Electric Machine Flux Control for Demagnetization Prevention
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Solution Overview
Problem
Electric machines face limitations in torque output due to temperature-dependent magnetic field loads, leading to potential demagnetization and reduced performance, necessitating restricted operating ranges and varying vehicle acceleration based on temperature.
Innovation Solution
Implementing a method with two operating modes for the electric machine, where the magnetic stator flux is reduced at higher temperatures to prevent demagnetization, allowing the machine to operate safely and efficiently by reducing current amplitudes and opposing magnetic fields during active short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric machine operates at high temperature, then the magnets are exposed to higher opposing magnetic fields which may cause demagnetization, but reducing the torque output limits the machine's performance and varies vehicle acceleration
Solution Approach 1:
The patent applies dynamics by making the magnetic stator flux adjustable rather than fixed. The control system dynamically adapts the magnetic stator flux based on operating conditions, allowing the electric machine to operate reliably at high temperatures while maintaining optimal torque output through real-time flux adjustment during active short circuit operations
Solution Approach 2:
The patent changes the magnetic stator flux parameter specifically during active short circuit operations at high temperatures. By reducing the magnetic stator flux in this specific operating condition, the opposing magnetic field on the magnets is reduced below the demagnetization threshold, while the torque output is maintained through controlled current adjustment
2Reliability
If the magnetic stator flux is reduced to prevent demagnetization at high temperatures, then the opposing magnetic field load on magnets decreases, but the torque output capability is limited
Solution Approach 1:
The system dynamically adjusts the magnetic stator flux based on real-time temperature and operating conditions. During active short circuit at high temperatures, the flux is reduced to protect magnets, while under normal operating conditions the flux is maintained at optimal levels for maximum power output, making the protection mechanism conditional rather than continuous
Solution Approach 2:
The magnetic stator flux parameter is changed specifically during active short circuit operations at high temperatures. The control system reduces the flux only in this specific condition to prevent demagnetization, while maintaining full flux capability during normal operation to preserve continuous power output and vehicle performance
3Reliability
If the torque is limited at higher temperatures to ensure reliable operation, then the opposing magnetic field is reduced, but the vehicle acceleration varies subject to temperature
Solution Approach 1:
The control system dynamically adjusts the magnetic stator flux during active short circuit based on temperature conditions, allowing the vehicle to maintain consistent acceleration characteristics across different temperatures. By adapting the flux rather than limiting torque universally, the system preserves driver-expected acceleration while protecting against demagnetization
Solution Approach 2:
The system takes preliminary anti-action by reducing the magnetic stator flux specifically during active short circuit operations at high temperatures, before demagnetization can occur. This targeted approach prevents the harmful effect (demagnetization) without unnecessarily limiting torque output during normal operation, thereby maintaining consistent vehicle acceleration
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
This approach prevents demagnetization and allows for increased continuous torque and power output while maintaining reliable operation across a wider temperature range, with reduced torque limitations compared to traditional methods, and ensures consistent vehicle acceleration.
Implementation Method 1
the magnetic stator flux of the electric machine is reduced in comparison to the magnetic stator flux of the electric machine when the electric machine is operated in the first operating mode
Implementation Method 2
The material properties of magnets are temperature-dependent. The greater the temperature of the magnets, the smaller the permissible opposing magnetic field load
Data Source
AI summary
The invention relates to a method and device for operating an electric machine (10) for outputting a predefined torque and a predefined rotational speed, comprising the following steps: providing (420) a first and a second operating mode for the operation of the electric machine (10); detecting (430) a temperature of the electric machine (10); and operating the electric machine (10) in the first operating mode (440) if the detected temperature falls below a threshold value, and operating the electric machine (10) in the second operating mode (450) if the detected temperature corresponds with the threshold value or exceeds same. During the operation of the electric machine (10) in the second operating mode (450), with the resulting output of the predefined torque and the predefined rotational speed, the magnetic stator flux of the electric machine (10) is reduced compared with the magnetic stator flux of the electric machine (10) during the operation of the electric machine (10) in the first operating mode (440), with the resulting output of the predefined torque and the predefined rotational speed.