Browse Prior Art Database

Power Supply Switch

IP.com Disclosure Number: IPCOM000091330D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Koranye, TD: AUTHOR

Abstract

Transient turnon noise is minimized in this circuit by connecting the AC source to the load at a time when the instantaneous voltage is at or near zero volts. The circuit at A shows a typical sixty cycle, three-phase, four-wire, switched power supply system with load 1 energized by phase one only when triac 2 is allowed to conduct. Triac 2 is turned on at a voltage slightly greater than zero when a circuit is completed through resistor 3 and the closed relay points 4.

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Power Supply Switch

Transient turnon noise is minimized in this circuit by connecting the AC source to the load at a time when the instantaneous voltage is at or near zero volts. The circuit at A shows a typical sixty cycle, three-phase, four-wire, switched power supply system with load 1 energized by phase one only when triac 2 is allowed to conduct. Triac 2 is turned on at a voltage slightly greater than zero when a circuit is completed through resistor 3 and the closed relay points 4.

Timing control circuit 5, which controls the closing of relay points 4, is connected between the neutral and the phase two leads. Circuit 5 is shown in detail at B. It includes a full-wave bridge rectifier which is energized when contacts 6 are closed. As long as start switch 11 is open, SCR7 conducts during each half cycle of phase two, preventing energization of relay coil 8. Closure of switch 11 allows relay coil 8 to energize on the next half cycle. The characteristic closure time of relay points 4 is approximately 1.5 milliseconds after zero voltage point of the phase two wave. Capacitor 10, in parallel with relay 8, delays the pickup time of coil 8 so that relay points 4 close at approximately the next zero crossover point of phase one. With relay points 4 closed, a circuit is completed through resistor 3 to turn triac 2 on at or near zero volts completing the circuit through load 1.

Relay 8 is maintained in its energized state each time its energizing voltage approaches ze...