240 grounded B with a VFD?

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cmaki

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I am looking at changing one of our old variable speed pulleys to a newer VFD setup. We have 240 grounded B at this current pump. Is there a danger to the VFD running a corner grounded system like this? This CGD stuff is still new to me and I don't want to spend a ton of the bosses money only to have it blow up.
 
It has to do with the way the MOVs (surge suppressors) that protect the front-end rectifier are referenced to ground, as well as any EMI / RFI filtering capacitors or Common Mode capacitors. That's because in all areas of the world EXCEPT the US, they never use delta power systems, everything is Wye, so the internal components are referenced to ground. If we connect them to a Delta system, the MOV or Filter reference point tries to become the Wye point for your entire grid, so the first ground fault you get will take them out, then you have nothing and the drive fails on the next spike or fault. In the case of a grounded delta system though, that will not happen happen because two of the phases are already referenced to ground, the other one IS at ground potential. So you should be fine. Where you have to worry about this is on UNGROUNDED delta systems, or on 240 "High Leg" delta systems where only one winding is grounded at a center tap. In that case, you have one set of windings in the transformer that has NO reference to ground, so if a GF happens there, once again you are toast.

If it were an ungrounded or High Leg delta system, that's when you have to be careful. Drives sold by primarily US based companies will have instructions on what to do and make it easy. A few of the larger EU and more reputable Asian mfrs will likely have instructions to modify the drives, but it may be more difficult than those from US based companies. For example if you dig deep in the fine print on a Siemens drive, you will find out that you basically have to disassemble the front-end of the drive to get access to the ground reference connection for the EMC filter and MOVs, so that you can cut the wire. For Allen Bradley drives, you just remove a jumper from inside the wiring access cover. Cheap Asian drives may not address it, they don't really engineer anything, they just copy cheaply. You find out when your drive blows, then they sell you a new one.
 
In a high leg delta, the other two windings are referenced to ground, just not directly at any winding terminal. That is how you get the 208V to ground/neutral on the high leg.

Tapatalk!
 
I contacted the manufacturer. (Masters Power Transmission) They do sell a kit to allow it to run 240 grounded B. It normally is ran by 460 (the product "specialist" said not 440 or 480. needs to be 460) I have 480 volts near by and I think I can tap into it. There is a 10 amp fused disconnect that is running a hydraulic lift table. That is drawing about 1.5 amps when running. I figure a 1hp motor to be drawing about 2.5 amp under normal conditions. The lift table only draws when moving up or down so most of the time there would just be about 2.5 amps drawn. Is the 10 amp fuses enough? Or is this just a bad practice all around? other option is to tap into the 480 main coming from the MCC (150amp for the entire unit). If the 10 amp isn't enough what size fuses would be enough?
 
cmaki said:
I contacted the manufacturer. (Masters Power Transmission) They do sell a kit to allow it to run 240 grounded B. It normally is ran by 460 (the product "specialist" said not 440 or 480. needs to be 460) I have 480 volts near by and I think I can tap into it. There is a 10 amp fused disconnect that is running a hydraulic lift table. That is drawing about 1.5 amps when running. I figure a 1hp motor to be drawing about 2.5 amp under normal conditions. The lift table only draws when moving up or down so most of the time there would just be about 2.5 amps drawn. Is the 10 amp fuses enough? Or is this just a bad practice all around? other option is to tap into the 480 main coming from the MCC (150amp for the entire unit). If the 10 amp isn't enough what size fuses would be enough?
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You kind of lost me on this. Are they proposing a mechnical vari-drive solution then? Because that is what they make, the old Reeves drives. So how does the VFD play into that? I thought that was what you were replacing?

If I missed something and you are using a VFD, then you have to refer to the VFD supplier's installation guide to know the fuse / circuit sizing you will need.
 
The old reeves drives are a mechanical vari speed. They have a new system called the Innovadrive. Its a direct drive motor to the reducer with a VFD controlling the motor. Look it up its pretty cool.
 
cmaki said:
The old reeves drives are a mechanical vari speed. They have a new system called the Innovadrive. Its a direct drive motor to the reducer with a VFD controlling the motor. Look it up its pretty cool.
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Pretty sure the transmission supplier does not mfgr that drive - whose is it? Find out and get their manual showing what fusing is required. I assume from your comments this transmission place does not offer a manual, even with their private label name on it?

Its a pretty wierd 'kit' that converts a 460v vfd drive to 230v: that sounds like a step up transformer? And at same time allows corner grounded delta. Also sounds fishy their expert says you cannot supply 440 or 480v to the standard drive - I haven't heard of such a narrow input spec on a vfd ever.
 
cmaki said:
The old reeves drives are a mechanical vari speed. They have a new system called the Innovadrive. Its a direct drive motor to the reducer with a VFD controlling the motor. Look it up its pretty cool.
Click to expand...

OK, I see now.

mike_kilroy is right, they don't make it, which likely explains the bad answer you got from their tech guy, because he apparently has no clue since he is so far removed from it. Here's the chain of possession, it's a little convoluted...

Master PT is brand labeling it from Leeson as part of a package with the motor. But Leeson doesn't make it either, Leeson brand-labels that drive from another company called AC Tech. But AC Tech is now owned by a German company called Lenze, who is who actually makes that drive (AC Tech used to make drives here in the US, but when Lenze bought them, all the new models come from Germany). So by the time info filters down from Lenze to Master PT, it gets to be kind of like that old "Telephone Line" game where the stuff that gets out at the end of the line barely resembles the original message.

They do have 240V drives, and FYI, the input voltage range of the drive is 170-264VAC, and for 480V drives it is 340 - 528VAC. So he definitely had no clue...

Being that they are German drives, they are not designed to be operated from ungrounded delta systems, at all, period. But again, you have a corner grounded delta system so that's fine. They do make a reference to issues with control circuit isolation on corner grounded 400-500VAC systems, but no issue mentioned on a 240V delta. I would not worry about it, but don't buy into the "kit" concept, tell them you want a 240V drive, or just use a 480V drive. Apparently the problem is that Master PT does not package this system with anything other than a 480V drive and motor, but trust me, they could do it for 240V, you just have to find the right person and the one you spoke to is not the guy.
 
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