Inverter Safety Plug Mechanical Interlock

Solution Overview

Problem

Existing inverter safety protocols require meticulous operator intervention to ensure disconnection from power grids and zero potential before maintenance, leading to potential hazards due to non-compliance with safety rules.

Innovation Solution

A safety plug mechanism that mechanically engages the inverter casing cover, disconnecting the inverter from both DC and AC load-current circuits when pulled, ensuring the cover cannot be opened unless the inverter is safely disconnected, with visible and accessible design elements to facilitate safe access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If safety rules are followed meticulously to ensure disconnection before maintenance, then safety is improved, but operation complexity increases

Engineering Contradiction:

ImprovesafetyVSAvoidoperation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by automatically disconnecting the DC circuit and discharging capacitors before the maintenance cover can be opened. The safety plug is pulled in advance to trigger disconnection and discharge sequences, ensuring hazardous voltages are eliminated before any physical access to internal electronics is possible. This automated preliminary safety action eliminates the need for operators to manually verify disconnection status.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system applies self-service through the mechanical interlock between the safety plug and maintenance cover. The cover itself becomes part of the safety mechanism, physically preventing opening until the safety plug is removed. This self-enforcing design ensures that only when the system has automatically completed disconnection and discharge can the cover be opened, making safety compliance automatic rather than dependent on operator memory or training.

Inventive Principle:

Principle #25Self-service

2Ease of operation

If safety rules are not followed, then operation simplicity is maintained, but harmful factors increase

Engineering Contradiction:

Improveoperation simplicityVSAvoidhazardous voltages

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a capacitor discharge circuit as an intermediary safety mechanism between the DC power source and the maintenance cover. When the safety plug is pulled, this intermediary circuit automatically discharges any residual voltage in DC-link capacitors through a discharge resistor, creating a time delay that ensures hazardous voltages are eliminated before the cover can be opened. This intermediary mechanism bridges the gap between simple cover removal and complex safety verification.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system applies beforehand cushioning by providing a time delay mechanism through capacitor discharge. The discharge circuit remains active for a predetermined period after the safety plug is pulled, cushioning against the possibility of premature cover opening. This time-based safety buffer ensures that even if someone attempts to open the cover immediately, residual voltages will have been dissipated, preventing electric shock hazards.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If the cover is opened for maintenance, then accessibility is improved, but safety risks increase if not properly disconnected

Engineering Contradiction:

ImproveaccessibilityVSAvoidDC voltages

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by automatically disconnecting the DC circuit and discharging capacitors before the maintenance cover can be opened. The safety plug is pulled in advance to trigger disconnection and discharge sequences, ensuring hazardous voltages are eliminated before any physical access to internal electronics is possible. This automated preliminary safety action eliminates the need for operators to manually verify disconnection status.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a capacitor discharge circuit as an intermediary safety mechanism between the DC power source and the maintenance cover. When the safety plug is pulled, this intermediary circuit automatically discharges any residual voltage in DC-link capacitors through a discharge resistor, creating a time delay that ensures hazardous voltages are eliminated before the cover can be opened. This intermediary mechanism bridges the gap between simple cover removal and complex safety verification.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8035045B2Inverter

Publication Date: 2011.10.11 SMA SOLAR TECH AG

AI summary

The subject matter of the invention is an inverter (1), comprising a casing (8) as well as at least one casing cover (2), said casing cover (2) being mechanically engaged with a safety plug (10), said safety plug (10) being in electrical connection with at least the one load-current circuit located on the DC side, the inverter being switched off or disconnected at least from the DC-side load-current circuit after removal of the safety plug from the casing (8).