Controlled switching

Details Controlled switching Controlled switching

1996-10-10

1998-09-15

Fleming, Fritz

Electricity: electrical systems and devices

Control circuits for electromagnetic devices

For relays or solenoids

361 2, H01H 4722

Patent

active

058088512

ABSTRACT:
A method of and apparatus for controlling the opening and/or closing of contacts of an electro-mechanical switching device in an alternating current circuit. Detection is made for the existence of a voltage having a level which is indicative of a back emf in a load circuit immediately following opening of the contacts, and if such a voltage level is detected an incremental adjustment is made in the phase angle at which successive actuations of the contacts are effected. This procedure is repeated under the control of a microprocessor until such time as the voltage which is indicative of back emf reduces to zero, this providing an indication that contact opening is occurring at a time corresponding to zero current crossing in the alternating current waveform.

REFERENCES:
patent: 4864157 (1989-09-01), Dickey
patent: 4897755 (1990-01-01), Polster et al.
patent: 5064998 (1991-11-01), Holling
patent: 5138514 (1992-08-01), Fowler et al.
patent: 5245256 (1993-09-01), Cassat et al.
patent: 5361184 (1994-11-01), El-Sharkawi et al.

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