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Joined: Mar 2005
Posts: 1,213
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I'm really surprised how much of a difference can be made by removing the neutral bond, I never would have guessed it would be this dramatic.
This generator has been on-site for about 6 weeks in this condition, I'm surprised nothing bad has happened.
Thanks for the responses!
Shawn.
p.s. the gen-set was feeding a single phase panel so C phase was not being used
If the system is balanced but the neutral is unbonded, there is still some natural capacitance to ground and small amounts of leakage current, etc, and the system will generally float close to ground. If the system is highly unbalanaced, though... like if you take a 3-phase generator and only use 1-phase, though, it will float well off ground, creating dangerous voltages. I'm glad nobody got hurt!
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Joined: Aug 2002
Posts: 402
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Not to mention the Fpe panel, you are asking for a fire. you're lucky it was isolated to one receptacle FPE panels are very common in Canada. We don't have the issue the USA panels had.
Last edited by jdevlin; 02/25/08 10:56 AM.
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Joined: Jul 2007
Posts: 85
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My concern was the unbalanced load. possibly putting an un due strain on the motor, and cutting its expected life. Also I'm not disagreeing, but did Fed pacific use all the quality panel parts in Canada and ship the bum ones throughout the U.S ?? I've witnessed a 20amp 277volt short dead to ground and the breaker never tripped, it welded the mc jacket to the ceiling grid and made some bad burn marks? I don't know why nothing tripped? but it got my attention. and I always triple check Fp breakers cause some in my expierience don't snap open when you shut them off. Just my2 cents.
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Joined: Oct 2007
Posts: 56
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At work this morning the site super told me that he is really surprised that there have been no problems with the generator since Friday. Three whole days! Before the bonding jumper was installed, the gen-set's electronic controller would shut the power off due to over-voltage, under-voltage, and other improper readings. This would sometimes happen several times a day.
As far as FPE being reliable up here; I wouldn't want to be in a situation where the only thing protecting me from harm is a FPE breaker.
I'm not sayin', I'm just sayin'.
Shawn.
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Joined: Mar 2005
Posts: 1,213
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My concern was the unbalanced load. possibly putting an un due strain on the motor, and cutting its expected life. Most 3-phase generators are designed to handle 100% imbalance, but must be derated; you're not going to get 50kW out of a 50kW 3-phase generator if you only use one phase, you're going to get about 28kW. The engine doesn't care, and the generator is just cables on a rotor, which is still balanced from an electromechanical standpoint. There's really nothing electrically or mechanically damageing about it aside from running the engine at less than half load all the time, and all the bad things that happen when you run a lightly loaded diesel engine too long.
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Posts: 21
Joined: September 2019
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