Calculation Apparatus for Three-Phase Motor Current Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting phase currents in three-phase brushless motors using one shunt current detection are inefficient due to high calculation complexity and long control cycles, which affect motor stability and increase costs.
Innovation Solution
A calculation apparatus that stores AD-converted current values after PWM signals rise and calculates phase current differences, reducing the amount of calculation required and shortening the control cycle by eliminating the need to evaluate which phase the detected current belongs to.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one shunt current detection method is used to reduce the number of current sensors, then cost is reduced, but calculation complexity increases and control cycle lengthens
Solution Approach 1:
The patent applies preliminary action by pre-identifying and storing the maximum phase and minimum phase information before AD conversion. The control unit determines which phases correspond to maximum and minimum voltage levels, stores this phase identification information, and then uses it during the current detection process. This preliminary preparation eliminates the need for complex real-time evaluation of which phase the detected current belongs to, thereby reducing calculation complexity while maintaining the cost benefits of one-shunt detection.
2Reliability
If one shunt current detection method is used to reduce the number of current sensors, then cost is reduced, but control cycle lengthens
Solution Approach 1:
By determining and storing the maximum phase and minimum phase information in advance, the patent eliminates time-consuming real-time phase identification during the control cycle. The pre-stored phase information allows for immediate calculation of phase currents from the single shunt measurement, thereby shortening the control cycle while maintaining cost efficiency.
3Difficulty of detecting and measuring
If bus current is sampled at appropriate timings to detect phase currents, then current detection is enabled, but the bus current section to be sampled becomes very short when pulse widths are close
Solution Approach 1:
The patent determines and stores the maximum phase and minimum phase information before the AD conversion process. This preliminary identification of phase relationships allows the system to correctly interpret the single shunt current measurement without requiring a long sampling window. By knowing in advance which phases are maximum and minimum, the system can accurately calculate all three phase currents even with very short bus current sections available for sampling.
Data Source
AI summary
A calculation apparatus 100 includes an encoder 101 configured to detect rising edges of PWM signals having at least three or more phases in each of the phases, and a register 103 configured to store, at a timing after the PWM signals having the respective phases rise and after AD conversion of a current value of a drive signal of a motor obtained by the PWM signals, a difference value between the AD-converted current value and a previous AD-converted current value for each phase.