Thermal Equivalent Circuit for Motor Temperature Calculation
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Solution Overview
Problem
Existing methods for calculating the temperature distribution in drive motors, such as the finite element and finite difference methods, are time-consuming and difficult to apply to the entire motor region, making it challenging to analyze heat and prevent thermal breakage effectively.
Innovation Solution
A system using thermal equivalent circuits that considers convection and conduction characteristics between motor components, allowing for real-time temperature calculation of each constituent element by establishing thermal conduction and convection circuits between various parts of the motor, including the housing, rotor, stator, shaft, and air gaps, based on input power, torque, and ambient temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If finite element method or finite difference method is used to calculate temperature distribution, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The motor is divided into multiple thermal zones (stator core, stator winding, rotor core, rotor winding, bearing, housing) with dedicated temperature calculation for each zone. This segmentation allows parallel computation of temperatures across different regions, significantly reducing total calculation time while maintaining precision through zone-specific thermal resistance and heat generation parameters
Solution Approach 2:
The patent replaces the traditional finite element/finite difference numerical computation system with an equivalent thermal circuit system. By modeling heat transfer as electrical current flow through thermal resistances, the complex partial differential equations are transformed into simpler algebraic equations that can be solved much faster while achieving comparable temperature distribution accuracy
2Manufacturing precision
If finite element method or finite difference method is applied to entire motor region, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The motor structure is segmented into discrete thermal zones, each represented by a thermal node in the equivalent circuit. This segmentation simplifies the continuous heat transfer problem into discrete, manageable units that can be independently characterized and then easily assembled into the complete thermal model
Solution Approach 2:
The patent substitutes the complex finite element mesh generation and matrix solving process with a thermal circuit model using standard electrical circuit analysis methods. This substitution dramatically reduces computational complexity while maintaining the ability to accurately predict temperature distribution throughout the motor
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 significantly shortens thermal analysis time, enables precise temperature calculation of motor components, and prevents thermal breakage by allowing for real-time monitoring and control of temperature, thereby improving motor durability.
Implementation Method 1
a control portion establishing a thermal equivalent circuit using the inputs of the input portion and convection or conduction characteristics between constituent elements of the motor
Implementation Method 2
establishes a thermal convection equivalent circuit between the first shaft exposed portion and the interior air
Data Source
AI summary
A system of calculating temperature may include: a motor including a housing having opened ends, a cover connected to the housing to close at least one of the opened ends, a shaft rotatably disposed in the housing and having one end which penetrates through a center portion of the cover, a rotor fixed on an exterior circumference of the shaft in the housing and the cover, a stator fixed on an interior circumference of the housing, and an air gap formed between an exterior circumference of the rotor and an interior circumference of the stator; an input portion receiving a real time input and a predetermined input; and a control portion establishing a thermal equivalent circuit using the inputs of the input portion and convection or conduction characteristics between constituent elements of the motor, and calculating a temperature of each constituent element using the thermal equivalent circuit.