Drive Electronics for Moving Magnet Type Linear Motor Compressor
Singh Gour, Abhay
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An inexpensive drive circuit to operate a moving magnet type linear motor compressor up to 100 W power is described. It is a Pulse-Width Modulated (PWM-based) circuit with provisions to adjust the frequency, modulation index of the sine wave, frequency of the carrier wave, etc. It is a simple circuit without any need for software development, as discrete electronic components are used in the circuit, and no microcontroller is used. Power MOSFETs are used in the H bridge circuit for driving the linear motor with opto-coupler isolation to eliminate any EMI interference from the motor to the gate circuit. The required logic states are generated using a toggle circuit and the PWM wave form is generated using off-the-shelf operational amplifiers. The circuit is designed to operate with D.C. power supplies of ±5V and +12V. Hence, it can be conveniently operated from the power supply of a Pentium IV computer. This way, the need for developing a specialized D.C. power supply for the electronics is avoided. The developed circuit is capable of providing up to 100 watts of power to drive a single compressor. With suitable modifications, it can be adapted to operate dual opposing compressors of each 100 W. The circuit design, schematic, working principle of the circuit, and the performance are discussed.