# Calculating total voltage/current for 3-phase?

Consider I have a 3-phase generator with the following measurements:

Phase 1 (A): 22.8828A
Phase 2 (A): 22.9922A
Phase 3 (A): 22.9219A

Phase 1 (V): 239.7656V
Phase 2 (V): 241.8594V
Phase 3 (V): 245.9375V

I will like to know what is the total current generated, as well as the voltage value. Additionally, I want to find the power too.

What I am thinking is that the 3-phase current and voltage will just average respectively and then applying P = sqrt(3) * pf * I * V to find the power?

I would appreciate some clarification.

I would appreciate some clarification.

If you had a supply of 2 volts and another supply of 4 volts and each powered a 1 ohm resistor, the wattages would be 4 watts and 16 watts respectively. The total power is 20 watts.

What I am thinking is that the 3-phase current and voltage will just average respectively

So let’s try this. The average voltage is 3 volts and into two lots of 1 ohm resistors, that’s a total power of 9 watts plus 9 watts. That’s a total of 18 watts and not 20 watts.

How inaccurate an assumption are you prepared to accept?

P = sqrt(3) * pf * I * V

That’s assuming that the load is linear i.e. produces a sinusoidal current from a sinusoidal voltage. If it isn’t linear then power factor is somewhat meaningless.

Given that you are specifying phase voltage in your question then the root 3 isn’t relevant for either total power or single phase power. This is the formula for total 3 phase power with a linear load: -

Picture from here.

Notice that the above formula uses line voltage and not phase voltage. If phase voltage were used (as per the detail in your question) then total power is 3 x and not root 3 x.

I will like to know what is the total current generated, as well as the voltage value. Additionally, I want to find the power too.

The total current is zero as what goes out on one phase must come back on the others. Your concept of "total current" doesn't work on a three-phase system.

You could add the currents (taking the power-factor into account) to work out the equivalent single-phase current that would produce the same power.

What I am thinking is that the 3-phase current and voltage will just average respectively and then applying P = sqrt(3) * pf * I * V to find the power?

As @Andyaka has pointed out you are giving the phase to neutral voltages so you'll use $$\ P = IV \times pf \$$ where pf is the angle between the single phase voltage and current. Your approach will work if the system is balanced. If not then the correct approach to finding total power is to sum the powers in each phase.

I think you could round down your measurements to three significant digits. That sort of precision is unlikely.

• You took your time to spot the error lol! Feb 2, 2020 at 18:11
• Not thinking straight. Thanks. Imagine that i do this as part of my jobfrom time to time! Feb 2, 2020 at 18:14