Segmented Rotor Magnet Poles for High-Speed Motor Field Weakening
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Solution Overview
Problem
In permanent magnet motors, increased flux linkage at higher rotor speeds leads to higher induced voltage, which hinders motor output and rotation speed.
Innovation Solution
The motor design includes a stator with series-connected windings and a rotor with alternating magnet poles and non-magnetic portions, allowing for field weakening flux generation that reduces induced voltage, enabling higher speed rotation by synchronously exciting the windings and strategically positioning magnet poles and non-magnetic portions to distribute radial force and reduce vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotor is driven to rotate at a higher speed, then the motor output increases, but the induced voltage increases due to increased flux linkage, which hinders rotation at higher speeds
Solution Approach 1:
The rotor is divided into multiple rotor parts (first rotor part and second rotor part) arranged in the axial direction. Each rotor part has magnet poles and non-magnetic portions arranged alternately in the circumferential direction. This segmentation allows different rotor parts to contribute differently to flux generation, enabling field weakening control that reduces induced voltage while maintaining high-speed rotation capability.
Solution Approach 2:
Different regions of the rotor are given different magnetic properties. Specifically, non-magnetic portions are strategically positioned in the rotor parts to create localized areas that do not contribute to flux linkage. This local differentiation allows the motor to control flux distribution, reducing induced voltage in specific regions while maintaining overall motor output during high-speed operation.
2Speed
If field weakening current is applied to reduce induced voltage, then higher speed rotation is enabled, but demagnetization and copper loss increase
Solution Approach 1:
By segmenting the rotor into multiple parts with alternating magnet poles and non-magnetic portions, the flux linkage is naturally reduced without requiring excessive field weakening current. This structural segmentation achieves speed enhancement with minimal energy loss compared to conventional single-rotor designs.
Solution Approach 2:
The non-magnetic portions in the rotor, which could be considered as reducing the overall magnetic strength, are strategically positioned to enable field weakening control. This converts what might be seen as a deficiency (reduced flux linkage) into a benefit (reduced induced voltage allowing higher speed rotation with acceptable copper loss).
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 design allows for optimal reduction of induced voltage during field weakening, enabling higher speed rotation while minimizing demagnetization and copper loss, and provides mechanical balance to reduce vibration.
Implementation Method 1
a stator, which is formed by windings wound around a stator core, and a rotor, which uses permanent magnets opposing the stator as magnet poles. The windings of the stator are supplied with drive currents to generate a rotation field that rotates the rotor.
Implementation Method 2
when the rotor is driven to rotate at a higher speed, an increase in flux linkage resulting from the permanent magnets of the rotor increases the induced voltage generated at the windings of the stator.
Implementation Method 3
The flux toleration portion tolerates generation of a flux linkage resulting from a field weakening current at the second winding.
Data Source
AI summary
A motor includes a stator including windings and a rotor. The windings include a first winding and a second winding connected in series. The rotor includes a plurality of rotor parts arranged in an axial direction. Each of the rotor parts includes a first magnet pole unit including a permanent magnet and a second magnet pole unit opposing the second winding at a rotational position of the rotor where the first magnet unit opposes the first winding. The second magnet pole unit applies a weaker magnetic force to the stator than the first magnet pole unit. The rotor parts each include an equal number of magnet poles. The first magnet pole units of the rotor parts are located at positions deviated from one another in a circumferential direction. The second magnet pole units of the rotor parts are located at positions deviated from one another in the circumferential direction.