We all know that traditional Chinese medicine uses four diagnostic methods: observation, auscultation and olfaction, inquiry, and palpation.
In fact, the testing of frequency converters is the same, with the industry-specific methods of observation, smelling, questioning, and palpation!
see
Visual inspection can reveal signs of burning on circuit board components, spillage, bulging, or deformation of main circuit energy storage capacitors, cracks in rectifier and inverter modules, and arcing or burning marks at component terminal connections. Shake the inverter enclosure to listen for unusual noises or any residue from damaged components spilling out. Smell for a burnt odor to pinpoint the source of the smell. Also, check for faults such as capacitor leakage or module breakdown/explosion.
If the inverter shows signs of burning or sparking, it is highly likely that the inverter is damaged, meaning that the main components inside the inverter have been burned out.
smell
Using one's sense of smell, faults can also be diagnosed based on the odor of the frequency converter. For example, overheating, short circuit, or breakdown faults may be detected by smelling burnt, smoke, or the odor of plastics, rubber, paint, etc., which are released when heated.
ask
When a frequency converter malfunctions, maintenance personnel, much like doctors examining patients, must first understand the detailed "symptoms." This involves inquiring with the equipment operators or users about the frequency converter's usage, its history of failure, and the entire process of the malfunction.
When taking over a faulty frequency converter, the first step is to communicate appropriately with the user to understand the equipment's usage and the cause of the fault. This will facilitate targeted troubleshooting and reduce the return rate of faults.
(1) The cause of equipment damage is during operation, during deceleration and stopping, or due to abnormal load, etc.
(2) The power supply status of the equipment, whether the three-phase power supply is balanced, and whether there is a missing phase or excessive voltage.
(3) Load conditions, working conditions of the load motor, whether it is a large inertia load (such as a fan or centrifuge), whether there is a requirement for timed deceleration and stopping, or DC braking control, whether a braking unit is installed, etc.
(4) Whether the equipment has a history of fault repair, and whether it has been repeatedly sent for repair in a short period of time due to the same fault phenomenon.
(5) Environmental conditions of the equipment. Are there excessively humid or high-temperature conditions?
While the inquiry doesn't need to be exhaustive, it should aim to gather as much information as possible about usage and malfunctions. The inverter's failure rate is closely related to user parameter adjustments and the on-site mechanical and electrical environment. For example, if the inverter is driving a large inertial load and needs to be stopped periodically, the absence of a braking unit and braking resistor can cause abnormal voltage increases in the DC circuit due to back-generating power from the motor, damaging the inverter power module or energy storage capacitor. Simply replacing the damaged module will lead to further damage within a short period, causing economic losses and adverse effects for both the user and the repair technician.
Due to abnormal power supply, the rectifier module is repeatedly damaged, and the equipment needs to be sent for repair. Relevant measures must be taken to solve the power supply problem in order to fundamentally prevent the frequent damage of the frequency converter.
Successful repairs depend not only on the repair itself, but also sometimes on the cooperation and participation of the user. Helping users resolve (or providing relevant suggestions) on-site application issues can often significantly reduce the failure return rate.
cut
When starting measurements, use a multimeter as your "eyes." Without disassembling the inverter, measure the forward and reverse resistance values between the inverter's main circuit terminals—R, S, T power input terminals, U, V, W output voltage terminals, and P, N DC circuit terminals. This will allow you to "see" the approximate damage to the main circuit. Furthermore, testing before powering on (to avoid recklessly powering on when there is a serious short circuit fault in the main circuit) is a good habit that maintenance personnel must develop.
Inverter IGBT Measurement Methods (Click to view: Causes and Measurement Methods for Inverter IGBT Damage)
Feeling like I've mastered the ultimate skill of "observation, auscultation, inquiry, and palpation"
You can transform into a "little blue man" anytime.
However, we still need to remind everyone...
Inverter fault detected
You should call immediately.
Seek professional help to handle it.
Please don't try to handle it yourself!
