how to calculate power of three-phase PWM which drive BLDC

hitbuyi · Nov 3, 2012

i have a bldc drive board, it has three wires to connect a bldc motor, now i want to calculate the efficiency of the drive board according to following 2 steps

1, measure input power, using DSO to measure voltage V and current I ,Pi =V*I
2, measure output power, i think if i can get power of one wire Po, the total
power is 3*Po,and

efficiency = 3*Po/ Pi
but i found the voltage wave of the wire is 20k PWM, and current is square,

how to calculate the Power Po?

thank u in advance.

ScottWang · Nov 3, 2012

Assuming PWM duty cycle is 50%/50%.
3*Po/ Pi → 3*Po/V*(I/2)

hitbuyi · Nov 12, 2012

ScottWang said: ↑

Assuming PWM duty cycle is 50%/50%.
3*Po/ Pi → 3*Po/V*(I/2)
Click to expand...

i still do not know how to decide U, I, since V is pwm, and I is exponential,not DC

how to calculate power of three-phase PWM which drive BLDC

hitbuyi Thread Starter New Member

ScottWang Moderator

hitbuyi Thread Starter New Member

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