If you want to buy ac induction motor, know two ways to estimate the speed of an induction motor
In order to improve the reliability of the motor system, the speed estimation method without speed sensor can be used as an alternative or redundancy. At present, there are two main types of speed estimation methods. The first type of method is based on the mathematical model of the motor, such as the full-order state observer, the extended Kalman filter, the sliding model observer, and the model reference adaptive system. The accuracy of the mathematical model, Inevitably affected by the change of motor parameters during use; The second kind of method uses the inherent magnetic convex pole structure characteristics of the motor to obtain the motor speed information, such as rotor groove harmonic method and high-frequency signal injection method, etc.. This kind of method has strong robustness to the motor parameter changes, and has certain advantages in reliability and stability.
The rotor Anisotropy of the cage induction motor is weak, and it is suitable to use the magnetic convex pole generated by the rotor slot effect to estimate the speed. The high-frequency signal injection method will increase the torque pulsation of the motor, and at the same time, the rotor convex pole effect is required to be higher. Therefore, this paper follows the idea of rotor groove harmonic method to carry out research.
Since the 1990s, scholars at home and abroad have begun to use rotor groove harmonics in stator currents to estimate motor speed. The method is simple and inexpensive. However, its application scope is limited by the motor structure. When the ratio of the number of rotor slots to the number of pole logarithms of the motor is odd or fractional, the rotor grooves in each slot of the stator are neutralized by the induced electromotive force. No rotor groove harmonic current is generated. In addition, the rotor groove harmonic value in the motor stator current is very small, especially when the motor is light loaded or the stator phase voltage is small, and the amplitude difference is not large compared with the harmonic and electromagnetic noise in the nearby frequency domain.] , which reduces the accuracy and reliability of speed measurement.
