Superconducting DC Homopolar Motor

Superconducting DC Homopolar Motor

Full-scale, 36.5-megawatt superconducting DC homopolar motor under development

Background

General Atomics is developing a full-scale, 36.5-megawatt, 120-rpm superconducting DC homopolar motor for ship propulsion.

Integrated electric drive is widely regarded as the best approach for achieving lower life cycle costs and reduced manning. The superconducting DC homopolar motor is considered to be a conceptually superior alternative to AC motors for electric drive systems. It has the following advantages:

Significantly quieter, smaller, and lighter than AC motors
More efficient than the AC motor systems
Control is more straightforward and simpler than the AC motor systems
Suited to simpler and less costly ship electrical distribution architectures

Successful testing of 3.7 MW motor led to contract to develop full-scale 36.5 MW unit

Under earlier contracts, GA designed, fabricated, and tested a test-stand motor at the 300- kilowatt level and upgraded this motor to the 3.7-megawatt level for further testing. Ongoing research and development efforts by the Navy and industry are now focusing on improving the performance and reliability of the motor’s current collectors or “brushes.” Dry current collectors presently under development show promise for greatly reduced wear rates that may result in no maintenance between ship overhaul cycles.

Motor Design

Homopolar motor model in half section

Homopolar motors are simple in design and offer the potential for a large weight reduction when compared to conventional motors. Because there are no multi-pole components in the motor, it is expected to be acoustically quiet enough to permit hard mounting directly to the ship’s hull. In order for the homopolar motor to fully exploit the advantages of reduced size and weight, the field coils must be superconducting. The coils in GA’s motor will be conduction-cooled using compact reliable devices called cryocoolers, which do not require the use of bulk liquid cryogens.

GA has developed and demonstrated the reliability of conduction-cooled superconducting systems for the Navy under high shock and vibration environments that are suitable for full-scale homopolar motors.

Ongoing research and development efforts by the Navy and industry are now focusing on improving the performance and reliability of the motor’s current collectors or “brushes.” Dry current collectors presently under development show promise for greatly reduced wear rates that may result in no maintenance between ship overhaul cycles.

For more information, contact:
Will Creedon, Program Manager
will.creedon@ga.com