Browse Prior Art Database

Motor Start Switch

IP.com Disclosure Number: IPCOM000075864D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Marckel, AO: AUTHOR

Abstract

This start switch controls the operation of capacitor start motor 10, in such a manner that the start switch produces only very low levels of conducted current and voltage transients and radiated "E" and "H" field noise.

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Motor Start Switch

This start switch controls the operation of capacitor start motor 10, in such a manner that the start switch produces only very low levels of conducted current and voltage transients and radiated "E" and "H" field noise.

The start switch is composed of three principal sections: control circuit 12, main power triac 14, and start winding triacs 16.

Control circuit 12 accepts a 24 volt DC control signal on terminals 18 and 20, and then switches the main power triac 14 on at the proper time (close to 0 voltage between AC power input terminals 22 and 26) to start motor 10 with little electrical noise. The 24 volt DC signal applied across terminals 18 and 20 may be random with respect to the voltage on the AC power input across terminals 22 and 26. Transformer 28 reduces the AC voltage to a nominal 13 volts AC and is connected in such a manner that the secondary voltage of 13 volts is in phase with the main terminal 30 voltage of power triac 14. This assures that triac 14 is operated in the two switching quadrants which require the lowest gate current (in lead 32) for turn on. When motor 10 is off, the two control silicon-controlled rectifiers (SCR's) 34 and 36 will be on (one for the plus cycle and the other for the minus cycle). Relay 38 is controlled by the 24 volt DC signal applied between terminals 18 and 20, and relay 38 includes normally open contacts 40 and normally closed contacts 42. When relay 38 is energized, contacts 42 are opened to thereby open the SCR gate circuits 44 and 46, and the accompanying closure of contacts 40 closes gate circuit 32 to main power triac 14. The SCR 34 or 36 which was on continues to stay in conduction until the AC control voltage on circuit 44 or 46 approaches 0 volts, and then the SCR 34 or 36 goes off. The next AC wave is then fed directly through circuit 32 through closed switches 40 to turn triac 14 on. SCR's 34 and 36 remain off, and tria...