What is the Cause of Current Leakage in EV Charger? - SCU

What is the Cause of Current Leakage in EV Charger?

Some people who are using EV charger know that EV charger will have leakage current. Next, let’s analyze the reasons for electric vehicle leakage current.

The leakage current of high power EV charger is generally divided into four types, namely semiconductor component leakage current, power supply leakage current, capacitor leakage current and filter leakage current.

1. Leakage current of the original semiconductor of the EV charger

A very small current flows through the PN junction when it is cut off. D-S is forward biased, and G-S is reverse biased. After the conductive channel is opened, current will flow from D to S. But in fact, due to the existence of free electrons in the charging pile, the free electrons are attached to SIO2 and N+, resulting in leakage current in D-S.

2. Leakage current of EV charger power supply

In order to reduce interference in a switching power supply, an EMI filter circuit must be installed in accordance with the national standard. Due to the relationship of the EMI circuit, there is a tiny current to the ground after the switching power supply is connected to the market, which is the leakage current.

If it is not grounded, the computer shell will have a voltage of 110 volts to the ground, and it will feel numb if you touch the charging pile by hand. Finally, it will also affect the work of the computer.

3. Leakage current of EV charger capacitor

When the capacitor is applied with a DC voltage, the capacitor will have leakage current. If the leakage current is too large, the capacitor will heat up and be damaged. In addition to electrolytic capacitors, the leakage current of other capacitors is very small, so the insulation resistance parameter is used to express its insulation performance. However, due to the large leakage of electrolytic capacitors, the leakage current of the 1000v EV charger capacitor is used to express its insulation performance.

When the rated DC working voltage is applied to the capacitor, it will be observed that the change of the charging current starts to be large, and it decreases with time and reaches a more stable state when it reaches a certain final value. This final value of current is called leakage current. Where k is the leakage current constant, the unit is μa (v: μf).

4. The leakage current of the EV charger filter

The power filter leakage current is defined as the current from the filter housing to any end of the AC incoming line under the rated AC voltage. If all ports of the filter are completely insulated from the housing, the value of the leakage current mainly depends on the leakage current of the common mode capacitor CY, that is, it mainly depends on the capacity of the CY.

Since the leakage current of the filter involves personal safety, all countries have strict standards for the EV power module. For 220V/50Hz AC power supply, the leakage current of the noise filter is generally required to be less than 1mA.

The above is a related introduction about the causes of leakage current in EV charger. If you want to know more about EV charger, community charging stations, smart charging piles, car charging piles and so on, please feel free to consult us.

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