High Efficiency Permanent Magnet Machine Design
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Solution Overview
Problem
Current electric machines face challenges in achieving high power density while maintaining efficiency, as increased efficiency often results in larger size and weight, and reducing copper loss is hindered by the trade-off between wire cross-sectional area and magnetic saturation.
Innovation Solution
The design incorporates a laminated cylindrical rotor and stator with a large air gap, high magnetic flux density permanent magnets, and a three-phase winding scheme with optimized current density and coil turns to minimize copper and windage losses, along with a sensorless field-oriented control for improved efficiency and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If copper wire cross-sectional area is increased to reduce copper loss, then efficiency is improved, but slot area requirement increases leading to larger stator size and decreased power density
Solution Approach 1:
The patent changes the electrical parameters by operating at higher frequencies (e.g., 400 Hz or 800 Hz compared to standard 60 Hz), which allows for reduced copper cross-sectional area while maintaining acceptable copper loss levels. This parameter change enables smaller wire sizes and consequently smaller slot areas, directly resolving the contradiction between reducing copper loss and maintaining compact machine size.
2Loss of energy
If stator size is increased to accommodate larger copper wires, then copper loss is reduced, but power density decreases
Solution Approach 1:
The patent employs high-frequency operation (400 Hz or 800 Hz) as a parameter change that enables the use of smaller copper wires while maintaining acceptable copper loss. This allows the stator to be designed with smaller dimensions, thereby achieving high power density without sacrificing efficiency. The high frequency operation fundamentally changes the relationship between wire size and power density.
3Loss of energy
If tooth size is decreased to accommodate larger slot area, then copper loss is reduced, but magnetic saturation increases and current must increase resulting in decreased efficiency
Solution Approach 1:
The patent uses high-frequency operation as a parameter change that decouples the relationship between tooth size and copper loss. At high frequencies, the skin effect and proximity effect become significant, allowing for optimized winding designs that achieve low copper loss without requiring excessively large slot areas. This enables maintenance of adequate tooth dimensions to prevent magnetic saturation while still achieving low copper loss through the high-frequency operating parameter.
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 achieves higher power density with reduced size and weight, decreased heat generation, and enhanced efficiency by minimizing copper and windage losses, while maintaining overload capability and thermal management without active cooling.
Implementation Method 1
The electrical windings interact with the PMs to produce either mechanical or electrical energy. When configured as a motor, the electrical machine uses current flowing through the electrical windings to generate rotating magnetic fields which interact with the PMs attached to the rotor and cause the rotor and shaft to rotate.
Implementation Method 2
Copper loss is the term often given to heat produced by electrical currents in the conductors of transformer windings, or other electrical devices. Copper losses are an undesirable transfer of energy.
Implementation Method 3
Copper losses are an undesirable transfer of energy, as are core losses, which result from induced currents in adjacent components.
Data Source
AI summary
The present invention is a high efficiency permanent magnet machine capable of maintaining high power density. The machine is operable over a wide range of power output. The improved efficiency is due in part to copper wires with a current density lower than traditional designs and larger permanent magnets coupled with a large air gap. In a certain embodiment wide stator teeth are used to provide additional improved efficiency through significantly reducing magnetic saturation resulting in lower current. The machine also has a much smaller torque angle than that in traditional design at rated load and thus has a higher overload handling capability and improved efficiency. In addition, when the machine is used as a motor, an adaptive phase lag compensation scheme helps the sensorless field oriented control (FOC) scheme to perform more accurately.