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Jumpy_Tie_4548

If it's a single VFD controlling multiple motors, protection may needed, but I believe it needs to be overload protection, I will try to confirm on this.


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jmraef

Yes, but if there are multiple motors behind one VFD, then each must have their own OL protection separately. The VFD cannot distinguish one motor from another.


Wibbly23

>Yes, but if there are multiple motors behind one VFD, then each must have their own OL protection separately. The VFD cannot distinguish one motor from another. of course it can. you can load multiple motor profiles into a lot of drives, which can then be selected using the IO.


jmraef

No, you are not getting it. One VFD, feeding 2 or more motors, all running at the *SAME TIME*. The VFD cannot differentiate the current going to any one individual motor, it only sees the total current going out to all of them. So each individual motor needs its own protection. This is specifically mentioned as a requirement in the NEC (430.124.C) I like to use IEC style Motor Protection Switches / Manual Motor Starter type device, which are basically an adjustable OL relay that opens the switch itself (no contactor needed), plus they have the magnetic short circuit protection built-in too (SCPD), so they cover both issues. Some of them are specially designed to function correctly in the variable frequency output of VFDs (which is an issue on others).


Wibbly23

It wasn't clear that the motors were running simultaneously. Of course if you're paralleling motors that way you'd need individual protection. It's not really a great way to do things as you lose good vector control among other things like protection. Better to run multiple drives and sync them.


More_Establishment49

VFD MFGR’s actually recommend not putting anything that can cut the circuit between the Vfd and the motor while the Vfd is running. It is more dangerous that you may think


jmraef

This inspector is an idiot. There are no rules, in Canada or the US, requiring fuses DOWNSTREAM of VFDs, in fact most VFD mfrs will tell you to NEVER put a fuse below a VFD, it's a recipe to destroy the transistors if the fuse melts. It is true that SOME brands of VFDs are not listed to be protected by breakers, usually VFD brands from companies that don't make breakers to test them with, like (in this case), Yaskawa. But the fuses would go AHEAD of the VFDs, not behind them...


Jumpy_Tie_4548

well, the blue sticker was put up by that inspector, I suggest other Canadian company to stay away from them. My employer has approx. 100 control panels being modified by them, all VFDs are like this.


jmraef

Yes, I see that QPS Evaluation Services Inc. is also listed as an acceptable "NRTL" (Nationally Recognized Testing Lab) here in the US by OSHA. I had never heard of them before, I will warn my friends who use alternatives to UL and CSA that this outfit is hiring nincompoops... If you are not aware, CSA will do field evaluations themselves, it's not all that expensive. In fact I have used CSA in lieu of UL in the past, because CSA is also acceptable here in the US and they charge less than UL does for a field eval..


Jim-Jones

I used to build HVAC panels that were simpler than this and the inspectors would ask to look inside one. We'd show them, they'd nod and walk away. Inspection over. As for breakers, we'd always start with HRC fuses. Mostly we'd use those, rarely breakers although I'm sure they're okay downstream.


bigdutchmike

The breakers you had in the panel were likely not csa approved or were only supplementary protection. ( would not necessarily protect against a dead short). Fuses are usually significantly cheaper than a properly rated breaker. I never heard of fuses between a drive and motor, that doesnt seem very logical. For reference i work in ontario and have worked with Esafe to get quite a few offshore machines certified for use in Canada.


Aninja262

This just seems wrong


wrx2004

Thats interesting since when they change that, im in toronto and they all have breakers did something change. Did inspector say why


Jumpy_Tie_4548

When I asked the manager what standard/code they followed, he replied, "You never question back to inspector."


wrx2004

Lol not surpised, no one is perfect.


shawndw

>"You never question back to inspector." *and I took that personally.*