DC Traction Motor Field Coil Current Bypass for Slip Control
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Solution Overview
Problem
Existing traction control systems for DC electric traction motors in locomotives often unnecessarily reduce torque output in all motors when wheel slip occurs, even if only some motors experience slip, leading to inefficient acceleration and increased wear on wheels and rails.
Innovation Solution
A method that involves bypassing electric current from the field coil of a slipping traction motor to another traction motor within the same series-parallel branch, maintaining high torque output in non-slipping motors while reducing torque in slipping motors by directing the bypassed current through the armature of the other motor, thus controlling the electric current in each field coil to optimize traction and prevent wheel slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the wheel torque is increased to maximize acceleration, then the acceleration performance is improved, but the wheel may slip on the rail causing wear and reduced productivity
Solution Approach 1:
The system dynamically changes the electrical parameters (voltage, current) supplied to each traction motor based on real-time slip detection. When slip is detected in a specific motor, the system adjusts the electrical parameters to that motor while maintaining normal parameters in non-slipping motors, optimizing acceleration while preventing wheel-rail adhesion loss.
Solution Approach 2:
The control system segments the traction motor control into independent controllable units. Instead of uniformly controlling all motors, the system can individually adjust the electrical parameters of each motor based on its specific slip condition, allowing precise torque control to maximize acceleration without causing or exacerbating wheel slip.
2Power
If the torque generated by the DC electric traction motor is increased beyond adhesion torque, then acceleration is improved, but wheel slip occurs causing wear and productivity loss
Solution Approach 1:
The system employs feedback control by continuously monitoring wheel slip conditions and using this information to adjust the electrical parameters supplied to each traction motor. When slip is detected, the feedback loop automatically reduces voltage or current to the affected motor, preventing excessive torque that causes wear, while maintaining high power output in non-slipping motors.
Solution Approach 2:
Instead of reducing power to all motors when one motor slips, the system applies partial action by selectively adjusting electrical parameters only to the slipping motor. This allows the non-slipping motors to continue operating at excessive torque levels to maintain acceleration, while the slipping motor receives reduced parameters to prevent wear.
3Reliability
If the back EMF is increased to decrease current and torque, then wheel slip is reduced, but the acceleration capability is compromised
Solution Approach 1:
The system applies local quality by making different electrical parameter adjustments to different motors based on their individual slip conditions. Instead of uniformly increasing back EMF across all motors (which would compromise overall acceleration), the system selectively increases back EMF or decreases current only in motors experiencing slip, maintaining high acceleration capability in non-slipping motors while ensuring reliable traction control where needed.
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
This approach effectively suppresses wheel slip while maintaining high tractive effort in non-slipping motors, enhancing locomotive productivity and reducing wear by precisely managing torque output during wheel slip events.
Implementation Method 1
The torque generated by a DC electric traction motor depends in part on the net voltage across the DC electric traction motor, which equals the difference between the external voltage supplied to the DC electric traction motor and the magnitude of the opposing 'back EMF' generated internally by the DC electric traction motor.
Implementation Method 2
The back EMF generated by a DC electric motor equals the product of the electric current in the field coil, the speed of the DC electric traction motor, and a constant.
Data Source
AI summary
A method of propelling a mobile machine is disclosed. The mobile machine may have a plurality of DC traction motors, including a first DC traction motor and a second DC traction motor. The method may include driving a first traction device with the first DC traction motor, the first DC traction motor including a first field coil and a first armature electrically connected in series. The method may also include driving a second DC traction device with the second DC traction motor electrically connected in series with the first DC traction motor, the second DC traction motor including a second field coil and a second armature electrically connected in series. Additionally, the method may include, in response to slippage of the first traction device, bypassing at least a portion of electric current flowing through the first field coil around the first armature. The method may also include directing at least a portion of the bypassed electric current through the second field coil and the second armature.