# vfd start-up



## SWDweller (Dec 9, 2020)

You've read enough specs in your area, where would this have come from? 
I remember a EE that used to spec all conduits to slope to a rigid ell and then drill a 1/8" hole for drainage. I ignored it and got caught. I then asked through channels where in the code that was mentioned. The issue went away. I did not bid any of that engineers work for almost a year.

Or better ask for the engineer to show you how to do the test with out hurting the equipment or violation of local safety concerns. Has a fault study been done, and coordination preformed.

Not fair that he has the good stuff and does not share


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## gpop (May 14, 2018)

SWDweller said:


> You've read enough specs in your area, where would this have come from?
> I remember a EE that used to spec all conduits to slope to a rigid ell and then drill a 1/8" hole for drainage. I ignored it and got caught. I then asked through channels where in the code that was mentioned. The issue went away. I did not bid any of that engineers work for almost a year.
> 
> Or better ask for the engineer to show you how to do the test with out hurting the equipment or violation of local safety concerns. Has a fault study been done, and coordination preformed.
> ...



Its a test done (pre feb 2022) on drives for a UL508C certificate i think. Some dumb arse engineer cut and copied the test used by UL and added that as a start up test. 
Could have been worse if the idiot had of copied the new UL testing standards then wanted us to short all the front side components. 

On a good note its nice to know that a drive can take that sort of abuse at least 3 times. Might not take a 4th


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## Almost Retired (Sep 14, 2021)

F---ing IDIOTS


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## splatz (May 23, 2015)

gpop said:


> Its a test done (pre feb 2022) on drives for a UL508C certificate i think. Some dumb arse engineer *cut and copied the test used by UL *and added that as a start up test.
> Could have been worse if the idiot had of copied the new UL testing standards then wanted us to short all the front side components.
> 
> On a good note its nice to know that a drive can take that sort of abuse at least 3 times. *Might not take a 4th*


I think that's true, something about the IGBTs in the drive can only take so much abuse, like the MOVs in surge protectors. There are a lot of tests UL does that are not suitable for commissioning, they don't have any intention of returning the drive to service after the torture tests. Wouldn't you void your warranty if you deliberately faulted the load side? Even if it survives, it may not be suitable to return to duty. There may even be something to that effect in the drive manual fine print.

So you could commission your drives, have a party, everyone pat each other on the back, but the next day you 'd have to replace all the drives, commission them again, party, lather, repeat. It would be like groundhog day with commissioning day but you never get to production day.


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## MotoGP1199 (Aug 11, 2014)

Hahaha, this literally made me laugh out loud. What an idiot. That is definitely a direct copy/paste from a standard.

You should hand the EE some dish washing gloves and sunglasses. Ask him to show you how to do it.


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## micromind (Aug 11, 2007)

I wonder if they would require testing of a fuse this way........


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## 460 Delta (May 9, 2018)

micromind said:


> I wonder if they would require testing of a fuse this way........


Why certainly, how else will you know if it will clear on a hard fault?


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## gpop (May 14, 2018)

micromind said:


> I wonder if they would require testing of a fuse this way........


Haven't seen it in the 700 page electrical document but i know they wanted breakers tested to full AIC until it was explained that the breaker was only rated to do that once in its life and then it was scrap. 

All ground connections are to be cad welded . Going to make wiring the motors a lot more fun let alone the plc.


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## Almost Retired (Sep 14, 2021)

did they leave out the words grounding grid to building steel ?
you may want to go have a _reality check_ with the "engineer"


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## paulengr (Oct 8, 2017)

I would subject a drive to that no problem. Just install the correct size semiconductor fuses in front of it. Semiconductor fuses are rated based on the total let through energy.

When you file under UL for product testing you send them 3 drives for every size you are going to sell. You may get them back but in questionable condition.

Breakers would not normally but can be tested at AIC at least at lower AIC ratings. There is a huge difference between 35 kA at 1 V compared to 480 V. And that’s assuming you can get there. When you are testing impedance limits how much you can push. On a 40 kA tester (4000B) if I can only connect to the breaker with #1 AWG cables I’d be lucky to exceed 2-3 kA.


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## JRaef (Mar 23, 2009)

UL has required VFDs to have motor short circuit protection built-in since I think around 2005, because it came up that there can easily be a big discrepancy between the VFD line side SC protection and the size of the motor, meaning the motor was not being properly protected by the line side fuses or breaker. But in the UL testing standards, it only had to be able to do it (I thought) 2 times, not indefinitely, and if the VFD FAILED on the 2nd shot from the standpoint of the transistors blowing out (i.e. _becoming _the fuse), that was OK, so long as the motor was no longer getting power. But adding that to the field acceptance test is ludicrous! 

I once built a huge motor control system for complex overhead cranes at a government nuke facility in Idaho. It was being operated under contract by Westinghouse at the time, and we used all Westinghouse breakers. As part of the acceptance tests, they did current injection testing of all of the motor circuit protectors in the starters to make them trip at 1700% of the motor FLC. Every single breaker (there were over 100). About 10% of them "failed" by their criteria, because if it took longer than 1 second to trip, *three times in a row*, they considered that a fail. We had to tell them that expecting an MCP to trip 3 times in a row was unrealistic, but that was their criteria. Turned out they were getting that from the NEMA design specs. We had a WESTINGHOUSE engineer from the CB department write them a letter stating that it was a test procedure on the DESIGN, not for each individual breaker, and the breaker was NOT required to survive the test and be useable. So finding out that they had tested ALL of the breakers this way, Westinghouse (CB group) told Westinghouse (nuke operating group) that all of those breakers would NOT be covered under warranty! We had to replace them all at their expense...


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## paulengr (Oct 8, 2017)

Westinghouse MCPs are an interesting design. They used the then little known Klochner Moeller current limiting “hairpin” inductor design to keep the current low during tripping. I’ve heard it current limits at 10x rating so you must have really lit it up to generate enough prospective current to hit17x.


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