Three-Phase Motor Current Detection Circuit Segmentation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional motor driving devices face difficulties in directly detecting the maximum current value in three-phase motors, especially when the current direction is ambiguous, leading to challenges in securing safety during operations.

Innovation Solution

A current detection circuit that identifies the maximum current phase and detects the maximum current value by adding current values of other phases when the current direction is predetermined, allowing for easy detection regardless of current direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If direct detection of maximum current value is attempted in three-phase motor, then measurement precision can be achieved, but device complexity increases and ease of operation deteriorates due to difficulty in determining current direction

Engineering Contradiction:

Improvemaximum current value detectionVSAvoidcurrent detection circuit

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The current detection is segmented by phase. The detection circuit separately processes current values from each phase (Ia, Ib, Ic) and identifies which phase contains the maximum current. This segmentation allows the use of simpler detection methods for each phase while collectively achieving accurate maximum current detection without complex directional analysis.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of directly detecting the maximum current by analyzing current direction (which is complex), the invention inverts the approach by detecting the minimum current value among the three phases. Since the sum of three-phase currents is zero (Ia + Ib + Ic = 0), the phase with the maximum current can be identified by finding which phase does not have the minimum current value, thereby simplifying the detection circuit.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If direct detection of maximum current value is attempted in three-phase motor, then measurement precision can be achieved, but ease of operation deteriorates due to difficulty in determining current direction

Engineering Contradiction:

Improvemaximum current value detectionVSAvoidcurrent detection operation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The detection operation is segmented into simple steps: (1) acquire current values from each phase, (2) compare the values to identify minimum, (3) determine maximum based on the minimum identification. This segmented approach makes the operation straightforward and eliminates the need for complex directional analysis, significantly improving ease of operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The detection operation is inverted by finding the minimum current phase instead of directly searching for the maximum. This inversion simplifies the operational logic to basic comparison operations, making the detection process easier to implement and execute without requiring complex directional determination.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If maximum current detection function is added to motor driving device, then reliability improves for safety operations, but device complexity increases

Engineering Contradiction:

Improvesafety operationVSAvoidmotor driving device

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The maximum current detection function is merged with the existing current detection circuitry used for motor control. The same circuit that measures phase currents for control purposes also performs the maximum current detection by comparing the measured values. This merging eliminates the need for separate detection hardware, maintaining reliability while avoiding additional device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The current detection circuit is designed with multi-functionality, serving both the motor control function (by providing phase current values) and the maximum current detection function (by comparing these values). This universal approach allows the device to achieve safety operations through maximum current detection without adding dedicated separate components, thereby avoiding increased device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9263977B2Current detection circuit, motor driving device, magnetic disk storage device, and electronic appliance

Publication Date: 2016.02.16 ROHM CO LTD

AI summary

A current detection circuit for detecting a maximum current value in a three-phase motor includes an identifier configured to identify a maximum current phase having the maximum current value among phases of the motor, and a detector configured to detects the maximum current value by summing current values of phases other than the maximum current phase when the current direction in the maximum current phase is a predetermined first direction.