Cause and treatment of no display failure of Fuji

Cause and treatment of no display fault when Fuji frequency converter starts up

cause and treatment of no display fault when Fuji frequency converter starts up:

fault phenomenon: no display when Fuji (frn5.5g-4ce) 5.5kW frequency converter starts up

1. Fault cause detection and analysis: This Fuji (frn5.5g-4ce) 5.5kW frequency converter has no response when it is powered on and started up. When measured with the instrument, there is no voltage output with the lithium Nevada project located in Nevada, the United States. The preliminary diagnosis is that there is a fault in the power supply part or the CPU base plate power supply is short circuited to the ground. Disassemble the shell and re energize the CPU base plate to measure that there is no short circuit, so it is determined that there is a fault in the power supply part, When checking the power supply part, it was found that there was a "squeak" sound. After careful identification, it was found that the sound was emitted by the transformer in the switching power supply part, so it was judged that the threshold value of the starting voltage of the switching power supply was low. When measuring with a multimeter, it was found that only about 13V voltage was still falling. When checking the power supply starting IC, it was found that the reference voltage had been lower than the minimum required value of 16V, It belongs to the situation that the switching power supply cannot be activated and the whole machine cannot work normally due to the low undervoltage locking threshold. When measuring the current limiting resistance, no open circuit or value change was found, and the switch tube showed no signs of damage. After replacing the power supply and starting the IC, the fault still existed without any change

2. Treatment: after Zhou Si's consideration, he drew the switching power supply part of the circuit. Through circuit analysis, it was found that there was a 15uf/25v electrolytic capacitor supplying the starting IC voltage after the current limiting resistor. Its important role was to activate the switching power supply to realize constant torque or constant power speed regulation startup and make it work normally. Therefore, it was suspected that it was caused by the variation of the electrolytic capacitor, The length of the cord should be appropriate. After replacing an electrolytic capacitor of the same type, the fault is still not solved. Replace it with an electrolytic capacitor 22uf/50v that is larger than the voltage withstand voltage of the original capacity. Turn on the power supply of the host, controller and computer system in sequence. If the problem is really solved, there is voltage output, and the display shows it. After analysis, it is found that the original electrolytic capacitor is used to activate the switching power supply startup