Motor with SCR Drive

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augie47

augie47

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State Electrical Inspector (Retired)
I have a 300 HP motor on a baghouse with a control cabinet. Based on the contactor, I thought it was a across the line starter however I behind the control board I can see some heat-sinks and SCR notation.
It's an older drive and the only nameplate info is 360 amps input and 300 HP output.
My initial reaction was to check Code compliance per 430.122, however, it does not seem to be a true "variable speed drive".
In this situation where there is obviously some sort of soft start, should the conductors be sized at 125% of the drive nameplate and the disconnects at 115% drive nameplate & 300 H P rated ?
Previously the install was connected with a 400 amp fusible disconnect and 500 kcmil which seems undersized based on motor rules.
 
augie47 said:
I have a 300 HP motor on a baghouse with a control cabinet. Based on the contactor, I thought it was a across the line starter however I behind the control board I can see some heat-sinks and SCR notation.
It's an older drive and the only nameplate info is 360 amps input and 300 HP output.
My initial reaction was to check Code compliance per 430.122, however, it does not seem to be a true "variable speed drive".
In this situation where there is obviously some sort of soft start, should the conductors be sized at 125% of the drive nameplate and the disconnects at 115% drive nameplate & 300 H P rated ?
Previously the install was connected with a 400 amp fusible disconnect and 500 kcmil which seems undersized based on motor rules.
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I think it is probably a soft start of some sort. It should be handled just like a conventional MS IMO.
 
Going to assume you know for sure its an AC motor, not DC.

Baghouse fans means it's likely a 99% chance it's soft starter. If it were an old SCR based AC drive, you would see a big transformer associated with it, and/or a big stack of capacitors. If not, it's a soft starter and petersonra is right, you treat it like any other motor starter circuit. The contactor is likely a bypass contactor so that the starter can be in a sealed enclosure, like NEMA 12.

A 400A fused disconnect may be fine actually if it is part of a factory built starter and it was UL listed that way. Can't comment much on the conductors because you don't say if those are feeders, motor leads or internals from the fused disc. to the soft starter and bypass contactor. If they are internals, and again this is a factory built UL listed starter, they might be fine. Slightly different rules apply compared to field installation conductors.

If you post a mfr name or model number I can probably tell you what it is.
 
Thanks, guys.

Jraef: The only legible name (I'm sure you've seen foundry bag house electrical :D ) is "Safetronics"
"
 
Saftronics (no "e", it was originally South African Electronics) no longer makes soft starters since being bought by Emerson, they just brand-label them from Australia now. But they never made SCR based drives, so it is for sure a soft satrter (again, assuming it's not DC, because they did make DC drives).

When they did make soft starters, they would have been UL listed, so any internal wiring issues would not need to be further deliberated, unless you just flat out don't agree with it and want to change it, which is always your perogative.
 
Thanks.
My concern was with the field wiring. I was jsut wondering if this type controller fell under Art 430 Part X.
Issues have been resolved.
(Somewhat interesting side note: I was somewhat surprised to see the 400 amp fusible disconnect on the operating system had been sufficient for the 300 hp motor. On further investigation, the 400 amp 480 disconnects contained 600 amp 240 fuses.:D.. they fit )
 
Jraef said:
Saftronics (no "e", it was originally South African Electronics) no longer makes soft starters since being bought by Emerson, they just brand-label them from Australia now. But they never made SCR based drives, so it is for sure a soft satrter (again, assuming it's not DC, because they did make DC drives).
Click to expand...
A blast from the past. Bonne Posma, I think, had something to do with it. As charming a fellow as you'd care to meet in a month of Sundays.
 
Besoeker said:
A blast from the past. Bonne Posma, I think, had something to do with it. As charming a fellow as you'd care to meet in a month of Sundays.
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Yep, met him a few years ago (well, maybe more than a few). He backed out of Saftronics long before the Emerson buy out. I think he made the most out of that deal, it had gone down hill quite a bit after he backed away to pursue his traction vehicle drives for fuel cell powered vehicles. You're right, really nice guy.
 
Jraef said:
I think he made the most out of that deal, it had gone down hill quite a bit after he backed away to pursue his traction vehicle drives for fuel cell powered vehicles.
Click to expand...
Saminco maybe?
We had some dealings with the guy when we were making four quadrant DC drives.
 
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