Itt Corporation

Sequence Controls Inc.

William Harry Kemp

Victor Joseph Shideler

An apparatus for controlling the speed of an induction motor includes a first winding and a second winding. The first winding and second winding are adapted to be coupled to an AC source for supplying an AC input signal. A first switching device is coupled to the first winding and a second switching device is coupled to the second winding. Each of the switching devices is operative in a low impedance state enabling current to flow through the associated winding of each switching device and a high impedance state preventing significant current flow through the associated winding of each switching device. A controller switches each of the switching devices from the high impedance state to the low impedance state in a sequence for controlling the current in the windings, which induces a phase shift between the AC voltages across the windings.

Current modulation motor controller

A power supply for a variable speed AC motor includes a waveform generator for generating a periodic pulsed waveform according to a desired motor speed, an adjustable source of DC potential, and an inverter coupled to the waveform generator and to the source of DC potential. The inverter provides an AC pulse train to the AC motor, the pulse train having waveform characteristics according to the pulsed waveform generated by the waveform generator to obtain the desired speed. The voltage amplitude of the pulse train provided to the motor is proportional to the DC potential whereby motor currents can be controlled at the desired motor speed by varying the DC potential.

Voltage, phase and frequency control by miniature inverter system

A carrier frequency based system employs a capacitive probe which is located at a predetermined desired fluid detection level in a fluid containing vessel. The probe forms one plate of a capacitor where the other plate is formed by the fluid in which the probe is immersed. A carrier frequency is injected into the fluid by means of a suitable oscillator and at a frequency which is close to the system resonant frequency. When the probe is immersed in fluid, the probe will receive a predetermined carrier frequency of an amplitude determined by the system. The output of the probe is coupled to suitable sensing circuits which monitor the amplitude of the signal frequency coupled to the probe. When the fluid level recedes and therefore a portion of the probe or the total probe is out of fluid, the capacitance of the system changes. A different signal from the injected carrier frequency is now applied to the probe indicating to the sensing circuit that the probe is not immersed and therefore indicating an alarm condition. The output of the sensing circuit is monitored by control circuitry which can operate an alarm indicating to the user that the probe is not fluid immersed and that preventive measures should be taken. The fluid sensing probe utilizing the carrier injected frequency can discriminate between fluid and foam, 'probe fouling' and probe shorting and is relatively fail proof.

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Clayton, Canada

William Harry Kemp