Railroad Vehicle Control Device Low-Speed Malfunction Detection
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Solution Overview
Problem
Railroad vehicle control devices face challenges in promptly detecting malfunctions such as open phases in the three-phase AC output from the inverter, especially in low-speed areas, which can prevent normal motor operation.
Innovation Solution
A vehicle control device with a controller that monitors the PWM modulation rate and rotor frequency, determining a malfunction when the modulation rate exceeds a threshold in low-speed areas and uses current detectors to identify if the malfunction is an open phase by comparing detected current values with predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional malfunction detection methods are used, then the system can detect malfunctions in normal operating conditions, but detection precision deteriorates in low-speed areas
Solution Approach 1:
The patent changes the detection parameters based on operating conditions. In low-speed areas, it uses PWM modulation rate as the detection parameter instead of conventional current-based parameters, which enables effective malfunction detection across the entire speed range including low-speed conditions where conventional methods fail
2Reliability
If the system monitors multiple parameters continuously, then malfunction detection capability improves, but device complexity increases
Solution Approach 1:
The patent implements dynamic parameter selection where the detection method automatically switches based on operating conditions. The controller dynamically chooses between PWM modulation rate monitoring and conventional current monitoring based on vehicle speed and operating mode, maintaining high reliability without requiring permanently active complex monitoring systems for all conditions
Solution Approach 2:
The system changes detection parameters based on operating conditions. In low-speed areas, it uses PWM modulation rate; in other conditions, it uses conventional current parameters. This conditional parameter change maintains detection reliability while avoiding the complexity of continuously monitoring all parameters at all times
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
Enables prompt detection of malfunctions and identification of open phases in low-speed areas, ensuring timely intervention to maintain normal motor operation and prevent accidents.
Implementation Method 1
a converter (5) converting an input AC power into direct-current (DC) power and outputs the direct-current (DC) power. The inverter (6) converts a DC power output from the converter (5) into an AC power
Implementation Method 2
A vehicle control device with a controller that monitors the PWM modulation rate and rotor frequency, determining a malfunction when the modulation rate exceeds a threshold in low-speed areas
Implementation Method 3
uses current detectors to identify if the malfunction is an open phase by comparing detected current values with predetermined thresholds
Data Source
AI summary
A vehicle control device according to one embodiment includes an inverter converting a DC power to a three-phase AC power and supplying the three-phase AC power to a motor driving a vehicle. A detector detects a current value between the inverter and the motor. A controller PWM-controls the inverter based on a current value detected by the detector, a speed command signal, and a rotor frequency of the motor. The controller determines occurrence of a malfunction when a PWM modulation rate is equal to or higher than a predetermined value and the rotor frequency is equal to or lower than a predetermined value.