usage of step up transformer

[alfred.lost]

havn't really seen one. I am really not sure. I want to know if a set up like this could make sense under Low voltage in legal sense.

Moderator note: This new user changed their user name. Here is their original post.

I am working as a client's Maintenance Engineer on Machines and some facilities so I am not qualified to make good judgments on Electrical Projects. I want to know if you have ever used a step-up and step-down transformer pair to reduce loss and voltage drop for some long cables in a low-power and low-voltage situation. Can anyone tell me how far apart a pair of transformers will make sense? In this case, I am looking at a 380 to 600v setup.

 

[Carultch]

havn't really seen one. I am really not sure. I want to know if a set up like this could make sense under Low voltage in legal sense.

Moderator note: This new user changed their user name. Here is their original post.

I am working as a client's Maintenance Engineer on Machines and some facilities so I am not qualified to make good judgments on Electrical Projects. I want to know if you have ever used a step-up and step-down transformer pair to reduce loss and voltage drop for some long cables in a low-power and low-voltage situation. Can anyone tell me how far apart a pair of transformers will make sense? In this case, I am looking at a 380 to 600v setup.

Transformers have a working principle that works in either direction, but they may be designed to work better in one direction than the other. The actual turns ratio may be designed to compensate for internal losses, assuming power flows from primary to secondary (as MFR identifies primary and secondary). The topology and taps may also be built assuming the source grid is on the MFR-identified primary side.

Issues to consider:
1. What topology (delta vs wye on each side), and isolated vs autotransformer, do you need? The most common load-side topology you'd likely want, is a grounded wye, so that 600V is fixed at 347V to ground, instead of floating. It's common to have delta on the grid side, but wye-to-wye and autotransformers could also get you a grounded wye secondary.
2. Taps. Usually the primary side is equipped with adjustable taps, to fine-tune the voltage. You'd just need to think in reverse to select the tap you need, if taps are on the secondary instead.
3. Complying with 240.21(C) for secondary conductors.
4. NEC rules for separately-derived systems (SDS). The secondary of any isolated transformer, is a separately derived system.

I would recommend checking with the manufacturer to make sure the transformer you have in mind can be used this way, before committing to a particular transformer.

 

[don_resqcapt19]

There are also losses in the transformers, so you would have to include those in any calculation of the cost effectiveness of this set up. It could very well be that the use of a larger conductor would be a cheaper installation and have less I²R losses than installing two transformers.

 

[alfred.lost]

Really thank you very much. my electrical engineering degree seems not to be a waste of time.

1.I more things i will also need to consider.
can I do this after original cable installation. will 4p armor cable work well @ 380V as well as 600V? I will also need to consider expanding capacity , say double, few years down the line if I choose to use larger cable only.


2.They are all for car charger. will it make sense to use delta , floating on the entire run?

 

[electrofelon]

Just be careful and follow Dons advice and make sure to include no load and load losses, their monetary cost and voltage drop, when comparing. Many people just leave these out and go step up step down when it is not the best choice.