Compressor Operating State Detection From Power Cable Magnetic Fields
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Solution Overview
Problem
Existing methods for determining the operating state and rotational speed of compressors require electrical contact, specialized personnel, and cannot distinguish between standstill, idling, and load run states, especially for variable-speed drives, and are costly and complex.
Innovation Solution
A contactless method using a detection element to measure the magnetic field generated by a compressor's power supply cable, analyzing the frequency spectrum to determine the operating state and rotational speed without precise knowledge of magnetic field strength or RMS values, utilizing devices like Rogowski coils and Hall sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If potential-free contacts are tapped in the control cabinet to determine operating state, then operating state information can be obtained, but the installation requires electrically instructed personnel and the compressor must be disconnected from the electrical mains
Solution Approach 1:
The patent replaces the electrical contact-based measurement system with a magnetic field-based contactless measurement system. Instead of tapping potential-free contacts in the control cabinet, the invention uses a detection element that measures the magnetic field generated by the power supply cable current, thereby determining operating state and rotational speed without electrical contact or disconnection requirements
Solution Approach 2:
The patent introduces the magnetic field as an intermediary between the power supply cable and the detection element. The detection element detects the magnetic field generated by the current in the power supply cable, which serves as a mediator to extract operating state information without direct electrical contact, eliminating the need for electrical installation expertise
2Measurement precision
If reflex pulse counting with optical sensors is used to determine rotational speed, then speed can be measured, but the optical sensor must be mechanically attached and cannot distinguish between standstill, idling and load run states
Solution Approach 1:
The patent replaces the mechanical optical sensor attachment system with a contactless magnetic field-based detection system. Instead of mechanically attaching an optical sensor to the shaft, the invention uses a detection element that contactlessly measures the magnetic field generated by the power supply cable, from which both rotational speed and operating state can be determined
Solution Approach 2:
The patent makes the detection element universal by enabling it to perform multiple functions: determining operating state (standstill, idling, load run), determining rotational speed, and providing this information for both fixed-speed and variable-speed compressors through a single contactless measurement approach
3Reliability
If active current measurement is performed at the supply line, then operating state can be determined, but precise knowledge of magnetic field strength and RMS values is required
Solution Approach 1:
The patent changes the measurement parameter from absolute magnetic field strength and RMS current values to the frequency spectrum characteristics of the magnetic field. By analyzing the frequency spectrum of the magnetic field signal, the system can determine operating state and rotational speed without requiring precise knowledge of the absolute magnetic field strength or RMS values, thereby reducing measurement precision requirements
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 reliable, fast, and inexpensive determination of compressor operating states and rotational speed, suitable for both fixed and variable-speed drives, without the need for electrical contact or precise measurement of magnetic characteristics.
Implementation Method 1
detecting a magnetic field over a time range by means of a detection element, wherein the magnetic field is generated by a current of at least one phase of a power supply cable
Data Source
AI summary
The invention relates to a method for the determination, in particular for contactless determination, of an operating state of a compressor (1) and/or a rotational speed of a compressor drive (2), in particular of a variable-speed or fixed-speed compressor drive (2), having the following method steps:detecting a magnetic field over a time range by means of a detection element (3), wherein the magnetic field is generated by a current of at least one phase (L1, L2, L3) of a power supply cable (4);determining the frequency spectrum of the magnetic field over the time range;analyzing the frequency spectrum of the magnetic field in order to determine an operating state of the compressor (1) and/or in order to determine a rotational speed of the compressor drive (2).