Motor driving device and air conditioner including the same
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Solution Overview
Problem
Existing motor driving devices face challenges in efficiently driving both compressor and fan motors using the same input AC power, especially when employing low-capacitance capacitors, which result in pulsating DC link voltage and reduced smoothing operations, leading to inefficient motor driving and low power factor characteristics.
Innovation Solution
The motor driving device incorporates a rectifier to rectify input AC power, a boost converter to boost the rectified power, a first capacitor to store pulsating voltage, a first inverter to output AC power to the compressor motor, a second capacitor to store rectified power, a second inverter to output AC power to the fan motor, and a voltage dropper to drop the voltage across the second capacitor, enabling stable operation of both motors using a low-capacitance capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a low-capacitance capacitor is used in the motor driving device, then the device size and cost are reduced, but the DC link voltage pulsation increases and smoothing operation becomes insufficient
Solution Approach 1:
The patent divides the capacitor system into two separate capacitors: a first capacitor connected to the compressor inverter and a second capacitor connected to the fan inverter. This segmentation allows each capacitor to be optimized independently, enabling the use of low-capacitance capacitors while maintaining stable voltage supply to each motor.
Solution Approach 2:
The patent introduces a voltage dropper as an intermediary component between the second capacitor and the fan inverter. The voltage dropper converts the higher voltage from the rectifier into a suitable lower voltage for the fan motor, enabling the second capacitor to be charged to a higher voltage level that provides better smoothing without requiring large capacitance.
2Use of energy by moving object
If the same input AC power is used to drive both compressor motor and fan motor, then power efficiency is improved, but voltage distribution and motor control become complex
Solution Approach 1:
The patent segments the power distribution system into two independent power supply paths: one path supplies the compressor motor through the first capacitor and first inverter, while the other path supplies the fan motor through the second capacitor and second inverter. This segmentation simplifies voltage distribution control while maintaining efficient use of the same input AC power.
Solution Approach 2:
The patent applies different voltage levels and capacitor configurations to different parts of the system based on their specific requirements. The first capacitor is charged to a voltage suitable for the compressor motor, while the second capacitor is charged to a higher voltage that is then stepped down by the voltage dropper for the fan motor, optimizing each local power supply configuration.
3Volume of stationary object
If low-capacitance capacitors are used, then device size is reduced, but torque ripple increases and motor driving smoothness deteriorates
Solution Approach 1:
By separating the capacitor system into two independent capacitors, each can be sized appropriately for its specific motor load. The first capacitor provides sufficient smoothing for the compressor motor, while the second capacitor, charged to a higher voltage, provides adequate smoothing for the fan motor through the voltage dropper, both using smaller total capacitance than a single large capacitor would require.
Solution Approach 2:
The patent changes the voltage parameter of the second capacitor by charging it to a higher voltage level and using a voltage dropper to step it down. This parameter change allows the second capacitor to provide effective voltage smoothing with smaller capacitance, thereby reducing torque ripple while maintaining compact device size.
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 configuration allows for smooth motor driving, reduced torque ripple, and improved power factor, enabling efficient operation of both compressor and fan motors with increased voltage usage and stability, even when using low-capacitance capacitors.
Implementation Method 1
a rectifier to rectify input AC power
Implementation Method 2
a boost converter to boost the rectified power from the rectifier
Implementation Method 3
a first capacitor to store a pulsating voltage from the boost converter
Implementation Method 4
a first inverter including a plurality of switching elements, the first inverter outputting, to a compressor motor, AC power transformed using a voltage across the first capacitor
Implementation Method 5
a second capacitor to store the rectified power from the rectifier
Implementation Method 6
a second inverter including a plurality of switching elements, the second inverter outputting, to a first fan motor, AC power transformed using a voltage across the second capacitor
Implementation Method 7
a voltage dropper to drop the voltage across the second capacitor
Data Source
AI summary
A motor driving device and an air conditioner including the same are disclosed. The motor driving device includes a rectifier to rectify input AC power, a boost converter for boosting the rectified power from the rectifier, a first capacitor to store a pulsating voltage from the boost converter, a first inverter for outputting, to a compressor motor, AC power transformed using a voltage across the first capacitor, a second capacitor to store the rectified power from the rectifier, a second inverter for outputting, to a first fan motor, AC power transformed using a voltage across the second capacitor, and a voltage dropper to drop the voltage across the second capacitor, and to output the dropped voltage. In accordance with this configuration, the compressor motor and fan motor can be driven, using the same input AC power, even though the motor driving device uses a low-capacitance capacitor.