Method for selecting a frequency converter for a refrigerant compressor unit
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Solution Overview
Problem
Existing methods for selecting frequency converters for refrigerant compressor units often result in unnecessary costs due to overspecification, as they do not optimize the selection based on the specific working states and operating frequencies of the compressor units.
Innovation Solution
A method that selects a frequency converter by determining the working state operating current value and matching it with the maximum converter current value, ensuring the converter can reliably operate the compressor unit while avoiding unnecessary overspecification, using experimentally determined drive data and considering the equivalent circuit of the drive motor to calculate the operating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency converters are selected to not limit potential working states of the refrigerant compressor, then the reliability and operational flexibility are improved, but the cost increases due to unnecessary overspecification
Solution Approach 1:
The patent changes the selection parameter from a conservative maximum current rating to an optimized current value calculated based on specific working states and operating frequencies. By calculating the actual operating current requirements using drive data and equivalent circuit models, the frequency converter can be sized precisely for the application needs rather than using overspecified standard ratings, thus reducing cost while maintaining reliability.
2Reliability
If frequency converters are overspecified to ensure sufficient current capacity, then the reliability is improved, but the cost increases due to unnecessary capacity
Solution Approach 1:
The patent performs preliminary calculation of the working state operating current value before selecting the frequency converter. By using drive data and equivalent circuit models to calculate the actual current requirements in advance, the selection process determines the minimum sufficient capacity needed, avoiding both overspecification and underspecification of the frequency converter capacity.
3Ease of operation
If a standardized selection method is used for frequency converters, then the ease of operation is improved, but the manufacturing precision of the selection optimization deteriorates
Solution Approach 1:
The patent replaces the mechanical/engineering judgment-based selection process with a calculation-based method using equivalent circuit models and drive data. This substitution of the selection methodology provides precise, objective determination of current requirements while maintaining ease of operation through systematic calculation procedures that can be implemented using standard engineering tools and software.
Data Source
AI summary
In order to improve a method for selecting a frequency converter for a refrigerant compressor unit comprising a refrigerant compressor and an electric drive motor in such a way that the frequency converter is optimised for the application in question, it is proposed that a working state suitable for the operation of the refrigerant compressor unit is selected in an application field of an application diagram of the refrigerant compressor, that an operating frequency is selected for this selected working state, and that, on the basis of drive data, a working state operating current value corresponding to the selected working state and the selected operating frequency is ascertained for the operation of the refrigerant compressor unit.