Advantages "220V Cooling Fan" PWM control mode is simple drive circuit, a very good starting characteristics, transistor heat dissipation and small. The disadvantage is that stress increases the fan, inconvenient to use speed alarm sensors, alarm sensors and the speed of the motor with the same power supply, such as electrical power frequency to 20Hz ~ 160Hz turned on or off, the sensor will also turn off or on, thus lose their detection. "220V Cooling Fan" in the PWM control method, a fan of the rated voltage (for example 12V fan of 12V power supply) or zero voltage, but the fan is not running at full capacity, so it's back electromotive force will be reduced, which will It causes a current PWM ON period may be greater than normal. Although a significant impact "220V Cooling Fan" design allows to handle large total battery, but the fan start-up phase, the current will increase by 30 times per second, which will fan reliability. Nevertheless, PWM is still the ideal choice for cost-sensitive applications.