Motor Drive Overcurrent Protection With Redundant Hardware Circuits

Solution Overview

Problem

Conventional motor drive devices require costly and time-consuming software-based evaluations to ensure compliance with the VDE standard's redundancy requirements for single-phase direct-current motor protection, leading to inefficiencies in assessing and maintaining the duplicated protection function.

Innovation Solution

A motor drive device with independent first and second drive circuits, current detection circuits, and protection circuits that use hardware-based redundancy to detect overcurrents and control the energization of the motor, eliminating the need for software evaluations by ensuring the protection function meets the VDE standard without software program evaluation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If software-based processing is used to generate two stop commands for protection function duplication, then the VDE standard compliance can be achieved, but the evaluation requires high cost and long evaluation period

Engineering Contradiction:

Improveprotection function redundancyVSAvoidevaluation period

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces software-based protection function duplication with a hardware-based solution. Two independent protection circuits are implemented in hardware, each capable of independently detecting overcurrent conditions and generating stop commands. This hardware implementation eliminates the need for software program evaluation while ensuring VDE standard compliance through physical circuit redundancy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The protection function is segmented into two independent protection circuits rather than using a single software-based system. Each protection circuit operates independently with separate signal lines, allowing parallel evaluation and eliminating the sequential software evaluation process. This segmentation enables simultaneous hardware verification of both protection paths.

Inventive Principle:

Principle #1Segmentation

2Reliability

If software-based processing is used to generate two stop commands for protection function duplication, then the VDE standard compliance can be achieved, but the evaluation requires high cost

Engineering Contradiction:

Improveprotection function redundancyVSAvoidevaluation cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces software-based protection function duplication with a hardware-based solution. Two independent protection circuits are implemented in hardware, each capable of independently detecting overcurrent conditions and generating stop commands. This hardware implementation eliminates the need for software program evaluation while ensuring VDE standard compliance through physical circuit redundancy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of time

If hardware-based protection circuit is used to generate two stop commands, then the evaluation cost and time can be reduced, but the design complexity of drive circuit and wiring pattern increases

Engineering Contradiction:

Improveevaluation periodVSAvoidwiring pattern complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The protection function is segmented into two independent protection circuits rather than using a single software-based system. Each protection circuit operates independently with separate signal lines, allowing parallel evaluation and eliminating the sequential software evaluation process. This segmentation enables simultaneous hardware verification of both protection paths.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a copied redundancy architecture where the second protection circuit is essentially a copy of the first, both processing the same current detection signal independently. This copying approach simplifies the overall design by using identical circuit topologies rather than complex interconnections, making the wiring pattern more manageable while ensuring independent operation.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS11777438B2Motor drive device

Publication Date: 2023.10.03 NIDEC SERVO CORP

AI summary

A motor drive device includes a first drive circuit to control an energization period of a first upper arm switch and a first lower arm switch connected to one end of a coil, a second drive circuit to control an energization period of a second upper arm switch and a second lower arm switch connected to another end of the coil, a current detection circuit to detect current flowing through the coil and output a current detection signal indicating a detection result of the current, a first protection circuit to determine whether overcurrent has occurred based on the current detection signal and output a first enable signal indicating a determination result to the first drive circuit, and a second protection circuit to determine whether overcurrent has occurred based on the current detection signal and output a second enable signal indicating a determination result to the second drive circuit.