What is the function of discharge coil of polypropylene capacitor

Polypropylene capacitor is used to discharge the capacitor when the capacitor is transferred for maintenance, It can reduce the rated voltage of the capacitor to less than 0.1 times in 5 seconds. When the capacitor is disconnected from the power supply, the two poles are in the state of energy storage. After the whole group of capacitors is disconnected from the power supply, the stored charge energy is very large. Therefore, a certain voltage remains on the two poles of the capacitor. The initial value of the residual voltage is the rated voltage of the capacitor bank. If the capacitor bank is connected again under the condition of charge, if it is closed again When the gate is put into operation, it may produce great impact, closing inrush current and high overvoltage. If the electrical workers touch the capacitor, they may be injured or burned by electricity. In order to prevent electric charge, gate and personal injury, the capacitor must be equipped with discharge device at home. In a DC circuit, a capacitor is equivalent to an open circuit. Capacitor is a kind of component which can store charge, and it is also one of the most commonly used electronic components.

Selection of discharge device

one The resistance value of discharge coil should make the residual voltage of capacitor bank drop below 65V within 30s after the capacitor bank is cut off (the initial discharge voltage is the rated voltage of the power grid). For the capacitor bank with frequent automatic switching, the residual voltage on the capacitor bank should be reduced below the initial value within the time interval from breaking to putting into operation again. Therefore, special discharge should be adopted for capacitor The discharge devices of fd2-1.7/6 and fd2-1.7/10 made in China can reduce the residual voltage to 50V in 20s when applied to high capacitor bank with capacity of 5000KVA

2、 The capacity of discharge coil should be able to meet the requirements of long-term operation conditions, but it should not be too large. The larger the capacity is, the longer the discharge time is, the greater the power loss is. In order to reduce the loss of discharge coil, it is generally stipulated that the loss of discharge coil per kvar capacitor should not exceed 1W

The discharge coil is actually a magnetoelectric voltage transformer. In the early days, voltage transformer was used as discharge coil. At present, the voltage sampling of many compensation devices is from the secondary end of the discharge coil.