## Three phase unbalanced load flow

## Three phase unbalanced load flow

(OP)

A balanced 240V a.c. phase-to-phase three phase ( A-B-C ) star connected source of equal negligible positive and negative sequence impedance and no connection to earth (ground) supplies single phase 240V a.c. incandescent lamps.

Each lamp is connected between 240V phase-to-phase at 5 m intervals along a three core ( A-B-C ) cable with the objective of achieving three balanced line cable currents ( A-B-C ) . Eg. lamp connections A-B, B-C, C-A .....

Can anyone suggest how the load flow currents and can be calculated

Each lamp is connected between 240V phase-to-phase at 5 m intervals along a three core ( A-B-C ) cable with the objective of achieving three balanced line cable currents ( A-B-C ) . Eg. lamp connections A-B, B-C, C-A .....

Can anyone suggest how the load flow currents and can be calculated

## RE: Three phase unbalanced load flow

Hence, the current in A-B-C lines will be that in any of the three circuits (same current as the loads are balanced) multiplied by sqrt3.

## RE: Three phase unbalanced load flow

" ... A balanced 240V a.c. phase-to-phase three phase ( A-B-C ) star connected source.... no connection to earth .... supplies single phase 240V a.c. incandescent lamps. Each lamp is connected between 240V phase-to-phase....( A-B-C ) cable ...achieving three balanced line cable currents ( A-B-C ) . Eg. lamp connections A-B, B-C, C-A .....Can anyone suggest how the load flow currents and can be calculated "1. Your source ABC is in

Yformation. Neutral is non-earthed. VAB =VBC =VCA =240 V .1.1 Attention: Take note that VAB , VBC, VCA are 120deg apart.

2. Your 240V lamps are connected in

Dformation, across AB, BC, CA.3.

YouNEEDto know thewattageof the lamps in order to calculate the current through each lamp.3.1. The Current through each lamp will be the same=balance = i =W/V, where V=240V , W=wattage W.

4.1. The current from the source will the same=balance IA=IB=IC ... A.

5.

The source current IA=IB=IC = 1.732 x current through each lamp, see above 3.1.Che Kuan Yau (Singapore)

## RE: Three phase unbalanced load flow

## RE: Three phase unbalanced load flow

## RE: Three phase unbalanced load flow

OK except that there is no neutral, so the phase voltages are not defined. If you assume balanced 3Ø voltages, then if the loads are unbalanced, the phase currents will not sum to zero. They have to aum to zero because there is no neutral. See the attached Excel workbook.

## RE: Three phase unbalanced load flow

## RE: Three phase unbalanced load flow

## RE: Three phase unbalanced load flow

If it is convenient to choose to pick a point in the center of the Y for the purpose of calculation, the fact that it is not defined with respect to ground does not matter either.

Caution - sometimes the ground reference matters, it depends on the question.

## RE: Three phase unbalanced load flow