Motor Drive Apparatus Dynamic Braking Control

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Solution Overview

Problem

Motor drive systems, particularly in washing machines, experience noise and component damage during dynamic braking due to collisions between rotor bush, coupling, and gear components, and there is a risk of overcurrent in the DC-side capacitor.

Innovation Solution

A motor drive apparatus with a DC-side capacitor, an inverter unit, and a shunt resistor, controlled to gradually increase the phase current through bottom switches before dynamic braking, minimizing noise and collision forces, and limiting current flow to prevent overcurrent.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If dynamic braking is performed on the motor to achieve quick stopping, then stopping speed is improved, but noise is generated due to collisions between rotor bush and coupling or coupling and gear portion

Engineering Contradiction:

Improvestopping speedVSAvoidnoise

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The controller performs preliminary action by gradually increasing the phase current through bottom switches before executing dynamic braking. This preparatory current increase reduces the inertia difference between rotor bush and pulsator/drum, preventing collisions and noise generation while achieving quick stopping

Inventive Principle:

Principle #10Preliminary action

2Loss of energy

If gear ratio of the gear portion is increased to reduce power consumption, then energy efficiency is improved, but noise increases due to larger inertia difference causing more severe collisions

Engineering Contradiction:

Improvepower consumptionVSAvoidnoise

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The controller changes the parameter of phase current gradually before braking occurs. By increasing the phase current through bottom switches in advance, the system compensates for the larger inertia difference created by high gear ratio, preventing collisions and noise while maintaining energy efficiency

Inventive Principle:

Principle #35Parameter changes

3Speed

If dynamic braking is performed to achieve quick braking, then braking speed is improved, but component failure risk increases due to collision forces

Engineering Contradiction:

Improvebraking speedVSAvoidcomponent durability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The controller performs preliminary action by gradually increasing the phase current through bottom switches before dynamic braking. This reduces the inertia difference and prevents collisions between components, protecting them from damage while achieving quick braking

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The gradual increase of phase current acts as a cushioning measure before braking. It softens the impact by reducing the inertia difference between rotating components, preventing collision forces that could cause component failure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Power

If phase current is increased rapidly during dynamic braking to improve braking performance, then braking effectiveness is improved, but overcurrent risk increases in DC-side capacitor

Engineering Contradiction:

Improvebraking powerVSAvoidcapacitor safety

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The controller performs preliminary action by gradually increasing the phase current through bottom switches before dynamic braking. This controlled gradual increase prevents overcurrent in the DC-side capacitor while still achieving effective braking performance

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The controller applies dynamics by adjusting the phase current gradually rather than abruptly. The bottom switches are controlled to increase current in a dynamic, controlled manner, balancing braking effectiveness with capacitor safety

Inventive Principle:

Principle #15Dynamics

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 solution effectively reduces noise and collision forces between motor components during dynamic braking, ensuring safety and preventing component failure by stabilizing the braking process and managing current flow.

Implementation Method 1

an inverter unit comprising multiple top switches and bottom switches, performing a switching operation so as to convert power stored in the DC-side capacitor into alternating current power

Methodology Applied

Scientific EffectElectrical switching:

Implementation Method 2

a shunt resistor for detecting a current flowing through the DC-side capacitor

Methodology Applied

Scientific EffectOhm's law: Ohm's Law

Implementation Method 3

a motor having a rotor configured to perform a rotational motion and a stator wound with a coil

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11139760B2Motor drive apparatus and control method thereof

Publication Date: 2021.10.05 LG ELECTRONICS INC

AI summary

A motor drive apparatus includes: a DC-side capacitor charged with direct current power; an inverter unit comprising multiple top switches and bottom switches, performing a switching operation so as to convert power stored in the DC-side capacitor into alternating current power, and outputting the converted alternating current power to a motor; a shunt resistor for detecting a current flowing through the DC-side capacitor; and a controller for controlling the inverter unit to perform dynamic braking for stopping the motor. Before the dynamic braking is performed, the controller controls the inverter unit to gradually increase a phase current flowing through the bottom switches.