Inverter-Based Electric Motor Temperature Determination
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Solution Overview
Problem
Existing methods for determining the operating temperature of electric motors in household appliances are costly and inefficient, particularly when dealing with large numbers of items, and often require additional protective circuits or temperature sensors.
Innovation Solution
A method that associates an inverter with an electric motor, allowing for calibration of measured operating parameters to accurately determine the motor's temperature without additional sensors, using a fixed pairing of components throughout their service life, which simplifies the structure and reduces production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional temperature sensors or protective circuits are integrated into motor windings to protect from overheating, then motor protection reliability is improved, but production costs increase significantly
Solution Approach 1:
The inverter performs self-calibration by using its own existing operating parameter measurements (current, voltage, frequency) to determine motor temperature, eliminating the need for external temperature sensors. The system serves itself by leveraging already-present measurement capabilities rather than requiring additional protective hardware
Solution Approach 2:
Physical temperature sensors and protective circuits are replaced with an electronic calculation method that uses electrical parameter measurements (current, voltage, frequency) processed through calibration data and thermal models to determine temperature and trigger protection
2Device complexity
If traditional temperature measurement methods are used without calibration, then device complexity is reduced, but measurement precision deteriorates due to manufacturing tolerances
Solution Approach 1:
The inverter performs calibration measurements during manufacturing before the product reaches the customer. This preliminary action captures the specific characteristics of each motor-inverter pair, storing calibration data that compensates for manufacturing tolerances in subsequent temperature calculations
Solution Approach 2:
The system changes the parameters used for temperature determination from direct physical temperature measurement to indirect calculation based on electrical parameters (current, voltage, frequency) combined with calibration-specific correction factors, improving precision without adding hardware
3Reliability
If motor models with temperature-related variables are used to control the motor, then operating temperature control is improved, but computing power requirements increase
Solution Approach 1:
Instead of implementing a full complex motor model, the system uses a simplified approach that applies calibration data and basic thermal relationships to achieve sufficient temperature control accuracy with reduced computational requirements
Solution Approach 2:
The system transforms the temperature control problem from requiring complex real-time motor modeling to using calibrated electrical parameter measurements combined with simplified thermal calculations, reducing the computational burden while maintaining control effectiveness
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 method effectively determines the operating temperature of electric motors with high accuracy, reducing the influence of manufacturing tolerances and requiring less computing power compared to traditional methods, thereby protecting the motor from overheating without the need for additional sensors.
Implementation Method 1
a measured value acquisition of at least one operating parameter of the electric motor can be calibrated by the inverter in order to arrive at more precise results when determining the operating temperature
Implementation Method 2
calculate a temperature change in the motor windings from a change in the current flow through a motor winding via a change in the temperature-dependent resistance
Data Source
Figure 1
AI summary
The method involves assigning an inverter (12) to an electric motor (10) and calibrating a measurement detection of an operating parameter of the electric motor by the assigned inverter. A measured value of the operating parameter of the electric motor is detected by the assigned inverter. The operating temperature of the electric motor is determined based on the measured value and the calibration result of the assigned inverter. Independent claims are included for the following: (1) a method for controlling an inverter; (2) a device for determining an operating temperature of an electric motor of an electrical household appliance; and (3) an electric household appliance with a drive motor.