Center tapped 120v secondary. Dairy

[ptonsparky]

Working at a good sized dairy yesterday and encountered a small single phase transformer that was connected 480v primary with a 120v secondary. The secondary center tap was grounded making it 60 volts to ground (Green EG) and 120v Line to Line (Black to White). There are at least three of these setups in each building supplying 120v for the immediate area of each transformer. Guessing they used this method to limit "stray voltage" in the free stall area. I never ran across this before, is this a common practice?

 

[petersonra]

all of australia is done this way. is that common enough for you?

 

[ptonsparky]

Dairies only or the whole enchilada?

 

[petersonra]

Dairies only or the whole enchilada?

My understanding is all residences are done this way at the very least.

 

[Besoeker]

all of australia is done this way. is that common enough for you?

Australia 240 V 50 Hz

http://www.kropla.com/electric2.htm

 

[petersonra]

Australia 240 V 50 Hz

http://www.kropla.com/electric2.htm

perhaps it is only ICP that are done this way.

 

[Speedskater]

Article 647 for Sensitive Electronic Equipment covers balanced (60V / 60V) 120 Volt circuits.

 

[kwired]

Although I have never seen that before the advantage would be there is likely no current on the neutral and therefore less potential for stray voltage. Using all 240 volt equipment and no 120 volt loads would accomplish same thing. There is too much 120 volt equipment out there for this to be very practical though.

 

[Besoeker]

perhaps it is only ICP that are done this way.

ICP?
Insane Clown Posse?

 

[kwired]

ICP?
Insane Clown Posse?

Probably - Industrial Control Panel.

 

[ptonsparky]

There is no neutral in this case. Just an equipment ground. The white that they were using should, could just as well been any color, except green of course.

 

[hurk27]

Very common power supply for server racks in IT rooms.

There has been some discussion on here about how breakers will react to the lower voltage under a fault.

 

[kwired]

Very common power supply for server racks in IT rooms.

There has been some discussion on here about how breakers will react to the lower voltage under a fault.

But breakers respond to current not voltage.

Too high of voltage is possibly an issue with the insulating properties of an item but low voltage should not be a problem.

Available fault current can effect the response time, but it also does at higher voltages.

Tell me what I am overlooking.

 

[Besoeker]

There is no neutral in this case. Just an equipment ground. The white that they were using should, could just as well been any color, except green of course.

I've seen this sort of arrangement on industrial control panels in UK. It was 55-0-55 with the centre tap grounded. Safety was cited as the reason.
110 Vac is typically used as a control voltage and as that went out to operator control stations I suppose it was perceived as a potential risk to operators.
Never held with it much myself.

But, in a dairy, the cows might have had udder ideas.......