How to repair and maintain the variable frequency power supply?

How to repair and maintain the variable frequency power supply?

Electronic equipment is inseparable from a reliable variable frequency power supply. The AC variable frequency power supply is widely used in almost all electronic equipment because of its small size, lightweight, and high efficiency. This article will introduce several common faults in variable frequency power supplies, analyze the causes, and finally give some maintenance skills for variable frequency power supplies.

Frequency conversion power supply failure 1: Blown fuse

In general, a blown fuse indicates a problem with the internal circuit of the power supply, or the rear end is overloaded (inrush current). Because the variable frequency power supply works under the condition of high voltage and high current, fluctuations and surges of the grid voltage will cause the internal current of the power supply to increase instantaneously, resulting in the fuse being blown. The key point should be to check the rectifier diode at the power input end, the high-voltage filter electrolytic capacitor, the inverter power switch tube (IGBT), etc., and whether their components are breakdown, open circuits, or damaged. If it is confirmed that the fuse is blown, first check whether the components on the circuit board are burnt and whether the electrolyte overflows. If the above situation is not found, use a fluke multimeter to measure whether the switch tube has a breakdown or short circuit.

Note: Do not start the machine directly after replacing the faulty component; likely, other high-voltage components are still faulty, which will cause damage to the replaced component again. It is recommended that you conduct a comprehensive inspection of the high-voltage components of all circuits before eliminating the blown a fuse.

Frequency conversion power supply failure 2: No AC voltage output or unstable voltage output

If the fuse is intact, there is no AC voltage output at all levels under load conditions. The following reasons mainly cause this situation: open circuit and short circuit in the power supply, failure of the overvoltage and overcurrent protection circuit, failure of the auxiliary power supply, the oscillation circuit does not work, the power supply is overloaded, and the rectifier diode in the high-frequency rectifier filter circuit Breakdown, leakage of filter capacitors, etc. When measuring the secondary components with a multimeter, if the output of the multimeter is still zero after the breakdown of the high-frequency rectifier diode and the load short-circuits fault is excluded, it can be determined that the control circuit of the power supply is faulty. On the other hand, if there is some voltage output, the pre-stage circuit is working normally, and the fault is in the high-frequency rectifier filter circuit. The high-frequency filter circuit comprises a rectifier diode and a low-voltage filter capacitor to form a DC voltage and output it. If the rectifier diode breaks down, the circuit will have no voltage output, and the leakage of the filter capacitor will also cause the output voltage to be unstable and other faults. Therefore, it is necessary to use a fluke multimeter to measure the resistance value of the corresponding component and compare it with the resistance value of other normal components to check the damaged component.

Frequency conversion power supply failure 3: Poor power supply load

Poor power supply load is a common fault, which generally exists in old-fashioned or long-term power supplies. The main reasons are the aging of various components, the unstable operation of switching tubes, and the lack of timely cooling. It is recommended that miners focus on checking whether the Zener diode has heat and leakage, whether the rectifier diode is damaged, and whether the high-voltage filter capacitor is damaged.

Frequency conversion power supply maintenance skills:

No matter whether you use a single-phase or a high-power three-phase variable frequency power supply, it is unavoidable that there will be no minor faults during use. So to avoid the frequent occurrence of these minor faults, it is still inseparable from our maintenance and maintenance of it. Therefore, the frequency conversion power supply needs to be regularly maintained after a long period of use.

1. Regularly clean the air filter, cooling air duct, and internal dust.

2. Check whether screws, bolts, and other plug-ins are loose.

3. Conductors and insulators should be wiped clean with alcohol in time.

4. Whether the UVW phase-to-phase waveform is a sine wave.

5. Measure whether the square wave of each waveform of the drive circuit is distorted.