I am renting a wood drying kiln at someone's machine shop location. He wants to charge me for the power usage for the kiln. the kiln has 3 heaters connected in delta and they are supplied 3 phase electricity. I have to pay him, but I do not how much energy is used.

I know the line amps and line voltage, but nothing else. The load is a resistive load. All three phases have 13 amperes load. Two line voltages are 120 volts at 180 degrees phase difference. Third line voltage is 240 volts at 90 degrees phase difference to each of the other two voltages. I would like to have the formula to calculate power for such unbalanced circuit.

Please help me if it is possible for you to do that.

Best regards,
Gulab Gidwani
[email protected]

 

Since they are resistive loads:
total power will be 2x120x13 + 240x13=6240W

You need to know the ON time for the heaters to calculate the kWhr.

 

As the currents are balanced it is not clear how it shall be an unbalanced circuit. is the resistance values known?

 

Just go buy a power meter. Most kilns do not operate at full load anyway all the time so even if you knew what the mac load was it won't tell you the actual amount of energy used.

 

Gulabg...

the specifics you provided, i.e., 3-ph delta, 120V, 240V, 90deg, and 180deg, are more associated with a 3-ph, 4wire, delta-connected, center-tapped (hi-leg) secondary distribution system.

Can you provide a hand-drawn sketch of your system?

Regards,
Phil Corso

 

The answer given by dwpatterson is almost correct.

my question is, how will you know when your heater gets ON and after what time span it gets OFF...?

I think it is probably in automatic temperature control mode...??
So it is very tough to measure the actual ON time.
if your heater stayed On for avg N hours for a day then your monthly consumption will be= 6.24*N*30 KWhr.

Now you decide how will you measure your actual N.
for unbalanced load, you may buy three single phase meter and connect them in three phase separately and measure the KW and finally sum up the three values. that's it.

 

Gulabg...

It can be readily calculated using only Voltage and Current magnitudes. All that is necessary is simple drawing of your setup, showing source arrangement, and load configuration.

If you want to, send it to [email protected]