Atlas Copco Aktiebolag

Institut Cerac Sa

Ludovicus J Van Nederkassel

Carl S Hartwig

A compressor drive system for controlling the gas pressure in a pressure gas volume (106) connected to the compressor (101). A brushless alternating current motor (23) is directly coupled to the compressor, which is driven with the same speed as the motor. The pressure in the gas volume (106) is sensed by pressure sensing means (109) connected to a converter (114). The converter simultaneously changes the amplitude and frequency of the drive voltage supplied to the motor (23). This is done in response to pressure changes in volume (106). The motor is stopped if the pressure exceeds a preset maximum value. A pressure gas container (104) is depressurized at motor stop to allow restarting without counter pressure on the compressor. Means (44) for controlling the amplitude and frequency of the drive voltage is provided so that the normal speed maximum load current is never exceeded during motor start.

Compressor drive system

Method and apparatus for controlling the operation of a motor driven compressor which is automatically unloaded when the receiver pressure reaches a predetermined maximum level and loaded when the receiver pressure reaches a predetermined minimum level by means of pressure actuated electric control means which are time delayed to start and stop the compressor motor and the unloading and loading operation in accordance with predetermined mode of operation. The compressor driving motor is controlled to stop immediately upon the receiver pressure first reaching the maximum pressure level whereupon time delay circuit means starts to measure a time interval during which the motor upon having been restarted in response to a restart pulse is prevented from further stoppage each time the maximum receiver pressure level is reached subsequent to the first, whereby the compressor can be brought on load immediately in response to demand for working medium during the measured time interval and whereby overheating of the motor between subsequent stoppages and restarts is avoided. Upon expiration of the measured time interval, the motor will stop running until the minimum receiver pressure is reached, unless the compressor should be on load at such time, in which case the motor will continue running until the compressor again is unloaded upon reaching the maximum receiver pressure level, whereupon the aforementioned cycle is repeated.

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Buggenhout, Belgium

Ludovicus J Van Nederkassel