bad power

[goontron]

Re: bad power

If you got 135V on both legs, at the same time, either primary voltage too high or wrong tap selected. Probably the former, since taps don't change by themselves- if the tx were to be shorting changing the ratio, it would be more "interesting," as skystorms' adventure has shown.


OTOH, if you've got 135-0-105, watch out! The single-phase (center tapped tx) service has a bad neutral- anywhere from the tx to the building.

Haven't I repeated myself enough???

no, no bad neutral here, just came back from the elec. service room..... 140v each phase on the big fuses the size of your head. oh and im the last one without one of those "smart" meters too. the individual disconnects to each apartment is zinsco..... no wonder it smells like ozone in there

the transformers were put in last year so it could be a wrong tap on them BTW

[kaboom]

Re: bad power

the transformers were put in last year so it could be a wrong tap on them BTW

Three, perhaps?

A- Three, with the center one being larger
B- Two, with one being larger
C- Three, all the same size
D- Two, both the same size

A is a delta, B is an open delta.
C is Y (208Y/120), D would be the same voltages, but single phase only (open Y).

There could also be several single phase center tapped txs as well.

http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
http://www.allaboutcircuits.com/vol_2/chpt_10/5.html

[goontron]

Re: bad power

Three, perhaps?

A- Three, with the center one being larger
B- Two, with one being larger
C- Three, all the same size
D- Two, both the same size

A is a delta, B is an open delta.
C is Y (208Y/120), D would be the same voltages, but single phase only (open Y).

There could also be several single phase center tapped txs as well.

http://www.allaboutcircuits.com/vol_2/chpt_10/1.html
http://www.allaboutcircuits.com/vol_2/chpt_10/5.html

[momaka]

Re: bad power

wholly thread revival batman!

Meh, nothing new here. RJARRRPCGP regularly does this. The Jesus Christ for threads .

(Sorry RJARR, nothing personal here... just pretty late here and for some reason I feel playful rather than sleepy).

[Elysarian]

Re: bad power

this thread reminds me of trying to explain to a farmer what was wrong with the supply to his new stable block...

we installed cctv in there to protect his thoroughbred horses an the power supplies kept failing, I was called in to sort it out and found that the neutral was floating (toward one f the phases) - meant he had 50v p-n on one side but close to 400v on the other two (our cctv happened to be on one of the high ones).

[SeanB]

Re: bad power

Had the minisub across the road do a dump one night at around 9, loud hum then bang and instant grill, fired by burning GRP housing. Called metro and reported it, and the fire brigade came and put out the fire and cut the jungle so the metro could get to it. They closed the road and brought in a crane during the night to lift the old cooked one off the base and replace it with a spare 100kVA unit. I still have the inside lamp, cooked black from soot, but still working.