Microprocessor based motor control system with phase difference detection
First Claim
1. A control circuit for a motor having a main winding and an auxiliary winding, said control circuit comprising:
- connecting means for selectively connecting a line voltage to the main winding and the auxiliary winding;
microprocessor means coupled to said connecting means, said microprocessor means including means to activate said connecting means to selectively energize the main winding and the auxiliary winding, said microprocessor means including means for determining the phase difference between the line voltage and the voltage between the main winding and the auxiliary winding by detecting zero crossings of the line voltage and zero crossings of the voltage between the main winding and the auxiliary winding, said microprocessor means including means for de-energizing the motor when said phase difference indicates a motor fault condition.
1 Assignment
0 Petitions
Accused Products
Abstract
The present invention involves a control system for a motor having a main winding and an auxiliary winding disposed on a stator. A microprocessor determines the phase difference between the line voltage and the voltage between the main winding and the auxiliary winding to determine the rotational status of the rotor. In a moving rotor, a measurable phase difference exists. This phase difference can be measured by monitoring the zero crossings of the respective voltages. One method of measuring the phase difference is to check the logic state corresponding to the voltage between the main and auxiliary windings when a predetermined time period has elapsed after a zero crossing of the line voltage. Another method measures the time delay between the zero crossings of the two voltages. The control system of the present invention is particularly adapted for use with single phase AC motors having a main winding and an auxiliary winding disposed electrically out of phase on the stator. The control system of the present invention is also particularly adapted for use with compressors and appliances associated with a refrigeration system having a cabinet temperature detector. The refrigeration system of the present invention includes a motor housing detector to deenergize and prevent motor start if an overheat condition exits, and a user setting device to allow a user to manually add an offset to the temperature setting. Additional control functions can be easily added using extra input and output leads provided on the microprocessor.
-
Citations
37 Claims
-
1. A control circuit for a motor having a main winding and an auxiliary winding, said control circuit comprising:
-
connecting means for selectively connecting a line voltage to the main winding and the auxiliary winding; microprocessor means coupled to said connecting means, said microprocessor means including means to activate said connecting means to selectively energize the main winding and the auxiliary winding, said microprocessor means including means for determining the phase difference between the line voltage and the voltage between the main winding and the auxiliary winding by detecting zero crossings of the line voltage and zero crossings of the voltage between the main winding and the auxiliary winding, said microprocessor means including means for de-energizing the motor when said phase difference indicates a motor fault condition. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A control circuit for a motor having a main winding and an auxiliary winding, said control circuit comprising:
-
a plurality of solid state switches for selectively connecting a line voltage to the main winding and the auxiliary winding; a microprocessor coupled to said plurality of solid state switches, said microprocessor controlling said plurality of solid state switches to selectively energize the main winding and the auxiliary winding, said microprocessor including first instructions that enable said microprocessor to determine the phase difference between the line voltage and the voltage between the main winding and the auxiliary winding by detecting zero crossings of the line voltage and zero crossings of the voltage between the main winding and the auxiliary winding, said microprocessor including second instructions that enable said microprocessor to de-energize the motor when said phase difference indicates a motor fault condition. - View Dependent Claims (7, 8, 9)
-
-
10. An apparatus comprising:
-
a motor having a main winding and an auxiliary winding; connecting means for selectively connecting a line voltage to said main winding and said auxiliary winding; microprocessor means coupled to said connecting means, said microprocessor means controlling said connecting means to activate said connecting means to selectively energize said main winding and said auxiliary winding, said microprocessor means including means for determining a phase difference between the line voltage and the voltage between said main winding and said auxiliary winding by detecting zero crossings of the line voltage and zero crossings of the voltage between said main winding and said auxiliary winding, said microprocessor means including means for de-energizing said motor when said phase difference indicates a motor fault condition. - View Dependent Claims (11, 12, 13, 14)
-
-
15. An apparatus comprising:
-
a motor having a main winding and an auxiliary winding; a plurality of solid state switches for selectively connecting a line voltage to said main winding and said auxiliary winding; a microprocessor coupled to said motor and said plurality of solid state switches, said microprocessor controlling said plurality of solid state switches to activate said plurality of solid state switches to selectively energize said main winding and said auxiliary winding, said microprocessor including first instructions that enable said microprocessor to determine a phase difference between the line voltage and the voltage between said main winding and said auxiliary winding by detecting zero crossings of the line voltage and zero crossings of the voltage between said main winding and said auxiliary winding, said microprocessor including second instructions that enable said microprocessor de-energize said motor when said phase difference is less than a predetermined limit. - View Dependent Claims (16, 17, 18, 19, 20)
-
-
21. A refrigeration system for cooling a chamber, comprising:
-
a thermostat disposed in thermal contact with said chamber; a compressor having a motor with a main winding and an auxiliary winding; connecting means for selectively connecting a line voltage to said main winding and said auxiliary winding; microprocessor means coupled to said thermostat, said motor and said connecting means, said microprocessor means controlling said connecting means to activate said connecting means to selectively energize said main winding and said auxiliary winding, said microprocessor means including means for determining a phase difference between the line voltage and the voltage between said main winding and said auxiliary winding by detecting zero crossings of said line voltage and zero crossings of the voltage between said main winding and said auxiliary winding, said microprocessor means including means for de-energizing said motor when said phase difference is less than a predetermined limit, said microprocessor means including means for energizing and de-energizing said motor based on temperatures sensed by said thermostat. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
-
-
30. A refrigeration system for cooling a chamber, comprising:
-
a thermostat disposed in thermal contact with said chamber; a compressor having a motor with a main winding and an auxiliary winding; a plurality of solid state switches for selectively connecting a line voltage to said main winding and said auxiliary winding; a microprocessor coupled to said thermostat, said motor and said plurality of solid state switches, said microprocessor controlling said plurality of solid state switches to activate said plurality of solid state switches to selectively energize said main winding and said auxiliary winding, said microprocessor including first instructions for determining a phase difference between the line voltage and the voltage between said main winding and said auxiliary winding by detecting zero crossings of said line voltage and zero crossings of the voltage between said main winding and said auxiliary winding, said microprocessor including second instructions for de-energizing said motor when said phase difference is less than a predetermined limit, said microprocessor including third instructions for energizing and de-energizing said motor based on temperatures sensed by said thermostat. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37)
-
Specification