Induction Motor Rotor Resistance Estimation via Maximum Torque Search
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Solution Overview
Problem
Existing methods for estimating rotor resistance in induction motors, such as blocked rotor tests and online magnetic flux estimation, suffer from significant errors and complexity, making accurate rotor resistance estimation challenging for precise vector control.
Innovation Solution
A system comprising an equivalent torque curve generation unit, minimum current operation point determination unit, equivalent current phase variable control unit, output torque detection unit, and rotor resistance determination unit, which generates and varies the rotor resistance to detect the maximum output torque, thereby accurately determining the rotor resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If blocked rotor test is used to estimate rotor resistance, then the estimation process is simple, but significant errors occur in the rotor resistance value
Solution Approach 1:
The patent changes the operating parameters from blocked rotor test conditions (slip=1) to minimum current operation point conditions on equivalent torque curves. This parameter change enables accurate rotor resistance estimation by operating the motor under specific current and torque conditions where the estimation is most accurate, rather than using simplified test conditions.
2Measurement precision
If conventional online magnetic flux estimation method is used, then rotor resistance can be obtained during operation, but the method involves complicated logic implementation and large estimation errors in certain regions
Solution Approach 1:
The patent extracts the rotor resistance estimation function from the complex online magnetic flux estimation method. By separating this specific function and implementing it through equivalent torque curve analysis at minimum current operation points, the system achieves accurate rotor resistance estimation without the complicated logic and large errors associated with conventional online methods.
3Reliability
If accurate parameter information is used for vector control, then precise torque control is achieved, but obtaining accurate parameters requires complex testing and calculation
Solution Approach 1:
The patent enables the induction motor to self-identify its rotor resistance parameter by operating at minimum current operation points on equivalent torque curves and detecting the operation point with maximum output torque. This self-service approach eliminates the need for complex external testing and calculation procedures, while providing accurate parameters for reliable vector control.
Data Source
AI summary
A system for estimating a rotor resistance of an induction motor includes: an equivalent torque curve generation unit to generate an equivalent torque curve based on output torques of the induction motor; a minimum current operation point determination unit to determine a minimum current operation point of the equivalent torque curve; an equivalent current phase variable control unit to variably control a rotor resistance of the induction motor when a stator current command of the minimum current operation point is applied to the induction motor; an output torque detection unit to detect the output torque of the induction motor when the rotor resistance is variably controlled; and a rotor resistance determination unit to determine a maximum torque among the detected output torques and determine an actual rotor resistance of the induction motor based on the rotor resistance when the maximum torque is generated.