Electric Vehicle Drive System Discharge Control via Grounding Switch
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Solution Overview
Problem
Conventional electric vehicle drive systems require a logic circuit and additional power source to control contactors for discharging filter capacitors, leading to increased circuit size and cost during inspection and maintenance.
Innovation Solution
An electric vehicle drive system with a grounding switch configured as a single-throw switch, connecting a resistor between the positive and negative electrodes of a filter capacitor, eliminating the need for additional control circuits and power sources for discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a logic circuit and additional power source are used to control contactors for discharging filter capacitors, then the discharge control is achieved, but the circuit size and circuit cost increase
Solution Approach 1:
The patent extracts the discharge control function from the complex logic circuit and power source system, and integrates it into the existing grounding switch structure. The grounding switch is modified to include a discharge contactor that activates when the grounding operation is performed, eliminating the need for separate control circuits and power sources while maintaining reliable discharge control.
Solution Approach 2:
The patent merges the discharge control function with the grounding switch operation. The grounding switch now serves dual purposes: grounding the filter capacitor and triggering the discharge of stored energy through the discharge contactor. This consolidation eliminates additional control circuits and power sources, reducing circuit complexity while maintaining functionality.
2Reliability
If multiple contactors are connected in series with a resistor for discharge, then the discharge function is achieved, but the circuit size increases
Solution Approach 1:
The patent extracts the discharge resistance function from the series contactor configuration and integrates it into the grounding switch structure. The discharge resistance is now part of the grounding switch assembly rather than a separate component in a series contactor chain, reducing the overall circuit footprint while maintaining the discharge function.
Solution Approach 2:
The patent merges the discharge resistance with the grounding switch structure, eliminating the need for separate series contactors and their associated wiring. The discharge resistance is integrated into the grounding switch assembly, significantly reducing circuit size while maintaining reliable discharge functionality.
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 simple and reliable discharge of filter capacitor charges while minimizing circuit size and cost, improving safety and reliability for operators.
Implementation Method 1
a filter capacitor that receives and stores therein power supplied from the overhead wire
Implementation Method 2
when the switching contact of the grounding switch is closed, the predetermined resistor is electrically connected between a positive electrode and a negative electrode of the filter capacitor
Data Source
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AI summary
An electric vehicle drive system includes an electric-vehicle power conversion device 11, an HB 2 that blocks an electric current flowing between an overhead wire 50 and the electric-vehicle power conversion device 11, and an EGS 4 that grounds the HB 2. The electric-vehicle power conversion device 11 includes a smoothing circuit unit 16 that includes a filter capacitor 16a that receives and stores therein power supplied from the overhead wire 50, an INV 12 that converts a DC voltage of the smoothing circuit unit 16 into an AC voltage to drive an electric motor 7 as a load, an LB 3 that blocks a power supply path between the HB 2 and the INV 12, and a BCH circuit 14 that consumes excess power, which cannot be returned toward the overhead wire 50. The EGS 4 is configured as a triple-pole single-throw switch. A brake resistance 15b included in the BCH circuit 14 is connected to a switching contact unit 5 of the EGS 4 such that when the switching contact of the EGS 4 is closed, the brake resistance 15b is electrically connected between the positive electrode and the negative electrode of the filter capacitor 16a.