Motor Winding Temperature via Resonant Frequency
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Solution Overview
Problem
Existing methods for determining the winding temperature of a motor winding are limited, as they either require direct temperature sensors that only measure local temperatures, or methods that can only be used when the motor is stationary, failing to provide a simple and reliable means to monitor temperature distribution during operation.
Innovation Solution
The method involves exciting the motor winding as an LCR resonant circuit using a PWM voltage to detect its resonant frequency, which is linearly dependent on temperature, allowing for temperature determination without additional sensors, by evaluating the step response of the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is installed in the winding to measure temperature directly, then temperature measurement capability is improved, but the measurement is limited to local temperature only and cannot reflect overall temperature distribution
Solution Approach 1:
The patent replaces the mechanical/physical temperature sensor system with an electrical measurement system. By measuring the winding resistance through voltage and current measurements and using the temperature-resistance relationship of the insulation material, the system determines temperature without physical contact sensors, thereby achieving both local and overall temperature assessment capabilities.
Solution Approach 2:
The patent introduces resistance measurement as an intermediary parameter to indirectly determine temperature. Instead of measuring temperature directly with a sensor, the system measures resistance (which has a known relationship with temperature for insulation materials) and calculates temperature from this intermediate measurement, enabling comprehensive temperature monitoring.
2Measurement precision
If winding resistance is measured to determine temperature, then temperature determination capability is improved, but the method can only be used when the motor is stationary
Solution Approach 1:
The patent employs periodic voltage application to the winding during motor operation. By periodically applying voltage and measuring the resulting current to calculate resistance, the system can determine temperature dynamically during operation rather than only when stationary, thus achieving continuous temperature monitoring.
Solution Approach 2:
The patent makes the resistance measurement system multi-functional by integrating it into the normal motor control circuitry. The same voltage and current measurement infrastructure used for motor control is also utilized for temperature determination, enabling the method to work both during stationary conditions and during motor operation.
3Reliability
If additional temperature sensors are installed in the winding, then measurement reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables the motor winding itself to serve as the measurement object. By utilizing the inherent electrical properties (resistance) of the winding insulation material that change with temperature, the system eliminates the need for separate temperature sensors. The winding's own characteristics provide the temperature information, reducing device complexity while maintaining monitoring 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
This approach enables reliable and simple monitoring of winding temperature during operation, providing accurate temperature readings without the need for special components or sensors, and improves accuracy by considering impedance.
Implementation Method 1
a motor winding can be assumed or viewed as a high-frequency excitable LCR resonant circuit composed of a coil L, a capacitance C and a winding resistance R
Implementation Method 2
An electrical oscillating circuit is a resonant electrical circuit consisting of a coil and a capacitor that can oscillate. In such an oscillating circuit, energy is periodically exchanged between the magnetic field of the coil and the electric field of the capacitor
Implementation Method 3
The resonant frequency of such an oscillating circuit of a motor winding is also almost linearly dependent on the temperature over a specific frequency range
Implementation Method 4
The temperature dependence of the motor winding is strongly or mainly determined by the temperature-dependent behavior of the insulation material of the winding wires, ie the temperature dependence of the dielectric of the motor winding
Data Source
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AI summary
The invention relates to a measuring method for determining the winding temperature (TW) of a motor winding (3) of an electric motor (2), comprising the following steps: a. Exciting the motor winding (3) by means of high-frequency vibration excitation in order to bring it into resonant vibration; b. Determining the resulting resonant frequency (fR) of the motor winding (3); and c. Determining the winding temperature (TW) from the detected resonant frequency (fR).