There is a need to do troubleshooting of large vfd inside their cabinets at times. We have six 500 amp breakers in our switchgear for the vfd's. Some have 2 some have 3 vfd's on a breaker. Each vfd also has its own breaker inside its cabinet. Would a maintenance switch at the switchgear breaker be a practical solution for work being done inside a vfd cabinet ? Would there be a disavantage to the other vfds ?
MAINTENANCE SWITCHES
- Thread starter jimbo123
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zog
Senior Member
- Location
- Charlotte, NC
Perhaps, but not enough info for us to say. I would consult with whoever did your arc flash study.
mayanees
Senior Member
- Location
- Westminster, MD
- Occupation
- Electrical Engineer and Master Electrician
If attention was already paid to minimizing the incident energy level associated with either case, two or three VFDs per breaker, then a maintenance switch may not provide much improvement.
This is to say that VFD current is typically limited to something under 200% of the motor fla, or even less, and the instantaneous tolerance may already be adjusted for that, leaving little room for improvement.
If incident energy wasn't optimized in the Study that determined the existing IE level, and for example they allowed across-the-line starting current tolerance, that incident-energy minimization adjustment would be the first step, and may get the HRC to an acceptable level.
As Zog stated, start with the Power Study.
John M
This is to say that VFD current is typically limited to something under 200% of the motor fla, or even less, and the instantaneous tolerance may already be adjusted for that, leaving little room for improvement.
If incident energy wasn't optimized in the Study that determined the existing IE level, and for example they allowed across-the-line starting current tolerance, that incident-energy minimization adjustment would be the first step, and may get the HRC to an acceptable level.
As Zog stated, start with the Power Study.
John M
It would be a great benifit for us to be able to speak to the engineer who conducted the study and ask questions concerning their findings and some of the recommandations he made. Being one of the electricians and not part of the mamagement team we are excluded from all communcations with the study firm, everything goes through management . So when it comes down to it someone at our company location will give his intupertation. You can rest asure he has zero electical or mechanical knowledge.
We realize there is more to following the labels on the equipment.
Being able to post here helps us a great deal with our jobs as we are not out in the field anymore so we post and wait for seminars
to pickup information about different issues in the trade.
Thanks for the advice and help.
We realize there is more to following the labels on the equipment.
Being able to post here helps us a great deal with our jobs as we are not out in the field anymore so we post and wait for seminars
to pickup information about different issues in the trade.
Thanks for the advice and help.
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