Maintenance skills of Jinan converter switching power supply
In the maintenance of frequency converter, we often encounter the problem of switching power supply failure. We can choose to use "look, smell, ask and measure" to judge the specific situation of the failure: open the power supply shell, check whether the fuse is broken, and then observe the internal situation of the power supply. If the PCB of the power supply is found to be burnt or the components are broken, we should focus on the components here. And related circuit components.
Smell: smell the inside of the power supply to see if there is any burning element.
Q: ask about the process of power supply damage and whether the power supply is operated in violation of regulations.
Quantity: before power failure, use a multimeter to measure the voltage at both ends of the high-voltage capacitor. If the switch power supply fails to vibrate or the switch tube is open circuit, in most cases, the voltage at both ends of the high-voltage filter capacitor is not discharged. This voltage is more than 300 volts, so be careful. Use a multimeter to measure the positive and negative resistance at both ends of the AC power line and the charging condition of the capacitor. The resistance value should not be too low, otherwise there may be a short circuit inside the power supply. The capacitor shall be able to charge and discharge.
When the frequency converter switching power supply maintenance skills, switching power supply does not start, we usually need to check whether the switching frequency is correct, whether the protection circuit is blocked, voltage feedback circuit, current feedback circuit is no problem, whether the switch breaks down, and so on.
The transformer of switching power supply is heated or makes a "Ho Ho" sound, generally the switching frequency is not correct.
The output voltage of switching power supply is flickering. Generally, there is a short circuit at the secondary side.
The specific maintenance skills of the common problems of switching power supply are as follows: the specific problems are analyzed in detail, and the problems of switching power supply are basically involved.
(1) the direct cause of fuse breaking in switching power supply, breakdown of switch tube / power thick module / rectifier diode, breakdown and leakage of 100uF / 400V large capacitance, internal fragmentation of degaussing resistance.
(2) the most common reasons for the voltage free output of each output end of the switching power supply, the open circuit of the fuse resistance in the AC 220 V rectifier filter circuit, and the open circuit of the resistance between the base of the switch and the positive pole of the 100uF / 400V large filter capacitor.
(3) the most common reason for the small voltage output is the breakdown of the switch tube when the switch power is only turned on; the 2.2uf ~ 100uF electrolytic capacitor on the left side of the switch transformer in the switch power supply fails; there is leakage.
(4) the most common causes of low output voltage of switching power supply are local short circuit of switching transformer, breakdown of triode and diode in PWM circuit, leakage of triode in optocoupler, etc.