Refrigeration – Automatic control – Preventing – removing or handling atmospheric condensate
Patent
1996-08-29
1998-06-16
Tanner, Harry B.
Refrigeration
Automatic control
Preventing, removing or handling atmospheric condensate
62155, 62156, F25B 4702
Patent
active
057653828
ABSTRACT:
An adaptive defrost control for a refrigerator is shown in which a single linear power supply (12) and microprocessor (U1) is used for both the adaptive defrost and cold control functions. According to a feature of the invention, a zero current crossing point switching scheme may be used to improve relay cycle life. According to another feature, a calibration procedure based on line frequency may be used to obtain multiples of a selected unit of time for any accumulated compressor run time and defrost heater energization times. According to another feature a sample and hold technique may be used to distinguish between noise and valid signals. In a modified embodiment, a toroid (40) has a primary connected to a common line leading to the compressor motor (24) and defrost heater (26) to provide a signal (ST) which, when taken with the state of relay contacts in respective lines energizing the compressor motor and defrost heater, as determined by the microprocessor, results in monitoring the compressor and defrost heater energization time. In another embodiment, a motor start control incorporating a PTC element (28) is combined with the adaptive defrost control. A double pole, single throw relay (K4) initiates both the compressor motor starting and refrigerator heater functions and open circuits the PTC element after starting has been completed in order to conserve power. In a modified embodiment the latter relay (K4) is used to start the compressor motor without the PTC element (28).
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Lisauskas Richard J.
Manning William R.
Suita Thomas E.
Sun Thomas W.
Baumann Russell E.
Donaldson Richard L.
Grossman Gene E.
Tanner Harry B.
Texas Instruments Incorporated
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