초록 ▼

The present invention involves control and protection circuit for a compressor motor which includes an inductively activated contactor for controlling the flow of current to the compressor motor. The circuitry of the present invention includes a plurality of current detectors associated with each ph

The present invention involves control and protection circuit for a compressor motor which includes an inductively activated contactor for controlling the flow of current to the compressor motor. The circuitry of the present invention includes a plurality of current detectors associated with each phase winding of the compressor motor for sensing the current in each phase winding. The sensed currents are combined in a predetermined manner and used to provide protection against an overcurrent condition, single phase operation and light loading condition. Additional detector circuits are also connected to the present control and protection circuit to provide protection against high temperature in the compressor motor windings, high temperature in various component of the compressor motor, and undervoltage in the power supply. A temperature detector disposed inside the cooling chamber also provides for cycling of the compressor motor to maintain the temperature in the cooling chamber at within a predetermined temperature range. The inductive coupling is activated by a protection timer and an oscillator. The protection timer deactivates the oscillator when a trip signal is received from the detector circuits. A predetermined time delay is provided by the protection timer to prevent spurious trips of the compressor motor.

대표청구항 ▼

[ What is claimed is:] [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,

[ What is claimed is:] [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; anda 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.