Peak Demand Calculation - Stuck on U

I = 1000,000VA/(1.73x415)V = .....A, for S = 1000 kVA, 3 phase, 415 V.

I = 1000,000VA/230V = ....A, for S= 1000 kVA, single phase, 230 V,

makes a big difference on consumption so

72.64x1000/1.73x230=182.56A VS 72.64x1000/1.73x400=105A

Where did I get 1.73x230 from ??? I'm sure it is used

??? Your main supply is either 230 V or 415 V. Which is it?

P. S. I is for one leg.

So as I have 3 phase 415 supply, 105A is correct ?

72.64x1000/1.73x230=182.56A VS 72.64x1000/1.73x400=105A

So as I have 3 phase 415 supply, 105A is correct ?

72.64x1000/1.73x230=182.56A VS 72.64x1000/1.73x400=105A

Why are you even using the 72.64X1000/230Xsqrt3? It doesn't apply! The "230" is volts!

105 Amps is correct.

Or to put it another way when I use 1.73x230 what result is that giving me ..?

Thanks v.much Bill I didn't know if by using 230V what I was getting. Using 400V gives me a lower reading than I expect. As the supply cable is quite warm to touch ..

kva x 1000/1.73 x E =Amps ..

Dear All,

As shown in the formula;

I = (kVA x 1000)/U, then the calculation is using 72.64 multiplication factor.

Can someone explain me how to get this multiplication factor?

I am really do not understand where is 72.64 factor coming from? What I am thinking, the formula above is only for finding the current. Please correct me if I am wrong.

See below what I understand in finding the peak load demand.

For selection and sizing of the electric equipment such as Gas Turbine Generator (GTG) and Emergency Diesel Generator (EDG), we apply the following formula (may be different with others, but it is look like similar with ETAP).

Peak Load Demand = (Continuous running loads x A) + (Intermittent running loads x B) + (Standby loads x C) + the biggest standby load.

in which diversity factor A=100%, B=50% and C=0%.

Running loads, intermittent loads and standby loads are listed in load list.

Regards,

72.64 would be the number of kVA's. Where did you get the number? I assumed that you knew the number of kVA's your equipment required is 72.64 . . .

Hi guest,i believe u guess right or very sure of the information u have given us above.

U as above is 415volts. Why 230v,415v and 400v guess? and root3(1.732)?

In a 3 phase network system,determining factor is root3=1.73. If yr network 3phase voltage is 415v,single phase will be 415/1.732=240v; If it is 400v,single phase will be 400/1.732=230v; and if it is 380v,single phase will be 380/1.73=219v(220v).

Assuming we have 415v 3 phase supply (not 240v single phase),KVA-72.64;I-unknown, Our U will be 415v.

Apparent power S=root3 x U x I (For 3 phase system); I = S/root3.V =72.64 x 1000/1.732x415 =72640/718.78 =101 Amps.

This is the current value u need.However,with the above amperage,the board main breaker may be in the range of 150A-200Amps mccb.200Amps prefarably.

Patrick Whowha

Thanks Bill, I am realize that 72.64 is kVA system instead of multiplicatin factors, and thanks also for Patrick that your explanation can be accepted by us.