VFD Compressor IGBT high temp shut down 1

[sayan12]

A VFD is driving a screw compressor according to demand for air. The compressor starts and stops on cut in and cut out pressures. Occasionally the compressor is shutting down on IGBT high temp alarm within a few seconds of starting. What could be the reasons?

 

[Skogsgurra]

Many, many reasons possible. As a first test,I would reduce the cut in pressure. That makes for fewer starts per hour (how many does the spec allow?) and also reduce torque at start.
If there is a manufacturer/supplier at hand (where in the world is this?) they may have better tips.
I presume that settings, specs and grid voltage are OK. If not, there is something to start with.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

For VFD novices, screw compressors are a tricky application with VFDs. I agree with Gunnar but take it a step further. Often times people replace starters with VFDs on screw compressors and just use the VFD like a starter without reconsidering what the system is CAPABLE of now. The cut-in pressure is now something that is less important, because you CAN just reduce the speed instead to match the pressure demand, thus reducing the number of times the motor must start and stop altogether. But by just replacing the starter with a VFD and using it in the same way, EVERY time the VFD has to start the motor, you are thermally stressing the transistors as they accelerate it. Running it for longer periods allows them to cool off, but under heavy use, the pressure switch drops out and restarts it again too soon. The thing that you need however is a pressure TRANSDUCER giving an analog value to a PID loop in the VFD instead of just a pressure SWITCH, and someone that understands how to make that work in your system.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[Skogsgurra]

Of course, Jeff! Use the VFD for what it is best at - like running continuously instead of a starting device. Should have thought of that. But it requires some work, so the easy test may be a way to find out what the problem really is. Also, I forgot to mention ambient temperature and clogged air filters. Or even the fan running. Which isn't Always the case.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LionelHutz]

I agree, no point in having a VFD if it just starts and stops. Use a pressure transducer and speed control the compressor according to the air demands.

As to the problem, my first thought was that the unloader valve was malfunctioning and not unloading the compressor.

 

[itsmoked]

Likely this is a VFD that came with the compressor as a packaged product.

Have you checked the cooling fan(s) for operation?
Have you checked the filters in the cooling fan circuit as being clean and clear?
Has the environment changed?

I was just at a site where the compressors were in a poorly ventilated corner of the building and so day and night were in an ambient more than 10F higher than the rest of the facility.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[John2025]

To 2nd itsmoked, we have a vfd screw compressor that blew the drive after 18 months because the cooling fins got clogged with dust, cottonwood seeds, etc (no filter on the fan). We've been disassembling and cleaning every other year since replacing the drive and we've been good for the last 10 years (knock on wood). Added a filter to the fan, too.

 

[itsmoked]

Are you saying you've just cleaned the filter(s) and you're still experiencing IGBT shutdowns?

If, yes.

Is the local ambient high? If yes, what is it?

What make and model compressor is this?

Is your air utilization up from what it used to be?


Keith Cress
kcress -

http://www.flaminsystems.com