Pantograph Yoke Force Sensor for Railway Current Capture
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Solution Overview
Problem
At high speeds, the low contact force between the pantograph's contact strips and the catenary leads to electric arcs and fluctuations in current transmission, while excessive force can damage the catenary and its supports, necessitating a method to accurately measure and control the contact force without disrupting the pantograph's operation.
Innovation Solution
Integrating a yoke as a force sensor that merges with the existing structure, equipped with test beams and extensometer gauges or accelerometers, to measure contact force while minimizing disruption and maintaining aerodynamic profile, thus ensuring accurate and stable current collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact force between the pantograph and catenary is increased to prevent contact breaks and electric arcs, then the current transmission quality is improved, but the risk of damage to the catenary and its supports increases
Solution Approach 1:
The patent implements a feedback control system using a force sensor to measure the actual contact force between the pantograph and catenary. The measured force is processed by electronic circuitry that generates control signals to adjust the pneumatic cylinder pressure, thereby maintaining the contact force within the optimal range (5-15 daN) to prevent both contact breaks and catenary damage
Solution Approach 2:
The system dynamically adjusts the contact force parameter by controlling the pneumatic cylinder pressure based on real-time measurements. The force sensor provides continuous feedback that enables the system to change the contact force parameter adaptively, maintaining it within the optimal range regardless of operating conditions such as speed variations
2Measurement precision
If a force sensor is integrated into the pantograph structure to measure contact force, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The force sensor is integrated directly into the existing pantograph structure, specifically into the articulation joint between the pantograph arm and the bow support. This merging approach allows the sensor to become part of the load-bearing structure, measuring contact force through the natural mechanical connection without requiring separate mounting hardware or additional structural elements
Solution Approach 2:
The integrated force sensor serves multiple functions: it measures the contact force between the pantograph and catenary, provides feedback for control system adjustment, and becomes an inherent part of the pantograph's mechanical structure. This multi-functionality reduces the need for separate measurement and control components
3Measurement precision
If the sensor is placed close to the bow to measure contact force accurately, then the measurement precision is improved, but the sensor becomes more susceptible to electromagnetic effects and electric arcs
Solution Approach 1:
The patent uses galvanic isolation as an intermediary protective measure between the force sensor and the electromagnetic environment. The sensor is electrically isolated from the pantograph structure through galvanic isolation techniques, preventing electromagnetic interference and electric arcs from affecting the sensor measurements while allowing mechanical force transmission
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
The solution allows for precise measurement of contact force, reducing electric arcs and fluctuations, while maintaining the pantograph's aerodynamic resistance and preventing damage to the catenary, thus enhancing the quality of current collection and safety.
Implementation Method 1
The sensor comprises strain gauges integral with a test piece, which is inserted into the mechanical support chain of the pantograph
Implementation Method 2
the test beams of the yoke are weakened to increase their sensitivity, advantageously by recesses for receiving extensometer gauges
Implementation Method 3
the yoke includes a housing for receiving an accelerometer
Implementation Method 4
When, under the combined action of pneumatic cylinders and damping springs, the articulated frame is deployed, the head rises against the catenary and is held there with a contact force
Implementation Method 5
under the combined action of pneumatic cylinders and damping springs
Implementation Method 6
As the motor advances, the bow slides against the catenary and remains in contact with it
Implementation Method 7
Near the catenary, the sensor is subjected to the electromagnetic effects induced by the strong currents which circulate there and by the appearance of electric arcs
Implementation Method 8
It is also protected against these effects by electrical filtering and galvanic isolation provided on the electrical measurement circuits
Data Source
Figure 1~2
Figure 3~4
AI summary
The pantograph (1) comprises a friction bow (3, 4) for contacting a catenary, at least one bow support (25, 26), a yoke (15, 16) attached to suspension means (2; 5, 6) and to which the bow support (25, 26) is fixed, and at least one sensor for measuring the contact force of the bow (3, 4) on the catenary. The yoke (15, 16) constitutes the sensor. It has two flanges, each comprising a test beam and means for limiting its deflection.