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Multi-winding Homopolar Electric Machine Offers Variable Voltage at Low Rotational Speed

Oak Ridge National Laboratory

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Technology Marketing SummaryA nineteenth century invention by Michael Faraday, the Faraday disc machine, has undergone a twenty-first century improvement at ORNL. Now known as a homopolar electric machine, the ORNL invention offers greater (and variable) voltage output at low rotational speeds without a gearbox. Previous designs have been restricted to low voltage output at high rotational speed, thus requiring heavy and expensive gearboxes.DescriptionThe invention incorporates multiple turns of wire for the current to traverse, similar to the windings of a toroidal coil, thus producing greater voltage at lower rotational speeds. The current flow through the machine’s vessel interacts with a constant magnetic field, and each turn of wire increases the voltage of the machine, allowing reduction of the rotational speed. The device can be used as either a motor or a generator.Benefits
  • Variable voltage and speed design
  • Internal mechanism allowing for low speed, high torque applications
  • No gearbox
  • Longer life and reduced cost when operated at low speed (e.g., wind power)
Applications and Industries
  • Wind turbines and power industry generators
  • Applications requiring low speed, high torque operation without a mechanical gearbox
More InformationInventor:
Charles W. Van Neste
Biosciences Division
Oak Ridge National Laboratory
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 8,247,942
Multi-winding homopolar electric machine
A multi-winding homopolar electric machine and method for converting between mechanical energy and electrical energy. The electric machine includes a shaft defining an axis of rotation, first and second magnets, a shielding portion, and a conductor. First and second magnets are coaxial with the shaft and include a charged pole surface and an oppositely charged pole surface, the charged pole surfaces facing one another to form a repulsive field therebetween. The shield portion extends between the magnets to confine at least a portion of the repulsive field to between the first and second magnets. The conductor extends between first and second end contacts and is toroidally coiled about the first and second magnets and the shield portion to develop a voltage across the first and second end contacts in response to rotation of the electric machine about the axis of rotation.
Oak Ridge National Laboratory 08/21/2012
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
UT-B ID 200902309DevelopmentAvailable10/20/201012/08/2010

Contact ORNL About This Technology

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