Delta to Y step up transformers 3

[tveltre]

Im looking to step up the voltage on 120/208 volt, 3 phase, 4 wire distribution system to 460 volt, delta, 3 phase, 3 wire... here's my question, Do I need to carry through the transformer a neutral or can i simply omit this connection?.

tveltre@tomvpe.com

 

[redtrumpet]

The transformer creates two electrically isolated circuits or systems; therefore, it is not possible to "carry through" a neutral. The 208Y/120 V 3 phase, 4 wire system, by definition, has a system neutral conductor and requires the neutral point of the transformer to be connected to this system neutral conductor. The system neutral point is also required by code to be connected to ground.

The 460 (more commonly 480) V, 3 phase, 3 wire delta system, by definition, does not have a neutral point and no neutral conductor is required.

 

[gordonl]

redtrumpts post assumes the transformer delta is on the 480V side of the step-up transformer. If the 480V winding is Y then whether or not you use the neutral will be dependant on the loads you plan to connect. If all your loads are three phase {ie motor(s)} then the neutral is not required, if single phase (ie lighting) it probably is.

Regardless, the systems are isolated and the neutral does not carry through. But the Y would have to be connected to ground and neutral for the 480V system if you needed a 480V 4 wire system with Y winding at 480V, and only ground if it's three wire.

I hope I'm not confusing.

 

[gordonl]

I realize the last line of my post wasn't totally accurate, but an ungrounded system is probably unlikely or not recommended for this situation. (Sounds like it wouldn't be monitored)

 

[tveltre]

To clarify my question here; The distribution scenario consist of providing 460 volt/3 phase power to 3 phase motor loads to take advantage of the reduced conduit and feeder size.. The primary distribution system is 120/208 volt, 3 phase, 4 wire.. The secondary distribution system would be 460 volt, 3 phase, 3 wire.. the question is, Do I need to connect a neutral on the four wire, 120/208 volt, 3 ph delta system to the primary connection of the transformer? or simply, can I provide a delta to delta xfrmr?

Tveltre

 

[redtrumpet]

gordonl - I didn't assume a delta connection on the 460 V side, the originator of the thread stated that information.

tveltre - Both gordonl and myself stated the neutral does not carry through because the circuits are electrically isolated. Based on your second posting, it appears you do not have a clear understanding of delta and wye systems. In that case, I would advise you to retain a qualified professional before proceeding.

 

[busbar]

To add to already good comments-- A typical example can be found at

http://www.electro-mechanical.com/7700-94.pdf

The 208 delta—480Y/277V (T204 series) is specifically intended for use in stepup applications. As far as economies of higher-voltage operation, transformer losses should be factored in to any economic calculations, similar to losses from voltage drop in cables. Transformers are fairly efficient devices, but consume some electrical energy under loaded and no-load conditions.

 

[redtrumpet]

gordonl - after reading the latest postings on this thread, I realized I should have thought about this more. I accepted tveltre's initial statement of a 480 V delta system without thinking about what the best transformer connection would be on the 480 V side. I then wandered off into system definitions, more of an ivory tower approach and probably not really helping out tveltre at all. As you and busbar have pointed out, the correct transformer is a 208 V-480Y/277 V transformer. Stars for you both. Next time I will try to fully extract my head from my rear before replying.

 

First of all, I am not an electrician, but I have a question about step up transformers. I have a 208-240/60/1 refrigerated cabinet which draws 13 amps at a job site in which they only have a 120 volt outlet availabe. Is there a step-up transformer that can be installed to solve this problem? Are these step-up transformers UL approved?

 

[iiee]

Yes, there is. You could refer your requirement to some transfomer manufacturer like G.E.; COOPER; SQUARE D; FEDERAL PACIFIC.

 

Hi Everyone, I'm new to this forum and seeking advice. How hard would it be to find an inexpensive/common 208 three phase primary to 460 three phase secondary transformer. I'm looking into purchasing a welder that requires 460 three phase and my shop only has 208 three phase. What will a used/surplus transfromer cost? TIA, Nick

 

I have a problem that has caused me so many trouble!! I hope someone can help me on this

the question is I got two identical 50kVA 400/2000V single phase transfers operating in parallel that is supplying a computer of 40kVA at 2000V and 0.80 PF leading.
I did a short cct test measured on the primary side of the transformer and Vprimary =31.622V and Pprimary=1250W
I want to find the primary voltage of the transformers neglecting no load losses and magnetizing effects and also the efficiency of the transformer bank operating for this load

thx.. I tried to look up books to solve this but I cannot..it is so hard!!! Please help me