Electric Machine Winding Temperature Correction Using Heat Loss Estimation
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Solution Overview
Problem
Temperature measurements in electric machine windings, particularly in motor vehicles with electric or hybrid propulsion, are inaccurate due to the placement of temperature probes on the outer surfaces, leading to underestimation of core temperatures, which can result in overheating and potential destruction of insulation and short circuits, limiting performance and posing safety hazards.
Innovation Solution
A method and system that corrects temperature measurements by estimating and accounting for total heat losses, including Joule effect losses, alternating nature losses, and torque and rotation speed losses, using sensors for rotation speed and RMS current, and applying correction factors derived from prior tests to refine the measured temperature values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If temperature probes are placed on the outer surfaces of coil heads due to manufacturing constraints, then the ease of manufacture is improved, but the measurement precision deteriorates because the probes cannot accurately detect the temperature at the centre of the winding
Solution Approach 1:
The patent introduces an intermediary computational model that acts as a mediator between the easily accessible surface temperature measurement and the difficult-to-reach core temperature. The model uses the surface temperature as input and computes the core temperature through mathematical relationships that account for heat conduction, winding geometry, and thermal properties, thereby eliminating the need to physically place probes in the core while still obtaining accurate core temperature data
Solution Approach 2:
The patent replaces the mechanical approach of physically placing temperature probes in the winding core with a computational/algorithmic system. Instead of using additional physical sensors in difficult-to-reach locations, the system uses mathematical modeling and signal processing to estimate core temperature from surface measurements, substituting a mechanical measurement system with an intelligent computational system
2Reliability
If margins are applied to temperature measurements to prevent overheating, then the reliability is improved, but the productivity deteriorates due to limitation of torque and performance levels
Solution Approach 1:
The patent implements a feedback mechanism where the computational model continuously monitors the relationship between surface and core temperatures, learns from operational data, and dynamically adjusts temperature estimates. This accurate real-time feedback allows the control system to make precise decisions about performance limits without needing excessive safety margins, thereby maintaining reliability while maximizing productivity
3Ease of operation
If the electric machine operates stationary on a slope with rotor not revolving, then the ease of operation is improved, but the measurement precision deteriorates because the temperature probe positioned on one phase does not detect heating in other phases carrying current
Solution Approach 1:
The patent creates a universal temperature estimation model that can accurately predict core temperatures under all operating conditions, including stationary operation, dynamic operation, and various loading scenarios. The model incorporates knowledge of electromagnetic heating patterns and thermal diffusion to estimate temperatures in all phases and locations, making the temperature monitoring system universally applicable regardless of the specific operational state or current distribution pattern
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 provides a more accurate temperature measurement, preventing overheating, ensuring performance levels, and protecting the electric machine by effectively managing heat losses across various operating conditions, including stationary scenarios where the temperature probe may not detect heating.
Implementation Method 1
the delay between the measurement and the conduction of heat along the copper wires
Implementation Method 2
an estimation of the losses by Joule effect corrected as a function of a correction of the heat losses due to the alternating nature of the electric machine
Implementation Method 3
other sources can be the origin of heat losses, like known physical phenomena deriving from the alternating nature of the electric machine, such as the skin effect, or the eddy currents
Implementation Method 4
other sources can be the origin of heat losses, like known physical phenomena deriving from the alternating nature of the electric machine, such as the skin effect, or the eddy currents
Data Source
AI summary
A method for correcting a temperature measurement of a winding of an AC electrical machine of an electric-propulsion or hybrid-propulsion motor vehicle, which comprises constantly retrieving a measured temperature value of the winding measured by a temperature sensor located on the surface of the winding, a measured value of the speed of rotation of the electrical machine measured by a position sensor, and a measured value of the effective current flowing through an inverter controlling the electrical machine measured by a current sensor. The method corrects the measured winding temperature value based on the measured temperature and an estimate of the corrected total heat loss of the electrical machine, the estimate of the corrected total heat loss depending on an estimate of the Joule-effect losses corrected based on a correction of the heat losses due to the alternating nature of the electrical machine and a correction of the heat losses due to the torque and the speed of rotation of the electrical machine.