Isolated adjustable frequency AC inverter control
First Claim
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1. An induction motor control circuit comprising:
- a low voltage logic circuit including a digital controller for generating motor control commands;
means for supplying low voltage control signals to the controller;
a high voltage DC source;
an inverter comprising a plurality of controlled switches for coupling the high voltage DC source to an induction motor;
an inverter control circuit referenced to the high voltage DC source and responsive to the motor control commands for generating inverter switching signals to actuate the controlled switches; and
isolation means coupled between the low voltage logic circuit and the inverter control circuit for transmitting the motor control commands from the logic circuit to the inverter control circuit while isolating the low voltage logic circuit from the source of high voltage.
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Abstract
The control for an AC inverter includes a low voltage microcontroller referenced to ground potential and a waveform generator coupled to the microcontroller through a serial data link including optical isolation devices. The waveform generator floats at the negative bus potential of the DC source for the inverter. The waveform generator produces switching signals for the inverter under control of the microcomputer. The waveform generator, serial communications circuitry and other support circuits are all part of a single application specific integrated circuit.
236 Citations
7 Claims
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1. An induction motor control circuit comprising:
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a low voltage logic circuit including a digital controller for generating motor control commands; means for supplying low voltage control signals to the controller; a high voltage DC source; an inverter comprising a plurality of controlled switches for coupling the high voltage DC source to an induction motor; an inverter control circuit referenced to the high voltage DC source and responsive to the motor control commands for generating inverter switching signals to actuate the controlled switches; and isolation means coupled between the low voltage logic circuit and the inverter control circuit for transmitting the motor control commands from the logic circuit to the inverter control circuit while isolating the low voltage logic circuit from the source of high voltage. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An induction motor control circuit comprising:
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a low voltage user interface circuit including a user input device for entering operator commands and a controller connected to said user input device for receiving said operator commands and generating corresponding motor control commands; a source of high voltage DC electricity; a plurality of semiconductor controlled switching devices connected to said source of high voltage DC electricity and the induction motor having selectable conducting and nonconducting states; a waveform generator directly connected to said plurality of semiconductor controlled switching devices for controlling said conducting and nonconducting states of said plurality of semiconductor switching devices in accordance with received motor commands for control of the motion of the induction motor, whereby the waveform generator is connected to the high voltage DC electricity; and an isolation device coupled to said user interface circuit and said waveform generator circuit for transmitting said motor commands from said user interface circuit to said waveform generator circuit while isolating said user interface circuit from said source of high voltage DC electricity.
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Specification