The present invention relates to a control method of a
low voltage operation
constant speed air conditioner, which is characterized in that the rotary speed of an indoor
electric motor is adjustable, when the network
voltage is changed, a conduction angle of a controlled
silicon in a motor-drive circuit is adjusted in order to stabilize the rotary speed of the indoor
electric motor, the different rotary speed shifts of an outdoor
electric motor are changeable, under different ranges of the network
voltage and / or different external disk temperature of the outdoor condenser, the outdoor electric motor operates on the different rotary speed shifts, controlling compressor overflowing protection, the closing down overflowing protection of the compressor is fed with the protection current value lower heat protector before the
system heat protector feeds protection, and the batch restart of the compressor are completed within the
setting time after feeding protection. The air conditioner of the present invention can be normal starting under 180V even under the condition of lower electric
voltage and keep operation, the abnormal
noise can be avoided when the
electric network fluctuates, and the present invention can be active closing down protection and rapidly be automatic
recovery normal running after electric voltage resumption.