Transformer problems ?

[tesi1]

WHAT WOULD BE THE RESULTS OF A 3-PHASE DELTA-WYE 30 KVA X-FMR
480 x 208/120 4-WIRE. IF IT WAS LABELED AT THE FACTORY INCORECTLY SUCH AS A 60 CYCLE
BUT IT WAS REALLY A 50 OR 25CYCLE UNIT.! WE ARE HAVING A PROBLEM
WITH POPING THE POWER SUPPLY ON 4 DESKTOP COMPUTERS. WE HAVE
CHECKED ALL GROUNDING & NEUT. CONNECTIONS. TAPS, WINDING CONNECTIONS, ALL BRANCH CIRCUIT CONNECTIONS FROM THE PANEL TO
THE OUTLETS, ALL VOLTAGES ARE AT 119 TO 121 VOLTS, WE REGROUNDED
THE MAIN PANEL, XFMR, & BUILDING STEEL, MEASURED FROM OTHER POSS-
IABLE GROUND AND OR REFERENCE POINTS AND FOUND NO MAJOR PROBLEM,
WE HAVE FOUND NO FLOATING NEUTRALS, OR GROUNDS WITH VOLTAGE DIFFERENTIAL ON THEM.

 

[hillbilly1]

It will put out the same frequency that is put in, regardless of labeling. You say no "floating neutrals" but are you sure? Sounds like XO is not bonded to ground. Grounding electrodes should not be the only ground it has, the equipment ground from the source should also be tied to XO.

 

[hillbilly1]

Also quit shouting!

 

[templdl]

Why have you concluded the transformer was mislabled as 60hz at the factory? Are you leaving us to assume that the transformer was order as 50HZ or 25HZ?

You have left a lot of information our of your inquiry which prevents getting an accurate answer.

Now, this is only and assumtion. If the transformer was designed and built for 60HZ and you are supplying it with 50hz the transformer may be going into saturation where the promary current spikes and the secondary voltage takes a nose dive.
Also, if one were to apply 25hz to it the transformer would definitely not work.

 

[LarryFine]

A transformer is more efficient with greater frequency, which is why aircraft use 400Hz. There should be no detrimental effect.

It sounds like you need an event recorder.

 

[brother]

WHAT WOULD BE THE RESULTS OF A 3-PHASE DELTA-WYE 30 KVA X-FMR
480 x 208/120 4-WIRE. IF IT WAS LABELED AT THE FACTORY INCORECTLY SUCH AS A 60 CYCLE
BUT IT WAS REALLY A 50 OR 25CYCLE UNIT.! WE ARE HAVING A PROBLEM
WITH POPING THE POWER SUPPLY ON 4 DESKTOP COMPUTERS. WE HAVE
CHECKED ALL GROUNDING & NEUT. CONNECTIONS. TAPS, WINDING CONNECTIONS, ALL BRANCH CIRCUIT CONNECTIONS FROM THE PANEL TO
THE OUTLETS, ALL VOLTAGES ARE AT 119 TO 121 VOLTS, WE REGROUNDED
THE MAIN PANEL, XFMR, & BUILDING STEEL, MEASURED FROM OTHER POSS-
IABLE GROUND AND OR REFERENCE POINTS AND FOUND NO MAJOR PROBLEM,
WE HAVE FOUND NO FLOATING NEUTRALS, OR GROUNDS WITH VOLTAGE DIFFERENTIAL ON THEM.

Have you tried pluggin into another outlet with the computers to see if the problem follows it??? are you sure the power supply/computer is not an issue?? like someone said, you need a recorder to find the voltage or current readings.

Sounds like a loose neutral off hand. Are you sharing neutrals on any of the ciruits?? You retighten the main neutral in the panel and the transformer?

 

[BJ Conner]

A transformer is more efficient with greater frequency, which is why aircraft use 400Hz. There should be no detrimental effect.

It sounds like you need an event recorder.

Not necessarly so. The amount of iron needed in a transformer goes down as frequency gos up. A 400 cycle transformer don't weigh much.
You can run a 50 cycle at 60 cycles because the 50 has more iron. You may be able to a 60 cycle at 50 ( depends on the physical diemensions) but it may saturate and give you a chopped sin wave out.

Airplanes us 400 cycle because it's lighter and because some guy named Sperry invented a gyroscopic compass. A 2-pole 400 cycle motor has an inherrent speed of 24,000 RPM. Which makes a good gyrocompass.
If you went to school in the dim past you may have got to play with selsyns in lab. They were 400 cycle position indicator/trasmitters that pointed the guns on a B-29.

 

[hillbilly1]

I got to play with a 400 hz generator years ago, replaced a motor/generator set with an electronic one at an Air Force base right after 9/11. The old one weighed 1500 lbs, and I couldn't get it out with a crane due to overhead power lines. Built a special tandem axel trailer for my four wheeler, and pulled it out. Had less than 48" clearance between the wall and three large A/C condensors. The the motor/generator was 42". They used it to test aircraft equipment.

 

[Jraef]

1. 480-208Y120 is not a voltage used in an country that also uses 50Hz, so your theory of factory mislabeling doesn't hold water.
2. Not sure what you mean by "popping" a power supply. Is it over heating? Is it fused and the fuse is blowing?
3. Loose neutral sounds like a good starting point to me. Hard to find with meters etc. because you have to be looking at it at the exact moment something happens. A recording meter over a period of time would be a better plan.

 

[brian john]

1. As noted popping??????
2. You say there is no voltage differential between neutral ground THERE SHOULD BE.
3. You also say you grounded at the panel, if you grounded at the transformer you have circulating current. Most likely not this issue but should be corrected.
4. Use a disturbance analyzer or hire a firm to investigate this.
5. Often in pursuit of power issues end users OVERGROUND, which in itself can set up issues. Though highly unusual for this to damage power supplies.
6. I'd go with a possible loose neutral issue.