chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Do any VFD manufacturers make VFD’s that will operate on a corner grounded system?
Thanks
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Thanks
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Corner grounded delta and VFD’s
- Thread starter chris kennedy
- Start date
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The drives usually give you the option of floating the drive front end. There is a removable grounding screw. But imo you would be asking for trouble trying to do that.
Consult the drive manufacturer and if they warn you away from that, that's good advice. A cheap small throwaway drive it may run and not matter too much. But a large expensive one, it's by nature looking for a grounded Y supply to run at the manufacturer's expected reliability, with the factory grounding screw properly installed.
Consult the drive manufacturer and if they warn you away from that, that's good advice. A cheap small throwaway drive it may run and not matter too much. But a large expensive one, it's by nature looking for a grounded Y supply to run at the manufacturer's expected reliability, with the factory grounding screw properly installed.
- Occupation
- Licensed Electrician
I believe SqD does.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Elsewhere in the world they don’t use delta power systems, so drives are not designed for that inherently. It’s something to be VERY careful about because it could end up putting the warranty burden on you.
For the most part, the major players who serve North America, like A-B, ABB, Schneider, Eaton, Toshiba, Siemens and Danfoss will have installation options for adapting their drives for delta power sources. But there may be consequences of using those options in terms of eliminating some protective elements and requiring that you add others back in, such as SPDs and GFPE. In some cases it may void their UL listing and/or their warranty. You have to check up front.
Some of the smaller, mostly Asian players tend to pretend the issue doesn’t exist, but will bury a “CYA” statement in their instructions somewhere telling you that the drive can only be used on a solidly grounded wye system, however they often use IEC terminology that we (North Americans) have never heard of.
For the most part, the major players who serve North America, like A-B, ABB, Schneider, Eaton, Toshiba, Siemens and Danfoss will have installation options for adapting their drives for delta power sources. But there may be consequences of using those options in terms of eliminating some protective elements and requiring that you add others back in, such as SPDs and GFPE. In some cases it may void their UL listing and/or their warranty. You have to check up front.
Some of the smaller, mostly Asian players tend to pretend the issue doesn’t exist, but will bury a “CYA” statement in their instructions somewhere telling you that the drive can only be used on a solidly grounded wye system, however they often use IEC terminology that we (North Americans) have never heard of.
Jraef do you ever see 240Y/139 or 220Y/127 systems used for VFD's instead?
I have noticed South America uses 220Y/127 (a ANSI C84.1 range B) allot, which might still be in spec for standard 120/240 'loadcenter' type breakers.
What voltage is the corner grounded system 240V?
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chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
No, 480V
Reverse fed transformers with 480 delta primaries now the secondary
I have 3 facilities with these systems
Currently serving old equipment but owners are contemplating new
Been pricing 240V primary 480y/277V secondaries
150kVa $6000
Reverse fed transformers with 480 delta primaries now the secondary
I have 3 facilities with these systems
Currently serving old equipment but owners are contemplating new
Been pricing 240V primary 480y/277V secondaries
150kVa $6000
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
When you buy a 240V “drive isolation transformer”, the secondary is 240Y139.
You can also buy 480V drive isolation transformers, 480D to 480Y277. Using one of those also eliminates the need for a line reactor, so if you were planning on a LR, just substitute it with the DIT.
Jpflex
Electrician big leagues
- Location
- Victorville
- Occupation
- Electrician commercial and residential
Corner grounded Delta transformer systems are known to confuse people. According to mike holt one random? corner phase is to be grounded and bonded to the case of the transformer. Apparently, code requires this conductor to be phased white or gray but many People outside of code apply alternate color tape to the conductor because this is also a point of phase potential? Apparently this is safe but confuses people. I can see that bonding this phase to the case will give the transformer the same potential to this phase conductor and ground thus eliminating shock potential between these points? However, this is still a voltage generating point? I don’t fully understand this yet?
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Isolation transformers are my go to in these situations.
In my current position my customer is considering replacing 3 antique’s with new CNC’s fed from one panel board.
That’s why I’m looking at one 150kVa transformer ahead of the panel board in question.
My OP was a long shot inquiry into the possibility of ordering the new CNC’s with VFD’s that would work on a corner grounded 480 delta.
Thanks all
In my current position my customer is considering replacing 3 antique’s with new CNC’s fed from one panel board.
That’s why I’m looking at one 150kVa transformer ahead of the panel board in question.
My OP was a long shot inquiry into the possibility of ordering the new CNC’s with VFD’s that would work on a corner grounded 480 delta.
Thanks all
- Occupation
- Licensed Electrician
A grounded corner is just a grounded conductor. A grounded neutral is just a grounded conductor. See if this post from Larry Fine helps. It's not about corner grounded but it is the best explanation of the neutral I have come across and if that makes sense to you then corner grounding should also.
https://forums.mikeholt.com/threads/understanding-the-neutral-conductor.140537/
Jpflex
Electrician big leagues
- Location
- Victorville
- Occupation
- Electrician commercial and residential
Doesn’t make sense because a neutral or ground connection is made at the end (Load side) of a coil (secondary winding) while the Phase line voltage begins at the top of the coil (secondary winding)
electrons apparently don’t want to take path of coil (secondary) which would be shortest path top to bottom of coil (secondary) but want to travel out top of coil then through load and return to bottom (farthest path ) of coil or (secondary) and reverse on alternate cycle.
Placing a wire at the corner or top of coil where current electrons are ready to travel as explained above makes no sense for safety or place to make a bond or ground connection.
electrons apparently don’t want to take path of coil (secondary) which would be shortest path top to bottom of coil (secondary) but want to travel out top of coil then through load and return to bottom (farthest path ) of coil or (secondary) and reverse on alternate cycle.
Placing a wire at the corner or top of coil where current electrons are ready to travel as explained above makes no sense for safety or place to make a bond or ground connection.
I do not think it matters. The 3 phase input supplies a small control transformer then power goes directly to rectifier that supplies the DC Buss . With 480 volts the DC Buss is usually between 655 to 675 volts. Would clear it with the drive manufacturer. Starting around 100 HP drives some drives will have a small single phase transformer with no primary fuses feed off the 480 volt input to supply power to 220 volt cooling fans.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
When it comes to drives that are designed for wye systems with equal voltage to ground on all three input lines, use on any delta system becomes an issue. Ungrounded delta has capacitive effects that may put voltages all over the place, corner ground has full line to line volts to ground on two lines, a high leg delta has about 87% of line to line volts on one leg to ground.
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