Why can't the UPS input front end be installed with a leakage protection switch under popularization?

by:Power Kingdom     2021-06-16

UPS is an uninterruptible power supply. It is a process of AC-DC (commonly known as rectification) and then DC-AC (commonly known as inverter). When the city power exists, the rectifier rectifies to The battery is charged, and the AC DC voltage is used for the inverter at the same time. When the mains power fails, the battery pack directly outputs the DC voltage to work for the inverter and output standard AC power.

   The current traditional UPS basically works in an online mode, that is, a pure online mode. The UPS directly rectifies the input AC mains. Without power factor compensation, it will be connected to the transmission line. It causes serious harmonic interference, especially when silicon controlled rectifier is used, the interference is even worse. This is a common problem of general UPS.

The operating principle of the    leakage protection switch is: There are two groups on an iron core: an input current winding and an output current winding. When there is no leakage, the input current and the output current are equal. If the vector sum of the two magnetic fluxes is zero, no electric potential will be induced on the third winding, otherwise the induced voltage will be formed on the third winding, which will be amplified to push the actuator and trip the switch.

   Add a leakage protection switch in front of the above UPS. Although the UPS has no leakage phenomenon, the magnetic flux vector sum formed in the iron core due to higher harmonics cannot be zero due to the magnetic hysteresis of the iron core. As a result, an illusion similar to leakage appears, causing the leakage protector to trip frequently.

   Therefore, try to avoid using circuit breakers (switches) with leakage protection at the AC input end of the UPS.

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