AC/DC Rotor Coil Power Transfer Without Slip Rings
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Solution Overview
Problem
Traditional wound field synchronous machines require an auxiliary power source for the rotor field and mechanical slip rings, which have limited lifetime and prevent liquid cooling, leading to reduced power densities and maintenance needs.
Innovation Solution
A field wound synchronous electric machine with separate AC and DC coils, where the AC coil carries induced AC current from the stator and a rectifier converts it to DC current for the DC coil to generate the magnetomotive force, eliminating the need for mechanical slip rings and enabling wireless power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical slip rings are used to supply power to the rotor field, then the rotor can be energized, but the lifetime is limited and maintenance is required
Solution Approach 1:
The patent replaces the mechanical slip ring system with an electromagnetic induction system. The stator windings generate a rotating magnetic field that induces current in the rotor windings, eliminating the need for mechanical electrical contacts. This substitution of mechanical power transfer with electromagnetic power transfer resolves the lifetime and maintenance issues of slip rings while maintaining reliable rotor field energization.
2Reliability
If mechanical slip rings are used for rotor power supply, then the rotor can be energized, but liquid cooling is prevented
Solution Approach 1:
By replacing the mechanical slip ring system with wireless electromagnetic power transfer, the patent removes the mechanical barrier that prevented liquid cooling. The rotor windings can now be directly accessed and cooled with liquid coolant channels, enabling thermal management while maintaining the rotor field power supply through electromagnetic induction from the stator.
3Reliability
If traditional wound field synchronous machines are used, then the rotor field can be energized, but power density is reduced
Solution Approach 1:
The elimination of slip rings and associated mechanical components through electromagnetic induction reduces the overall machine size and weight. The rotor design can be optimized with direct liquid cooling and more efficient magnetic circuit paths, increasing the power output per unit volume or weight. This resolves the contradiction by enabling higher power density while maintaining reliable rotor field energization through the wireless power transfer 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 solution enhances power transfer efficiency, reduces stress on semiconductor devices, decreases current/torque ripple, and limits circuit size, while allowing for more efficient thermal management and reduced maintenance.
Implementation Method 1
an auxiliary coil configured to carry an AC current induced by an AC current flowing in the stator
Implementation Method 2
a rectifier electrically coupled to the auxiliary coil and the primary coil of a first rotor winding of the rotor windings. The rectifier is configured to receive the AC current induced in the auxiliary coil and to generate the DC current in the primary coil
Implementation Method 3
a primary coil configured to carry a DC current that defines a respective one of the fixed rotor poles. The fixed rotor poles interact with the stator poles to produce relative forces between the rotor and the stator
Data Source
AI summary
A stator defines multiple stator poles with associated stator windings. A rotor defines multiple fixed rotor poles with associated teeth with a ferromagnetic material. The fixed rotor poles have associated rotor windings configured to be energized substantially by the stator. Each of the rotor windings is associated with the tooth. Each of the rotor windings includes an alternating current (AC) coil (or auxiliary coil) configured to carry an AC current induced by an AC current flowing in the stator. A direct current (DC) coil (or primary coil) defines a rotor field energizable by magnetic fields produced by the stator windings to produce relative forces between the rotor and the stator. The DC coil is at least partially powered or controlled by the AC coil.