Transformer problem.

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CIECO

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I know this is a NEC blog, but we seam to have some brite people here. I have a small commercail building with 2 30 HP hydrolic elevators. The elevator company started up elevators today and I got a call from from one of my guys that when they start the elevators the temp lights go out. I took a ride over and checked it out, I have a 800 amp 480 volt service and feed a 300 kVA transformer and the lights an phase A go out for a second phase B blink a bit and phase C looks good. checked the voltage and currant and at 208 start up the voltage drops to about 160 AB and 190 BC the currant looke even and the top of the swing of the analoge meter was about 175A. Opened the transformer checked the pri voltage and was rock solid, phase A to ground was 90 phase B 120 phase c was 122 and with out the start up all were 122. Took the reading with a Fluke scope meter set for voltage trend.
Checked the taps all the same and all tight The Y is welded solid, and I have no clue? any buddy have any ideas.
 
Check all your connections from the primary feeder source to the secondary connections. Also, what is does the voltage do on the line side of the transformer on start up? Check that and check your loads during start-up. Usually, the more information you get, the clearer the picture is.
 
Are your neutral and ground bonded together on secondary side? Not trying to be insulting...I forgot once and a short in a light fixture gave me all kinds of crazy symptoms.
 
CIECO said:
Opened the transformer checked the pri voltage and was rock solid, phase A to ground was 90 phase B 120 phase c was 122 and with out the start up all were 122. Took the reading with a Fluke scope meter set for voltage trend.
Checked the taps all the same and all tight The Y is welded solid, and I have no clue? any buddy have any ideas.
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Little confused. You said the primary was 480 volts.
 
Have you had the transformer TTR'd, meggered?

Or did you check the ratios of each coil unloaded?

Checked the tap settings.

What is the unloaded voltage. Phase to neutral

What is the loaded voltage. Phase to neutral

IF YOU HAVE A BAD COIL PHASE TO NEUTRAL IS THE BEST WAY TO ISOLATE THE ISSUE.

Do you have access to a load bank or can you use the elevators for step loading one operating then the other.

Check primary and secondary simultaneously.
 
From what I can figure I have phenomenia known as a bad transformer. Will be calling Siemens on monday.
 
Quote: "Opened the transformer checked the pri voltage and was rock solid, phase A to ground was 90 phase B 120 phase c was 122 and with out the start up all were 122"

I assume these numbers are for the secondary side because they are way out for a 480V primary. The 90V on phase A to ground/160V A-B is suspicious and I'd bet that the A phase primary winding is open somewhere. Did the manufacturer clean the epoxy off of the tap on the A winding? One more test you could do is to open the primary disconnect and check continuity through each primary winding.
 
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CIECO said:
From what I can figure I have phenomenia known as a bad transformer. Will be calling Siemens on monday.
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I usually try yo know the reason before I call the manufacture for warranty issues that way you can be ahead of the game. You be surprised how many electricians and factory people know less that you may and the proof is when they try to snowball you with BS.
 
It has continuity its drawing currant on phase A. I have seen taps burn off of transformers and this is what it acts like but I checked the taps they are striped and tight. I checked all the lug pads for bad welds and I can not see how the turns in a new transformer can be shorted. Plus no load all three phases are the same so I do not believe there is a turn to turn short.
 
I have seen issue with the primary xfmr that is supplying the 480 having a problem from the utility, Have you ruled that out as an issue ?
 
CIECO said:
From what I can figure I have phenomenia known as a bad transformer. Will be calling Siemens on monday.
Click to expand...

You havent figured out anything yet, or done any real testing/troubleshooting. Try answering the best questions asked so far
brian john said:
Have you had the transformer TTR'd, meggered?

Or did you check the ratios of each coil unloaded?

Checked the tap settings.

What is the unloaded voltage. Phase to neutral

What is the loaded voltage. Phase to neutral

IF YOU HAVE A BAD COIL PHASE TO NEUTRAL IS THE BEST WAY TO ISOLATE THE ISSUE.

Do you have access to a load bank or can you use the elevators for step loading one operating then the other.

Check primary and secondary simultaneously.
Click to expand...

Brian is giving some very good advice here that you are ignoring. If you cant do thee tests, have a testing company come out and so them for you, they will give you an independent assessment of what to do.
 
From what I can tell, your 'problem' only occurs during the start-up of the hydraulic elevator motors.

Have you ruled out the motors and branch circuit wiring? If the normal L-L, L-N, L-G, and N-G voltages are within expected limits, at the transformer and at the load, during 'low' current conditions the problem may well be the wiring or the load. Normally I would not expect the start-up of 3-phase motors to cause such massive L-N voltage unbalance.
 
When you say the temp lights go out, are they HID's? You may already be pushing the limit on voltage drop on their feeds, and with the additional voltage drop induced by the startup current of the motors may be enough to extinguish the arc temporarily.
 
zog said:
You havent figured out anything yet, or done any real testing/troubleshooting. Try answering the best questions asked so far

Brian is giving some very good advice here that you are ignoring. If you cant do thee tests, have a testing company come out and so them for you, they will give you an independent assessment of what to do.
Click to expand...

I have not been ignoring any one. The lights are incadescant. and phase a to neutral is a big drop,from what I could see with a Fluke scope meter was under 90volts on start up but the lights blink big time.
 
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