Electricity: motive power systems – Constant motor current – load and/or torque control
Patent
1987-03-05
1989-04-18
Dobeck, Benjamin
Electricity: motive power systems
Constant motor current, load and/or torque control
318345D, 318434, H02P 516
Patent
active
048230570
ABSTRACT:
The motor control for a universal or D.C. electric motor controlled by opposing SCRs in parallel includes a comparator for controlling timing of firing of the SCRs based on a comparison of a sensed motor speed error signal and a synchronous ramp and also includes a circuit for sensing motor current as representative of motor torque and generating a motor shut-down signal when the sensed torque or current is greater than a setpoint value. When the shut-down signal is generated, the sensed speed error signal is overridden or prevented from being input to the comparator by deactivation (reverse biasing) of a current switch (diode) and results in the SCRs being deactivated. When the motor is restarted, a soft start circuit provides an alternate gradually increasing speed signal to the comparator in lieu of the sensed speed error signal for a selected short time after restart to gradually increase motor speed. After the selected time, the alternate speed signal itself reactivates the current switch (diode) by removing the reverse bias to allow the sensed speed error signal to again be input to the comparator to control motor speed. A novel integral differential amplifier is also provided as part of the speed error signal circuit.
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Dobeck Benjamin
Giangiorgi Richard A.
Greenlee Textron Inc.
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