Screw air compressor, variable frequency control, overcurrent and overheating in rare earth permanent magnet synchronous motors!
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Two new three-phase brand air-cooled screw air compressors have been installed, controlled by frequency converters; during testing yesterday, motor overcurrent protection triggered and caused the machines to shut down one after another. The motor temperature also reached 103°C in a very short time, forcing an interruption of the testing. I seriously suspect I’m being used as a guinea pig by the air compressor manufacturer! This type of high-power, low-energy-consuming air compressor using permanent magnet synchronous motors may not be technically mature. The motor manufacturer will be at the site the day after tomorrow... I would like to ask an expert: 1. Are high-power permanent magnet synchronous motors mature yet? (The rated power on the nameplate is 315 kW at 380 V.) 2. What causes the motor to experience overcurrent and an increase in temperature? (Suspected to be related to the frequency converter) 3. Are there any recommended manufacturers for selecting frequency converters? Thank you! !
Firstly, your description is too simple, which makes the problem more complicated. 1 The energy-saving benefits of permanent magnet motors are well-established and beyond doubt. Variable frequency control saves energy but cannot operate at low speeds. 2 Many frequency converters do not recognize permanent magnet motors; there is simply a mismatch. Choose an inverter that is compatible with permanent magnet motors; many brands are available. The 3-screw air compressor is designed for heavy-duty use; therefore, a G (heavy-duty) frequency converter, one higher in capacity, should be selected, as this has a significant impact on heat generation. It’s very likely that the frequency converter you chose is too small and cannot handle the load. 4. The frequency converter should be isolated from the air compressor; in particular, the intake air must be cool outside air, with powerful fans used for exhaust. 5 The only thing left is to set the parameters. Pay attention to the location of the pressure detection. I have dealt with many situations like yours, but these are the key points; this is just my humble attempt to provide some insights. Wishing you success in your work.
Thank you for getting back to me. It was due to the quality of the motor; we replaced it with two motors of the same model made by another manufacturer, and they have been in use for over a month now.
It's good that the problem is solved. All other details have been taken into account; it’s just that the issue with product quality wasn’t considered. Ah,. . . . Wish you success in your work.