What current profile gives the best Power Correction Factor (the least losses)?
A sine wave in-sync with the voltage?
20W User
PFC thoughts
What current profile gives the best Power Correction Factor (the least losses)?
A sine wave in-sync with the voltage?
Last edited by ashiekh; 03-13-2018 at 06:38 PM.
Jun Fu capacitor advocate
Yes, when the current is in phase with the voltage, you will have a power factor of 1, which is the most ideal.Originally Posted by ashiekh
A resistive load (say a good old wire heater) should have a power factor of 1.
20W User
I tried a few current shapes, and so far none have beat the sine wave for losses. I even think I now have a proof of why the current needs to follow the voltage (for minimum losses), that works for all voltage shapes (not just sinusoidal); using ideas from functional analysis.
A strange exception to a resistive load being ideal:
Imagine a bulb whose filament resistance increases with temperature, it is pure resistive, but has higher resistance at high voltages, and so will have a non-sinusoidal current curve and so higher cable loses than an equal load with constant resistance.
Interestingly, the larger the primary capacitors, the worse the power factor issue (assuming no correction), due to reduced conduction angle; by the same reasoning the smaller the load the worse the power factor issue.
Last edited by ashiekh; 03-14-2018 at 08:05 PM.
200W User
Well, P = I dot V. If the objective is to minimize I while P and V are constant, obviously the phase between any components should be zero. Also, any harmonics from a non sinusoidal current waveform will be orthogonal to a sinusoidal voltage waveform and will have no contribution to the overall power output and be waste as well.
P = sum ( I_i V_j )
= sum ( |I_i| |V_j| int sin w_i t sin w_j t dt )
= |I_i||V_i| int sin w_i t sin w_i t dt
20W User
Nicely argued
Last edited by ashiekh; 07-11-2018 at 08:20 PM.
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