PTC thermistors for motor starting

PTC thermistor for starting refrigerator compressor: Refrigerator compressor is driven by single-phase induction motor. The start-up of motor needs to overcome the inertia of itself, and also the load the back-action strength of high-pressure refrigeration agent, which requires high start-up current and torque. When the motor is operat normally, the torque required will decrease substantially. Therefore, usually the following start-up circuit(Figure1)is adopted to establish PTC thermistor in series in start-up coil. When the motor is connected with power, PTC is in low resistance, and the motor is started under the joint functioning of start-up coil, and after 0.4-3s, the resistance of PTC will increase by several orders of magnitude because of its own heat, which is equivalent to cutting off start-up coil to enable normal operation of major coil, so that the starting process is accomplished. PTC thermistor for starting frequency conversion air-conditioner: When starting frequency conversion air-conversion, the voltage is added to the whole wave filtration circuit through PTC components to recharge the capacitor stably to the preset value, and the power module IPM begins to work and transform inversely the input DC voltage into 3 lines of AC power added on the coils of 3-phase motor, to enable the normal operation of motor. In the mean time, after the capacitor is recharged to the preset value, the IPM will output DC voltage into 3line of AC power added on the coils of 3-phase motor, to enable the normal operation of motor. In the mean time, after the capacitor is recharged to the preset value, the IPM will output DC low voltage to the relay pick-up switch to short-circuit and stop the PTC components.(Figure2) The function of series PTC components in main loop is to avoid the impact of high current on rectification wave-filtration circuit and consequently the damage of energy-conservation components during the initial period of galvanization that is, PTC components function as a buffer and protector. Besides, in case of the failure(unable to pick up normally) of relay, PTC components will have high resistance, which can protect the circuit.