Vehicle Inverter Overheating Protection via Dynamic Torque Limiting
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Solution Overview
Problem
Existing protective devices for vehicle inverters reduce drivability when a motor operates at low speed and generates high torque, as they apply torque limits based on element temperature, leading to oscillatory temperature variations and increased torque variation.
Innovation Solution
A protective device for vehicle inverters that includes a maximum element temperature calculation unit, an element temperature output limit coefficient calculation unit, a basic torque limit value calculation unit, and a torque limit value determination unit, which calculates and applies a torque limit based on the maximum element temperature to prevent overheating while minimizing drivability reduction by dynamically adjusting the torque limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque limit is applied in accordance with element temperature, then inverter element overheating is prevented, but torque variation increases leading to reduction in drivability
Solution Approach 1:
The patent applies dynamics by making the torque limit value changeable over time rather than fixed. The torque limit value is dynamically adjusted based on the element temperature and the number of times the torque limit has been applied, allowing the system to adapt to varying thermal conditions and reduce torque variation during motor operation.
Solution Approach 2:
The patent changes the parameter of torque limit value based on temperature conditions and application history. When element temperature exceeds the threshold, the torque limit value is set to a first value; when temperature is within the threshold, it is set to a second value. This parameter change approach allows flexible control to maintain drivability while protecting against overheating.
2Reliability
If torque limit is applied rapidly in accordance with maximum element temperature, then overheating protection is improved, but torque limit variation increases reducing drivability
Solution Approach 1:
The patent applies preliminary action by setting a predetermined number of times for torque limit application before fully enforcing the limit. This allows the system to prepare for and gradually apply torque limitation, preventing sudden drastic changes in torque that would cause drivability issues while still providing timely overheating protection.
Solution Approach 2:
The patent implements periodic action through the element temperature output limit coefficient calculation, which applies torque limit a predetermined number of times before transitioning to continuous limitation. This periodic approach smooths out torque variations while maintaining effective temperature control.
Data Source
AI summary
This invention provides a protective device for a vehicle inverter, with which an inverter element can be protected from overheating while preventing a reduction in drivability. The protective device for a vehicle inverter includes a maximum element temperature calculation unit that calculates a maximum element temperature among respective element temperatures of the inverter, and an element temperature output limit coefficient calculation unit that calculates an output limit value corresponding to the maximum element temperature, sets a current output limit value as a current output limit coefficient when the current output limit value is smaller than a preceding output limit coefficient, and sets, as the current output limit coefficient, a value obtained by adding a predetermined value determined in advance to the preceding output limit coefficient when the current output limit value equals or exceeds the preceding output limit coefficient.