Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1994-07-28
1996-08-13
Fleming, Fritz M.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361160, H01H 4704
Patent
active
055462685
ABSTRACT:
An electromagnetic switch includes separable contacts, an electromagnet having a coil which is energized to close and hold closed the separable contacts, a power supply for applying current to the coil, and a closed-loop control circuit for sensing and regulating, throughout a contact closure cycle, the current applied to the coil to a selected current reference. The current reference may include a closing current reference for closing the contacts and a holding current reference for holding the contacts closed. The control circuit may include a microcomputer for generating the current reference and, further, may include a first switching circuit and an associated control circuit for actuating the first switching circuit between enabled and inhibited states, a second switching circuit and an associated control circuit for actuating the second switching circuit between conductive and non-conductive states, a feedback circuit for sensing the coil current and generating a related feedback signal, and a comparator circuit for comparing the current reference and the feedback signal, and for inhibiting the second switching circuit whenever the feedback signal is greater than the current reference. The microcomputer may include control signals defining states corresponding to a predetermined closing current reference and a predetermined holding current reference. One of the control signals may attenuate the feedback signal, in order to provide the closing current reference. The electromagnetic switch may alternatively include a circuit for generating a time-variable current reference in order to substantially follow a predetermined magnet pull curve of the electromagnet.
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Hurley Rick A.
Innes Mark E.
Palmer Nelson R.
Eaton Corporation
Fleming Fritz M.
Moran Martin J.
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