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hello friend in order to control the speed of an ac motor you canachive that either by controlling voltage supplied to it or by controlling the frequency given to it
Hello
which kind of AC motor is it ?
if it is an induction motor , you can not control its speed by controlling the voltage as its output torque will decrease dramastically. However , you can control its speed by changing the frequency
you should read something about space vector pulse width modulation (SVPWM)
Regards
Ahmed Salah
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if it is an induction motor , you can not control its speed by controlling the voltage as its output torque will decrease dramastically. However , you can control its speed by changing the frequency...
To be more precise, voltage to frequency ratio should be kept constant for precise control. But do not forget, that all theory is not about voltage across motor terminals and for example determining of internal "resistors" in real time is almost nightmare thanks to their relation to temperature.
Sorry, I have forgotten a lot of theory during years, but I would personally never dream about induction motor controlled by 8051 itself, because some DSP coprocessing is "a must" for correct flux calculation. If you really want ac motor control, try to focus yourself on synchronous motors with permanent magnet. If you will design three phase generator circuitry and control, the rest is done almost in no time.
I have a similar project done with SVPWM. I had used a 80196 to control the speed of the 3-phase motor, by this technique. I can be of help, if the requirement is given in detail
hi
speed of induction motor is function of suppy frequency and voltage.
so we can controll speed by controlling either speed or freq,but in order to keep output torqe constant over the operating range we have to keep v/f ratio constant.
if we dont maintain this ratio constant motor current will rapidly inqrese and it might be damage our motor and inverter
I think V/F ratio must be kept constant for frequencies over the nominal frequency.
But for lower speeds (lower frequencies) , V can be kept constant while changing the speed by changing the frequency.
use other than the 51 for better operation because there will be problem of reset of mc during operation. For that keep distance between mc and triac .
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