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Inverters with Common DC link vs individual inverters


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#1 easyser

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Posted 07 July 2006 - 08:19 AM

Hi All !

We have 3 nos 50 KW and 2 nos 37 KW ,1500 RPM motors to be driven through a VFD.

Which solution should be preferred in this case ; Inverters for each motor with Common DC link or individual inverters for each motor.

Thanks,
easyser

#2 mariomaggi

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Posted 07 July 2006 - 10:12 AM

Dear easyser,
is it better to have a luxury car or a 4-wheel car? tongue.gif

There are too many variables involved in this decision! I think that - generally speaking - it is necessary to have a more detailed description of the specific application, otherwise we can only write general statements that could be not so useful for the specific case.

Personally I'm oriented to a common DC bus solution, but there are cases where AC supply is preferred, if there is not enough experience to manage DC buses (i.e.: what happens after a short voltage dip).

Regards
Mario




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#3 jraef

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Posted 07 July 2006 - 08:09 PM

I agree with Mario, not enough information.

However one thing that you can consider is the risk / benefit issue. The only really valid reason for going with a common DC bus on multiple drives is to take advantage of an application where one or more of the drives will be in regen while the others are motoring. In other words, you are maximizing the use of your power. If all of your drives will be motoring, there is no advantage to going with a common DC bus, it buys you nothing.

The risk to weigh against that is that if your common DC rectifier has a problem, you will lose ALL of your motor controls, not just one of them. Also, any problem in the transistors of one drive can have and effect on that common rectifier and put you in that situation. With separate drives, everything is isolated.
"He's not dead, he's just pinin' for the fjords!"




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