Ferromagnetic Rotor Shaft with Magnetized Poles for High-Speed Stability
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Solution Overview
Problem
Existing rotors with permanent magnets in electric motors experience mechanical instability and sinusoidal voltage issues due to shear forces and adhesive failures at high rotational speeds, leading to potential detachment and inefficient voltage processing.
Innovation Solution
A rotor design featuring a rotor shaft with interlocking, flattened regions for improved mechanical connection and magnetization in a non-radial direction to create a more square-wave voltage waveform, enhancing both mechanical stability and voltage processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If permanent magnets are adhered onto a metal rotor shaft using adhesive connection, then the rotor can be assembled, but at high rotational speeds the adhesive connection fails due to extreme centrifugal forces and high shear forces, causing permanent magnets to detach
Solution Approach 1:
The patent replaces the adhesive mechanical connection system with a magnetic field-based connection system. The rotor shaft is made ferromagnetic and is magnetized to create magnetic poles that attract the permanent magnets, replacing the adhesive bonding mechanism with a magnetic field interaction that can withstand high centrifugal and shear forces at rotational speeds exceeding 10,000 rpm.
Solution Approach 2:
The patent changes the magnetic properties of the rotor shaft by magnetizing it to specific magnetic pole configurations (e.g., two-pole, four-pole arrangements). This parameter change creates magnetic attraction forces that dynamically counteract the centrifugal forces and shear forces experienced during high-speed rotation, providing reliable connection without adhesive failure.
2Reliability
If permanent magnets are tightly mounted on the rotor shaft to prevent slip, then mechanical stability improves, but the adhesive connection experiences extremely high load and may fail
Solution Approach 1:
The patent eliminates the adhesive connection system entirely and replaces it with magnetic attraction between the ferromagnetic rotor shaft and the permanent magnets. This substitution removes the adhesive strength limitation while maintaining tight mechanical coupling through magnetic forces that scale with the magnetic field strength and can withstand extreme centrifugal and shear loads.
3Reliability
If a sinusoidal voltage waveform is generated in generator operation, then the motor runs smoothly, but switching the sinusoidal voltage in digital environments is disadvantageous and complex
Solution Approach 1:
The patent changes the voltage waveform parameter from sinusoidal to square wave by adjusting the commutation timing and control strategy. The motor controller switches the stator coil voltages in a square-wave pattern rather than sinusoidal modulation, which simplifies the digital switching requirements while the magnetic field interaction and rotor design maintain smooth operation characteristics.
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 design provides improved mechanical stability and allows for easier processing of square-wave voltages, reducing the risk of detachment and simplifying voltage control, while maintaining high rotational speeds without mechanical resonance issues.
Implementation Method 1
The rotor shaft (10) comprises a mounting portion (12) in which a plurality of permanent magnets (21, 22, 23, 24) are mounted. The rotor shaft (10) is made ferromagnetic and is magnetized.
Implementation Method 2
Particularly at high rotational speeds, centrifugal forces acting on the permanent magnets are extreme.
Implementation Method 3
Shear forces between permanent magnets and rotor shaft are also high, in particular when the motor is under load
Implementation Method 4
The rotor shaft (10) is made ferromagnetic and is magnetized. In the embodiment shown in FIG. 1b, the rotor shaft (10) is magnetized such that two magnetic north poles N and two magnetic south poles S are formed.
Implementation Method 5
Such a permanent magnet synchronous motor can also be operated as electric generator. Here, the rotor is driven by mechanical force, and the movement of the rotor with its permanent magnets effects an induction voltage in the at least three stator coils.
Data Source
AI summary
A rotor includes a rotor shaft with a mounting portion along a mounting region of the shaft; and a plurality of permanent magnets mounted in the mounting portion on the rotor shaft, wherein the rotor shaft includes, in the mounting portion, a region with a radius reduced with respect to a circular cross-section, such that a radially measured thickness of a permanent magnet is greater in the region than in an adjacent region with non-reduced radius of the rotor shaft.