Brushless Wound Field Synchronous Machine Rotor Design
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Solution Overview
Problem
Wound field synchronous machines require maintenance-intensive brushes and slip rings for current supply to the rotor, which is problematic in traction applications and adds size, weight, and cost when using rotating transformers for wireless power transfer.
Innovation Solution
A brushless wound field synchronous machine design that uses a stator with independently controlled rotating magnetic fields to induce current in an induction winding on the rotor, which is then rectified to supply a field winding, eliminating the need for brushes and slip rings by integrating a wound rotor induction machine with a wound field synchronous machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brushes and slip rings are used to supply current to the rotor, then the machine can operate as a wound field synchronous machine with excellent performance, but maintenance requirements increase
Solution Approach 1:
The patent extracts and eliminates the brushes and slip rings from the wound field synchronous machine by integrating an induction winding on the rotor that is wirelessly excited by the stator's rotating magnetic field, thereby removing the maintenance-intensive components while preserving the wound field functionality
Solution Approach 2:
The patent merges the induction machine and synchronous machine functionalities into a single hybrid machine where the rotor contains both induction winding and field winding, allowing the machine to operate with brushless excitation while maintaining synchronous performance characteristics
2Ease of repair
If a rotating transformer is used for wireless power transfer to the rotor, then brushes and slip rings are eliminated, but the machine size, weight, and cost increase
Solution Approach 1:
The patent makes the stator winding perform multiple functions: it simultaneously acts as the armature winding for torque production and as the excitation source for the rotor's induction winding, eliminating the need for a separate rotating transformer and reducing overall machine weight
Solution Approach 2:
The patent combines the excitation system and power conversion system into the rotor itself by placing the induction winding and field winding on the rotor, allowing wireless power transfer through magnetic coupling without requiring additional heavy components like rotating transformers
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 reduces maintenance requirements, avoids the use of rare-earth magnets, and operates efficiently at high speeds with reduced losses, while maintaining torque production and compatibility with standard inverters.
Implementation Method 1
The first rotating magnetic field interacts asynchronously with the induction winding to produce an alternating current in the induction winding
Implementation Method 2
The rectifier changes the alternating current to a direct current that is supplied to the field winding
Implementation Method 3
The field winding interacts synchronously with the second rotating magnetic field
Data Source
AI summary
An electric machine includes a stator having a stator winding disposed thereon. A rotor is electromagnetically exposed to the stator. A field winding and an induction winding are disposed on the rotor. A rectifier is electrically coupled to the induction winding and the field winding. Upon application of a voltage to the stator winding, the stator winding produces a first rotating magnetic field and a second rotating magnetic field that has a different spatial frequency than the first rotating magnetic field. The first rotating magnetic field interacts asynchronously with the induction winding to produce an alternating current in the induction winding. The rectifier changes the alternating current to a direct current that is supplied to the field winding. The field winding interacts synchronously with the second rotating magnetic field.