"Bob AZ" wrote in message
oups.com...
But we are dealing with a resistive load. No inductance or
capacitance.
A resistive load will not concern itself with phasing. So the 3
phase
thing is moot.

If we had a 3 phase device that has an ouput function, motor,
transformer or the like then we would be dealing with other things
like
is the 3 phase Delta or WYE? And is the loading on the 3 phase,
phase-to-phase or phase to neutral/ground.
Bob AZ


OK, for ease of calculations, letrs say we have a 2400 watt 240 volt
single phase heater. The line current is 2400/240, or 10 amps.

Now, a 2400 watt 3 phase heater is 800 watts per phase. The three 800
watt elements are wired in delta. The load current for each element is
800/240, or 3.33 amps.

By drawing the vector diagram of the 3 load currrents and and some
trig, the line currrent for each leg is 3.33 * square root of 3, or
5.77 amps

And 5.77 * square root of 3=10


Resistance can be used if you prefer. Say we have 3 heater elements
that measure 15 ohms. If one was connected across a 240 volt single
phase line, the power dissipated would be 240 * 240/15, or 3840 watts,
with a current of 16 amps. Three of those in parallel would be 11,520
watts total, with a current draw of 48 amps.

Now, wire those three elements in delta. Each element is still across
240 volts, so each one still dissipates 3840 watts (for a 11520 watt
total) and draws 16 amps. But since it's three phase, the line current
is 16 * square root of 3, or 27.7 amps.

And 48 /square root of 3 also =27.7...

It's still early-I hope all those numbers are right, lol...