new MV drive on old motors

[ePOWEReng]

I am working on a project installing a Medium Voltage drive an old induction motor (4160V, 2000HP). I am interested in hearing peoples thoughts on the different drive technologies and manufactures out there. For instance, ABB offers a standard PWM inverter at 4160V, 2000HP with an sine wave filter on the inverter output. Toshiba offers a multi-step PWM inverter at 4160V, 2000HP.

Which of these drives or others are easier on the motors as far as dv/dt at the motor terminals? Are there other manufacturers or technologies that are better? Any other thoughts on the subject?

Thanks for the responses.

 

[Skogsgurra]

There's also Robicon. They have a multi-level output. Robicon was bought by Siemens a couple of years ago.

I would say that anything with a sine filter in it is preferred before steep waveforms. Even if those steps are reduced in height. The main problem with old motors is ozone production in voids between winding and stator slot walls. The PWM waveforms produce a lot more ozone than a soft waveform does and ozone destroys insulation over the years.

The problem is that it is difficult to predict what will happen. If the drive isn't very critical (but most drives that size usually are) and there is a big cost difference in favour of it - then I might go for a multi-level inverter.

But I would definitely seek advice before doing that. Like you have done here.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ePOWEReng]

Toshiba (and probably Robicon) also optionally offer a dv/dt filter on the multi-level inverter output.

ABB drive has a SINE wave filter on the output of the inverter.

So I am gathering that dv/dt filters don't get rid of as much of the voltage harmonics as a SINE filter. Can anyone expand on this? Any more about the comparison of the above technologies?

Thanks.

 

[macmckim1]

the MV drives that I have worked with
- ABB
- GE
- Rockwell
- Siemens - Robicon
- Toshiba

I think these days all have common mode volage elimination that allow these MV drives to be used on any MV motor

 

[electricpete]

The common mode volage elimination prevents bearing currents, but does not prevent high spikes of voltage and dv/dt, correct?

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[electricpete]

Got some information in the email which showed I was wrong - common mode voltage elimination does help protect the windings as well.

My mistake. Thanks for the info macmckim1

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[ePOWEReng]

Any other comments? I was hoping for some more discussion.

I have heard that ABB's customer service is not very responsive. Any seconds? Any other comments about customer service?

Any other comments regarding MV drive selection?

Thanks.

 

[jraef]

Robicon's "Perfect Harmony" drive is specifically designed for this application. The oldest MV motor they have successfully retrofitted was one built in 1942!

 

[ePOWEReng]

I noticed that Robicon uses HV-IGBT technology for up to 10MVA and uses the IGCT on the larger sizes.

Why don't they offer the IGCT technology at lower sizes?

I was under the impression that IGCTs were easier (less dv/dt) on motors than the IGBTs due to the slower rise time of the output transitors. Is this true?