If all devices connected to a 400V 3 phase power system are balanced and have a perfect power factor, can we assume the voltage between each phase and neutral is 230V?

Why: I want to measure real power consumption of a 3 phase air conditioner, but can only use current clamps. If I can make the assumption that the voltages are 230V, then I would measure each phase separately and just add up the kWh together.

  • 1
    \$\begingroup\$ If you are connected to a real city grid the voltage will vary, if you are ok with that as an inaccuracy of your measurement you can assume the nominal grid voltage. \$\endgroup\$ – PlasmaHH Apr 5 '18 at 8:54
  • 1
    \$\begingroup\$ Yes, I'm ok with that inaccuracy. If I measured the voltage in a standard outlet, could I assume that in most cases it would be the same as in the 3 phase system? \$\endgroup\$ – Tomas Svitil Apr 5 '18 at 10:10
  • 1
    \$\begingroup\$ If you have the voltage of an outlet of the same grid, you can assume that at least that phase has the same voltage at your AC unit, but the other phases may be a bit off, though in most bigger grids not that much \$\endgroup\$ – PlasmaHH Apr 5 '18 at 10:12
  • 1
    \$\begingroup\$ Great, this answers my question. Do you want to move it into the answer? \$\endgroup\$ – Tomas Svitil Apr 5 '18 at 10:12
  • 1
    \$\begingroup\$ Assuming the air conditioner has a perfect power factor means your calculated power is 5 to 30 percent high plus or minus the 5% line voltage variation. \$\endgroup\$ – Charles Cowie Apr 8 '18 at 12:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.