Converter Torque Monitoring via Auxiliary Value Comparison
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Solution Overview
Problem
Existing methods for monitoring torque in electric motors operated by converters are inadequate for ensuring safety, as they rely on time-consuming speed evaluations and may not prevent injuries due to delays in shutdown, especially when unauthorized access occurs.
Innovation Solution
A method that continuously monitors the torque of electric motors by recording motor current and auxiliary values, determining maximum torque limits, and comparing them with expected values to prevent exceeding safe torque levels, using sensors and control systems to interrupt power supply if limits are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If speed evaluation is used for safety monitoring, then the system can detect unsafe conditions, but the time delay in shutdown causes injury risk to persist
Solution Approach 1:
The patent calculates a maximum permissible auxiliary value in advance based on the first maximum torque and detected motor current. This preliminary calculation enables the system to compare the actual auxiliary value against a pre-determined safety threshold, allowing for immediate shutdown when the auxiliary value exceeds the maximum permissible value, thereby eliminating the time delay associated with evaluating speed changes.
2Reliability
If torque monitoring is implemented to prevent injury, then safety is improved, but the system complexity increases
Solution Approach 1:
The patent uses an auxiliary value (such as motor voltage or magnetic flux) as an intermediary parameter to indirectly monitor torque. Instead of directly measuring torque, the system monitors the auxiliary value which has a functional relationship to torque derivation. This intermediary approach simplifies the monitoring system while maintaining safety, as the auxiliary value can be obtained from existing sensors without requiring complex torque measurement apparatus.
Solution Approach 2:
The patent replaces direct mechanical torque measurement with electrical parameter monitoring. By using electrical quantities (current, voltage, or magnetic flux) that are already available in the converter system, the invention substitutes complex mechanical torque sensing with simpler electrical measurements and calculations, thereby reducing device complexity while achieving torque monitoring safety.
3Reliability
If maximum torque limits are enforced to ensure safety, then injury prevention is improved, but the operational flexibility is reduced
Solution Approach 1:
The patent dynamically determines the first maximum torque based on the position of the rotor relative to the stator. This means the torque limit is not a fixed value but varies according to the motor's operating state. By adapting the maximum torque limit to the current rotor position and operating conditions, the system maintains safety while allowing optimal performance within safe boundaries, thus preserving operational flexibility.
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
Enhances safety by promptly detecting and preventing excessive torque, reducing the risk of injury and accidents by ensuring the electric motor is torque-free when unsafe conditions are detected, thus improving operational safety.
Implementation Method 1
the current sensor comprises a Hall sensor suitably positioned within a slot of a slotted ring of soft magnetic material
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method (26) for monitoring the torque of an electric motor (2) operated by means of a converter (4). An electric motor current (I) and an auxiliary value (30) are detected. A first maximum torque (Mmax1) is determined. Furthermore, based on the first maximum torque (Mmax1) and the detected motor current (I), an expected maximum auxiliary value (38) is determined. The detected auxiliary value (30) is compared with the expected maximum auxiliary value (38). The invention further relates to a converter (4) comprising semiconductor switches (16) for controlling the energy flow to an electric motor (2).