Design and Analysis of Power Controller for Moving Magnet Linear Motor Compressor
Sriram Prabhu, K.
MetadataShow full item record
Permanent magnet linear motors (PMLM) are widely used in the design of pulse tube cryocoolers. In this paper, we discuss the design and analysis of a power controller used to drive the dual opposing piston type motors used in the pulse tube cryocoolers. The microcontroller dsPIC30F6010A drives two single phase H - bridge inverters which are used to drive both the motors. Pulse width modulated (PWM) technique is implemented to drive the inverter circuit. By varying the duty cycle of the PWM wave the voltage amplitude can be varied and the output frequency of the inverter can be varied by varying the carrier frequency of the PWM modulator. The phase difference between the two inverters can also be varied. This is used to synchronize the twin motors and overcome any existing phase difference due to the mechanical systems. Variation in performance of the PMLM caused by the variation in the applied voltage and frequency is illustrated. Simple square PWM modulation, trapezoidal PWM modulation and sine PWM modulation techniques are implemented by controller programming. Motor performances for these modulation techniques are discussed. It is also shown that the current wave form contains less harmonic content in the case of sine modulation.