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MOTOR-COMPRESSOR HEATER USING ELECTRONIC MOTOR CONTROL

IP.com Disclosure Number: IPCOM000005826D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2001-Nov-09
Document File: 1 page(s) / 69K

Publishing Venue

Motorola

Related People

Charles J. Schmitz: AUTHOR

Abstract

In a typical residential or small commercial air conditioner (or heat pump), it is desirable to keep the temperature of the motor compressor warmer than its surrounding so that the freon doesn't get absorbed into the oil and cause problems with the compressor. This is usually accomplished by installing a discrete heater on the compressor and selec- tively exciting the heater when the compressor and/or its drive motor are not running and are therefore not self generating the needed heat.

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MOIVROLA Technical Developments Volume 10 March 1990

MOTOR-COMPRESSOR HEATER USING ELECTRONIC MOTOR CONTROL

by Charles J. Schmitz

   In a typical residential or small commercial air conditioner (or heat pump), it is desirable to keep the temperature of the motor compressor warmer than its surrounding so that the freon doesn't get absorbed into the oil and cause problems with the compressor. This is usually accomplished by installing a discrete heater on the compressor and selec- tively exciting the heater when the compressor and/or its drive motor are not running and are therefore not self generating the needed heat.

   An emerging trend in air conditioners today is to use a variable speed motor to drive the compressor. This allows better control of conditioned air humidity (and the comfort) and also improves efficiency (thus more BTU's per watt). With these variable speed motor techniques, the motors used are typically of the DC Brushless type or the three phase induction type, both of which require the electronic motor control driving them to generate a variable frequency, three phase, alternating current, power source to drive the motor. The motor will only provide continuous rotation when an alternating current is applied to it and at a frequency for which the motor is designed (i.e. if it is designed to operate over 30 Hz to 120 Hz range, applying a current at 1,000 Hz or 10,000 Hz will not cause the motor to turn).

   When direct current is applied to such variable speed types of motor, there is no continuous rotation of the motor; however, the energy that goes into the motor is used up...