about v/f control
about v/f control
(OP)
hi chaps. i want to ask you about the role of the air-gap flux in the motors with regard to v/f control, everywhere it is written that v/f is kept constant to keep the magnetizing current constant, but why??? what is the relation between flux and torque? I also wonder the air-gap flux and torque relation , how can we show this by formulas..thank you in advance...






RE: about v/f control
The simple math is that flux in Vs/m2 is proportional to voltage times time (volts times seconds, hence Vs). Since the area of half a period of a sine wave is proportional to period length, it follows that you have to reduce V when period length is increased (which is identical to decreasing the frequency.
It is possible to elaborate that simple relatioship ad nauseam and many text-books do.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: about v/f control
RE: about v/f control
Since we need to change the frequency to change the speed, we also need to keep the V/Hz ratio constant so that the motor operates at optimum flux at all frequencies.
There are many basic texts covering this. Just google on and be educated.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...