Single phase transformer performance

[DunnWright Construction]

Been a licensed General Contractor since 2000, back when General Contractors could do just about anything. Apprenticed under my uncle an electrical contractor/Vietnam Vet, who would answer all my questions, he's no longer with us. 250 amp single phase running 4/0 overhead 680 max run in RV park that is experiencing voltage drop down to 90 volts on hot days when everyone is running multiple AC units. Anyone have working experience with affordable transformers? Thanks in advance.

 

[Hv&Lv]

Lots, but thats not going to fix the problem. You put in a step up transformer to get you from 90 to 120, the AC cuts off, nominal goes up, what does the XF go to?
you need to fix the problem with the small conductors.
Parallel maybe...
either that or your overloading the entire service and the supply XF so much it’s bringing total V down.

 

[LarryFine]

Anyone have working experience with affordable transformers? Thanks in advance.

You need to remember that electricity isn't free, in the physics sense. Any power used to boost voltage is seen by the source and wiring as additional load current, which increases voltage drop even more. And as stated, you will have no voltage regulation.

It sounds like you need a better power distribution set-up.

 

[Besoeker3]

Parallel maybe...
either that or your overloading the entire service and the supply XF so much it’s bringing total V down.

No maybe about it.

 

[Russs57]

The only reasonable thing that I know that would work....assuming you want to put some type of transformer at the end of that 680' run of 4/0.....would be a constant voltage transformer. Bottom line, I don't think you would like the cost.

I guess you could buy two transformers and run 480 or 600 volts on the overhead 4/0. I don't think you would like that cost either.

 

[electrofelon]

Anyone have working experience with affordable transformers? Thanks in advance.

.

Don't get me wrong:. On one hand, transformers are awesome amazing devices. On the other hand, they are just awful for situations like yours. These situations with severe voltage drop, step up/step down transformer arrangements, compensating for drop, etc....in my experience, they are just not the solution 97.3% of the time, after you weigh tranny costs, losses forever....aluminum wire is cheap.....what's even cheaper is 15kv concentric primary: $2/ft, one cable needed for single phase. Don't even bother doing VD calcs with that, have a cookie instead.

 

[Hv&Lv]

No maybe about it.

Don’t know why you say it like that..
There is a maybe involved.

If the loads are too great parallel won’t fix the problem either.
Only way to know if parallel will work for sure is to know the loads at the end.

 

[junkhound]

And speaking of transformers, what is the POCO feed to the service?
It is what may be overloaded.
say 300 ft average ft of 4/0, at 200 A drops to say 110 volts, another 400 ft at just say 50 A drops just 3V.

Perhaps your poco xfmr is dropping the other 17 volts? Does the poco distribution xfmr feed anyone but the RV park?
Your RV park may be drawing over 200 A, 24 kVA single phase, poco probably (if like Potelco does here) only installed a 25 kVA (240V!) and is undersized for your hot summer day loads.

 

[Hv&Lv]

And speaking of transformers, what is the POCO feed to the service?
It is what may be overloaded.
say 300 ft average ft of 4/0, at 200 A drops to say 110 volts, another 400 ft at just say 50 A drops just 3V.

Perhaps your poco xfmr is dropping the other 17 volts? Does the poco distribution xfmr feed anyone but the RV park?
Your RV park may be drawing over 200 A, 24 kVA single phase, poco probably (if like Potelco does here) only installed a 25 kVA (240V!) and is undersized for your hot summer day loads.

Kind of what I was thinking in post #2
Ive seen this lots of times. Maybe a 10 hanging on a pole and it needs to be a 50.

 

[kwired]

He didn't say how many RV units there are, but sounds like there are multiple units, so 680 feet has to be questioned some and yes the source transformer can still be too small and contributing to the problem.