Patent GB-776550-A (GB)
Title: Improvements in or relating to regulated power supply equipments
Inventor: KELLY RICHARD
IPC: H04B3/44
Filed: 1954-05-14
Abstract: 776,550. Automatic current control systems. STANDARD TELEPHONES & CABLES, Ltd. May 6, 1955 [May 14, 1954], No. 14183/54. Class 38 (4). [Also in Group XXXIX] The repeaters of a submarine cable are supplied with D.C. power by a " master " power unit at one end of the cable and a " slave " power unit at the other. The two power units are identical in construction and can be switched either manually or automatically for " master " or " slave " working as required. When acting as "master" the unit provides a constant current for all output voltages up to the maximum required for the total number of repeaters. When acting as " slave " the unit provides a constant current of slightly higher value than the " master " for output voltages up to 40 to 45 per cent of the maximum, and thereafter the current is reduced at an approximately constant rate with increasing output voltage, so that at about 50 per cent of the maximum voltage, the current from the " slave equals that from the " master and the two units share the load equally. If the " slave " should fail, the " master supplies the whole system. If the " master should fail, the " slave " automatically changes over to " master " working. " Master " operation.-The submarine cable is connected at 6, 7 for energization by a rectifier RN supplied from A.C. mains 1, 2 via a saturable reactor MA1 the control winding of which is energized by a magnetic (or thermionic) amplifier MA2 in accordance with the output current of a diode 5. This diode 5 which is magnetically controlled by coils AW, MW is connected across an auxiliary stabilized supply 8, 9 and its output signal appears across the series resistor R3. The coil MW carries the output current of the rectifier RN and regulates for a constant current output. The coil AW provides a fixed counter-bias and is connected by relay contacts HV2, HV3 across the auxiliary supply 8, 9 in series with a resistor VR2. " Slave " operation.-The unit is similar in all respects to the " master " except that the relay contacts HV2, HV3 are changed over so that for output voltages above the predetermined 40 to 45 per cent of maximum value, the coil AW is progressively energized to aid the coil MW and so reduce the output current. In one embodiment the coil AW is connected in series with a rectifier MR 1 across one diagonal of a voltage-sensitive bridge R1, VR1, V1, R2, V2 which is connected across the output terminals of the rectifier RN. In a modification, Fig. 3 (not shown), the coil AW is energized in acoord. ance with the difference between the voltage tapped off VR1 (as above) and the voltage drop across the coil MW-which is assumed to be constant. In another modification, Fig. 4 (not shown), the entire bridge of Fig. 1 is in series with a further resistor and rectifier. A large number of minor alternatives for most of the circuit elements is listed. Change-over arrangements.-If a " slave " unit is called upon to supply the entire load, the rise in output voltage changes over a marginal voltage relay MVR thereby energizing a relay HV, Fig. 5, which locks up over contact HV1, and changes over contacts HV2, HV3 (as above described) for " master " working. A manual key Kl, when closed, locks in relay HV and ensures " master " working, and a manual key K2, when opened, breaks the self-locking circuit of relay HV and so the unit changes back to " slave " working unless load conditions are such as to operate relay MVR. Specification 768,029 is referred to.