Low cost, protective start from coast circuit

Details Low cost, protective start from coast circuit Low cost, protective start from coast circuit

1986-09-24

1988-06-14

Smith, Jr., David

Electricity: motive power systems

Induction motor systems

Primary circuit control

318785, H02P 144

Patent

active

047514507

ABSTRACT:
Low cost, low part content motor control circuitry is provided, including blanking interval circuitry (42, 25) for preventing immediate connection of the start capacitor (5) of a single phase AC induction motor to the AC source (4) upon energization of the motor, to protect the start capacitor (5) and the start switch (6) against an overcurrent condition if the motor is de-energized while in the running mode and then re-energized while still coasting above a given speed, and to particularly prevent burn-out of the start capacitor (5) and/or start switch (6) upon reapplication of electrical power after a momentary power outage. Differently sized capacitors (42, 24) provide an early cross-over of auxiliary winding voltage relative to main winding voltage at the input of a quad comparator chip (31-34) to disable a turn-on signal for the start switch (6). Differently sized capacitors (42, 25) at the input of the chip provide the blanking interval and continue to disable the turn-on signal until auxiliary winding voltage decreases below a threshold value corresponding to a threshold speed less than or equal to cut-out speed.

REFERENCES:
patent: 3258668 (1966-06-01), Milligan
patent: 3671830 (1972-06-01), Kruper
patent: 4196462 (1980-04-01), Pohl
patent: 4605888 (1986-08-01), Kim
patent: 4622506 (1986-11-01), Shemanske et al.
patent: 4658195 (1987-04-01), Min
patent: 4670697 (1987-06-01), Wrege et al.

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