公开(公告)号：US3590352A

公开(公告)日：1971-06-29

申请号：US3590352D

申请日：1969-04-28

Applicant: SQUARE D CO

Inventor： RIES ROBERT G ,  RETZER KENNETH W

IPC: H02P7/298 ,  H02P5/06

CPC classification number: H02P7/298

Abstract: A speed control circuit for a series field direct current motor. The circuit includes a reed relay that has a movable contact responsive to the current flow through the field and a resistance in a shunt circuit with the field. The reed relay through a transistor and a contactor causes the shunt circuit to be interrupted when the current flow through the motor increases above the predetermined value. The reed relay has a pair of coil windings arranged so that one of the windings generates a magnetic flux that opposes the flux generated by the current flow through the field and the other provides an output flux which adds to the flux generated by the field current so that movable contact will operate with a snap action. The flux outputs of each of the pair of coils is individually adjustable so the response of the relay to the upper and lower limits of a range of field current flow may be individually adjusted. The circuit further includes a capacitor which will cause the flux output of one of the coils to momentarily increase when the reed relay initially responds to an excess current in the field circuit.