Fault Analysis and Detection Methods on Defective Modified Power Inverter?

Defective modified power inverter have following situations:

One. Red led light, buzzer alarm

1. Undervoltage protection (low voltage protection) over-voltage protection: the operating range of 12V system is 11V-16V, and 24V system is 22V-30V. When the battery voltage is below or above this range, the inverter will not work properly.

2. Temperature protection: the inverter work for a period of time, the temperature of the whole inverter will slowly rise as the temperature rises, the fan of the inverter will first starts, when the temperature of the mosfet rise to 90 degrees, the inverter will be alarm to protect, temperature protection.

3. Overload protection: when the power of the appliance or surge power(any appliance with motor inside has surge power) over the overlaod range of the inverter, the red led will turn on, alarm to protect.

4. Thermistor off: if the thermistor is damaged, the inverter will be red light, and alarm to protect, so when this situation happens, need to use the multimeter and adjust it to DC200V position, and then test the DC input voltage to see if it is in the working range. Also, need to know what is the appliance and the watts of this appliance, with motor or not, what is the working time.

Two. Green light on, abnormal output voltage

AC output voltage, as to 220v item, only shows 140v, as to 110v item, only shows 70v, there are two situations:

1. only one AC fuse got burnt, the corresponding mosfet maybe also got burnt.

2. The waveform of the AC side drive maybe only shows half-waveform, due to the damaged component on the circuit board or the circuit breaker. If the voltage is abnormal, need to check if the AC fuse got burnt, adjust the multimeter to diode position, and then test the mosfet(the black pen touches the second leg, and the red pen touched the third leg), the normal reading is about 380, if the reading is very small or very large, then the mosfet is damaged; at this time, need to test the corresponding resistor, the right reading is 220 ohm.

Three. Green light on, normal voltage when no-load, very low voltage when load. There are two situations:

1. DC fuse maybe got burnt;

2. The PWM signal output shows abnormal on the controll board.

3. Testing method: open the inverter, adjust the multimeter to diode position and then test the DC fuse, if it shows 0, then it is good; if it shows 1, then it is bad, at this time, need to test the corresponding mosfet(the black pen touches the second leg, and the red pen touched the third leg), the normal reading is about 420, if the reading is very small or very large, then the mosfet is damaged; at this time, need to test the corresponding resistor, the right reading is 10 ohm.

Four. No response on the led light, no response when turn on the inverter.

Testing method: open the inverter, check inside to see of there has any loosing connections or any burnt parts; if not, then adjust the multimeter to diode position, and then test the switch to see if it works when it switches to “ON”; then test the 1st leg and the 20^th leg of the CPU on the big board to see it shows 5V.