## Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

## Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

(OP)

Hello to all. Should the following formula be used to calculate the voltage drop of the motor in the delta condition in a star-delta system considering that there are 2 cables between the panel and the motor and the current of this cable is 1/1.73 of the motor current?

voltage drop=Irated/sqrt(3)*(2*R*cos(phi)+√(1-cos(phi)^2)*2*X)

voltage drop=Irated/sqrt(3)*(2*R*cos(phi)+√(1-cos(phi)^2)*2*X)

## RE: Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

## RE: Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

## RE: Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

".... Should the following formula be used to calculate the voltage drop of the motor in the delta condition in a star-delta system considering that there are 2 cables between the panel and the motor and the current of this cable is 1/1.73 of the motor current?.....Should the length of the cable be considered twice?"I look at it this way for your consideration.

1. For simplicity, take the motor (run/delta) or rated current be I A.

2. A SD starter, when in run/delta condition:

a) the

sourcecurrent is I A.b) the current flow through the

main contactor=the delta contactor=the current flow through each of the six conductors.c) the current is

[ 0.732 x I]A.3. The VD is calculated based on the current above 2. c).

4. For simplicity, the pf may be taken as 1.0, instead of the rated; as it varies within a small range, depending on the load.

Che Kuan Yau (Singapore)

## RE: Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

## RE: Formula for calculating motor voltage drop in delta condition in a star-delta motor circuit

"...Item c. is incorrect. It’s not 0.732 x 1. It is 1 / 1.732 which is .577 (58%)".Thank you Sir. My sincere apology for the typographical error.

Yes, it should be

[0.577 x I ]A.Che Kuan Yau (Singapore)