Motor Magnet Temperature Estimation Using Induced Voltage Timing
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Solution Overview
Problem
Existing magnet temperature estimation methods for motors face challenges in accurately estimating magnet temperature due to variations in induced voltage caused by rotor rotation, which affects the accuracy of temperature measurement.
Innovation Solution
A magnet temperature estimating device that includes a sensor to detect induced voltage and a controller to determine demand torque, using apertures as flux barriers to reduce temporal changes in magnetic flux, allowing for accurate temperature estimation by detecting induced voltage when magnets oppose coils, and utilizing average values or harmonic analysis for precise temperature calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If induced voltage is detected during motor operation to estimate magnet temperature, then temperature estimation can be performed, but the induced voltage varies due to magnetic flux changes during rotor rotation, reducing estimation accuracy
Solution Approach 1:
The controller determines demand torque in advance before detecting induced voltage. By checking whether demand torque is zero (motor not driving) beforehand, the system selects an appropriate timing for voltage detection when magnetic flux is stable, thus improving temperature estimation accuracy while avoiding the problem of varying induced voltage during operation
Solution Approach 2:
The patent uses demand torque determination as an intermediary condition to mediate between the need for temperature estimation and the stability of induced voltage. By using demand torque status as a selection criterion, the system indirectly identifies optimal detection timing without directly measuring magnetic flux variations
2Duration of action of moving object
If induced voltage detection is performed continuously to monitor magnet temperature, then real-time temperature monitoring is achieved, but the varying magnetic flux during rotor rotation causes large variations in induced voltage
Solution Approach 1:
Instead of continuous detection, the system performs periodic temperature estimation by detecting induced voltage only at specific intervals when demand torque is zero. This periodic detection approach maintains the ability to monitor temperature over time while avoiding the accuracy problems caused by varying magnetic flux during rotation
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
The solution effectively suppresses temporal variations in induced voltage, enabling accurate and individual magnet temperature estimation, improving motor performance and longevity by preventing irreversible demagnetization.
Implementation Method 1
a sensor (55) configured to detect an induced voltage induced in one of the plurality of coils (36) by rotation of the rotor
Implementation Method 2
apertures adj acent to each magnet in a rotation direction of the rotor are formed in the rotor... The temporal change in the induced voltage can be reduced more securely by the apertures functioning as the flux barriers
Data Source
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Figure 2B
AI summary
A magnet temperature estimating device for a motor including a rotor having magnets and configured to output a rotational motive force, and a stator having a plurality of coils opposing the rotor with a gap therebetween, is provided. The device includes a sensor configured to detect an induced voltage induced by rotation of the rotor, and a controller configured to control the motor by supplying power to the plurality of coils in response to an input of a detection signal from the sensor. Gaps adjacent to each magnet in a rotation direction of the rotor are formed in the rotor. The controller estimates a temperature of the magnet based on the induced voltage detected when the magnet opposes any one of the plurality of coils, according to the rotation of the rotor.