Regulator of steady frequency speed control system, due to the non-linear motor stator frequency stabilization In addition to the fundamental current, harmonic current, due to the presence of high harmonics, so that the motor loss and inductance increases, reducing the cos φ, thus affecting the output torque, and will produce six times the fundamental frequency pulsating torque. 
 The fifth harmonic frequency in the three-phase motor stator current F5 = 5F1, a space of negative sequence magnetic potential and magnetic field in the motor air gap, the speed of the magnetic field generated by the magnetic field rotational speed n11 n51 is the fundamental current five times, and rotate along with the fundamental magnetic field in the opposite direction, motor speed is fixed, and assuming that close to the n11, so that by the 5th harmonic magnetic potential induced in the rotor out of six times the fundamental frequency of the rotor current, no touch point regulator current effect on the synthesis of the air gap fundamental magnetic potential to produce six times the fundamental frequency pulsating torque. 
 But it generates a rotating magnetic field speed of 7 times the fundamental rotating magnetic field; harmonics; the speed, so the relative speed of the corresponding rotor current harmonics with the main air-gap magnetic field is six times the fundamental frequency, also produced a six times fundamental frequency of the pulsating torque. 
 Regulator at each voltage pulse time, the vector ψ1 move to the constant linear velocity in the zero-voltage segment to remain stationary, however, due to the vector ψ2 rotating at a constant angular velocity W1, the angle δ of ψ1 and ψ2 appeared, so the voltage The chopper is the main reason causing the high-frequency torque ripple frequency and output voltage pulse frequency of moments. This is due to the PWM inherent, in fact, non-contact voltage regulator high-frequency torque ripple is very difficult to eliminate, and superimposed on top of the low-frequency torque ripple. 
 Natural voltage waveform cycle polygon turn one weeks time required to determine the by ψ1 vector along. This method maintains the output voltage from zero to maximum value can be stable at the same time, can effectively eliminate the low-frequency torque ripple. 
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