Message Board Thread - "Transformer inside coil"

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Transformer inside coil smokedfish 3/21/2012
KVA: 2000/2666 60 HZ
VOLTAGE 12470 – 480 Y/277 3 PHASE
Maximum Ampere Load = 2000 kva = 2,000,000 va / (480 v √3) or 831.38 = 2406 amps
Actual load of 775 amps per Ø is only 32% of maximum load
Phase B is 75.7 º C hotter then the other 2 phases
Emissivity is set for 0.96 as I am usually looking at wire connections. It looks like the bottom of the coil towards the inside is generating the heat but I do not know. Any ideas on setting emissivity or what is heating up? The photo is 90 degrees off as I was laying of the floor looking through the air vents.
Re:Transformer inside coil IRsloopyeah 3/21/2012
Do you have any visuals of what you are looking at? Im kinda comfused of the IR image and what your talking about? Ask if you can get a flash suit and open up the cabinet so you can investigate the heat resistance better? When I look at connection points I set Emisivitys to .86 to .74 dont for get to set your referance temperature. haveing a hard time looking at your IR image?
Re:Transformer inside coil smokedfish 3/21/2012
Thanks for the tip on the emissivity. My job was to only find anomalies and not open the transformer. My readings at least prompted farther investigation my a contractor. The transformers have not been cleaned for years. Attached is a digital. Remember I was lying on the floor so it is 90 degrees off. Rotate it to the right.
Re:Transformer inside coil EDAZ 3/21/2012
Looks like a either a possible turn-to-turn short in the Phase B coil, or maybe a high impedance connection inside. I'm assuming you already made sure each phase is loaded equally.

Your emissivity of .96 should be close since you're looking at the temperature of the insulating material and not the actual copper conductor nor a connection point.

Regardless, the transformer should be taken offline and evaluated by a qualified person/firm.
Re:Transformer inside coil IRsloopyeah 3/22/2012
OK!!! now i see what you are talking about!! Yes EDAZ is correct i would use .96 for emissivity. some times as i have seen the connections to the coils of the transformer may have resistance and may be causing the different temps on the phases!suggest you use a IR window if it is a concern. but if i have to open up a cabinet i shut power off and open up the cabinet. Turn power back on shoot with a high votage arc flash suit and scan from a safe distance.

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