Frequency Converter Thermal Protection Using Pre-calculated Current Limits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for thermal protection of frequency converters are complex and require high processor capacity, as they involve calculating thermal models during operation to limit junction temperature, which does not account for semiconductor module temperature and output frequency effectively.
Innovation Solution
A method using pre-calculated data to determine the allowable output current based on measured semiconductor module temperature and switching/output frequencies, eliminating the need for real-time thermal modeling and simplifying the protection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real-time thermal modeling is used to calculate junction temperature, then thermal protection accuracy is improved, but device complexity and processor capacity requirements increase
Solution Approach 1:
The patent pre-calculates and stores thermal characteristics data (thermal resistances and capacitances) before operation. During runtime, the control circuitry only needs to retrieve this pre-stored data and perform simple calculations based on measured temperatures and operating conditions, avoiding complex real-time thermal modeling while maintaining protection accuracy
Solution Approach 2:
The patent creates a simplified representation of the thermal model by storing key thermal parameters (thermal resistances and capacitances) in memory. This copied thermal characteristic data allows the system to approximate junction temperature without implementing the full complex thermal model, reducing computational requirements while preserving essential thermal protection functionality
2Ease of operation
If fixed current limit is used for thermal protection, then implementation simplicity is improved, but protection effectiveness deteriorates at low temperatures and frequencies
Solution Approach 1:
The patent implements dynamic current limiting by continuously adjusting the current limit based on measured semiconductor module temperature and operating frequency. The control circuitry calculates an appropriate current limit using pre-stored thermal characteristics and applies this dynamic limit to prevent both overheating at high temperatures and unnecessary restriction at low temperatures, ensuring reliable protection across all operating conditions
Solution Approach 2:
The patent changes the current limit parameter dynamically based on temperature and frequency conditions. By retrieving pre-calculated thermal characteristics and adjusting the current limit according to actual operating conditions, the system maintains simple implementation while achieving adaptive protection that responds to changing thermal and operational states
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 effective thermal protection for semiconductor components by limiting output current to prevent overheating without the complexity of real-time thermal modeling, ensuring the junction temperature does not exceed safe limits.
Implementation Method 1
The losses in the semiconductor component can be divided into conduction losses and switching losses
Implementation Method 2
estimate the junction temperature using thermal resistances and thermal capacitances in a thermal model
Implementation Method 3
The losses in the semiconductor component can be divided into conduction losses and switching losses, both of which are dependent on the current flowing through the component
Data Source
AI summary
A method for thermal protection of a frequency converter and a frequency converter includes means for controlling the output current of the frequency converter. The method includes the steps of determining predetermined data points which define a thermal current limit for a semiconductor component of the frequency converter at specific temperatures at plural switching frequencies, and determining predetermined data points which define a thermal current limit for the semiconductor component at specific temperatures at a zero converter output frequency. The method also includes determining the highest allowable thermal current as a function of a measured temperature, a determined switching frequency, and a determined output frequency based on the defined data points, and limiting the output current of the frequency converter to the determined highest allowable thermal current.