Electricity: motive power systems – Induction motor systems – Braking
Patent
1981-02-23
1983-07-26
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Braking
318762, H02P 324
Patent
active
043956700
ABSTRACT:
A hybrid electrical braking method and system are provided for tool equipment having induction motor drives. This hybrid electrical braking can be used to advantage in various types of induction motor driven tool equipment where it is desirable rapidly to stop rotation of the motor rotor and tool, whenever the motor is turned off, for example in food processors of the type having a working bowl mounted on a base containing the induction motor, with tool drive means in the bowl for removably supporting a rotary food processing tool driven by the induction motor. The new electrical braking rapidly halts coasting of the rotor and tool by utilizing in sequence two different electromagnetic braking processes, producing rapid but gentle braking effect after the motor has been turned off. During a first portion of this sequence, the starting capacitor is switched into series with both the "START" and "RUN" windings, thereby producing rapid initial braking action, lasting for approximately 50 milliseconds, slowing the rotor to approximately one-half of normal running speed. As soon as the motor has been slowed, a half-wave rectified D.C. current injected through the RUN winding, producing a unidirectional magnetic field in the motor, rapidly brakes the rotor to a halt. Thus, the rotor is rapidly, smoothly braked down to a few RPM in a very brief time after the motor is turned off. Also, in accordance with one aspect of this invention, a novel method and system for automatically injecting D.C. braking current into the winding of an induction motor are provided rapidly braking the rotor down to a few RPM when the motor is turned off, this D.C. being automatically stopped after a predetermined brief time.
REFERENCES:
patent: 3341758 (1967-09-01), Plumpe, Jr.
patent: 3475669 (1969-10-01), Oltendorf
patent: 3617837 (1971-11-01), Beck
patent: 4241302 (1980-12-01), Benjamin
Cuisinarts, Inc.
Smith Jr. David
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