Siemens VFD (Variable-frequency Drive) maintenance example

Siemens VFD (Variable-frequency Drive) maintenance example 1: Siemens MMV 6SE3221 4.0kW VFD (Variable-frequency Drive) maintenance

Static measurement shows that the inverter module is normal, and the rectifier module is damaged.

Fault analysis and judgment: Damage to the rectifier module is usually caused by DC load overload, short circuit and component aging.

Measuring the reverse resistance value between PN (the positive meter pen of the multimeter is connected to N, and the negative meter pen is connected to P) can reflect whether there is an overload short circuit phenomenon in the DC load. The measured resistance value between PN is 15052, and the normal value should be tens of kiloohms, indicating that the DC load is overloaded; the inverter module is normal and can be ruled out; check the filter large capacitor and the voltage equalizing resistor are normal; measure the brake switch device Damaged short circuit, remove the brake switch device and measure the resistance value between PN and normal.

Replace the brake switch device, and the VFD (Variable-frequency Drive) resumes working. This fault may be caused by the fact that the deceleration time of the VFD (Variable-frequency Drive) is set too short, and a large braking current is generated during the braking process to damage the braking switch device VT. When the brake switch device is damaged and short-circuited, the brake resistor is directly placed between PN to generate a large current (about 1/2 of the rated current).

?During VFD (Variable-frequency Drive) operation, the load current of the rectifier module is the sum of the normal load current and the current flowing through the braking resistor, and the rectifier module is damaged due to long-term overload. If the production process allows, increasing the deceleration time can avoid this failure from happening again.

Siemens VFD (Variable-frequency Drive) maintenance example 2: Siemens MM420 VFD (Variable-frequency Drive) maintenance 37kW

The static detection inverter module is normal, and the rectifier module is damaged.

Detect that the reverse resistance between PN is less than the normal value. Disassemble the VFD (Variable-frequency Drive) and find that there are traces of liquid flowing out of the large filter capacitor on the printed circuit board of the large filter capacitor combination. Further inspection has two large filter capacitors that are damaged and have serious leakage. Replace the capacitor, clean the printed circuit board of the filter and large capacitor combination, and then measure the reverse resistance value between PN and normal, and the VFD (Variable-frequency Drive) returns to normal operation. Such failures can be avoided if daily inspections and regular maintenance are carried out as required.

Siemens VFD (Variable-frequency Drive) maintenance example 3: Siemens MM430 VFD (Variable-frequency Drive) maintenance 11 kW

The static detection inverter module is normal, and the rectifier module is damaged.

The reverse resistance value measured between PN is within the normal range, and no abnormality is found in the main circuit part. The initial judgment is that the rectifier module is naturally aging and damaged. However, during the cleaning and inspection process, it was found that there were signs of component damage in the drive circuit, and a component was damaged during further measurement, resulting in the drive output always being at a high level.

Replace the rectifier module and repair the drive circuit. During the operation of VFD (Variable-frequency Drive), one of the driving circuits is suddenly damaged, so that the output is always maintained at a high level, causing the two inverter switching devices on this bridge arm to be turned on at the same time to form a short-circuit large current. The rectifier module is damaged first and loses high-voltage direct current, which avoids damage to the inverter module.

Siemens VFD (Variable-frequency Drive) maintenance example 4: Siemens MM430 VFD (Variable-frequency Drive) maintenance 75kW

Static detection shows that the inverter module is damaged, and the rectifier module is normal.

Fault analysis There is a trace of damage to the resistance along the way.

The damage of the inverter module is mostly caused by the damage of the drive circuit. Check the drive circuit and it turns out that the IOM resistor is damaged and short-circuited. 'This is the pull-up resistor at the output end of the optical disaster isolator 4506. This pull-up resistor is damaged and short-circuited, so that the signal sent to T95 at the output end is always high level regardless of whether the input of the 4506 is high or low. The level between we and WE is always high, and when the VFD (Variable-frequency Drive) is running, the two switching devices of the same bridge arm are turned on at the same time and the inverter module is damaged. Replace the resistor, the drive circuit works normally.

The damage of this resistor is accidental, and the exact cause of the damage is difficult to determine. It may be an accidental electric spark burning, and the greater possibility is the quality of the resistor itself. The reasons for the damage to the inverter module caused by the short circuit of the resistor damage have been mentioned above. In addition, the design of this circuit is that the pull-up resistor is connected to the output terminal of the 4506 optical isolator after passing through a 47552 resistor, which protects the safety of the optical isolator. If there is no such resistor, the pull-up resistor is directly connected to the output terminal of the optical isolator, and the damage of the pull-up resistor and the short circuit will cause the damage of the optical isolator.

Siemens VFD (Variable-frequency Drive) maintenance example 5: Siemens VFD (Variable-frequency Drive) maintenance 7.5kw

No fault is displayed.

?The VFD (Variable-frequency Drive) high-voltage DC power supply is normal, the operation panel has no display, and there is no low-voltage DC power supply on the VFD (Variable-frequency Drive) control circuit, which belongs to the switching power supply circuit does not work.

Check that the voltage on the drain D of the switching tube VT is normal, and it is measured that there is no pulse signal on the control pole G but only a DC voltage. The output signal of the UC3844 is abnormal. After inspection, the UC3844 is damaged, and the switch tube is also damaged. Replace UC3844, replace the switch tube, VFD (Variable-frequency Drive) back to normal.

The fault is caused by the high output current level after the UC3844 is damaged, which makes the switch tube in the conduction state for a long time and the over-current causes the switch tube to be damaged for a long time.

Siemens VFD (Variable-frequency Drive) maintenance example 6: Siemens MM420 VFD (Variable-frequency Drive) maintenance 7.5kW

Display F0003 (undervoltage).

?The VFD (Variable-frequency Drive) is connected to the power supply, and the operation panel displays an undervoltage fault. The measurement of the three-phase power supply voltage is normal, and the measurement of the high-voltage DC power supply between PN is also normal. This is a false undervoltage fault, and the problem lies in the voltage detection protection circuit. First check the voltage sampling circuit, Figure 8-40 is part of the circuit of the resistor divider voltage sampling circuit. Measure 3 resistors, the resistance value basically does not change, check the capacitor C3, it is dry and has a serious leakage phenomenon. Solder the capacitor C3; and turn on the power again. The undervoltage fault display disappears. It is determined that the problem lies in the C3 capacitor. Replace the capacitor, the undervoltage fault display no longer appears.

Siemens VFD (Variable-frequency Drive) maintenance example 7: Siemens MM