Segmented Rotor Magnets for Low-Loss Brushless Work Motors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless motors experience performance degradation due to eddy-current losses in permanent magnets, leading to increased temperature and reduced magnetic forces, which affects motor efficiency.
Innovation Solution
The design incorporates an inner-rotor-type brushless motor with magnetic-pole parts comprising discrete permanent magnets arranged alternately in the circumferential direction, with gaps between them to prevent eddy current conduction, and a stator core with pole arcs that protrude radially, optimizing the ratio of opening width to magnet width to reduce eddy-current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If continuous permanent magnets are used in the rotor, then the motor can generate sufficient magnetic force, but eddy-current losses occur causing temperature rise and magnetic force degradation
Solution Approach 1:
The permanent magnets are divided into multiple independent segments along the circumferential direction, with insulating gaps between adjacent segments. This segmentation prevents eddy currents from forming continuous loops within the permanent magnets, thereby reducing eddy-current losses and the associated temperature rise while maintaining sufficient magnetic force generation capability
2Productivity
If the rotor operates at high speed, then the motor productivity increases, but eddy-current losses increase causing performance degradation
Solution Approach 1:
By segmenting the permanent magnets into discrete units separated by insulating gaps, the patent eliminates the continuous conductive path that causes eddy-current losses during high-speed operation. This allows the motor to maintain stable magnetic force and reliable performance even at high rotational speeds where eddy-current losses would normally increase
3Power
If the permanent magnets are positioned to maximize magnetic flux, then the induced voltage constant increases, but eddy-current losses increase causing temperature rise
Solution Approach 1:
The patent segments the permanent magnets along the circumferential direction with insulating gaps between them. This segmentation interrupts the eddy current paths while preserving the magnetic flux distribution needed for high induced voltage constant, thereby achieving high power output without the temperature rise that would normally accompany maximized magnetic flux positioning
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 effectively reduces eddy-current losses, maintaining magnetic force and motor performance by minimizing temperature rise in the permanent magnets.
Implementation Method 1
there is a possibility that eddy-current losses will occur within the permanent magnets of the rotor
Implementation Method 2
an inner-rotor-type brushless motor comprising a rotor and a stator, which is disposed around the rotor
Data Source
AI summary
An electric work machine (1) includes: a brushless motor having a stator disposed around a rotor (30); and an output part driven by the rotor. The rotor has a rotor core (31) and first and second magnetic-pole parts (34S, 34N) disposed around a circumferential direction of the rotor core. When the induced voltage of the brushless motor is given as Va, the power-supply voltage of the brushless motor is given as Vb, the rotational speed of the brushless motor is given as ω, a first induced voltage constant, which is expressed by Va/ω, is given as Ea [V/krpm], a pole-pairs count, which is the number of the first magnetic-pole parts or the second magnetic-pole parts, is given as Pi, and a second induced voltage constant, which is expressed as Ea/Pi, is given as Eb [V/krpm·pole-pairs count], the motor satisfies the condition: Eb≤0.025×Vb.