I've been told that the incoming power to our property is 480 from the pole and that we have a 240v 300A service panel (large house & properties). What I can't figure out is how this is done without a transformer and I've never seen a transformer anywhere near or in the panel and I see the single cable entering the house and patched into the panel. How does this work. Also, do some homes get 240 service instead of 480 or is 480 the standard in the US. I thought maybe we had 480 b/c it used to be a farm.


Kind of unrealated, I was wondering if there would be any losses if a 1:1 transformer would be used. Basically the standard transformer shaped like a square/box with the metal core and empty area for the wires with metal outer section. It could be built to whatever size is needed (gauge wise) and as many turns as necessary for best performance. So if 100A is needed, IDK what size wire would be needed for this, but it seems at least 8g, and maybe 40-80 turns then the other winding would be the same. If a transformer such as this were set up, would there be any (or much, and if so how much) power lost? I'm assuming it may get warm, so energy lost as heat. It could be contained in a container of mineral oil (or other non conductive material) if necessary. I would assume that this transformer would isolate the building from the grid, is that correct? That would eliminate any power spikes, electrical strikes to wires down line and maybe even EMP issues?

 

Assume that you have supply from a 240 - 0 - 240 Centre Tapped Transformer. That means 3 lines coming in for distribution.

 

The area network is always three-phase, anywhere. Most of World places uses 380/220 V 50 Hz network, however there are some few strange countries, who ignores the international standards (even about the plug standards violate in most quirky way - who may booze so heavy until invent the plug with plane lamelles instead of round?, worser may be only the plugs with fuse inside - UK), and one of that countries are not so small at all, I mean US. But not about that is the question.

So, the meaning of slash in that label figure is this: before it is shown the Voltage between any two phase wires, I mean A to B, B to C and A to C. Yet figure after slash shows Voltage between any of phase and ground, I mean A to gnd, B to gnd or C to gnd.

Ought be mentioned that 220*sqrt(3)=380 as well as the peak Voltage after full wave rectifier with capacitor is 310 V for 220 V one phase network and 530 V for three phase 6 wave 380 V recifier (the Voltage loss on diodes already included). This is the basic reason why most of power igbt are rated for 600 and 1200 Volts not any other spannung.

Bit more focus-pocus stays with power calculation. To calculate the three phase currents knowing the power, for example the 3,3 kW, man has a two strategies - or to divide the 3,3 kW to all phases by formula i(lin)=i(tot.DC) / sqrt(3) or better to memorize take the assumption that each phase input on the power is 1/3 thus the task is reduced to calculate i in the ONE-phased system, example`s case 220V and 1,1 kW gives 5 Amps what totally from 3 phases gives 3,3 kW.

 

I thought maybe we had 480 b/c it used to be a farm.

A lot of farms around my area have three phase, just not 480V. That is usually the voltage for industrial . Most farm 3PH is 120/208 4 wire Wey. So that would give you your 240V 120V for the house with no transformer. This will explain it better - https://ctlsys.com/support/electrical_service_types_and_voltages/

 

In simple terms: three phase 240V means each phase to ground is 240V. Between any two phase wires=240root(3)=415V. That is a more usual three phase distribution voltage for 240V systems, but there are other voltages used such as 440V,. 480V.
I would doubt you had 480V because that would be 280V rms for a single phase to ground, which is over most supply limits for 240V.

 

In simple terms: three phase 240V means each phase to ground is 240V. Between any two phase wires=240root(3)=415V. That is a more usual three phase distribution voltage for 240V .

Or Generally a 3phase transformer with a Star neutral, where in turn the neutral is earth grounded.
This is the method used in UK etc, seldom seen in N.A. for residential use.
Max.

 

I can never understand how a voltage of 208 if achieved from any of these configurations. If there is 240 - 0 - (-240) that is a total differential of 480. But where does 208 come from?

I always thought it was a single strand wire that entered the house and the voltage comes from the differential between that voltage and the earth voltage. So there is no transformer in each house that breaks down the V from a single wire into the 240 - 0 - (-240) with a center tap?

 

The 580v 3ph transformer sitting in the corner of my yard has a 120-0-120 volt 1ph secondary, the 0v or neutral is taken to ground at the service panel.
The 208 is a 3 phase transformer usually used for lighting distribution in N.A., each phase to neutral is 120vac.
Max.

 

In simple terms: three phase 240V means each phase to ground is 240V. Between any two phase wires=240root(3)=415V. That is a more usual three phase distribution voltage for 240V systems,

This is what I had come across in India. It is not uncommon to see 380V AC due to voltage drop!

 

well you said that "YOU HAVE BEEN TOLD" so that means you do not know 100% sure, i assume.
perhaps there is a transformer down the block, and that is sent down to several houses, then direct into yours.
here where i live in some neighborhoods, there can be 1 transformer feeding up to 8 houses, the secondary ( 240VAC ) is sent down as fare as 3 or 4 poles.. to all the houses, so it may appear you have no transformer..have a walk and follow the lines and maybe you see the transformer.
here we have typically 14.2KV primary lines, and transformers drop it to (120-0-120 ) 240Vac that is typical.