All,
I have a motor (of which I do not have a nameplate to verify HP rating), which belongs to a process. The process owner wants to purchase a new motor, but with no nameplate, we are unsure of what to purchase (a new motor was purchased at one point and it turned out to be wrong). The motor...
Hi All,
Can anyone recommend some good references for the subject line topic? I'm mostly thinking about motor selection, but any references are appreciated.
Thanks,
Mike
Mike
Hi All,
I'd like to get some feedback on what others have done in regards to the rebuilding/rewinding of motors, sizes 25HP and above. In my opinion, meggering is not that great a test. Are there any other tests you all do? Do you even bother rebuilding motors of this size? In my former...
Hey All,
I didnt' think about it much, but IEEE red book does not give any guidance about the inclusion of single phase motors in fault calculations. Am I missing something,...any reason for this?
Mike
Hi All,
What are your thoughts on this for Low Voltage systems? Is this a concern for phase conductors? Is it a concern for equipment grounds? Can anyone direct me to some papers concerning this? I looked in the Buff Book, but I'm not satisfied with the discussion. If there are any rules...
Hi All,
While I'm still very much learning about this subject, as I look in the standard, there's no talk of ground fault settings for breakers. Probably an ignorant question, but why?
Mike
All,
I just want your view on an installation challenge. I have an existing generator system (13.2kV), and I need to install a new UPS system on it. However, I do not have a spare output breaker, so do you think it's wise to use an existing breaker, and "double-lug" so to speak on it to feed...
Does anyone find this new section a bit confusing as I do?? It talks about the "grounded conductor", but the tables referenced are the "equipment grounding conductor".
Mike
Hi All,
I have a situation, where I'm looking at adding a 4th gen., to an existing system because of increased, anticipated load. The only problem is, my initial studies indicate that I would exceed my existing fault current levels. My thought is to add the 4th gen, and put a current limiting...
All,
I wondered if anyone on this forum has used this device: http://www.investek.org/products/PhaseLiner_tech.htm
We had a local rep. come in and present this to us. The idea is to put these on our Computer Room AC units (easily a couple hundred units or more when this is all said and...
All,
I have a test report for a 1800kW, 600V diesel gen. set and the Ta for this gen. is .0004 seconds. That seems awfully fast, considering some of the other units that I have data sheets for are around .05 to .07. Does this seems strange to anyone else??
Mike
Gents,
I have an issue w/ a 2000HP chiller, and wondered if I could get some insight. Originally, the chiller was fed by a 2000kVA, 4160V substation, that was about 30 yrs. old. We then replaced the substation transformer with a new one (I think the only change may have been the new one had a...
Hi all,
Does anyone know what the IEEE median life expectancy of a motor control center is?? Let's just assume normal useage and maintenance.
Thanks,
Mike
All,
Is there an IEEE standard that says, TYPICALLY with ongoing maintenance and normal use, a unit substation, dry type transformer(from 1000kVA to 5000kVA) is End of Life after??? I seem to recall a figure of 30 years, but I'm not finding it.
Mike
With today's advent of power factor correcting power supplies, I wondered how many of you out there(that have raised floors and UPS backup), have seen increasing leading power factor? I have heard of static UPS's dumping the critical load once the power factor starts to go leading.
Mike
http://www.ieee-pcic.org/Subcommittees/safety/2000agenda.htm
I know there has been some discussions about arc blast calcuations, etc. The above link will take you to a Power Point presentation done by Dick Doughty. It's very good, and it's what I used to base my calculations on. I hope it...
Gents,
I just want a sanity check. Say I have a 3ph bolted fault on the secondary of a unit substation ahead of it's secondary main. The primary is protected by a current limiting fuse. Will the fault be cleared by the primary fuse(this is assuming of course there is enough fault current...
Hey All,
Wanted to know if anyone on the forum has run across motor bearings pitting because of bearing currents caused by common mode voltages from VFD's. I've a situation at my plant where this phenomenon is occurring. We've decided on shaft grounding kits to alleviate this problem. Any...
Hey guys,
In the new NEC, it states in section 695.4B, that overcurrent protection between a standby gen. and fire pump controller shall be selected to provide short circuit protection only. Does this imply that one could use an MCP to protect the circuit from short circuit events?
