3 Phase to Single Phase

I am not an electrical engineer, but to my knowledge three phase 460 v delta to three phase Y 208 V will give you 120 V between each phase and neutral. The size of the transformer and the current availavle I will leave up to a qualified engineer or electrician to answer.

thanks for the input

OK, that's rite! You need 3-phase delta/Y transformer (460/208 V).

100 A circuit breaker can protect a transformer from 65 kVA to 83 kVA on 460 V (125% maximum plus next higher standard rating of circuit breaker <American NEC, 450.3(B)>).

What will you have on your secondary is: (277 V / 120 V)*100 A = 230 A on each phase maximum (if you use 83 kVA transformer), or about 180 A minimum (if you use 65 kVA transformer). 277V is the voltage of your phase to neutral (should your 460 V system have the neutral), and 120 V is your desired voltage (also phase to neutral) -- just to make it simpler for you.

Then you need 200 A -- 250 A-rated panel (depending on transformer you chose) where you will put your 27 -- 33 single-phase 20 A circuit breakers or 9 -- 11 3-phase 20 A circuit breakers.

You can put more circuits than that if your circuits will not be fully loaded or/and will not work simultaneously.

57

57 what?

You asked the question

Answer 57 20A 120V supplies

Yes, this sounds good....

480v = 4 * 120volts...so, R to Y = Y to B = B to R = (4 bulbs in series).....

next, each phase can give 100 A and bulb rating is 20 Amp....... so, We can connect {5 * (4 bulbs in series) } in each R to Y, Y to B, B to R......

Finally, the total no. of bulbs that we can connect is = 4 (due to voltage division) * 5(due to current division) * 3 (due to Phase division)

= 4 * 5 * 3

= 60 (bulbs that we can connect as per the question).........

Why do you think his voltage is actually 480? First, even if the nominal voltage supplied by the utility is 480 the actual voltage is probably not 480. It might be anywhere from 504 if they are right close to the substation all the way down to 460 if they are near the end of a heavily loaded circuit. Second, many industriies that receive service at primary voltage still step down to 460 volts, especially if they have old equipment. It is too bad that too many people still refer to house voltage as 110 when it is closer to 120 and the same goes with 220 - 240 and 440 - 480 in commercial installations, but it is also incorrect to make a flat statement that the voltage is 480.

Whatever the "actual" voltage is does not matter- when you are talking about power issues, you need to talk about "standard" values- so, you are talking about 480 VAC, (Wye or Delta), 240 VAC (Wye or Delta), 208 VAC (Wye) and 120 VAC in the United States. Similar break-downs exist for other parts of the world.

I suspect we may need to clarify a detail here. When you say 3 -100 Amp circuits, are you referring to the three wires of a single 100 Amp, 3 phase source, or do you really have 3 - 3 phase circuits (9 wires minimum)?

If i consider your source to be 100amp,460volt,3 phase,your multiple single phase of 120v,20amps would be taken from your source above.

Simply pick a phase and neutral and supply your 20amps circuits.

Apparent power of source S=√3VI=1.732×460×100=79.672KVA

Apparent power of each single phase s=VI=120×20=2.400KVA

You will have as much as about 79.672kva ÷ 2.400kva =33 circuits. If you use active power formular-√3vicosφ and vicosφ,you will get same result.

PATRICK WHOWHA

energygod makes a good point in that the equipment supplying the power would be rated at 480 not 460. Consequently the number of outlets would be higher by 20V times 100A times Sqrt(1.73) divided by 2.4Kw per outlet.

The supply transformers most likely have taps to adjust the output voltage to rated voltage. And realistically a full load distributed among so many individual outlets would require a lot of equipment to be making simultaneous energy demands. The desigs is based on what is supposed to be possible, however unlikely it may be.

depends on how many 120v circuits you want

prob the best way is a 480v 3ph to 208v 3ph transformer

kva could 10-50, depending on how much power you need ( expensive)

put that into a 208v 3ph panel(200-250A), and line to neutral will be 120v

that would give you 20 circuits at 20A, assuming 50kva transformer

http://www.50hz.com/unitsize.htm?gclid=CMqowa3Yz6MCFSH5iAodg34guw#design

Thanks for all the reply's. between all of the different ideas i figured what i need to have done.

thanks again