Single-Inverter Multi-Motor Braking to Reduce Overcurrent Risk

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Solution Overview

Problem

Conventional motor driving apparatuses face issues with excessive current flow when braking multiple motors with a single inverter, leading to risks of inverter failure and motor demagnetization due to overcurrent.

Innovation Solution

The apparatus performs braking operations on a subset of motors connected to a single inverter, strategically managing the current flow by controlling the connection switching device to reduce the overall current through the inverter and motors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If braking operation is performed on multiple motors simultaneously with a single inverter, then the braking function is improved, but the current flowing through the inverter and motors increases excessively causing overcurrent risks

Engineering Contradiction:

Improvebraking functionVSAvoidovercurrent

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent divides the braking operation into sequential phases rather than simultaneous execution. The controller performs braking on the first motor first, then after a predetermined time interval, performs braking on the second motor. This temporal segmentation reduces the peak current flowing through the inverter at any given moment, preventing overcurrent damage while still achieving effective braking for both motors.

Inventive Principle:

Principle #1Segmentation

2Productivity

If braking operation is performed on multiple motors simultaneously, then the stopping efficiency is improved, but the risk of inverter failure and motor demagnetization increases

Engineering Contradiction:

Improvestopping efficiencyVSAvoidinverter and motor safety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The controller performs preliminary braking action on the first motor before initiating braking on the second motor. By applying a predetermined time interval between the start of braking operations on different motors, the system prepares the inverter to handle the current load sequentially rather than simultaneously, preventing inverter failure and motor demagnetization while maintaining acceptable stopping efficiency.

Inventive Principle:

Principle #10Preliminary action

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

This approach effectively reduces the risk of inverter failure and motor demagnetization by minimizing current flow during braking operations, enhancing the reliability and efficiency of the motor driving system.

Implementation Method 1

performs braking operation to stop the motors by forming a current path between the inverter and the motors to allow regenerative current to flow therethrough

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11264924B2Motor driving apparatus and refrigeration cycle equipment

Publication Date: 2022.03.01 MITSUBISHI ELECTRIC CORP

AI summary

In a motor driving apparatus including an inverter connectable to n motors (n being an integer not less than 2) each including a rotor having a permanent magnet, braking operation is performed on i (i being an integer from 1 to n−1) of the n motors, and then braking operation is performed on j (j being an integer from 1 to n−i) of the n motors other than the i motors. It is possible to reduce the risks of failure of the inverter and demagnetization of the motors due to overcurrent by reducing current flowing through the inverter and the motors when the braking operation is performed.