In a message dated 5/9/2009 4:53:20 PM Eastern Daylight Time,
plohstreter@mail.hockaday.org writes:
Found this on a web site for a UPS.
Output Power Capacity
600 Watts / 750 VA
Isn't a Watt = VA ? Why the difference?
No, a watt isn't a voltamp. Watts are equal to the power factor time the
voltamps. This is because the circuit has capacitance and/ or induction.
Actual power is watts , not voltamps.
P_true= PF*P_app
P_app (apparent power is voltamps)
PF =cos[theta] where theta is the lag or lead in current from voltage due
to the reactance in the circuit.
cos[[theta]= P_true/P_app
Nominal power factors run between . 8 to .9 in most units.