New transformer smoking

[LouisianaApprentice]

I was helping a coworker on a job where they were rushing to get utility power switched over into a 3000 amp MDP to temporarily feed 1 step down transformer. The transformer collected a bunch of dust from sitting up on the job for nearly a year.

Its tapped and terminated correctly and all legs read the correct voltage 480/277 primary, 120/208 secondary but when turned on the transformer itself starts to smoke and i think its coming from the windings. Could this just be dust or do yall believe this is indicative of another problem.

Monday i guess i will try to pull the conductors on secondary side off and check for a phase to phase short. Should i look into getting a megger for the windings?

 

[xptpcrewx]

I was helping a coworker on a job where they were rushing to get utility power switched over into a 3000 amp MDP to temporarily feed 1 step down transformer. The transformer collected a bunch of dust from sitting up on the job for nearly a year.

Its tapped and terminated correctly and all legs read the correct voltage 480/277 primary, 120/208 secondary but when turned on the transformer itself starts to smoke and i think its coming from the windings. Could this just be dust or do yall believe this is indicative of another problem.

Monday i guess i will try to pull the conductors on secondary side off and check for a phase to phase short. Should i look into getting a megger for the windings?

It could be nothing or something serious. It would basically blow apart if it was a phase to phase short, so you can rule that out. Why not vacuum it before placing into service to eliminate dust as a possible reason? I know you said it was a rush job, but now you’ll be spending more time troubleshooting it.

Btw, you can’t do a phase-to-phase megger test on a transformer because the windings are all common. You can go primary-to-ground, secondary-to-ground, and primary-to-secondary.

 

[LouisianaApprentice]

It could be nothing or something serious. It would basically blow apart if it was a phase to phase short, so you can rule that out. Why not vacuum it before placing into service to eliminate dust as a possible reason? I know you said it was a rush job, but now you’ll be spending more time troubleshooting it.

We vacuumed as i brushed it with a small handbrush but there was a ton of dust in the laminations.

 

[LouisianaApprentice]

I guess ill just have to find out monday, the smoke is definitely coming from inside.

 

[xptpcrewx]

I guess ill just have to find out monday, the smoke is definitely coming from inside.

Note: If the core laminations are damaged/shorted, then this will increase eddy currents and overheating.

 

[LouisianaApprentice]

Note: If the core laminations are damaged/shorted, then this will increase eddy currents and overheating.

Wouldnt the voltage be spiked in 1 direction though if this was the case? How could u rule this out with a meter?

 

[xptpcrewx]

Wouldnt the voltage be spiked in 1 direction though if this was the case? How could u rule this out with a meter?

Spiked voltage in one direction? I’m not following…

You test it by performing an insulation resistance test from the core to ground, IR scan/hot-spot checks of the core, and by doing a good ol’ visual inspection for blistering/delamination/rust/mechanical damage/etc. What’s the size of this transformer btw?

 

[LouisianaApprentice]

Spiked voltage in one direction? I’m not following…

You test it by performing an insulation resistance test from the core to ground, IR scan/hot-spot checks of the core, and by doing a good ol’ visual inspection for blistering/delamination/rust/mechanical damage/etc. What’s the size of this transformer btw?

Sorry im new to working on the more technical side of commercial. I believe its 5kva i just figured with higher eddy currents it would lead to a voltage spike idk how all this works because i have no formal training in this. This transformer was dinged up in handling we had to order new panels for the case of it. When i looked at the laminations they looked good just full of dust. I wanted to get a bottle or compressor on it to blow it out but we didnt have time or anything there to do that and it had to happen that day.
We dont have a thermal camera. And i dont even know if they have a megger on hand if thats what u mean by insulation check from core to ground. How would u do that put it to the X0 tap and check to ground? Im sorry im trying to learn thanks for the help.

 

[xptpcrewx]

Sorry im new to working on the more technical side of commercial. I believe its 5kva i just figured with higher eddy currents it would lead to a voltage spike idk how all this works because i have no formal training in this. This transformer was dinged up in handling we had to order new panels for the case of it. When i looked at the laminations they looked good just full of dust. I wanted to get a bottle or compressor on it to blow it out but we didnt have time or anything there to do that and it had to happen that day.
We dont have a thermal camera. And i dont even know if they have a megger on hand if thats what u mean by insulation check from core to ground. How would u do that put it to the X0 tap and check to ground? Im sorry im trying to learn thanks for the help.

