A capacity-controlled free piston electrodynamic compressor

A double acting free piston 50 Hz electrodynamic oscillating compressor has been designed and investigated. The power input of the compressor is about 200 W, its maximum stroke is 20 mm, and its cylinder diameter is 20 mm. The compressor includes a two coil linear motor with permanent magnet, optimized for the pressure ratio required. The compressor capacity can be controlled by means of control of the stroke, being in turn dependent of the applied voltage or the voltage waveform. Comparison of experimental results, ie regarding efficiency of the motor (up to 75%), stroke control and pV-diagram, with results of computer simulation shows a good agreement. The above compressor is intended for refrigeration purposes. A larger version, with a power input of about 2 kW will be used in a controllable heat pump system.