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Multiple winding sensing control and protection circuit for electric motors

  • US 5,784,232 A
  • Filed: 06/03/1997
  • Issued: 07/21/1998
  • Est. Priority Date: 06/03/1997
  • Status: Expired due to Fees
First Claim
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1. A control and protection circuit for a compressor motor having a plurality of motor windings, comprising;

  • a current detector circuit having a plurality of current detectors, each said current detector associated with a winding of the compressor motor and having an output, each said current detector output providing a current level signal corresponding to the current in the respective winding, said current detector circuit having means connected to said current detector outputs for combining said current level signal in a predetermined manner to provide a combined current level signal;

    a switch circuit disposed between the compressor motor and an AC power source, said switch circuit changeable between a first state which allows current to the compressor motor and a second state which interrupts current to the compressor motor; and

    a current control circuit disposed between said current detector circuit and said switch circuit, said current control circuit including an oscillator having a logic gate with an input operatively connected to said current detector circuit and an output connected to control a first solid state switch adapted to provide an oscillating output and an inductive coupling circuit having an inductive coupling element with an input connected to said first solid state switch output and an output connected to a second solid state switch, said second solid state switch adapted to place said switch circuit in said first state in response to the presence of said oscillating output and in said second state in response to the absence of said oscillating output, said current control circuit activated to provide said oscillating output from said oscillator and enable said inductive coupling circuit and place said switch circuit in said first state when said combined current level signal is below a predetermined current threshold level, said current control circuit deactivated to interrupt said oscillating output from said oscillator and disable said inductive coupling circuit and place said switch circuit in said second state when said combined current level signal exceeds said predetermined current threshold level.

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