Motor Core Steel Sheet Composition for Iron Loss Reduction
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Solution Overview
Problem
High-speed motors used in cordless appliances and drones face inefficiencies due to high iron losses at frequencies other than maximum output, where current phase advance control is employed, leading to increased copper loss and difficulty in maintaining high rotational speed, and existing materials like Si gradient steel do not adequately reduce losses.
Innovation Solution
A motor using a steel sheet with specific composition and thickness, including 0.010% or less C, 2.0% to 7.0% Si, 2.0% or less Al, and 0.05% to 1.0% Mn, with a sharp change in magnetic flux density and eddy-current loss reduction, allowing for effective control of magnetic flux density and reduced iron loss at lower rotational speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of windings of the coil is increased to apply large current for controlling magnetic flux density, then magnetic flux density control is improved, but counter electromotive voltage increases making high rotational speed difficult
Solution Approach 1:
The patent changes the magnetic properties of the iron core by optimizing steel sheet composition and thickness, which improves magnetic flux density control characteristics. This allows effective control with fewer coil windings, thereby reducing counter electromotive voltage and enabling high rotational speed operation.
2Quantity of substance
If non-oriented electrical steel sheets are used for iron cores to reduce cost, then manufacturing cost is reduced, but eddy-current loss increases at high excitation frequencies
Solution Approach 1:
The patent changes the chemical composition parameters of the steel sheet by adding specific amounts of Si (2.0-7.0%), Al (0.01-1.0%), Mn (0.05-1.0%), and Ti (0.003-0.03%), which increases electrical resistance and reduces eddy-current loss. This allows the use of cost-effective non-oriented electrical steel sheets while achieving low eddy-current loss at high excitation frequencies.
Solution Approach 2:
The patent optimizes the local quality of the steel sheet by controlling the concentration and distribution of alloying elements to specifically address eddy-current loss in the iron core, while maintaining overall cost-effectiveness through the use of standard non-oriented electrical steel sheet manufacturing processes.
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
The motor achieves higher efficiency, downsizing, and higher speed by minimizing iron loss during operation at rotational speeds lower than maximum, with an average motor efficiency over 85% under various driving conditions.
Implementation Method 1
The loss caused in the iron core is classed into the hysteresis loss and the eddy-current loss. As is known, the eddy current loss becomes dominant with an increase in the excitation frequency.
Implementation Method 2
a magnetic flux density changing area where a change ΔB in magnetic flux density to a change ΔH=50 A/m in a magnetic field, is equal to or higher than 0.50 T
Data Source
AI summary
A motor comprising a steel sheet used as a core material of the motor, wherein the steel sheet includes a composition including: by mass %, 0.010% or less of C; 2.0% to 7.0% of Si; 2.0% or less of Al; 0.05% to 1.0% of Mn; 0.005% or less of S; 0.005% or less of N; and balance Fe and inevitable impurities; the steel sheet includes a magnetic flux density changing area where a change ΔB in magnetic flux density to a change ΔH=50 A/m in a magnetic field, is equal to or higher than 0.50 T; a thickness of the steel sheet is 0.05 mm to 0.20 mm; and an eddy-current loss of the steel sheet, at 1000 Hz−1.0 T, is equal to or less than 0.55 of a total iron loss.