350HP VFD
- Thread starter SpiderMT
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Probably in the right ball park if it includes the transformer.
Going 18-pulse is for limiting the supply side harmonics.
Have you considered going active front end? It's usually what we do at that sort of power and upwards.
The inverter will be more expensive but it could eliminate the need for a transformer depending or where you are getting the supply from.
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petersonra
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- Location
- Northern illinois
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- engineer
It sounds insane to me but a lot depends on what all the quote includes. The cost of 18 pulse drives means we never sell them, so I have little experience upon which to base a guess on cost, but the magnitude of the number just seems very high to me. But, again, it depends on what it includes.
mtfallsmikey
Senior Member
Seeing what it has cost for smaller VFD's in my buildings, my guess is that figure is in the ballpark
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Are 18 pulse drives that much more expensive than regular drives?
based on what we paid for a regular 600HP drive a few months ago, the number being bandied about makes little sense to me. but again, it depends a lot on what is included in the price.
This brochure from AB suggests just the 18 pulse 350HP drive by itself would be about $40,000 (see page 3).
http://literature.rockwellautomation.com/idc/groups/literature/documents/br/drives-br007_-en-p.pdf
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
Without knowing the full scope of supply, that's nearly impossible to tell. An off-the-shelf 350HP open chassis 6 pulse drive would be far far less, but that doesn't meet the spec, right? So to become 18 pulse, the drive has to have, at a bare minimum, either two transformers ahead of it, each with a 120 degree phase shift compared to the other two phases, or a custom 18 pulse autotransformer and a line reactor, then three separate rectifiers, a common DC bus with a choke and some added monitoring systems. Add to that an input circuit protection scheme, overall enclosure and some massive blowers to keep it all cool and bingo, the $$$ add up fast.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
That would represent the ADDED cost, it was meant to compare against OTHER means of mitigating harmonics. The total cost would include the drive itself, then any other options.
I wish they hadn't worded that brochure the way they did, I get that call at least once per week...
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petersonra
Senior Member
- Location
- Northern illinois
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- engineer
so what they are claiming is it is $40k more than a std 350HP drive? since they can be had for under $20k, that would still be less than half what was quoted to the OP.
I agree. Maybe the OP can come back and shed some light on that.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Well again, a completely enclosed and configured combination drive (with input protection, reactors etc.) is going to be more expensive to start with than $20K. But I took a look, and you are right, it is not THAT much more; if it was simple, I think the total could/should have been well under $100K.
But again, we have no idea what the design spec is. For instance if they wanted a Bypass system, that is going to be very expensive at 350HP. I just did one with an 18 pulse drive, a Soft Starter as the bypass for the VFD, and another ATL starter as a bypass for the Soft Starter bypass; triple redundancy (mission critical system). By the time we were done with everything they wanted this 500HP drive was almost $300K!
Didn't mean to disappear, we are just slammed lately. The drive has a soft start bypass and line reactors. Don't have the spec in front of me but it sounds like the number was good. I was just worried because the cost was so much more than I'm used to. This is for a municipal water well and usually the projects I've done in the past have been a lot cheaper for the drive, actually usually just a soft start but we have done smaller VFD's too. I can go through the spec tomorrow and post the specifics if anyone is interested.
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