Following the above troubleshooting sequence can sometimes help us discover the fault point faster. Generally speaking, UPS faults can be roughly divided into the following situations:
1. Frequent UPS power switching and startup
The main reasons are as follows:
(1) Excessive interference or voltage fluctuation range in the 220V AC power grid;
(2) Improper adjustment of the working point for automatic voltage regulation control and conversion between mains power supply and inverter power supply;
(3) If used in conjunction with a generator, it may also be due to unqualified output voltage parameters of the generator.
2. The UPS power supply can only operate in the inverter power supply state and cannot switch to the mains power supply state. Since the UPS can operate in the inverter power supply state, it indicates that the relevant working circuit of the inverter is normal. The fault lies in the control circuit related to the mains power supply. The main reasons are as follows:
(1) The 220V input fuse of the AC power supply is blown, which may be due to a short circuit or overload in the output circuit; Wrong wiring of live and neutral wires at the input end of the mains power supply; Due to excessive surge current in the AC power supply and other reasons;
(2) Improper adjustment of the potentiometer for controlling the working point of the power supply conversion voltage resulted in a high conversion voltage;
(3) The secondary feedback winding of the main transformer is open circuited, resulting in no AC feedback voltage signal input;
(4) The communication voltage regulation control circuit has malfunctioned, causing the UPS to have no output within a specific voltage range.
3. The UPS power supply can only operate in the mains power supply state and cannot switch to the inverter power supply state. The normal operation of the mains power supply indicates that the mains voltage transmission and anti-interference control circuit are normal. The fault lies in the circuit related to the inverter power supply, and the reasons are as follows:
(1) If the working indicator light of the inverter stops flashing and remains on continuously, and the UPS power supply does not output, it may be due to the terminal voltage of each 12V battery being lower than the final voltage of 10.5V, causing automatic protection. In addition, it is also possible that the push-pull drive transistor of the inverter is damaged or the pulse width modulation component has no pulse output.
(2) If the working indicator light of the inverter goes out and the power supply does not output, it may be due to a blown fuse in the battery pack or a burnt out push-pull drive transistor in the final stage of the inverter, causing a short circuit in the battery pack. At this time, the voltage of the battery is usually very low, sometimes even zero. The specific reason is: internal auxiliary power circuit failure, serious imbalance in the output of the two arms in the push-pull underage drive circuit; Overcurrent protection circuit failure; The pulse width modulation component is damaged; There are five situations where the protection diode in the base circuit of the underactuated transistor is damaged.