Why do most power capacitors choose 450V or 480V for their rated voltage?

Rated voltage is one of the most important indicators for selecting power capacitors, and improper selection can affect the normal operation of reactive power compensation.

Among all low-voltage capacitors, rated voltages of 450V and 480V are the most common choices. Why? What occasions is it suitable for? Let's take a look at the editor's article today!

On the premise of ensuring the expected compensation effect, the rated voltage selected for the capacitor must be able to ensure that the capacitor itself can operate within the steady-state overvoltage range during operation.

When selecting the rated voltage of power capacitors, it is necessary to comprehensively consider factors such as the harmonic state or reactance rate of the power grid.

1. Pure capacitor compensation

When the budget or harmonic content of the power system is low, many companies choose pure capacitor compensation schemes. At this point, the rated voltage of the power capacitor must be higher than the actual voltage of the interface.

When a pure capacitor compensates for a regular 380V power supply system, the rated voltage of the power capacitor is preferred to be 450V.

Once the capacitor bank is connected to the grid end, the voltage will increase to a certain extent. In order to ensure the normal operation of power capacitors, a higher voltage level must be selected. In addition, in the actual operation of capacitors, the influence of voltage operation also needs to be considered. Overall, the rated voltage of power capacitors is a bit low, which can increase the failure rate. 450V is the best option.

2. Filter compensation

However, if there are many harmonics in the power system and they have adverse effects on related equipment, a filtering compensation scheme needs to be selected, that is, using power capacitors and reactors together. At this point, it is recommended to choose a rated voltage of 480V or higher for power capacitors.

After series connection of reactors, the operating voltage of power capacitors will correspondingly increase, and the voltage increase is closely related to the reactance rate.

When the reactance rate of the filter reactor is 7%, a capacitor with a rated voltage of 480V needs to be selected. Usually, a reactance rate of 14% with a rated voltage of 525V is chosen, otherwise a series of faults may occur due to improper matching.