay group or to operate an alarm if a correction cycle is ineffective to clear a fault. Where changeover relay contacts are to be tested for faulty contacts as in Fig. 4, the occurrence of a fault causes the circuit to repeat the switching cycle in which the fault arose, while exciting the auxiliary windings so that the relay contacts are reversed and a complementary switching cycle occurs after which the cycle is repeated with de-energization of the auxiliary windings so that the relays again assume their original contact positions. A modification of the circuit of Fig. 5 is described (Fig. 8 not shown) for use with relay groups comprising make and changeover operative contacts in addition to make contacts only.