Common faults and handling methods
The faults occurring in the frequency converter are divided into external faults and internal faults. After determining external or internal faults, it is possible to narrow the inspection scope and improve work efficiency when repairing the frequency converter. The following are some common faults occurred in daily work and their handling methods.
1 Converter undervoltage reporting
The cause of the fault is an internal problem or an external problem with the frequency converter.
1.1 Internal issues
Using a multimeter to measure the PN voltage (normally 530V). If it is lower than 530V, measuring the three-phase RST again. If the three-phase RST is 380V, it is determined that the main circuit contactor is not engaged; If the three-phase RST is lower than 380V, there is a problem with the three-phase input line. If the PN voltage is normal, then measure 10V and 24V. If it is normal, there is a problem with the detection circuit; If it is not normal, it is a switch power supply fault.
If there is no response to power on and no alarm is given before operation, it may be that the rectifier bridge has failed; If undervoltage occurs when the load is increasing, real-time detection is required. It’s possibly due to a large capacitance failure.
1.2 External Issues
The line from the transformer to the frequency converter is too long, resulting in line loss, and it is necessary to install a reactor; The terminal from the air switch to the frequency converter is loose.
2 Frequency converter trips after being powered on
The cause of the fault is an internal problem or an external problem with the frequency converter.
2.1 Internal issues
Using a multimeter to measure the RST in pairs. If the resistance value is less than the normal value, the frequency converter is short-circuited; If overvoltage protection is reported, it indicates breakdown of the varistor. The most common fault is rectifier bridge breakdown, which accounts for approximately 80% of this fault.
2.2 External issues
The air switch with leakage protection cannot be used at the input of the frequency converter, otherwise this fault will be reported; Leakage of external equipment.
3 Converter Overcurrent Reporting
The cause of the fault is an internal problem or an external problem with the frequency converter.
3.1 Internal issues
Reporting when the frequency converter is powered on, then the circuit transformer is damaged; IGBT failure; The drive plate is damaged; Capacitor failure.
3.2 External issues
Disconnecting the line connecting the frequency converter to the motor and see if the fault is reported. If it doesn’t report then it indicates a motor fault or excessive load (leakage, short circuit, insulation fault); The frequency converter only reports when it is started, which may be due to a short acceleration time (disassemble the motor, measure the starting current, and if it is large, install a reactor); If the distance from the inverter outlet to the motor is greater than 50m, a series reactor is required.
4 No response when the inverter is powered on (black screen)
The cause of the fault is an internal problem or an external problem with the frequency converter.
4.1 Internal issues
Using a multimeter to measure whether the RST is powered on. If the PN is powered off, the main circuit is faulty (check whether the contactor and pre charging resistor are damaged); Using a multimeter to measure whether the RST is powered on. If the PN is powered on, the switching power supply may fail (insufficient voltage of the switching power supply may also lead to no response. You can measure whether the voltage is sufficient by measuring 24V and 10V; the rectifier bridge in the main circuit is completely burned (relatively rare)).
4.2 External Issues
Using a multimeter to measure RST, if there is no power, it is an external problem; The display screen is damaged.
5 Inverter panel flickers on and off
The cause of this fault may be an internal problem with the frequency converter.
There is a short circuit in the load on the secondary side of the switching power supply, and the switching power supply adopts current protection (such as when the fan of the small frequency converter is blocked). At this time, measuring the voltage swing of the control terminal 0 to 24V or 0 to 10V.
6 Overtemperature fault reported by frequency converter
There are two possible reasons for this failure, namely, internal problems with the frequency converter and external problems with the frequency converter.
6.1 Internal issues
Detecting circuit faults, such as temperature sensors, etc; Internal cooling fan failure.
6.2 External issues
Equipment overheating and exceeds the range of fan heat dissipation; The ambient temperature is high.
7 Disordered code and high power display on the inverter panel
The reason for the display of garbled code on the inverter panel or the display of high power on the inverter panel is an internal problem with the inverter, that is, a failure of the CPU main board’s storage chip, resulting in the loss of parameters.
8 Large difference between the displayed liquid pressure level and the actual value
The cause of this fault may be an external problem with the frequency converter, that is, the frequency converter has generated electromagnetic interference. It is necessary to find the problem item by item: ① three-phase input and three-phase output cables are shielded cables, and the shielding layer is grounded; ② Three phase input sleeve magnetic ring, wound several times; ③ Three-phase input string electromagnetic filter; ④ The control line uses shielded wire and the shielding layer is grounded; ⑤ Splitting slot for control line and three-phase input and output lines; ⑥ The distance between the control line and the three-phase input and output lines in a slot should be more than 10cm; ⑦ The control line and the main circuit line should intersect and be vertical; ⑧ The control line shall be covered with steel pipes; ⑨ Do not use multi-core wires for control wires; ⑩ Twisted pair cables are used for communication lines, with a shielding layer, and the shielding layer is grounded (usually single ended grounding, if not feasible, double ended grounding); ⑪The level gauge is faulty or the installation position is incorrect.
9 The frequency converter suddenly stops running without reporting a fault
The cause of this fault is generally an external problem with the frequency converter. The self-locking device of the intermediate relay in the starting circuit should be checked (directly using a short circuit contact to connect to 24V, or changing to panel control. If the problem is resolved, it can be determined that there is a problem with the relay); Electromagnetic interference; Poor contact of the panel plug.
10 When the frequency converter is stopped, overvoltage is often reported
The cause of the fault is an internal problem with the frequency converter or an external problem with the frequency converter.
10.1 Internal issues
If the RST and PN are normal, and the measured 10V and 24V are abnormal, it is a switching power supply fault; If RST and PN are normal, and 10V and 24V are measured to be normal, it is a detection circuit problem; If the problem occurs only during stopping, it is the feedback current caused by too short deceleration time, which can be solved by extending deceleration time or connecting a braking resistor externally.
10.2 External Issues
If the RST and PN voltages are high, there is an external problem.
Conclusion
The application of frequency converters in water pumps has the advantages of simple operation, high reliability, strong anti-interference, constant water supply pressure, and energy efficiency. To complete the production and water supply tasks with high quality and efficiency, the safe use of frequency converters is a top priority. Therefore, skillfully analyzing and handling various faults of frequency converters encountered in daily work is a necessary skill for maintenance personnel engaged in the application of frequency converters in water plants.
Post time: Apr-04-2023