230 VAC 3 Phase???

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mbrooke said:
Paging Jraef in 3, 2, 1...
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Hey, a guy’s gotta work some time...

jumper said:
IIRC, VFDs like wye not delta. But unsure.
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True, all VFDs are designed around a Wye system. There will be protection devices on the incoming line rectifier (MOVs) that are in a Wye pattern and referenced to ground. When connected to Delta sources, their ground connection will attempt to become the Wye point for the entire system and the first time there is a ground fault anywhere on that system, unrelated to the drive, the current will want to flow through that connection in the drive until it vaporizes the MOV, which will damage the drive. Some drives give you a way to disconnect that ground reference, some do not. RTFM, but understand that some of those that do not simply say something like “This drive is suitable for use only on an IT system...” or words to that effect. That’s an IEC terminology that means nothing to people here, but is referring to a solidly grounded Wye system. So anything that is NOT a solidly grounded Wye system is not suitable to use that drive on, which is basically any 240V system here (208V would be Wye). This is what you will see on a lot of Asian drive designs. It’s a coward’s way out in my opinion. They word it in a way that nobody understands, then when the drive tries, they say “Told you so!” and you are stuck with it.
 
Jraef said:
... all VFDs are designed around a Wye system. ...
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This question has come up often enough, and there are enough corner-grounded and high-leg systems out there, that it seems like someone, somewhere, would offer a compatible VFD. No?

One of my favorite things, ever, has to be telling the client they needed to find space & money for an isolation transformer when they thought the installation was complete. I don't remember the specs but I do remember the transformer was about the size of a Volkswagen microbus. (indoor installation)
https://www.youtube.com/watch?v=0IagRZBvLtw

On the other hand, it takes me about three minutes to diagnose the problem (it's one of the first things I look for) and I eventually look like a fartin' genius. A lot of the younger guys have never seen nor heard of a CG or HL service.
 
For the most part, drives designed BY and FOR North America address this issue, but delta power systems only exists here, so when EU and Asian based companies come here to peddle their wares, some of them don’t bother to adapt to our way of doing things. When I used to work for Siemens and we would gripe about issues like this, the response from Management was always something to the effect of “Well, North America is such a small percentage of our world wide sales, that we don’t need to change our products to address every little whim of yours.” Used to grind my gears over that...

On the original Siemens Micromaster Drives (my era with them), we in the US issued a “supplemental” instruction sheet with drives ordered here that told customers how to disconnect that ground reference. It involved disassembling the Front End of the drive to get access to the connection, then cut the green wire and tape off the ends. That went over like a lead balloon with customers ... I’m not sure if their newer drives are still like that, but it wouldn’t surprise me. Rockwell on the other had gives you a simple jumper to pull off or move. ABB, although foreign owned, build their US version drives here so they have a simple way to do it too. Those are the only ones I’ve ever had to do this on, but the subject has come up on Yaskawa and Mitsubishi drives, both of those are ones that tell you that you just can’t use them on anything other than “IT systems”. So in both cases I had to eat those drives and replace them.
 
Jraef said:
Hey, a guy’s gotta work some time...


True, all VFDs are designed around a Wye system. There will be protection devices on the incoming line rectifier (MOVs) that are in a Wye pattern and referenced to ground. When connected to Delta sources, their ground connection will attempt to become the Wye point for the entire system and the first time there is a ground fault anywhere on that system, unrelated to the drive, the current will want to flow through that connection in the drive until it vaporizes the MOV, which will damage the drive. Some drives give you a way to disconnect that ground reference, some do not. RTFM, but understand that some of those that do not simply say something like “This drive is suitable for use only on an IT system...” or words to that effect. That’s an IEC terminology that means nothing to people here, but is referring to a solidly grounded Wye system. So anything that is NOT a solidly grounded Wye system is not suitable to use that drive on, which is basically any 240V system here (208V would be Wye). This is what you will see on a lot of Asian drive designs. It’s a coward’s way out in my opinion. They word it in a way that nobody understands, then when the drive tries, they say “Told you so!” and you are stuck with it.
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Thanks :)

BTW, IT means isolated terra or an ungrounded neutral system.

TN is solid ground

TT is solid ground but the earth is the EGC between the structure and utility.
 
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