Dual-Inverter Motor Drive With Split DC Links for Low-Capacitance AC Input
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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, particularly when employing low-capacitance capacitors, which result in pulsating DC link voltage and reduced smoothing operations, leading to low voltage usage rates, torque ripple, and poor power factor characteristics.
Innovation Solution
A motor driving device configuration that includes 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, allowing for stable operation of both motors using a low-capacitance capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a low-capacitance capacitor is used in the motor driving device, then the device complexity and cost are reduced, but the voltage smoothing operation deteriorates, causing pulsating DC link voltage and poor power factor characteristics
Solution Approach 1:
The patent divides the single DC link capacitor 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 for each motor, thereby resolving the contradiction between reduced device complexity and maintained reliability.
2Device complexity
If a single DC link capacitor is used for both compressor and fan motors, then the device structure is simplified, but the voltage usage rate decreases due to pulsating voltage and insufficient smoothing
Solution Approach 1:
The patent segments the power distribution system by providing separate DC link capacitors for the compressor and fan motors. This allows each motor to receive stable, dedicated voltage without being affected by the other's power demands, thereby increasing the overall voltage usage rate while maintaining simple device structure through the modular capacitor arrangement.
Solution Approach 2:
The patent applies local quality by optimizing the capacitor configuration specifically for each motor's power requirements. The first capacitor is sized and positioned to optimize compressor motor performance, while the second capacitor is optimized for the fan motor, allowing each component to operate at peak efficiency with appropriately tailored voltage stabilization.
3Use of energy by moving object
If the same input AC power is used to drive both compressor and fan motors, then the system efficiency is improved, but the voltage stability deteriorates when using low-capacitance capacitors
Solution Approach 1:
The patent segments the voltage stabilization function by assigning separate capacitors to each motor's power circuit. This segmentation isolates voltage fluctuations caused by each motor's operation, preventing them from affecting the other motor's voltage stability, thereby maintaining stable DC link voltage while efficiently using the same input AC power for both motors.
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 enables smooth motor driving with increased voltage usage rates, reduced torque ripple, and improved power factor, allowing for stable operation of both compressor and fan motors using the same input AC power.
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.