Hybrid Rotor Motor for High Starting Torque and Efficiency
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Solution Overview
Problem
Existing motors, such as induction and permanent magnet synchronous motors, face inefficiencies in starting torque and energy efficiency, with induction motors having high stator winding losses and permanent magnet synchronous motors requiring external drive systems and being prone to demagnetization during the casting process.
Innovation Solution
A self-start synchronous motor design combining principles of three-phase induction and permanent magnet synchronous motors, featuring a rotor with reduced cross-section cage bars and radially symmetrical magnets, allowing for high starting torque and synchronous operation without external drive systems, and minimizing demagnetization risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If induction motor is used, then starting torque is produced, but stator winding losses increase leading to reduced energy efficiency
Solution Approach 1:
The rotor structure is segmented into two distinct parts: permanent magnets for flux production and squirrel cage bars for torque production. This segmentation allows the motor to separately handle flux generation (eliminating stator winding losses associated with field excitation) and torque generation (providing high starting torque through cage bar currents), thereby resolving the contradiction between starting torque and energy efficiency
Solution Approach 2:
The invention merges the principles of permanent magnet synchronous motors (for efficient flux production) and induction motors (for robust starting torque) into a single hybrid rotor structure. This combination enables the motor to achieve both high energy efficiency during operation and high starting torque during startup, eliminating the need to choose between the two conventional motor types
2Loss of energy
If permanent magnet synchronous motor is used, then energy efficiency is improved, but external drive system is required increasing device complexity
Solution Approach 1:
The squirrel cage bars embedded in the rotor automatically generate the necessary starting current when voltage is applied, eliminating the need for external drive systems, variable frequency drives, or complex control electronics. The cage structure self-regulates the current flow during startup, providing autonomous self-starting capability while maintaining the energy efficiency benefits of permanent magnet excitation
Solution Approach 2:
The invention extracts and removes the complex external drive system requirement from the permanent magnet synchronous motor concept by incorporating a self-starting squirrel cage mechanism directly into the rotor. This extraction simplifies the overall system by eliminating variable frequency drives, current controllers, and protective relays, leaving only the essential permanent magnets and simple cage structure
3Ease of manufacture
If permanent magnets are placed before casting process, then rotor structure is formed, but demagnetization occurs during high temperature casting
Solution Approach 1:
The permanent magnets are pre-installed into dedicated slots in the rotor core before the squirrel cage casting process. The rotor core slots are designed to accommodate the magnets and provide mechanical retention, ensuring the magnets are securely positioned before exposure to high temperatures during cage bar casting. This preliminary placement allows the rotor structure to be formed with magnets already in position, avoiding subsequent installation complexity
Solution Approach 2:
The rotor core slots are designed with appropriate geometry and material properties to provide thermal protection and mechanical retention for the permanent magnets during the high-temperature cage casting process. The slot structure acts as a cushioning barrier, protecting the magnets from direct exposure to molten metal and extreme temperatures that would cause demagnetization, while still allowing the cage bars to be properly formed around the magnets
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 high starting torque and efficiency with zero rotor electrical losses, eliminating the need for external drive systems and reducing costs, while preventing demagnetization, thus providing a cost-effective and efficient self-starting solution.
Implementation Method 1
the magnet on the rotor stack assembly gets locked with a rotating magnetic field produced by the current flow in a stator winding
Implementation Method 2
as the current flow in a stator winding, a rotating magnetic field is produced leading to current in the short-circuited rotor bars, the current on the stator winding and rotor bars interacted with each other to form starting torque
Data Source
AI summary
The high efficiency motor employing the principle of three phase induction motor and permanent magnet synchronous motor includes a stator assembly and a rotor assembly. The rotor assembly includes a rotor shaft, a rotor stack assembly, a rotor cover and end ring. The rotor stack assembly includes a stamping stack, a conductor bar and a magnet. The stamping stack has dedicated slots for the conductor bar and the magnet. The rotor cover is fitted on the rotor stack, wherein both axial ends of the rotor cover are closed by end rings.