Electric Motor Rotor Temperature Control Using Speed Estimation
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Solution Overview
Problem
Conventional electric motor control systems for vehicles do not consider the rotation speed of the motor, leading to excessive output limitations at low speeds and inefficient operation, as they assume high-speed conditions, resulting in reduced performance and potential demagnetization of permanent magnets.
Innovation Solution
A control apparatus that estimates the rotor temperature using stator, refrigerant, and rotation speed information to adjust the output characteristics and drive conditions of the electric motor, preventing excessive limitations at low speeds and ensuring efficient operation across speed ranges while preventing demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If output control is performed without considering rotation speed based on stator temperature and oil temperature, then permanent magnets are protected from demagnetization at high speeds, but output is excessively limited at low speeds and motor efficiency is reduced
Solution Approach 1:
The control apparatus changes the parameter used for temperature estimation from static parameters (stator temperature, oil temperature) to a dynamic parameter that includes rotation speed. This allows the system to adapt the output control strategy based on the actual operating conditions, preventing demagnetization at high speeds while avoiding unnecessary output limitations at low speeds.
Solution Approach 2:
The system transitions from static temperature-based control to dynamic rotation speed-aware control. By incorporating rotation speed information into the temperature estimation and control logic, the system can dynamically adjust output limits according to actual thermal conditions, optimizing both protection and performance across different operating ranges.
2Reliability
If high-speed rotation assumptions are made for all operating conditions, then demagnetization risk is controlled, but motor performance is unnecessarily restricted during low-speed operation
Solution Approach 1:
The control system changes from using fixed high-speed assumptions to using rotation speed as a variable parameter in temperature estimation. This allows the system to differentiate between high-speed and low-speed conditions, applying appropriate control strategies for each regime and avoiding unnecessary power restrictions during low-speed operation.
Data Source
AI summary
A control apparatus includes: a rotor temperature estimation unit estimating a temperature of a rotor based on stator temperature information from a first temperature sensor for identifying a temperature of a stator, refrigerant temperature information from a second temperature sensor for identifying a temperature of refrigerant used to cool an electric motor, and rotation speed information about the rotor from a resolver for identifying a rotation speed of the rotor; and an electric motor control unit controlling at least one of an output characteristic and a drive condition of the electric motor based on the temperature of the rotor estimated by the rotor temperature estimation unit.