Motor driving apparatus, refrigeration cycle system, air conditioner, water heater, and refrigerator

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Solution Overview

Problem

Conventional motor driving systems face issues with changing coil connection states while avoiding potential differences between contacts, which can lead to arc generation and contact sticking, resulting in electromagnetic contactor failure.

Innovation Solution

A motor driving apparatus that includes a mechanical switch, an inverter generating alternating voltage, and a control device that changes coil connection states while the alternating voltage output from the inverter is zero, using PWM signals to control the switching elements and prevent potential differences between contacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If coil connection states are changed while electromagnetic contactors are opened/closed, then the coil connection states can be changed, but arcs may be generated between contacts causing sticking and failure

Engineering Contradiction:

Improvecoil connection state changingVSAvoidelectromagnetic contactor reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control device stops the inverter output before changing the coil connection states of the electromagnetic contactors. By preliminarily stopping the alternating voltage output, the potential difference between contacts is eliminated before the switching operation, preventing arc generation and contact sticking.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The inverter output is controlled to maintain zero potential difference across the electromagnetic contactor contacts during the coil connection state change. This equipotential condition ensures that no arcs are generated when the mechanical switch operates, thereby preventing contact sticking and improving reliability.

Inventive Principle:

Principle #12Equipotentiality

2Reliability

If inverter output is stopped to change coil connection states, then arc generation is prevented, but the motor driving operation is interrupted

Engineering Contradiction:

Improveelectromagnetic contactor reliabilityVSAvoidmotor driving continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system performs periodic switching between Y-connection and Δ-connection modes by temporarily stopping the inverter output, changing the coil connection states, and then resuming operation. This periodic interruption is strategically timed to minimize impact on overall motor driving continuity while ensuring reliable contactor operation.

Inventive Principle:

Principle #19Periodic 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 allows for reliable changeover of coil connection states without generating a potential difference between contacts, reducing the risk of arc discharge and contact sticking, thereby enhancing the reliability of the electromagnetic contactors.

Implementation Method 1

an inverter that generates alternating voltage from direct voltage and outputs the alternating voltage to the motor

Methodology Applied

Scientific EffectInversion (electrical):

Implementation Method 2

a mechanical switch that changes coil connection states of a motor

Methodology Applied

Scientific EffectElectrical switching:

Implementation Method 3

the control device causes the mechanical switch to change the coil connection states while the alternating voltage output from the inverter is zero

Methodology Applied

Scientific EffectVoltage control:

Data Source

PatentUS11329587B2Motor driving apparatus, refrigeration cycle system, air conditioner, water heater, and refrigerator

Publication Date: 2022.05.10 MITSUBISHI ELECTRIC CORP

AI summary

The motor driving apparatus includes a switch that is a mechanical switch for changing coil connection states of a motor; an inverter that generates alternating voltage from direct voltage and outputs the alternating voltage to the motor; and a control device that controls the switch and the inverter. The control device causes the switch to change the coil connection states while the alternating voltage output from the inverter is zero.