Will the asynchronous motor pole change the number of speed control can also be combined with the frequency converter
but the use of the inverter is based on changes in the load by changing the frequency of power into the motor at any time speed control, you can achieve a smooth and accurate stepless speed control is Now widely used in a speed control method, especially for the load often change or often in the light load operation of the motor.
As you said the asynchronous motor after a very logarithmic change can be achieved on the speed of the "coarse tune", and then use the inverter is equivalent to add a "fine tune" device, but it seems a bit expensive, but to To see what you are on the occasion of the worthless.
Of course, because the factors that determine the speed of asynchronous motor power supply voltage, frequency and motor pole pairs, so asynchronous motor speed can be achieved by changing the number of magnetic pole pairs, but this method needs to make a greater motor changes, Trouble, and change the number of poles can only achieve a single speed change;
