Rail PMSM Inverter Layout for Short-Circuit Current Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing drive systems for rail vehicles using permanent magnet synchronous motors (PMSM) face issues with short circuit failures in voltage detectors and regenerative currents, leading to decreased acceleration performance and potential device burnout, and require complex retrofitting due to space and compatibility constraints.
Innovation Solution
A three-phase AC motor drive device with a specific arrangement of motor cutout contacts, voltage detectors, and current detectors, allowing for detection of short circuit currents even in failure states, and enabling easy retrofitting and space-efficient installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the voltage detector and current detector are installed on the inverter device side, then the installation space is saved, but the short circuit current cannot be detected when the motor cutout contactor is released
Solution Approach 1:
The patent segments the detection functions by providing separate voltage detector and current detector units that can be independently positioned. The voltage detector is installed on the inverter device side while the current detector is installed on the motor side, allowing each detector to optimally perform its specific function without interfering with the other's operational requirements
Solution Approach 2:
The motor cutout contactor serves as an intermediary element that controls the electrical connection between the inverter device and the motor. By strategically positioning the detectors relative to the contactor, the system ensures that the current detector remains able to detect short circuit currents even when the contactor is released, while the voltage detector stays on the inverter side for space efficiency
2Reliability
If the motor cutout contactor is provided to disconnect the motor from the inverter device, then the safety is improved, but the acceleration performance decreases due to continuous short circuit current flow
Solution Approach 1:
The patent implements feedback mechanisms through the voltage detector and current detector that continuously monitor the system state. When a short circuit failure is detected, the detectors provide feedback signals that trigger the motor cutout contactor to disconnect the motor, preventing continuous short circuit current flow and allowing the system to recover and resume normal acceleration performance
Solution Approach 2:
The motor cutout contactor acts as a protective measure prepared in advance. By having the contactor pre-installed and the detection system ready, the system can quickly respond to short circuit failures before they cause severe damage or prolonged performance degradation, thus cushioning the impact on acceleration performance
3Measurement precision
If the voltage detector terminals are connected to both phases, then the voltage detection is improved, but the short circuit current detection capability is lost when the contactor is released
Solution Approach 1:
The patent separates the voltage detection function from the current detection function by using distinct detectors. The voltage detector with terminals connected to both phases accurately measures voltage for control purposes, while the current detector positioned on the motor side independently monitors short circuit currents, ensuring both functions operate effectively regardless of contactor state
Solution Approach 2:
The motor cutout contactor serves as a mediator that controls the electrical path. By positioning the current detector on the motor side of the contactor and the voltage detector on the inverter side, the system maintains the ability to detect short circuit currents through the current detector even when the contactor disconnects the motor from the inverter
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 device ensures stable operation by detecting short circuit currents and regenerative braking, allowing continuous vehicle operation with optimal security measures, and simplifies installation by maintaining compatibility with existing systems.
Implementation Method 1
When the PMSM rotates, an induced voltage occurs between terminals of the motor due to a magnetic flux of a permanent magnet
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
This three-phase AC motor drive device is provided with: a load; an inverter device 1 for driving the load; an MCOK_A_4 connected between the inverter device 1 and the load and electrically connecting or disconnecting the inverter device 1 to or from the load; a voltage detector 21a having terminals respectively connected to the circuits of at least two phases to detect the voltages between the three phases; and a current detector 11 for detecting the currents of the three phases. In the connection from the inverter device 1 to the load, the inverter device 1, the MCOK_A_4, the voltage detector 21a, the current detector 11, and the load are aligned in this order.