Contraves Goerz Corporation

Control Systems Research, Inc.

James G Weit

Charles W Newcamp

A high response motor controller is disclosed which operates directly from a multi-phase AC power line without a DC link. The controller directly converts power from a fixed frequency multi-phase input to a D.C. or variable frequency output current. The output frequency is not limited by the AC power line frequency and the switching frequency is independent of the AC power line frequency. Controlled switching devices are connected between the multi-phase power input line and the power output line. Analog input signals are compared with signals representative of actual motor currents to produce current error signals. These current error signals control the conduction state of the controlled switching output transistors by a two state modulation process. The controlled switching output devices required to conduct the commanded motor current are selected by sensing and logically comparing the relative voltages of the various AC input line phases to utilize the phase lines having the greatest potential difference therebetween.

Switching controller directly operable from AC

A brushless tachometer is disclosed which provides a DC output voltage which is a direct function of an instrumented shaft's rotational velocity. The DC voltage is bi-directional, changing sign when the shafts direction of rotation is reversed. The disclosed tachometer preferably utilizes a brushless printed circuit resolver having a large number of poles. The sine and cosine outputs from the resolver are fed to a phase shifting circuit which provides two output signals whose frequencies are related to the speed of rotation of the shaft being instrumented. The frequency of one of the signals increases as the shaft speed increases while the frequency of the other signal decreases as the shaft speed increases. These two signals having frequencies related to shaft speed are fed to frequency to voltage converters. The outputs from the frequency to voltage converters are fed to a differential amplifier whose output is the DC signal which is indicative of the direction and the speed of rotation of the shaft.

Brushless DC tachometer

A brushless printed circuit resolver for converting a shaft angular position to a voltage signal, defined by the envelope of a carrier, which indicates the mechanical angle. The brushless resolver includes a stationary member having two conducting foils formed thereon which are capactively coupled to associated foils on a movable member. The capacitive coupling between these input foils remains constant as the movable member is moved. A pair of output foils are also disposed on a movable member and each is electrically connected to one of the movable input foils. A pair of shaped stationary output foils are mounted with a small separation from the movable output foils so that the capacitive coupling between the movable and stationary output foils varies as a determinable function. To get the desired output it is necessary that the movable output foils and the stationary output foils be relatively shaped so that capacitive coupling between the movable and the stationary output foils vary as the desired function. There can be two pairs of movable output foils, disposed in a quadrature relationship, which provides an output signal giving an unambiguous indication of shaft position. By having the rotor output foils properly configured, a resolver having any number of poles can be produced. The output signal defined by the envelope of the carrier can be a two phase, quadrature displaced signal such as sine and cosine indications, three phase 120.degree. displaced signals as for a synchro, or if desired other number of phases can also be provided. By proper formation of the foil pattern configuration, the output signal as a function of the rotary angle can be made to be a variety of shapes. Sinusoidal output envelopes will normally be provided for standard resolver-synchro circuits. Triangular output envelopes which have special advantages for some position applications can also be provided.

Brushless printed circuit resolver

A four-quadrant full-wave static converter having improved time response without current cross-over deadband. An alternating current wave is imposed on the direct current input signal, which generates gate pulses for appropriate thyristors at the desired firing angle. The applied alternating current signal can be of approximately the same magnitude as the converter deadband, so as the direct current signal varies from zero a portion of the control signal moves out of the deadband area. For fast response the magnitude of the alternating current signal can be greater than the deadband signal. As the magnitude of the direct current signal increases the relative magnitude of the alternating current signal is decreased, preventing a large DC component from being imposed on the supply during high current operations. Cycling of the imposed alternating current waves is synchronized with the firing angle point O to maintain system protection.

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Pittsburgh, PA, United States of America

James G Weit