By installing the latest IPM motor (internal permanent magnet motor) which contains a permanent magnet in the latest rotor, the compressor is made smaller and the rotation is made faster. If compared with conventional induction motors, the IPM motor does not cause electricity loss or slipping of the rotor, thus drastically enhances the motor efficiency. Combined with Mitsui Seiki's advanced inverter, the total efficiency also overrides that of single induction motors. Heat generation is reduced, leading to further energy saving. Also, the motor direct-coupled driving system eliminates the loss of power, improves the engagement and the machining accuracy of the compressor's main parts, and achieves the efficiency which is much higher than conventional machines.