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#1 bob

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Posted 16 October 2007 - 11:32 AM

Hi,

We have the option between a 1 MW 400 V VSD and a medium voltage 6,6 kV or 11 kV VSD. What are the medium voltage VSD commonly used on the market ? I have got some pretty good Robicon VSD at low voltage on site. I am looking for reliability and after sales service although the latter is more a question of proximity than anything else.

Thanks in advance.

Bob

#2 jraef

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Posted 16 October 2007 - 05:52 PM

Robicon (now owned by Siemens) is probably the premier MV VFD manufacturer in the world. I would stick with them especially since you already have their equipment on-site. Don't go with 11kV however, almost 1/2 of the cost of a MV VD is the switchgear and the switchgear for 11kV is a lot more expensive than 6.9kV because it is in a different voltage class.
"He's not dead, he's just pinin' for the fjords!"

#3 marke

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Posted 16 October 2007 - 06:41 PM

I agree, Robicon seems to have the reputation.
You are correct,
QUOTE
after sales service although the latter is more a question of proximity than anything else.

This is often more important than the product itself.
I find it actually comes down to individuals within the support organisation as well.

Best regards,

#4 niallnz

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Posted 16 October 2007 - 08:48 PM

The flip side to your question is the motor. A 1MW 400V motor can be rewond more easily than an MV motor, provided you winder has the stock of copper.

The ABB ACS1000 MV drive is very good, there are 5 of them in NZ that have been working perfectly for many years. I think there are about 18 ACS1000's in Australia that have also provided excellent service for many years. But like any drive if you size it correctly, house it correctly and maintain it correctly it will function as expected. Since MV drives are expensive the owner will put a lot more effort into the sizing, housing and maintenance.

Cheers
Niallnz

#5 bob

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Posted 17 October 2007 - 05:10 AM

Thanks all for the comments. How far are the construction of MV VSD differ from LV ones ? Are the IGBTs and rectifiers rated for MV applications ?
Thanks.

Bob

#6 anu_rags

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Posted 17 October 2007 - 05:43 AM

Dear All,

For a recent project, I took offer from TMEIC (Toshiba) India or TMGE (in USA) VFD for 6.6kv motor. I find their topolgy is very similar to Robicon drives and still are able to offer the drive at throw away price compare to Siemens and ABB. If this is going to be the trend then I believe it will be difficult to do retrofitting MV motors with LV drives using transformers. Any comments.

Anurag

#7 marke

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Posted 17 October 2007 - 07:08 AM

Hello Bob

The basic concepts can be similar between MV and LV, but MV introduces many issues that are harder to deal with than LV.

The output technology is typically IGBT or ICGT.
There are major limits due to the voltage ratings of the devices and so the output is usually made up of output cells in series. This raises potential issues with turn ON and turn OFF time. Each cell in a leg must turn ON and OFF at exactly the same time with equal switching times or one cell will have to withstand the full voltage.

For more information on the ICGT, see http://www.lmpforum....?showtopic=1242

Coupling the control signals to the gate drives is done by fibre optics to give the voltage isolation. This is not necessary in LV circuits.

Best regards,

#8 bob

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Posted 17 October 2007 - 10:55 AM

Hello Marke,

Thanks. I read that ABB goes to 4,16 kV with the ACS1000 and 10 k V with their megadrive , Siemens to 7,2 k V and Rockwell to 6,6 k V. I am looking for reliabilty and it appears that there are not so many MV drives commonly on the market and they are talking about a dozen ones in New Zealand and a little more in Australia. I am of opinion that the LV drives on the market , at least somes, have proved their reliability and the MV ones have yet to prove theirs.
I believe that for a one MW application, a 690 V one would be a safer option.
I would be glad to have your expert opinion.

Best regards.

Bob


#9 niallnz

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Posted 18 October 2007 - 11:58 PM

Hi Bob,

Have dig around on the ABB web site and you can find a lot of info on the ACS1000 and 1000i (has supply transformer integrated into the drive). ACS1000 now goes up to 6.6kV, but for a 1MW motor I would think that 3.3kV would be a good voltage that is 'standard' and should mean that the cost of the motor is not too high.

I only mentioned the drives in NZ and Aus as they are ones I know about, there are a number of refernce/case study docmuents on the ABB site detailiing ACS1000 installations all over the world in very different industries.

I agree though that for 1MW, 690 volts is a viable option and easier on the buget, but you will still need a transformer to get from either 400v supply up to 690V, or to convert a 400v drive output to 690 volts for the motor.

Cheers




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