IPM Motor Rotor Eddy Current Suppression via Soft Magnetic Body
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Solution Overview
Problem
In IPM motors, the protrusion of the rotor's end surface beyond the stator leads to magnetic flux perpendicular to the rotor's end surface, causing eddy currents and efficiency deterioration due to eddy current losses.
Innovation Solution
The integration of soft magnetic bodies outside permanent magnets in magnet structures, which are laminated with the magnets, suppresses eddy currents by increasing electrical resistivity and maintaining magnetic force, thereby improving motor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotor length is designed to be longer than the stator length to improve motor characteristics, then motor performance is improved, but eddy current loss increases due to magnetic flux perpendicular to the rotor end surface
Solution Approach 1:
A soft magnetic body is introduced as an intermediary component between the permanent magnet and the rotor core. This soft magnetic body serves as a magnetic flux shield that redirects the perpendicular magnetic flux at the rotor end surface, preventing it from inducing eddy currents in the rotor core while maintaining the beneficial motor performance characteristics
Solution Approach 2:
The magnetic properties of the rotor structure are modified by adding the soft magnetic body with specific magnetic permeability characteristics. This changes the magnetic flux distribution pattern at the rotor end surface, redirecting flux lines to reduce perpendicular components that cause eddy currents
2Power
If permanent magnets are embedded in the rotor to improve motor characteristics, then motor performance is improved, but eddy currents occur in the rotor end surface portion due to perpendicular magnetic flux
Solution Approach 1:
The soft magnetic body acts as a magnetic flux mediator that intercepts and redirects the perpendicular magnetic flux generated by the embedded permanent magnets. By positioning this soft magnetic body at the rotor end surface, the harmful perpendicular flux is redirected before it can induce eddy currents in the rotor core
Solution Approach 2:
The soft magnetic body is specifically positioned at the rotor end surface portion where the harmful perpendicular magnetic flux occurs. This localized solution addresses the specific problem area without requiring changes to the entire rotor structure or the permanent magnet configuration
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 enhances motor efficiency by reducing eddy current losses while maintaining torque and allowing for cost-effective production by simplifying assembly and reducing processing costs.
Implementation Method 1
a magnetic flux having a component perpendicular to the end surface of the rotor is likely to occur in an end surface portion of the rotor, and when such a magnetic flux fluctuates, an eddy current occurs in the end surface portion of the rotor
Implementation Method 2
an eddy current occurs in the soft magnetic body is suppressed
Data Source
AI summary
In an IPM motor according to one aspect of the present disclosure, in a magnet structure installed in a magnet hole, a first soft magnetic body is located outside a first permanent magnet in a radial direction. Since the first soft magnetic body has a higher electrical resistivity than the electrical resistivity of a rotor core, a situation where an eddy current occurs in the first soft magnetic body is suppressed. In the IPM motor, a deterioration in efficiency caused by an eddy current loss is suppressed, so that the efficiency is improved.