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AssigneeAnatole J. Sipin Company
InventorsAnatole J. Sipin, Herbert R. Carleton
Estimating the term…
Constant selected speed running of an electric motor, with a varying mechanical load, is achieved by intermittently pulsing the motor at full power and comparing the back EMF of the motor, between power pulses, with a selected speed voltage, to accordingly control application of the power pulses. A particular control circuit is disclosed which permits operation of a pocket-sized system, powered by a three cell battery, to achieve substantially constant speed, at normally varying loads, throughout a ten hour period, with back EMFs at selected values between 0.01 volt (motor barely turning) and 2.0 volts (high speed). The system is useful in a personal air sampler, used to monitor a workman's exposure to noxious ingredients of breathing air.
An electric motor speed control system comprising:
In a speed control system for an electric motor (24) including a power switch (25) connecting and disconnecting an armature of the motor to a power source (21) from which an operating voltage is applied, a comparator (50) having a first input to which a motor coasting signal voltage is applied, a second input to which a reference voltage is applied and an output (52) connected by a duty cycle modulator (60) to the power switch for controlling the speed of the motor, the improvement residing in a signal monitoring device (30) having means for operation thereof as a linear voltage amplifier continuously following the voltage across the motor armature to supply said signal voltage to the first input and means responsive to the operating voltage being applied to the motor for cutting off the signal voltage to the first input, feedback means (51) connected to the comparator (50) for operation thereof as a bistable switch controlled by the signal voltage, and current sensing means (70) connected to the modulator (60) for preventing application of the operating voltage to the motor through the power switch in response to overload current in the motor armature.
In a speed control system for an electric motor (24) including a power switch (25) connecting and disconnecting an armature of the motor to a power source (21) from which an operating voltage is applied, a comparator (50) having a first input to which a signal voltage is applied, a second input to which a reference voltage is applied and an output (52) operatively connected to the power switch for controlling the speed of the motor, the improvement residing in a feedback signal device (30) continuously connecting the motor armature to said first input for supply thereto of a signal voltage following the voltage across the motor armature, and delay means (31-41) for cutting off the signal voltage to the first input when substantially equal to the operating voltage whereby power pulses for the motor of substantially fixed duration are obtained.
Dependencies are inferred from the claim text.