bifurcated secondary on transformers

[mshields]

Where would I find the rules in the NEC for a transformer (specifically with a 4160V primary and 480/277V secondary) with a bifurcated secondary.

Specifically what the sum of the 2 secondary OCP's needs not to exceed?

Do the two secondary taps need to be the same size?

etc.

Thanks,

Mike

 

[gar]

151115-1415 EST

What is a "bifurcated secondary"?

See http://www.merriam-webster.com/dictionary/bifurcate for basic definition. bi as a prefix implies two.

Searching Google for bifurcated secondary produced mostly medical or biological results.

Using the string --- bifurcated secondary on transformers
produced this thread and results like http://www.ijirae.com/images/downloads/vol1issue1/MEE10080.March14.20.pdf

The string --- bifurcated secondary on transformers --- might imply to me a single secondary wound with two wires in parallel laid down side-by-side, or just two independently wound but nearly identical secondaries properly phased and paralleled.

.

 

[GoldDigger]

To me bifurcated implies two identical secondaries wired out to four terminals rather than be connected internally to form one center tapped winding. The physical construction could be identical except for the provision of the fourth terminal.
With only the three terminal version available you cannot construct the two out of three to full three phase conversion illustrated.

 

[mike_kilroy]

Where would I find the rules in the NEC for a transformer

Mike, I would say you don't and won't. How a transformer is built INTERNALLY is like a motor: how it is built internally is not your concern; just use the specs given by the manufacturer for the device.

Googling bifurcated concentric winding yields discussions that show WHAT it is - although again, I do not think it effects your life using it:

https://books.google.com/books?id=g...epage&q=bifurcated concentric winding&f=false

http://www.ustudy.in/node/2161

https://www.google.com/search?q=bif...X&ved=0CCQQsARqFQoTCI3f-uLjlckCFVLwYwodAeELnw

http://www.theijes.com/papers/v2-i4/part. (5)/B024508013.pdf

 

[ron]

Look at Table 450.3(A) or (B) Note #2 where it limits the total of the two output breaker to not exceed what it would be if there was just one.

 

[Gary Glaenzer]

Mike, I would say you don't and won't. How a transformer is built INTERNALLY is like a motor: how it is built internally is not your concern; just use the specs given by the manufacturer for the device.

Googling bifurcated concentric winding yields discussions that show WHAT it is - although again, I do not think it effects your life using it:

https://books.google.com/books?id=g...epage&q=bifurcated concentric winding&f=false


===========================

We see this in high-power broadcast transmitters, using a dual-secondary 3-phase transformer.

The transformer has two complete sets of windings, one set is connected wye, the other delta, forming what is called a '12-phase supply'. so named because there are 12 separate pulses of DC for every 60-Hz cycle.

In order to keep all the voltages as close to equal as possible, the windings are laid down in pairs, 'paired' in winding them so to speak.

See this page, 4th row down, just left of center.

https://www.google.com/search?q=tra...AcQ_AUoAmoVChMI2q68ufyVyQIVxC2ICh2B3w71&dpr=1

hope this helps

Gary

 

[GoldDigger]

Somehow I don't think that the usage of "bifurcated concentric" for motors necessarily tells us much about what bifurcated means in a transformer winding.

 

[templdl]

Interesting subject. I was with a major manufacturer of both liquid cooled and dry type transformers for 18 years and with a manufacturer of drytype transformers from the small control power transformers 6o transformers as large as 10mva and 35kv working with so very fine and accomplished transformer design engineers and I have never ran across this design requirements.
Has this subject been brought up simply out of curiosity and to stir the pot a bit?
I don't have access to the transformer brain trust as I once had who would have been able to easily explain this.