Motor drive device and air conditioner
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Solution Overview
Problem
Conventional motor drive apparatuses face challenges in reducing costs while increasing current capacity, as reducing chip area to lower costs leads to decreased current capacity when using switching elements as chips.
Innovation Solution
The motor drive apparatus employs multiple switching elements in parallel for each phase, with a control unit that adjusts pulse width based on current measurements to balance current flow, allowing for high current capacity and cost reduction by using wide band-gap semiconductors and optimizing PWM signal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the chip area of switching elements is reduced to lower cost, then manufacturing cost decreases, but current capacity decreases
Solution Approach 1:
The patent divides the current carrying function into multiple segments by using multiple switching elements connected in parallel. Each switching element chip has a reduced area (improving manufacturing cost), but the parallel combination achieves the required total current capacity. This segmentation allows independent optimization of chip size for cost reasons while maintaining system-level performance through parallel architecture.
2Quantity of substance
If multiple switching elements are used in parallel to increase current capacity, then current capacity increases, but current imbalance occurs
Solution Approach 1:
The patent implements feedback control by measuring the current flowing through each switching element and using this information to adjust the pulse width of PWM signals. The current detection unit monitors individual element currents, and the control unit modifies drive signals to balance current distribution. This closed-loop feedback mechanism dynamically compensates for variations in on-resistance and other parameters, achieving precise current balance despite manufacturing tolerances.
Solution Approach 2:
The patent changes the PWM pulse width parameter for each switching element based on detected current conditions. By dynamically adjusting the pulse width (a key control parameter), the system compensates for differences in switching element characteristics. Elements with higher current draw receive reduced pulse widths, while those with lower current draw receive increased pulse widths, thereby balancing the overall current distribution across parallel elements.
Data Source
Figure 1
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AI summary
A motor drive apparatus 100 driving a motor 8 as a three-phase motor converting direct current into three-phase alternating current, includes: inverter modules 5, 6, and 7 equivalent in number to phases of the motor 8; and a control unit 9 generating PWM signals used to drive the inverter modules 5, 6, and 7 with PWM. The inverter modules 5, 6, and 7 each include a plurality of switching element pairs connected in parallel, each of the switching element pairs including two switching elements connected in series.