Magnet Temperature Determination in Synchronous Machines
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Solution Overview
Problem
Existing methods for determining the magnet temperature in permanent magnet electrical machines are inaccurate, leading to conservative phase current limitations and reduced performance due to the assumption that rotor and stator temperatures are equivalent, resulting in inefficient operation.
Innovation Solution
Measuring phase voltage and rotational speed to determine magnet temperature using the inverse function T=f−1(ψ), where ψ is the generated magnetic flux, and storing this relationship in a characteristics map for precise magnet temperature calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnet temperature is estimated from stator temperature assuming rotor and permanent magnets are at approximately the same temperature, then measurement effort is reduced, but measurement precision deteriorates due to errors particularly in response to transient processes
Solution Approach 1:
The patent replaces direct physical temperature measurement (mechanical/thermal contact method) with an indirect electrical measurement method. By measuring phase voltage and rotational speed, and calculating magnet temperature through the inverse function T=f−1(ψ) using magnetic flux derived from voltage and speed, the system achieves accurate temperature determination without physical contact or complex thermal sensors in the rotor.
Solution Approach 2:
The patent introduces magnetic flux ψ as an intermediary parameter to determine magnet temperature. Instead of directly measuring temperature, the system measures phase voltage and rotational speed to calculate magnetic flux, then uses the pre-determined inverse function relationship to obtain temperature. This intermediary approach enables accurate temperature measurement while avoiding direct thermal contact with the rotating rotor.
2Reliability
If temperature threshold for phase current limitation is selected to be relatively low to maintain safety margin, then reliability is improved, but productivity deteriorates as maximum performance of the machine cannot be completely utilized
Solution Approach 1:
The patent implements a feedback mechanism by continuously measuring phase voltage and rotational speed to accurately determine actual magnet temperature through the inverse function T=f−1(ψ). This real-time temperature feedback replaces conservative fixed-threshold control, allowing the system to adjust phase current limitation dynamically based on actual temperature conditions, thereby maximizing performance while ensuring safety.
Solution Approach 2:
The patent changes the control parameter from a fixed conservative temperature threshold to a dynamically calculated actual magnet temperature derived from measured phase voltage and rotational speed. By using the inverse function relationship T=f−1(ψ) with pre-stored characteristics, the system adapts the temperature threshold to actual operating conditions, enabling higher performance utilization while maintaining reliability.
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
Enables more accurate magnet temperature determination, allowing the electrical machine to operate at higher temperatures with increased performance and appropriate protective measures only when the high threshold is reached.
Implementation Method 1
Magnetic flux ψ may be ascertained via the law of induction, for which the following applies: Uind=ωψ
Data Source
AI summary
A method for determining the magnet temperature of a permanent magnet electrical machine. The magnet temperature is able to be determined particularly simply and accurately if a phase voltage and the rotational speed of the electrical machine are measured, and the magnet temperature is determined from this.