Six-Phase Motor Torque Estimation from Independent Stator Currents
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Solution Overview
Problem
Six phase dual delta or dual star electrical machines require additional measurement systems for torque control, leading to common mode failures and increased costs due to shared hardware, and existing methods are inefficient in systems with low machine dynamics.
Innovation Solution
A method and apparatus for measuring torque in six phase electrical motors with two electrically independent stator winding arrangements, where current measurements from three windings of one arrangement are used to determine torque, and the second value of torque is calculated using currents from the other arrangement, allowing for independent control and safety monitoring without additional hardware redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional measurement systems are used for torque control in six phase machines, then torque measurement accuracy and functional safety are improved, but device complexity and cost increase due to shared hardware components
Solution Approach 1:
The patent segments the six-phase system into two independent three-phase winding arrangements (first and second arrangements). Each arrangement can independently provide torque measurement, allowing the system to use only one arrangement for measurement purposes. This segmentation eliminates the need for redundant measurement hardware across all six phases while maintaining functional safety through the ability to independently assess torque from either arrangement.
Solution Approach 2:
The patent extracts the torque measurement function from requiring all six phase measurements and demonstrates that torque can be accurately determined using current measurements from only one three-phase winding arrangement. This extraction removes the unnecessary redundancy of measuring all six phases when functional safety can be achieved through a single independent measurement path.
2Measurement precision
If current measurements are taken on all six phases, then complete torque information is obtained, but measurement hardware requirements and system cost increase
Solution Approach 1:
The patent applies partial action by measuring currents in only one three-phase winding arrangement (three phases) instead of all six phases. This partial measurement is sufficient to obtain complete torque information because the two winding arrangements are electrically independent and both contribute to the overall torque. The system achieves full torque measurement capability with reduced hardware by utilizing the independence of the winding arrangements.
3Reliability
If redundant measurement hardware is implemented for functional safety, then safety requirements are met, but common mode failures increase due to shared components
Solution Approach 1:
The patent segments the measurement function into two independent paths through the two three-phase winding arrangements. By configuring the system to use current measurements from only one arrangement for torque determination, the patent creates an independent measurement path that avoids shared hardware components. This segmentation eliminates common mode failures associated with shared shunts, amplifiers, and ADCs while maintaining functional safety through the independent measurement capability.
Solution Approach 2:
The patent extracts the functional safety requirement from the context of redundant hardware and demonstrates that safety can be achieved through software-based independent calculation of torque from a single measurement path. This extraction removes the harmful shared hardware components while preserving the safety function through independent computational assessment.
Data Source
Figure 1~2c
Figure 3a~3c
Figure 3d~4
AI summary
A method of measuring torque in a six phase electrical motor, said motor including a motor stator including two electrically independent stator winding arrangements (U,V,W), (X,Y,Z) each comprising three combined windings; said winding arrangements being symmetrical and offset by an angle γ to each other, such that each combined winding of the second stator arrangement has a corresponding combined winding in the first stator arrangement and offset thereto by an angle γ, said method comprising: a) determining the current (Iu, Iv, Iw) in the three combined windings (U,V,W) of the first stator arrangement and/or the current (Ix, Iy, Iz) in the three combined windings (X,Y,Z) of the second stator arrangement; b) determining the torque the currents determined from a).