Fan Stall Detection Using Frequency Converter Torque and Speed
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Solution Overview
Problem
Existing fan systems lack an effective method for detecting stall occurrences without external measurements, which can lead to reduced service life and reliability, as well as increased energy consumption and production losses.
Innovation Solution
A method and system that utilize rotational speed and torque estimates from a frequency converter, combined with fan characteristic curves, to determine the operating point and detect stall conditions by calculating RMS values of low-frequency components, thereby identifying when the fan is in a stalling region and exceeding a set limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external measurement equipment is used to detect fan stall, then detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The frequency converter uses its own internal current and voltage measurements to detect fan stall conditions. The control unit processes signals already present in the frequency converter without requiring external measurement equipment, making the system self-sufficient for stall detection
Solution Approach 2:
The invention uses the frequency converter's internal current and voltage signals as intermediaries to indirectly detect stall conditions. Instead of directly measuring fan parameters, the system analyzes electrical signals that reflect the fan's mechanical state, enabling detection without external sensors
2Reliability
If fan stall is not detected, then device complexity remains low, but reliability and service life decrease
Solution Approach 1:
The control unit continuously monitors current and voltage signals from the frequency converter and uses this feedback to detect stall conditions. The system compares real-time electrical measurements against expected values to identify abnormal operating conditions indicating fan stall
Solution Approach 2:
The invention replaces mechanical measurement systems with electrical signal analysis. Instead of using mechanical sensors to directly measure fan parameters, the system substitutes electrical current and voltage measurements that correlate with mechanical fan state, reducing mechanical complexity while improving reliability
3Use of energy by moving object
If frequency converter control is implemented, then energy efficiency is improved, but ability to detect stall without external measurements remains insufficient
Solution Approach 1:
The frequency converter is designed to perform multiple functions: it controls motor speed for energy efficiency and simultaneously detects fan stall conditions. The control unit processes electrical signals for both motor control and diagnostic purposes, making the device multi-functional without requiring separate detection equipment
Data Source
AI summary
Exemplary methods and systems of determining stall of a fan are disclosed, when the fan is controlled with a frequency converter. The method includes estimating a rotational speed (n) and the torque (T) of the fan. Transferring characteristic curves of the fan to the estimated rotational speed (n) of the fan, determining the stall region of the fan. Determining an operation point of the fan from the estimated rotational speed (n) and estimated torque (T) using the characteristic curves. Calculating RMS values of the low frequency components of the torque and rotational speed estimates (TRMS, nRMS) to obtain a low frequency parameter (S), and determining an occurrence of stall based on at least one of the operation point and the low frequency parameter (S).