Patent ID: 8734120
Filing Date: 2014-05-27
Classification: F04B,H02P

Abstract:
1. A method of starting a piston type compressor (C) driven by a permanent magnet synchronous motor (M) controlled by a frequency converter (FC), the method comprising at least following steps: a) indicating a position of a piston driven by the motor (M) at a highest pressure point of the compressor, and aligning a rotor of the motor (M) at an optimal starting angle prior to an actual compression operation by providing a pre-pulse at a certain frequency (f during rotation, measuring a load torque by means of the frequency converter, and indicating a maximum load torque point, and at an end of the pre-pulse, aligning the rotor of the motor (M) at the optimal starting angle of about 180 degrees from a maximum pressure angle, and b) at a beginning of the actual compression operation, setting a position of the rotor opposite to the maximum torque angle by feeding direct current to a stator winding, and starting the motor by supplying a maximum direct current to the motor (M) to give maximum torque and acceleration.