Motor Inverter Power Limiting via Current Sensor Thermal Estimation
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Solution Overview
Problem
Reducing the size of the connection line in a control device leads to excessive heating of the current sensor, causing deviations in estimated temperatures and frequent motor power output limitations, which affects power performance.
Innovation Solution
A control device that derives an estimated temperature of the current sensor based on coil and cooling medium temperatures, using a first-order lag process to calculate an estimated value closer to the actual temperature, and limits motor power output accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the area of the connection line is reduced to reduce the size of the control device, then the size is reduced, but the current sensor receives more heat from the connection line causing excessive heating
Solution Approach 1:
The system performs preliminary temperature estimation based on coil temperature and cooling medium temperature before the current sensor actually reaches excessive temperatures. By calculating the reached temperature and applying first-order lag processing, the system proactively limits motor power output before excessive heating occurs, preventing the problem rather than reacting to it.
Solution Approach 2:
The patent introduces an intermediate estimation mechanism that uses coil temperature and cooling medium temperature as intermediary variables to infer the current sensor temperature. This intermediary estimation approach allows the system to monitor and control current sensor heating indirectly through readily available temperature data from other components.
2Reliability
If the threshold of the current sensor temperature is reduced to prevent excessive heating, then the current sensor is protected, but the power output from the motor is limited frequently reducing power performance
Solution Approach 1:
The system implements a feedback control mechanism where the estimated current sensor temperature continuously informs motor power output decisions. By monitoring the estimated temperature and comparing it against thresholds, the system dynamically adjusts power output to protect the current sensor while maintaining maximum performance when safe, creating a closed-loop control system that balances protection and performance.
Solution Approach 2:
The patent changes the parameter used for temperature estimation from direct current sensor temperature measurement to an estimated temperature derived from coil temperature and cooling medium temperature. This parameter change allows for more nuanced control, enabling the system to distinguish between different heating scenarios and make more accurate decisions about when to limit power output.
3Device complexity
If the estimated temperature is derived only from cooling medium temperature, then the calculation is simple, but the estimated temperature deviates from the actual temperature of the current sensor
Solution Approach 1:
The patent merges multiple temperature sources (coil temperature and cooling medium temperature) into a unified temperature estimation for the current sensor. By combining these different thermal indicators through the reached temperature calculation and first-order lag processing, the system creates a more accurate and comprehensive estimate that reflects the actual thermal state of the current sensor better than any single source alone.
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 appropriate timing for limiting motor power output, protecting the current sensor and maintaining power performance by reducing excessive heating.
Implementation Method 1
a cooling device that cools the inverter with a cooling medium
Implementation Method 2
perform a first-order lag process on the reached temperature to calculate the estimated temperature
Data Source
AI summary
A control device is used in a motor device including a motor, an inverter that drives the motor, a cooling device that cools the inverter with a cooling medium, and a current sensor mounted on a connection line connecting the motor and the inverter, and the control device is configured to control the inverter. The control device includes an electronic control unit configured to derive an estimated temperature that is an estimated value of a temperature of the current sensor, based on a coil temperature and a cooling medium temperature, and to limit power output from the motor based on the estimated temperature, the coil temperature being a temperature of a coil of the motor, and the cooling medium temperature being a temperature of the cooling medium.