Rotating Transformer Rotor Position Sensing
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Solution Overview
Problem
Existing methods for angular position and velocity estimation in permanent magnet synchronous machines, especially at zero and low speeds, lack accuracy and are complex, costly, and reduce power density, making them unsuitable for large applications.
Innovation Solution
A system utilizing a rotating transformer with a primary coil on the rotor and a secondary coil on the stator, an inverter/active rectifier component, and a position and velocity decoder to estimate rotor position and velocity based on sense signals, eliminating the need for resolvers and improving power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is used to provide position information, then rotor position can be sensed, but system complexity and cost increase
Solution Approach 1:
The invention extracts only the essential position sensing function from the complex resolver system by using a simple rotating transformer with primary and secondary windings. This extracted approach provides the necessary position information without the complexity and cost of a full resolver system.
Solution Approach 2:
Instead of using a complex resolver, the system uses a simplified rotating transformer that copies the essential position-sensing functionality. The transformer windings provide position information through electromagnetic coupling, replicating the resolver's function with simpler, more cost-effective components.
2Measurement precision
If sensor windings are added to all pole elements of the stator, then accurate rotor position information is provided, but power density of the machine considerably decreases
Solution Approach 1:
Instead of placing sensor windings on the stator (which would reduce power density), the invention inverts the approach by placing the primary transformer winding on the rotor and the secondary winding on the stator. This configuration provides accurate position sensing while maintaining the stator's full power-capability since the stator windings are used for both power generation and position sensing.
Solution Approach 2:
The position sensing function is nested within the existing power generation structure. The rotating transformer is integrated into the motor structure, with the primary winding on the rotor sharing space with the permanent magnets, and the secondary winding on the stator utilizing existing stator slots or dedicated spaces without significantly impacting the power windings.
3Ease of operation
If Hall sensors are used for commutation, then rotor position with 60° resolution is provided, but measurement precision deteriorates
Solution Approach 1:
The invention changes the measurement parameter from discrete Hall sensor signals (60° resolution) to continuous transformer voltage signals. The rotating transformer provides continuous position information through the voltage induced in the secondary winding, enabling precise position detection with resolution far exceeding the 60° limitation of Hall sensors.
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 solution enhances the accuracy and reliability of rotor position sensing, reduces system complexity and cost, and maintains power density, enabling efficient operation in various applications including aerospace and ground vehicles.
Implementation Method 1
A primary transformer coil is wound on the rotor and is operatively connected to form a rotating transformer with the secondary transformer coil
Data Source
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AI summary
An electrical machine (100) includes a stator (102) having a stator winding (104) and a secondary transformer coil (106). A rotor (108) is operatively connected to rotate relative to the stator (102), wherein the rotor (108) includes a plurality of embedded permanent magnets. A primary transformer coil (110) is wound on the rotor (108) and is operatively connected to form a rotating transformer with the secondary transformer coil (106). An inverter/active rectifier component (112) is operatively connected to the stator winding (104) and the secondary transformer coil (106) to control the stator winding (104) based on a sense signal (Vsense) in the secondary transformer coil (106) received from the primary transformer coil (110).