Why does the frequency change when the frequency converter regulates the frequency?
That's for sure. The curve of voltage and frequency should be set according to the load condition, but after the rated frequency of the motor, the voltage is kept at the rated voltage
That's for sure. The curve of voltage and frequency should be set according to the load condition, but after the rated frequency of the motor, the voltage is kept at the rated voltage
Because the product of three-phase asynchronous motor stator phase voltage and frequency and flux is proportional to the frequency when the downward adjustment, if the sustain voltage is constant, the flux must be increased, this will cause the main magnetic saturation excitation current passing, the surge in motor damage.As a result, the voltage is usually adjusted down proportionally as the frequency is lowered down.However, when adjusting the frequency, the voltage is not adjustable in order to avoid the excessive voltage damage of the motor. Therefore, in the use of frequency converter overclocking motor, the magnetic flux will decline, the motor output torque characteristics will move to the left.
Main flux of motorM = U/ (4.44*f*N)In the upper model, the U is the stator voltage, that is, the output voltage of the inverter, f is the frequency, and N is the stator winding turn number.N is a constant.Obviously, when the frequency changes, if the voltage is constant, then the flux will change.The iron core of the motor is nonlinear, and when the flux changes, both too large (saturated) or too small (weak magnetic) is detrimental to the motor.Therefore, when changing the frequency, the voltage is changed, and the constant value of U/f is kept, so that the magnetic flux can be kept unchanged.
