If the charging circuit input is normal and the output is abnormal, disconnect the battery and test again. If it is still abnormal, the charging circuit is faulty;

If the input and output of the charging circuit are normal after the battery is disconnected, it means that the battery has been damaged due to long-term uncharged, over-discharged, or reached its life.

Problem three: A pair of power amplifier transistors of the inverter power stage are damaged. After replacing the same type of transistor, the reason for running for a period of time and then burning is because the current is too large.

Failure analysis:

Overcurrent protection has failed. When the inverter output overcurrent occurs, the overcurrent protection circuit does not work;

The pulse width modulation (PWM) component is faulty, the two complementary waveforms of the output are asymmetric, one has a long conduction time, and the other has a short conduction time, which makes the two arms unbalanced, and even the two arms are turned on at the same time, causing damage to the two tubes;

The parameters of the power tube are quite different. At this time, even if a symmetrical waveform is input, the output will be asymmetric. This waveform passes the output transformer and causes bias magnetism, that is, the magnetic flux is unbalanced. Accumulation causes the transformer to saturate and the current to increase sharply. And one burned out, the other burned out

Problem 4: After the UPS is turned on, there is no display on the panel, and the UPS does not work.

Failure analysis: Judging from the failure phenomenon, the failure is in the mains input, battery and mains detection part and battery voltage detection circuit:

Check whether the mains input fuse is burned out;

If the mains input fuse is intact, check whether the battery fuse is burned out, because some UPS will turn off all the output and display of the UPS when the battery voltage is not self-tested;

If the battery insurance is intact, Chifeng Yuasa Battery Factory checks whether the mains detection circuit works normally. If the mains detection circuit does not work properly and the UPS does not have the mains-free start function, the UPS will also turn off all outputs and displays.

If the city detection circuit works normally, check whether the battery voltage detection circuit is normal.

Question 5: When the UPS is connected to the mains, every time you turn on the UPS, you will hear the repeated action sound of the relay. The UPS panel battery voltage is too low and the buzzer is on.

Failure analysis:

This fault is caused by the battery voltage being too low, which causes the UPS to fail to start. Remove the battery and perform balanced charging first (all batteries are charged in parallel). If it is still unsuccessful, you only have to replace the battery.

Question 6: A backup UPS works normally when there is mains power, and the inverter has output when there is no mains power, but the output voltage is low, and the transformer emits loud noise.

Failure analysis:

The output from the inverter indicates that the final-stage drive circuit is basically normal, and the noise from the transformer indicates that the two arms of the push-pull circuit work asymmetrically. The detection steps are as follows:

Check if the power is normal;

If the power is normal, then check whether the output signal of the pulse width output circuit is normal;

If the output of the pulse width output circuit is normal, then check whether the output of the drive circuit is normal.

Question 7: When the UPS is turned on when the mains power supply is normal, the inverter's working indicator flashes and the buzzer emits intermittent beeps. The UPS can only work in the inverter state and cannot be switched to the mains operating state.

Failure analysis: Inverter power supply to mains power supply cannot be converted, indicating that there is a failure in the conversion part of inverter power supply to mains power supply. It is important to detect:

Whether the mains input fuse is damaged;

If the mains input fuse is intact, check whether the output of the mains rectifier filter circuit is normal;

If the output of the mains rectification filter circuit is normal, check whether the mains detection circuit is normal;

If the mains detection circuit is normal, then check whether the inverter power supply to the mains power conversion control output is normal.

Problem eight: When the load is close to full load, the mains power supply is normal, and the battery fuse is blown when the battery is powered.

Failure analysis: The battery fuse is blown, indicating that the battery supply current is too large. The detection steps are as follows:

Whether the inverter is broken down;

Whether the battery voltage is too low;

If the battery voltage is too low, check whether the battery charging circuit is normal;

If the battery charging circuit is normal, check whether the battery voltage detection circuit works normally.

Question 9: The UPS can only be powered by the city power and cannot be switched to inverter power.

Failure analysis: It is not possible to convert the mains to inverter power supply, which indicates that there is a failure in the conversion part of the mains to inverter power supply. It is important to detect:

Whether the battery voltage is too low and the battery fuse is intact;

If the battery part is normal, check whether the battery voltage detection circuit is normal;

If the battery voltage detection circuit is normal, then check whether the control output of the mains to inverter power supply is normal.

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