Patent
Alternating current motor speed control circuit
TLDR
In this paper, a free-running unijunction transistor relaxation oscillator was used for firing a controlled rectifier, the period of oscillation being a multiple number of half cycles of the line frequency and obtained by the selection of several resistors switched into the emitter circuit.Abstract:
An induction motor speed control circuit which creates submultiples of the power line frequency by selective switching of the line voltage to allow certain cycles representative of a bilateral network in the form of a frequency lower than that of the power source to pass through and operate the motor. The circuit employs a free-running unijunction transistor relaxation oscillator for firing a controlled rectifier, the period of oscillation being a multiple numberof half cycles of the line frequency and obtained by the selection of one of several resistors switched into the emitter circuit. A pulse generated by a zener diode at each of the zero crossings of the line voltage is superimposed by a transformer upon the sawtooth waveform generated by the relaxation oscillator with the result that the oscillator is synchronized to fire the rectifier precisely at the start of a new one-half cycle of the power line frequency. The circuit performs the conversion of the frequencies of large amounts of power at lower power levels and with inexpensive circuit components.read more
Citations
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Patent
Universal energy regulating controller circuit
TL;DR: In this article, a power controller for applying power to an induction motor or similar AC load has a variable drive circuit for staring and switching a portion of the AC input line power.
Patent
Control device for the electric fan
TL;DR: In this article, a control device for an electric fan comprising a power supply, a control means, a trigger pulse generator and a switch means, all connected in circuit with the motor of the electric fan, wherein the trigger pulse output of said trigger generator is connected to trigger switch means and is controlled through said control means to thereby achieve a stepless, variable speed control for the fan.
Patent
Electronic speed control circuits
Mark Potter,John Crawford +1 more
TL;DR: In this article, the voltage across the switching device, during the time it is off, is rectified, and used as the charging voltage for the phase firing circuit, with a resistor capacitor timing network determining the firing of the switching devices when the capacitor voltage reaches a predetermined value.
Patent
Motor drive unit and method for controlling the motor drive unit
TL;DR: In this article, an improved motor drive unit includes a zero-crossing voltage detector circuit composed of components (7, to 12) for detecting whether the voltage from an AC power supply (1) is zero crossing and a switching circuit for performing on-off control by means of a thyristor 27 so as to switch between energization and de-energization of the power supply to a motor.
References
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Patent
Regulated adjustable power supply having a primary current controlled by input and output voltages
Patent
Circuit for controlling frequency with voltage
TL;DR: In this article, a gate is controlled by the output of a comparator circuit which compares the amplitude of a ramp signal with the DC control voltage, and the gate passes the oscillator output pulses as long as the ramp signal amplitude is less than the control voltage.