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发表于 2016-10-13 11:28:42
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这是网上摘的：
How to convert RPM to the Frequency of the sinusoidal current that must be
generated for each phase, considering the number of pole pairs.
Suppose to have a 3 phase motor.
Suppose to have 20000 rpm, this means 20000 laps (mechanical) per minute.
And suppose that the motor is a 4 pole pairs.
The formula for calculate the mechanical frequency (MF) is:
MF = rpm/60
20000 rpm ==> laps (mechanical) per minute ==> 20000/60 = 333.33 per second (mechanical frequency)
To calculate the electrical frequency (Hz) is necessary multiplied the mechanical frequency by the number of pole pairs.
Hz = MF x Number_of_Pole
333.33 x 4 = 1333.33 Hz
This is the frequency of the sinusoid of current that must be generated for each phase.
But...
The sinusoid must be (Nyquist) at least twice but as we know it is not enough... we say that takes at least 10-12 times, (most
bigger is, the better is) to get an accurate reconstruction of the curve... the PWM frequency is our sampling frequency (in the
case in which the vector control is done every period of PWM).
So the PWM frequency is:
Fpwm >= 1333.33 * 12 = 16 KHz
Consider that 16 KHz is the minimum conditions.
If it is possible the suggestion is: go up in frequency but take care the switching losses.
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