Aug 27, 2020
Common faults of frequency converter
Switching power supply is damaged
Switching power supply damage is the most common failure of many inverters. It is usually caused by a short circuit in the load of the switching power supply. In the switching power supply circuit design of many inverters, our frequency conversion should be said to be relatively successful.
The fault is a common fault of the inverter. The IGBT module is damaged, which is one of the reasons for the SC fault alarm. In addition, damage to the drive circuit can easily cause SC fault alarms. In the design of the drive circuit, the upper bridge uses the drive optocoupler PC923, which is an optocoupler with an amplifier circuit dedicated to driving IGBT modules, and the lower bridge drive circuit uses the optocoupler PC929, which is a An optocoupler with an amplifier circuit and a detection circuit inside. In addition, motor jitter, three-phase current, unbalanced voltage, frequency display but no voltage output, these phenomena may be IGBT module damage. There are many reasons for the damage of the IGBT module. The first is the failure of the external load which leads to the damage of the IGBT module, such as a short-circuit of the load and a locked rotor. Secondly, the aging of the driving circuit may also cause the distortion of the driving waveform, or the driving voltage fluctuates too much to damage the IGBT, which will cause the SC fault alarm.
Overheating is a fault that is usually encountered. When encountering this situation, the first thing to think of is whether the cooling fan is running. Observing the outside of the machine, you will see whether the fan is running. In addition, for machines above 30kW, there is also a cooling fan inside the machine. The damage of this fan will also cause OH's alarm.
UV undervoltage fault
When there is an under-voltage fault, first check whether the input power supply lacks phase. If there is no problem with the input power supply, then we must check whether there is a problem with the rectifier circuit. If there is no problem, then it depends on whether there is a problem with the DC detection circuit. For a 200V class machine, when the DC bus voltage is lower than 190VDC, a UV alarm will appear; for a 400V class machine, when the DC voltage is lower than 380VDC, a fault alarm will appear. It mainly detects whether a voltage drop resistor is open.
GF ground fault
Grounding faults are also common faults. In addition to eliminating the cause of motor grounding problems, the most likely part of the fault is the Hall sensor. The Hall sensor is affected by environmental factors such as temperature and humidity, and the operating point is easy Drift occurs, causing GF to alarm.