The effect of circuit breaker protection switch on UPS

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 mains exists, the rectifier rectifies the battery to charge, and provides DC voltage to the inverter When the utility power fails, direct current (DC) voltage is directly provided by the battery pack to work on the inverter and output standard AC power.

At present, the traditional UPS works in the online mode, that is, in the pure online mode, the UPS directly rectifies the input AC mains power. Without power factor compensation, it will cause severe harmonic interference in the transmission line. , Especially in the case of thyristor rectification, the interference is even worse, which 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 group and an output current group. When there is no leakage, the input current and output current are equal. The vector of the two magnetic fluxes on the iron core If the sum is zero, no potential will be induced on the third winding, otherwise an induced voltage will be formed on the third winding, which will be amplified to push the actuator and trip the switch.

A leakage protection switch is added in front of the UPS. Although the UPS has no leakage, it cannot be zero due to the magnetic flux vector formed by the higher harmonics in the iron core and due to the hysteresis effect of the iron core. The false appearance makes the earth leakage protector trip frequently.

Therefore, in order to avoid frequent trips at the AC input of the UPS, avoid using circuit breakers (switches) with leakage protection.