Control of converter for motorized compressor used in automobile air conditioning system, motor rotational speed is altered when motor phase current amplitude falls into one of several set sub intervals

摘要

The interval between first (I1) and second ( alpha I2) is divided into three sub-intervals by placing between them fourth and fifth criteria ( alpha 14, alpha 15). The rotational speed of the motor (12) for a predetermined deceleration is reduced in a variable way during each interval, when the phase current amplitude has a value falling into one of the sub-intervals. Control method for a converter including switches which actuate a three phase motor in accordance with a frequency control signal from the exterior. A computing unit calculates the rotational speed and acceleration speed of the motor from a counter electromotive force signal from the motor. A sensor detects a phase current amplitude for the motor. The method includes the following: (a) stop motor activation when the phase current amplitude exceeds a first criteria (I1); decelerate the motors rotational speed to a predetermined level when the phase current amplitude is less than the first criteria (I1) but greater than a second criteria ( alpha I2) which is less than the first; accelerate the motors rotational speed to a predetermined level when the phase current amplitude is less than a third criteria ( alpha I3) which is less than the second criteria, alpha being a constant having a numeric value 0.9 /- ( alpha ) /- 1