Six common UPS power supply faults that you can fix yourself! ( Part 2)

3. UPS won’t start? First check the power supply and battery.

If you press the start switch but the UPS doesn’t respond, don’t immediately assume the equipment is broken. Common causes include: the battery has been unused for a long time and the voltage is too low to start; the input AC or DC power cord is not connected properly or has poor contact; there is a fault in the UPS’s internal power-on circuit; there is a fault or short circuit in the internal power circuit; or the internal power components may be damaged.

The troubleshooting steps proceed from simple to complex: First, fully charge the battery; if the battery has been idle for a long time, it may need to be charged for a while. Then, check the input AC and DC lines to ensure that the connections are secure and the contact is good. If it still cannot start, check the UPS’s power-on circuit and power supply circuit. Finally, check the internal rectifier, boost converter, inverter, and other power components to see if there is any damage.

4. Tripping immediately upon power-on? The problem lies with the circuit breaker or an internal short circuit.

If the input circuit breaker trips immediately upon UPS startup, this is mostly related to circuit overload or short circuit. Specific reasons may include: the input circuit breaker’s capacity is too small to meet the UPS’s startup requirements; a short circuit fault exists within the UPS; internal power components are damaged, causing circuit abnormalities; or the user’s mains circuit breaker may have leakage protection , which is incompatible with the UPS.

The solution is clear: First, check if the circuit breaker capacity is too small. If so, replace it with an input circuit breaker of appropriate capacity. If the problem is caused by a circuit breaker with leakage protection, replace it with one without leakage protection. If neither of these is the case, you need to check the rectifier, boost converter, inverter, and other power devices inside the UPS to check for short circuits or damage, and repair or replace them in time.