PURPOSE: To protect an air-conditioner by stopping a motor when a judging means detects an abnormality in the number of revolution of a fan motor, making a judgment whether the motor can be driven again, and driving the motor again for positive judgment whereas stopping the motor perfectly for a negative judgment.

CONSTITUTION: Means A detects the number of revolution of a motor (fan motor) 13 for driving a fan, means B judges abnormality in the number of revolution of the fan motor 13, means C stops the motor 13 temporarily, means D makes a judgment whether the motor 13 should be driven again, and means E drives the motor 13 again if means D makes a positive judgment. Consequently, when the motor 13 is stopped by means of a protective device P due to droppage of the number of revolution of the motor 13 or temporary abnormal noise, operation is reset automatically for an insignificant abnormality of fan whereas the fan is stopped perfectly for a significant abnormality.