3 phase power calculations

Hi All

I'm struggling to reconcile some 3 phase power calculations.  I've got a heater with 261 elements each at 3.161, watts this means that there are 87 per phase (delta) which is 275,007 W per phase.  I think to get the total I should multiply by 1.732, which gives 476,312 W, but the spec is 825 kW.  WHat am I doing wrong?



  • Well, assuing that you have not wired the heaters in delta when they are supposed to be star or the other way about, the power total, is simply the power total.

    The multiplier you mention is the ratio of the phase to phase voltage (400) to the phase to neutral voltage (230V) and is only needed when you have the current in a delta load, and wish to deduce the supply current in a single phase wire, But so long as you understand that 400V loads connect phase to phase and star ones connect phase to neutral, it matters not one jot - and heaters are easy, no power factors !!

    so the total power of 261 elements at 3 and a tad kW is 800 thousand watts...  Each phase is pulling 1/3 of that so 220kW per phase or about 1000A per phase.