Rotor Slit Layout for Lower Cogging Torque and Voltage Harmonics
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Solution Overview
Problem
Conventional rotors with slits between permanent magnet insertion holes and outer peripheral surfaces of rotor cores increase magnetic resistance, leading to higher harmonic components of induced voltage, resulting in increased vibrations and noise in electric motors.
Innovation Solution
A rotor design featuring a rotor core with a V-shaped permanent magnet insertion hole, outside slits between the magnet insertion hole and the outer peripheral surface, and inside slits between the magnetic pole center and outside slits, where the minimum distance from the first inside slit to the outer peripheral surface is longer than from other inside slits, reducing magnetic resistance and harmonic components of the magnetic flux density waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a plurality of slits are provided between permanent magnet insertion hole and outer peripheral surface of rotor core, then cogging torque is reduced, but inductance decreases and harmonic component of induced voltage increases
Solution Approach 1:
The patent implements local quality by dividing the rotor core into different functional zones with distinct slit arrangements. The first slits positioned between the permanent magnet insertion hole and outer peripheral surface target cogging torque reduction, while the second slits positioned between the magnetic pole center part and first slits are specifically designed to maintain inductance levels. This spatial differentiation allows the rotor to simultaneously achieve low cogging torque and sufficient inductance for reliable motor operation.
Solution Approach 2:
The patent applies segmentation by dividing the slit structure into two distinct sets: first slits for cogging torque control and second slits for inductance control. This segmentation allows independent optimization of each function - the first slits can be configured to maximize cogging torque reduction while the second slits are configured to maintain appropriate inductance levels, preventing the trade-off from becoming a net negative for motor reliability.
2Object-generated harmful factors
If multiple slits are added to reduce harmonic component of magnetic flux density, then cogging torque is reduced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the rotor core into distinct regions with different slit configurations. The first slits are positioned between the permanent magnet insertion hole and outer peripheral surface, while the second slits are positioned between the magnetic pole center part and the first slits. This segmented approach allows each slit set to address specific harmonic components independently, reducing overall magnetic flux density harmonics and cogging torque while maintaining manageable structural complexity through clear functional zoning.
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 effectively reduces vibrations and noise in electric motors by minimizing the harmonic components of induced voltage and cogging torque, while maintaining sufficient inductance, thereby enhancing motor performance.
Implementation Method 1
a plurality of slits provided between a permanent magnet insertion hole and the outer peripheral surface of a rotor core increase a magnetic resistance
Implementation Method 2
a harmonic component of a magnetic flux density waveform in an inter-pole part of the rotor is reduced
Implementation Method 3
a harmonic component of an induced voltage in a stator winding increases
Data Source
AI summary
A rotor includes a rotor core and a permanent magnet. The rotor core includes an outside slit provided between a permanent magnet insertion hole and an outer peripheral surface of the rotor core, and inside slits provided between a magnetic pole center part and the outside slit. A minimum distance from a first inside slit to the outer peripheral surface of the rotor core is longer than a minimum distance from any other inside slit except the first inside slit to the outer peripheral surface of the rotor core.