Isolation tranny

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chris kennedy

chris kennedy

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Location
Miami Fla.
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60 yr old tool twisting electrician
I have an isolation tranny, 460 delta pri to 460y/262 secondary that I moved. This is for a box folder/glue machine. I took xo to the tranny chassis where the primary and secondary EGC and the GEC are all bonded together. Energized this late today and tranny was making an unusual buzzing sound. Secondary voltages where slightly more imbalanced than the primary.

The following is a pic of how it was wired before I moved it. I believe I have wired it compliantly but the weird buzzing got me wondering. Never wired an isolation tranny that wasn't a fancy 517 type piece before.

Thoughts

 
chris kennedy said:
Those are #3's, no comment on the EMT connector chase nips?;)
Click to expand...

Yes, you forgot to tighten the set screws:)

What was input/output voltages and currents of each line?

Are all three primary taps connected to the same percentage input?

Is vibration being transferred to other objects and maybe was not in the original location making it seem louder than it really is?
 
Fired up late today just for hot check.(no load) I'll get better readings and pics tomorrow. Didn't look at where the taps where landed, my thought is the original installer didn't loosen the shipping bolts. I know, not very thorough on my part, rush job, no excuse.:ashamed1:
 
chris kennedy said:
Energized this late today and tranny was making an unusual buzzing sound. Secondary voltages where slightly more imbalanced than the primary.
Click to expand...
Unusual as in loud? Or as in being something other than 60 Hz? Or like metal to metal vibration? Or just different from what you are used to hearing? Did you hear it energized before it was moved?
Was there any secondary load when you checked it out?
Both the buzzing and the unbalanced secondary voltages could come from one phase being on a different tap from the others. That would cause circulating current in the delta secondary which could account for the buzzing.
Shipping bolts? Is the core spring mounted or on rubber isolators normally?
A turn-to-turn short caused by mishandling during shipping could also cause both buzzing and voltage imbalance.
If you can energize just one primary phase at a time you could narrow down the cause of buzzing, if isolated to one coil. But if the coil to coil connections are internally fixed then the best you could do would be, in effect, to energize one phase at full voltage and other two phases at half voltage each.
 
chris kennedy said:
Fired up late today just for hot check.(no load) I'll get better readings and pics tomorrow. Didn't look at where the taps where landed, my thought is the original installer didn't loosen the shipping bolts. I know, not very thorough on my part, rush job, no excuse.:ashamed1:
Click to expand...

This is not all that unusual of an oversight. As a former application engineer advising the tech to look for the shipping bolts to see if in fact are loosened or removed is the easiest satisfaction you can get when address a noise problem. I loved an easy answer.
 
ActionDave said:
Can say for sure I have never done it. Cannot say, definitively, that I would never do it. :cool:
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I find that hard to believe when looking at your location. You have never been 30-40 miles from the closest chase nipple and needed one right now?

Maybe doesn't happen that much with say 1-2" fittings or even larger, but I'm willing to bet it happens a lot with 1/2 and 3/4 inch.
 
Craptacular video

Craptacular video

This is the noise, still buggin me. Machine needs 470V and although I have a balanced primary I had to put 2 coils on tap 1 and one one tap 2 to get a balanced 470. Also noted in a no load condition 2.5A on the A & B primaries and 4A on C.

 
chris kennedy said:
This is the noise, still buggin me. Machine needs 470V and although I have a balanced primary I had to put 2 coils on tap 1 and one one tap 2 to get a balanced 470. Also noted in a no load condition 2.5A on the A & B primaries and 4A on C.
Click to expand...
The audio and the additional tap and current information suggest some things:

1. Not a good noise. :)
2. Do you get the noise when the transformer is unloaded or just when under load?
3. If unloaded, then the noise combined with the tap, voltage, and primary current information lead me to suspect a shorted turn (or two) in one of the primary or secondary windings.
That would cause the extra idle current in one or two primary windings. The shorted turn would produce a lot of noise from magnetic forces inside the winding, and it would drop the line-to-line output voltage on that phase.
4. What is the vector group of the transformer? That will tell us what to expect on the primary side if there is a shorted turn in one secondary.
A shorted turn in a primary winding should increase the current in that winding (line-to-line) rather than increasing the current in one primary phase conductor.
5. If the input voltages are balanced yet you need to use different taps on different phases to get a balanced no-load output, the transformer is defective. Possibly damaged in shipment?
6. If you leave it on long enough, something will get hot. But the inside of a coil may reach a damaging temperature locally before you notice an external temperature difference.
 
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chris kennedy said:
This is the noise, still buggin me. Machine needs 470V and although I have a balanced primary I had to put 2 coils on tap 1 and one one tap 2 to get a balanced 470. Also noted in a no load condition 2.5A on the A & B primaries and 4A on C.

Click to expand...
Are you saying that you taped the coils differently? That is a no no. There should be all tapped at the same point?
Also, that noise, is mechanical as if there are either loose laminates or some other metal part vibrating because it's within a magnetic field.
When a transformer is manufacture they do go through a dip and bake process. As such I we could be looking for A him and not a buzzing sound.
 
chris kennedy said:
Please explain.
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I can't see how the taps are connected is your picture (your picture is quite nice otherwise) but you post seems to imply that the connection from H1, H2, as nd H3 to the tap connections are at different are not all connected to the same tap, those white wires that originate from the H connections and go up and terminate on each coil. Since you also did note include a picture of the NP I will venture to take a guess the at you transformer has +(2)2-1/2% and -(2)2-1/2% taps as such each coil should have 5 tap points. Are all three coils taped the same?
 
templdl said:
Are all three coils taped the same?
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No, hence my concern. You are correct there are 5 taps for each winding. 2 are tapped to one and 1 is tapped to 2 to give these anal retentive European equipment guys on an unrealistic commissioning sched the balanced 470 they require.

My question to you sir is how would different taps cause an issue? This is a very expensive toy we are talking about and tranny failure/lose of production would be very bad. So please enlighten this obviously unqualified installer. :ashamed1:
 
chris kennedy said:
No, hence my concern. You are correct there are 5 taps for each winding. 2 are tapped to one and 1 is tapped to 2 to give these anal retentive European equipment guys on an unrealistic commissioning sched the balanced 470 they require.

My question to you sir is how would different taps cause an issue? This is a very expensive toy we are talking about and tranny failure/lose of production would be very bad. So please enlighten this obviously unqualified installer. :ashamed1:
Click to expand...

1. If the transformer is working properly, then with a balanced delta input the output should also be voltage balanced. Any corrective action by changing taps is fighting a symptom rather than a cause.
2. If you have, for example, a delta-delta transformer and you change the tap setting on one phase only, then the secondary voltages will no longer add vectorially to zero and you will be pretty much guaranteed to have a large no-load circulating current in both primary and secondary. Unless you are doing it to counteract an unbalanced primary delta source, in which case the problem should really be fixed at the source.
3. Since you have a delta-wye, the immediate consequences are not as bad, but see #1.

PS: Not necessarily unqualified, but working outside your comfort zone. There are people here who are experts in just about anything, but not in all things at once.
 
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I do have a no load amp imbalance even though my primary voltages are very close to balanced. This
was noted before and after I made the tap changes, taps were originally all on 2. Think I need to order these guy another tranny.

Thanks all.
 
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