Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1994-08-31
1996-09-17
Fleming, Fritz M.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361154, H01H 4704
Patent
active
055574947
ABSTRACT:
A drive circuit of an electromagnetic contactor including a series circuit of a surge absorber and a diode connected in parallel with the coil of the contactor, and a transistor connected in parallel with the surge absorber. There are two operation modes. In a first operation mode, the contactor is opened immediately after the contactor has been closed by a starting pulse. In a second operation mode, the contactor is opened after the contactor has been closed by a starting pulse and held by holding pulses following the starting pulse. In the first operation mode, the transistor is kept in an on state for a delay time after starting the contactor. This prevents the current due to counter electromagnetic force of the coil from flowing through the surge absorber before the current is reduced below the allowable level of the surge absorber by the transistor. This makes it possible to protect the surge absorber from being overheated. In the second operation mode, the transistor is turned off immediately after the DC power supply is removed. This makes it possible to open the contactor with little delay.
REFERENCES:
patent: 4947283 (1990-08-01), Kono
patent: 5134537 (1992-02-01), Buss et al.
patent: 5341032 (1994-08-01), Brambilla et al.
Ishikawa Kimitada
Ishikawa Minoru
Fleming Fritz M.
Fuji Electric & Co., Ltd.
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