5-kVA is tiny. What I’m describing is for larger dry-type transformers (500-kVA and above). You don’t want to blow it with compressed air as this will further imbed debris and particulate matter into the insulation. Vacuum is the recommended method. Megger is the name of the manufacturer but in the industry, it’s synonymous with an insulation resistance test. For larger transformers there is a bonding wire from the core to the frame ground. To do the test you would lift the bond and perform a withstand test (500-VDC for 1-min) between the core and the frame ground. The core should be completely insulated, but shifting and vibration due to shipping or just normal wear can tear through the isolation pad and create parallel ground connections (aka paths for eddy currents to circulate). I wouldn’t worry about any of this if you’re dealing with a 5-kVA transformer. Just buy a new one if it continues to smoke and exceeds it’s temp rise.

 

[LouisianaApprentice]

5-kVA is tiny. What I’m describing is for larger dry-type transformers (500-kVA and above). You don’t want to blow it with compressed air as this will further imbed debris and particulate matter into the insulation. Vacuum is the recommended method. Megger is the name of the manufacturer but in the industry, it’s synonymous with an insulation resistance test. For larger transformers there is a bonding wire from the core to the frame ground. To do the test you would lift the bond and perform a withstand test (500-VDC for 1-min) between the core and the frame ground. The core should be completely insulated, but shifting and vibration due to shipping or just normal wear can tear through the isolation pad and create parallel ground connections (aka paths for eddy currents to circulate). I wouldn’t worry about any of this if you’re dealing with a 5-kVA transformer. Just buy a new one if it continues to smoke and exceeds it’s temp rise.

Sorry not 5kva 50 i think its for a 200 amp 3 phase 208 panel

 

[xptpcrewx]

Sorry not 5kva 50 i think its for a 200 amp 3 phase 208 panel

Still tiny for what I’m talking about. Just clean it well with a good vacuum cleaner and a lint-free cloth (with isopropyl alcohol if needed) and make sure you have low resistance electrical connections. Sometimes the resin isn’t completely removed from the leads or taps after the VPI process, so you’ll need to scrub it off to expose the metal. Excessive dust in the windings will prevent the transformer from dissipating heat and cause the temperature to rise.

 

[LouisianaApprentice]

Still tiny for what I’m talking about. Just clean it well with a good vacuum cleaner and a lint-free cloth (with isopropyl alcohol if needed) and make sure you have low resistance electrical connections. Sometimes the resin isn’t completely removed from the leads or taps after the VPI process, so you’ll need to scrub it off to expose the metal. Excessive dust in the windings will prevent the transformer from dissipating heat and cause the temperature to rise.

Ok thanks for the advice was just trying to understand this issue as smoke from electrical equipment is always scary to me.

 

[Besoeker3]

Ok thanks for the advice was just trying to understand this issue as smoke from electrical equipment is always scary to me.

I think it most likely dust. Transformers have a very distinct acrid smell.

 

[hillbilly1]

Dust would not cause the transformer to smoke instantly, something else is going on. Pulled many a transformer coated in years of dust that failed for other reasons. If it arrived banged up, the core could of been damaged in shipment.

 

[Besoeker3]

Dust would not cause the transformer to smoke instantly, something else is going on. Pulled many a transformer coated in years of dust that failed for other reasons. If it arrived banged up, the core could of been damaged in shipment.

I think we need to see what the LouisianaApprentice has to find out.​

 

[hillbilly1]

I think we need to see what the LouisianaApprentice has to find out.​

Of course the op did not say what kind of dust. If it’s some kind of unusual dust, there might be a case made.

 

[retirede]

Could be a Cheech & Chong transformer?

 

[LouisianaApprentice]

This is the size of it idk what it could be its not burning the paint off its bellowing out from around the windings.

 

[LouisianaApprentice]

The smoke doesnt smell electrical like that funky burnt ballast smell.

 

[Besoeker3]

The smoke doesnt smell electrical like that funky burnt ballast smell.

As I said, Transformers have a very distinct acrid smell.