Railway Traction Chain Modulation Control for Rotor Loss Reduction
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Solution Overview
Problem
The existing traction chains for railway vehicles experience significant losses due to harmonic currents induced in the rotor by polyphase voltage, leading to heating issues from Joule and Foucault effects.
Innovation Solution
The traction chain incorporates means to vary the degree of modulation based on rotor speed, reducing the modulation rate when the rotor speed is low and increasing it when high, and adjusts the rotor magnetic flux accordingly to minimize harmonic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed modulation rate is used in the power supply system, then the control is simple, but significant harmonic losses and heating occur in the rotor
Solution Approach 1:
The patent applies dynamics by making the modulation rate variable rather than fixed. The control system dynamically adjusts the modulation rate based on the rotor speed to minimize harmonic losses. Specifically, the modulation rate is reduced when rotor speed is below a threshold value and increased when rotor speed exceeds the threshold, allowing the system to adapt to varying operating conditions and reduce energy losses in the rotor.
Solution Approach 2:
The patent changes the modulation rate parameter based on rotor speed conditions. By monitoring rotor speed and adjusting the modulation rate accordingly (reducing it at low speeds and increasing it at high speeds), the system optimizes performance and minimizes harmonic losses. This parameter change approach allows the power supply system to operate efficiently across different speed ranges.
2Temperature
If the modulation rate is reduced to minimize harmonic losses, then rotor heating decreases, but the power output may be insufficient at high speeds
Solution Approach 1:
The system dynamically adjusts the modulation rate based on rotor speed to balance temperature control and power output. At low rotor speeds, the modulation rate is reduced to minimize harmonic losses and prevent overheating. At high rotor speeds, the modulation rate is increased to ensure sufficient power output. This dynamic adjustment allows the system to maintain optimal temperature while delivering required power across different operating conditions.
3Power
If the modulation rate is increased to maintain power output at high speeds, then power delivery is sufficient, but harmonic losses and rotor heating increase
Solution Approach 1:
The patent changes the modulation rate parameter based on rotor speed thresholds. When rotor speed is below the threshold, a lower modulation rate is applied to minimize harmonic losses. When rotor speed exceeds the threshold, the modulation rate is increased to maintain sufficient power output. This conditional parameter change strategy optimizes the balance between power delivery and energy losses across different operating ranges.
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 reduces harmonic losses in the rotor, leading to lower heating and improved efficiency by optimizing the modulation rate and magnetic flux in response to varying rotor speeds.
Implementation Method 1
This polyphase voltage is pulse width modulated
Implementation Method 2
These induced harmonic currents generate losses by Joule and Foucault effect in the rotor
Implementation Method 3
These induced harmonic currents generate losses by Joule and Foucault effect in the rotor
Implementation Method 4
an electric motor comprising a shaft, a stator and a rotor, the rotor being rotatable around the axis of the shaft
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
This traction chain (10) for a transport vehicle includes an electric motor (12) comprising a shaft (22), a stator (24) and a rotor (26), a power supply system (14) receiving a direct current input voltage (DCD) and delivering a polyphase voltage to the motor (12), the system (14) having a modulation rate equal to the voltage amplitude of each phase of the motor divided by the direct current input voltage (DCD), and a sensor (20) for the rotational speed of the rotor (Vrotor).This traction chain (10) includes means for varying the modulation rate capable of decreasing the modulation rate relative to the modulation rate in the absence of means for varying the modulation rate, when the rotational speed of the rotor (Vrotor) belongs to a first interval of values less than a predetermined transition value, and capable of increasing the modulation rate relative to the modulation rate in the absence of means for varying the modulation rate, when the rotational speed of the rotor (Vrotor) belongs to a second interval of values greater than the predetermined transition value.