Locking devices and control circuitry for permanent magnet electric motors
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United States of America Patent
Stats
-
Dec 8, 1998
Grant Date -
N/A
app pub date -
Nov 13, 1995
filing date -
Nov 13, 1995
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A positive locking device is provided in order to prevent a motor from rotating after power has been removed. The positive locking device has a plate mounted on the motor which engages a disk or hub on the shaft of the motor. In another aspect of the invention, solid state circuitry for switching a permanent magnet motor and providing dynamic braking thereto is provided. The circuitry allows the back EMF generated by the armature coils of a permanent magnet motor to cause a current to flow through the motor when power is removed. This back EMF may be used to help produce smooth engagement of the locking device. In another aspect of the invention, a dynamic braking circuit for a dual armature permanent magnet motor is provided. By applying current to one or the other of two oppositely wound armature coils the motor is made to rotate in either direction. When power is removed from the active armature, this armature is short-circuited through a diode. The same diode is used to dynamically brake the motor when power is removed from the other armature. In both cases the spinning rotor will quickly slow down to facilitate smooth engagement of the positive locking device.
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