What is the difference between variable frequency motor and variable speed motor?
Give you a formula, you can understand their speed control principle: N (speed) = 60f (frequency) divided by P (magnetic pole logarithm) According to the formula, when you want to change the motor speed, there are only two ways to change The number of pole pairs and the frequency of the power supply. Speed ??motor is variable pole speed, that is, in this motor has 2 to 3 sets of windings, by changing the winding connection, to change the motor pole to change the rotation speed.
The variable frequency motor requirements are high, are special motor, so the general motor can not use the inverter to speed. According to the above formula, it can be seen that increasing the frequency, the motor speed will be faster, reduce the frequency of the motor speed is slow, variable frequency motor core is also a special material, because the ferromagnetic material There is a saturation period, to the saturation period, regardless of whether the motor current increases, the motor will not continue to increase the intensity of the magnetic field,
so the output torque will not change, that increase the current work is useless work. Variable frequency motors are generally used for deceleration, and in accordance with the law to adjust the voltage and frequency, that is, no matter how changes, the voltage divided by the frequency is a constant value.
