Rotor Resistance Identification And Online Evaluation Method Of Temperature Rise Of Induction Motor

In order to evaluate the energy efficiency of induction motor,the most commonly used low uncertainty methods are energy consumption analysis and equivalent circuit method.However,the above two methods are still faced with the following four difficulties for the motor operating in field.Firstly,most of the motors in field are not equipped with speed and torque sensors,resulting in the failure to evaluate the output power of the motor shaft and the efficiency of the motor can not be accurately evaluated;secondly,as rotor slot frequency is the most commonly used evaluation method of motor speed,it needs to know the number of motor rotor slot in advance,though this parameter can be obtained from the design list for laboratory motor,it is not easy to obtain in field;in addition,to complete the calculation of the losses in motor operation,it is necessary to know the equivalent circuit of the motor,but the rotor resistance varies greatly due to the temperature rise effect;finally,as to acquire the important index for evaluating the safety and health of the motor,the installation of wireless temperature sensor is expensive and complex,which also increases the invasion.In order to solve the above four difficulties,this thesis adopts the idea of combining parameter identification and equivalent circuit method to achieve the identification of rotor resistance and temperature rise of induction motor.The main work is summarized as follows.1)For the induction motor in the field,speed sensors are usually not installed and the rotor slot number is unknown,so the electrical quantity of the motor and the two special working conditions of the motor’s no-load and load operation are used to calculate the number of rotor slots of the motor,and the real-time speed is calculated by the motor rotor slot frequency method.2)Based on the on-line monitoring method of rotational speed,the identification of rotor resistance is realized under the condition of no-speed acquisition device with the model reference adaptive method,this model takes the result of the identified speed as a known quantity,and realizes the simultaneous identification of rotation speed and rotor resistance,then takes the resistance as the parameter in the equivalent circuit to calculate the losses and motor efficiency.3)And on the basis of obtaining the rotor resistance of the induction motor accurately,combined with the strict mathematical relationship between material winding resistance and temperature rise condition,assessment of rotor temperature is achieved.The above methods provide an important reference for the monitoring of the operating state of the motor without speed,torque and temperature sensor.