Vehicle Drive Rotor Mode Switching for Magnet Heat Control
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Solution Overview
Problem
Permanent magnet motors in vehicles experience demagnetization due to high temperatures caused by eddy currents, particularly in high-speed travel, leading to insufficient motor torque.
Innovation Solution
A vehicle drive system with a rotor having a cage section and a permanent magnet section, switching between synchronous and asynchronous operation modes based on temperature, using induced currents in the cage section to reduce eddy currents and maintain motor torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the permanent magnet section is disposed on the inner circumferential side of the cage section in the rotor, then the motor can generate maximum motor torque in the low speed range, but heat accumulation occurs in the permanent magnet section due to eddy currents, causing demagnetization and insufficient motor torque in high speed range
Solution Approach 1:
The invention dynamically switches between synchronous operation mode (using permanent magnet section) and asynchronous operation mode (using cage section) based on motor speed and temperature conditions. This dynamic operation mode selection allows the system to utilize the permanent magnet section for maximum torque at low speeds while transitioning to cage section-driven operation at high speeds to prevent overheating and demagnetization.
Solution Approach 2:
The invention changes the operational parameters by switching between synchronous and asynchronous modes, effectively changing how the motor generates torque. In synchronous mode, the permanent magnet section is actively utilized for high torque output. In asynchronous mode, the cage section becomes the primary torque generator, reducing eddy current losses and heat accumulation in the permanent magnet section.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Suppresses demagnetization of the permanent magnet section by reducing eddy currents, ensuring consistent motor torque across varying speeds and conditions.
Implementation Method 1
the rotor is rotated by using a magnetic force of the permanent magnet section
Implementation Method 2
when an eddy current is generated in the permanent magnet section due to a rotating magnetic field of the stator, a temperature of the permanent magnet section is likely to become higher
Implementation Method 3
the rotor is rotated by using an induced current generated in the cage section
Data Source
AI summary
A vehicle drive system includes a motor that has a cylindrical stator and a cylindrical rotor provided in the stator to be coaxially rotatable with a center axis of the stator and drives a front wheel of a vehicle by rotation of the rotor. The rotor has a cage section and a permanent magnet section provided on an inner circumferential side of the cage section and formed of a rare earth magnet. The vehicle drive system further includes a controller that executes a synchronous operation mode when a temperature of the permanent magnet section is lower than a predetermined temperature, and executes an asynchronous operation mode when the temperature of the permanent magnet section is equal to or higher than the predetermined temperature. In the synchronous operation mode, the rotor is rotated by using a magnetic force of the permanent magnet section.