## AC Motors

## AC Motors

(OP)

I'm trying to figure-out what would be the approximate max. or by calculation of phase currents I1,I2,I3 in a 3 phase-four wire system, with a given 1875KVA/380Vac, rated generator.(Balance load)

The question is for me to determined the type of CT's to be installed in 3 phases for add/shedding application. Pls. assist--Thanks

The question is for me to determined the type of CT's to be installed in 3 phases for add/shedding application. Pls. assist--Thanks

C.A.A.

## RE: AC Motors

## RE: AC Motors

## RE: AC Motors

{220V … 2.6A/kVA}

{480V … 1.2A/kVA}

{208V … 2.8A/kVA}

## RE: AC Motors

I would rather choose to look for a whole package power monitoring device that will feed information to my program which monitors status of the loading condition of my genset.

I have variable 220Volts load with respect to ground.

I understand that total current from power formula is equal to all phase current say-- Ia,Ib,Ic at full load condition right?

C.A.A.

## RE: AC Motors

## RE: AC Motors

I mean to say total current as per specification from 1875KVA. Would it be It=Ia=Ib=Ic?

Thanks for being prompt.

C.A.A.

## RE: AC Motors

It is likely that the only current of interest are the phase currents which are assumed equal, and can be used in the formula Stotal=sqrt(3)*VLL*Iphase.

(where S is va)

Note that if you represent the load as equivalent wye, the voltage across each phase is VLL/sqrt(3). We find the power across each of the single wye legs as:

S_singlephase=IV = Iphase*VLL/sqrt(3)

The total three-phase power is

S_three_phase = 3*S_singlephase

= 3*Iphase*VLL/sqrt(3)

= sqrt(3)*Iphase*VLL.

I'm not sure if that helps.

## RE: AC Motors

S = Van*Ia + Vbn*Ib + Vcn*Ic

or, the description of apparent power is the sum of the products of each phase-to-neutral voltage and its associated phase current. Clear as mud, right?

## RE: AC Motors

It helps me really.

csr

## RE: AC Motors