Inverter AC Cable Common-Mode Voltage Discharge Circuit
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Solution Overview
Problem
During maintenance of an inverter disconnected from the power grid, existing solutions require high-cost implementations to prevent electric shock from common-mode voltage of the AC cable relative to ground, as they rely on expensive isolated sampling networks with stringent insulation requirements.
Innovation Solution
A system comprising a control unit, a switch unit, and a discharge unit that generates a control signal based on the AC output voltage of the inverter to connect or disconnect the discharge unit with ground, effectively discharging the common-mode voltage of the inverter AC cable relative to ground without using isolated sampling solutions, thereby reducing implementation costs and preventing electric shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolated sampling networks are used to suppress common-mode voltage during maintenance, then safety against electric shock is improved, but implementation cost increases significantly
Solution Approach 1:
The patent extracts the essential safety function from the complex isolated sampling network and implements it through a simple discharge circuit consisting of a discharge resistor and switch. This circuit directly discharges the common-mode voltage from the AC cable to ground, achieving the same safety effect without the need for expensive isolated sampling networks and their stringent insulation requirements.
Solution Approach 2:
The patent employs a simple discharge resistor and switch that can be easily implemented and replaced if needed. This disposable-like approach uses inexpensive components to achieve the safety function, avoiding the need for costly isolated sampling networks while maintaining effective common-mode voltage suppression during maintenance.
2Reliability
If isolated sampling networks with stringent insulation requirements are used, then common-mode voltage suppression is improved, but device complexity increases
Solution Approach 1:
The patent extracts the core safety function from the complex isolated sampling network architecture and implements it through a simple discharge circuit. By removing the isolation requirement and directly discharging voltage to ground, the solution eliminates stringent insulation requirements while maintaining effective common-mode voltage suppression.
Solution Approach 2:
Instead of preventing common-mode voltage generation through complex isolation measures, the patent inverts the approach by directly discharging the voltage after it occurs. This reverse engineering approach simplifies the system by accepting the voltage generation and neutralizing it through a simple discharge path to ground.
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 system effectively discharges common-mode voltage of the inverter AC cable relative to ground during maintenance, avoiding electric shock risks while reducing implementation costs and maintaining safety without the need for high-cost isolated sampling networks.
Implementation Method 1
the discharge unit is configured to discharge the common-mode voltage of the inverter AC cable relative to ground when the switch unit is turned on
Data Source
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AI summary
A method and a device for suppressing a common-mode voltage of an inverter AC cable relative to ground are provided. A control unit generates a control signal according to a voltage of the AC side of the inverter. A switch unit connects or disconnects the discharge unit with ground or reference ground in response to the control signal. A discharge unit discharges the common-mode voltage of the inverter AC cable relative to ground when the switch unit is turned on. Therefore, during maintenance of the inverter when the AC switch is turned off, the common-mode voltage of the AC cable relative to ground can be discharged without using the isolated sampling solution in the conventional technology which has a high implementation cost and has a high requirement on the insulation class of the components, thereby avoiding the risk of electric shock to the maintenance technician.