1. After the module of the cooling fan of the charging pole is working, the control board gives a signal to draw the relay together and start the cooling fan of the charging pole to dissipate the heat, the current value of the capacitor charging instant is lower, so that the relay contacts can not bounce off because of spark sintering, but the pure AC fan can not rotate at a high speed due to the limitation of AC frequency, and can not meet the heat dissipation requirement of the terminal equipment, at the same time can not do soft start, start-up current instantaneous value mainly from the coil impedance, the lower the impedance, the start of the surge current will be greater. The principle of the 2.EC Fan is: AC-TO-DC, AC through the bridge rectifier, capacitor filter DC310V, through the IC PWM control switch tube on and off to control the charging pile cooling fan speed; 3. Due to the internal rectification filter, there is a filter capacitor in the circuit. The capacity of the filter capacitor is calculated according to the power. The empirical value is 1W 1uf. Due to the low ESR value of the capacitor, the surge current of high voltage charging is as high as tens of Amperes at the instant of charging, it is easy to cause relay contact sintering over time. At present, a NTC thermistor can be added to the EC Fan. The working principle of the NTC thermistor is that under normal temperature, the impedance is relatively large, and it has the effect of limiting current surge at the moment of electrification. With the increase of current, the heat quantity increases, and the impedance gradually decreases, if the NTC temperature does not drop enough during frequent shutdown start-up, the impedance will not recover. Restarting will result in a large surge current, which can also result in sintering of relay contacts.

http://www.dxymotors.com