Multi-Profile Sliding Rotor Electric Motor for Hoists
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Solution Overview
Problem
Existing fully cone-shaped rotor electric motors face limitations in power increase due to dimensional constraints, inefficiencies in starting current, and reduced switch speed of the braking mechanism, which restrict their application in high-power and frequency drive systems.
Innovation Solution
An asynchronous electric motor with a multi-profile, multi-sectional sliding rotor and stator, featuring radial bearings for axial displacement, a combination of conical and cylindrical rotor sections, and a common multi-profile stator coil, allowing for efficient power scaling and reduced starting current through constant air gaps in cylindrical sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the diameter of the middle section is increased to achieve higher power, then the power output is improved, but the overall dimensions of the electric motor increase significantly
Solution Approach 1:
The rotor is divided into multiple sections along its length, with different sections having different diameters. The middle section has a larger diameter for high power generation, while the end sections have smaller diameters. This segmentation allows the motor to achieve high power output without proportionally increasing the overall motor dimensions, as only a portion of the rotor volume needs to be large.
Solution Approach 2:
Different sections of the rotor are designed with different local qualities - the middle section has a larger diameter optimized for power generation, while the end sections have smaller diameters. This local differentiation allows each section to perform its specific function optimally without requiring the entire rotor to be large, thus achieving high power without significant increase in overall motor dimensions.
2Reliability
If a fully conical rotor design is used for efficient braking, then the braking mechanism reliability is improved, but the starting current increases due to variable air gap
Solution Approach 1:
The rotor is segmented into different sections with different geometries - the middle section is conical for braking action, while the end sections are cylindrical with constant air gaps. This segmentation allows the motor to benefit from both conical and cylindrical designs, achieving reliable braking while reducing starting current through the constant air gap sections.
Solution Approach 2:
Different sections of the rotor have different local qualities - the conical middle section provides efficient braking with axial force projection, while the cylindrical end sections maintain constant air gaps to reduce starting current. This local differentiation resolves the contradiction between braking reliability and starting current by optimizing each section for its specific function.
3Force
If a fully conical rotor with large active material volume is used, then the electromagnetic force is improved, but the brake mechanism switch speed decreases due to residual magnetization
Solution Approach 1:
The rotor is segmented into a conical middle section that generates electromagnetic force and cylindrical end sections with less active material. This segmentation reduces the total volume of active material compared to a fully conical rotor, thereby reducing residual magnetization and improving brake switch speed, while the conical middle section maintains sufficient electromagnetic force generation.
Solution Approach 2:
The conical middle section is optimized for generating electromagnetic force with sufficient active material, while the end sections have reduced active material volume. This local quality differentiation maintains the necessary electromagnetic force while reducing overall residual magnetization, thus improving brake mechanism switch speed without sacrificing force generation capability.
4Reliability
If a separate DC magnet and rectifier circuit are added for the braking mechanism, then the brake action is improved, but the device complexity increases
Solution Approach 1:
The braking function is merged with the existing three-phase AC motor structure. The conical rotor sections work with the AC stator magnetic field to generate axial braking force, eliminating the need for a separate DC magnet and rectifier circuit. This integration maintains reliable brake action while significantly reducing device complexity by utilizing the existing AC power system.
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 enables efficient power scaling without increasing motor dimensions, reduces starting current, and enhances braking mechanism switch speed by minimizing active material volume and maintaining constant air gaps, thus improving reliability and compatibility with frequency drives.
Implementation Method 1
Its action is accomplished by the axial projection of the electromagnetic forces occurring between the stator and the rotor when feeding the stator coil
Implementation Method 2
the rotor current decreases smoothly, and with it the axial force, providing the action to the braking mechanism
Data Source
Figure 1
AI summary
The electric motor is designed to drive hoisting mechanisms of hoists / cranes and will find application in industry. The electric motor with a multi-profile, multi-sectional, sliding rotor comprises a housing (4) at one end of which is mounted a front bearing shield (8) and at the other end there is a rear bearing shield (9) and a brake mechanism (5) including at least a brake with a friction element (51) and a braking shield (52). A stator (2) with a coil (6) is mounted in the housing in which stator is mounted a rotor (1) with a shaft (3). The shaft (3) of the rotor (1) is supported on radial bearings (23) positioned in the bearing shields, where the radial bearings (23) allow axial displacement of the shaft (3) with the rotor (1) relative to the stator (2). The rotor (1) comprises two or more rotor sections longitudinally disposed, at least one of which is conical (11), with a small cone diameter directed towards the front end bearing shield, and at least one of the rotor sections is cylindrical (12) and the stator (2) is partially conical and also has two or more sections (21, 22) corresponding to the number, shape and position of the sections (11, 12) of the rotor (1).