PURPOSE: To prevent the motor winding wire from causing damage at the change-over of the titled device by a method wherein a thermal timer is provided to stop energizing a compressor during the designated time at the changing from small pole operation to multiple pole operation by electrifying said timer, in a air conditioner provided with a pole number changing type motor driven compressor.

CONSTITUTION: Magnetic coils 24, 25 of a magnetic switch which changes the two-pole or four-pole connection respectively, are provided to a pole number changing type motor driven compressor 2 of a outdoor unit 1. Said magnetic coil 24 of said two magnetic coils is connected to a contact R'1-b to which a switch R'1 is changed-over and connected at the time the power source switch of a indoor unit 3a is set ON. Said magnetic coil 25 is connected to a continuous closed contact 26"a of a themal timer 26. Said timer 26 is provided with a switch 26" heated by the electrifying to a timer part 26' of a heater and the like, and said switch 26" is changed-over after the passage of a designated time. A protective relay 27 for self-retaining is provided between a continuous closed contact 26"a of said thermal timer 26 and power source E1. A switch 27' is provided in the circuit of said timer part 26' and a switch 27" is provided in the circuit of said magnetic coil 25. Said two switchs 27' and 27" are closed by electrifying of said protective relay 27.