SCR MOTOR SPEED CONTROL WITH PLUG SENSING CIRCUIT

• Main Author: SMITH A,US
• Format: Patent
• Language: English
• Published: 09.01.1973
• Subjects: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORSOR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; GENERATION

A control system for controlling energy directed from a power source to a DC variable speed motor includes a main SCR, series connected with the motor, an oscillator, a sawtooth generator, a reference operational amplifier, and a firing pulse generator. The output of the sawtooth generator is summed with the output of the reference operational amplifier and directed to the firing pulse generator. When the summed output of the reference operational amplifier and the sawtooth generator exceeds the threshold voltage of the firing pulse generator, the firing pulse generator will fire to effect conduction of the main SCR to direct energy to the motor. A commutating circuit is provided for turning the main SCR off during each cycle of the oscillator. The commutating circuit includes a secondary SCR and a LC resonant circuit both of which are parallel connected to the main SCR. The LC resonant circuit acts to reverse bias the main SCR upon conduction of the secondary SCR. A regulated power supply is also provided to energize the various components of the control system. The regulated power supply includes a negative power supply which comprises an astable multivibrator and a diode-capacitor matrix for directly converting a positive voltage to a regulated negative voltage.