Inverter Thermal Management for Electric Machine Torque
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Solution Overview
Problem
Existing inverters for electric machines face limitations in current output due to junction temperature constraints, particularly at low fundamental frequency operations, leading to reduced performance compared to higher frequency operations.
Innovation Solution
A method and system with thermal management that includes an electronic data processing system to estimate junction temperatures of semiconductor devices in an inverter, determining the hottest device, and adjusting the duty cycle to manage heat dissipation, thereby optimizing the current output capability across different frequency operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the inverter operates at low fundamental frequency to provide high torque, then the torque output capability is improved, but the junction temperature of semiconductor devices increases beyond maximum limits
Solution Approach 1:
The patent applies dynamics by making the inverter's current output capability dynamic rather than static. The controller continuously adjusts the maximum allowable current based on real-time temperature estimates of semiconductor devices. This allows the inverter to operate at higher currents when temperatures are low and reduce current when temperatures approach limits, enabling sustained high torque output at low frequencies without exceeding thermal constraints
Solution Approach 2:
The patent changes the parameter of current output capability based on temperature conditions. By estimating junction temperatures and adjusting the maximum current limit accordingly, the system adapts its operating parameters to maintain both high torque capability and safe temperature levels. This parameter adjustment enables the inverter to provide enhanced stall torque while preventing overheating
2Reliability
If the inverter limits current output to maintain junction temperature below maximum, then the reliability of semiconductor devices is improved, but the current output capability deteriorates at low frequencies
Solution Approach 1:
The patent implements feedback by continuously estimating junction temperatures of semiconductor devices and using this information to adjust the maximum current output capability. The controller monitors temperature estimates and dynamically modifies current limits to maintain reliable operation while maximizing productivity. This closed-loop feedback enables the system to operate at higher current levels than traditional fixed-limit systems while maintaining device reliability
Solution Approach 2:
The system transitions from static current limiting to dynamic current capability adjustment. By continuously adapting the maximum current output based on real-time temperature estimates, the inverter maintains both reliability and optimized productivity across varying operating conditions, particularly at low frequencies where thermal accumulation occurs
3Force
If the inverter provides high current output at stall conditions, then the stall torque capability is improved, but the heat dissipation exceeds the thermal management capacity
Solution Approach 1:
The patent changes the operating parameters by adjusting the maximum current output based on estimated junction temperatures. This enables the inverter to provide high stall torque when thermal conditions permit while preventing excessive heat dissipation when temperature limits are approached. The dynamic parameter adjustment optimizes the balance between torque capability and thermal management
Data Source
AI summary
A temperature estimation module estimates each junction temperature of a corresponding semiconductor device, among a plurality of semiconductor devices, for each phase of an inverter. The temperature estimation module or the data processing system determines a hottest device with a highest junction temperature among the semiconductor devices. A thermal adjustment module or data processing system determines if the highest junction temperature parameter is less than maximum junction temperature parameter for the respective semiconductor device or deciding whether or not to adjust a duty cycle of the semiconductor devices.