Re: why do we use 1.73?
Well, I should go to bed, but I'll get it started anyway. This usually takes an hour in the classroom with a digital projector, etc, etc.
It depends on where you are in math with regard to vectors, etc.
First of all, in a three phase system, the three voltages are "out of phase" with each other by 1/3 of a cycle or 120 degrees.
So you see that in a wye connection -
a. line voltage (E-line) = phase voltage (E-phase) x 1.732
b. line current (I-line) = phase current (I-phase)
In a delta connection, it is the opposite -
a. line voltage (E-line) = phase voltage (E-phase)
b. line current (I-line) = phase current (I-phase)x 1.732
The next thing to tackle is the power formula. To keep things simple, let's assume the load is non-inductive, with 100% power factor.
Single phase power - W (watts) = E (volts) x I (amps)
For three phase power, the formula used depends on whether you use the
phase volt and amp values or the
line volt and amp values.
Using phase values - W = E-phase x I-phase x 3
Using line values - W = E-line x I-line x 1.732
Make any sense so far?
Ed
[ September 19, 2003, 07:26 AM: Message edited by: Ed MacLaren ]