DDU Magnetics, Inc.

DDU SRG - The New Switched Reluctance Generator

A switched reluctance generator (SRG) can deliver very high power density at low cost. Disadvantages include high torque ripple (the difference between maximum and minimum torque during one revolution) which can cause audible noise and mechanical vibration when operated at low speed, and until recently, the complexity of designing and controlling them. Our disruptive technology is based on the discovery we made in the evolution of SAM(tm) the Stationary Armature Machine, using our unique asymmetrical winding geometry to create co-linear radial d and q axis phasors to eliminate cogging torque, maintaining a saliency ratio of 1.


The DDU SRG is comprised of a proprietary stator winding coil layout which serves to eliminate torque ripple without complex software, using our asymmetric switching sequence which is analogous to a 16 cylinder engine firing one cylinder at a time. Solid state switches connected to each winding group distribute power evenly without periodic pulses. In wind turbine application DDU’s SRG is virtually maintenance free. Operating in a direct drive configuration it eliminates the need for a gearbox or ac to dc rectifier while generating distortion-less ‘ripple free’ direct current power directly to an inverter.

Applicable topologies include:

Commutation is brushless for all topologies and comprises a stepped sequence switching pattern using a passive network of diodes for generators and an active network of solid state switches for motors and switched reluctance machines. The topologies are scalable from sub-fractional to above NEMA custom machines purpose built for slow spinning winding turbines or high speed impeller driven machines. Other applications include low cost high efficiency tractive drive for automotive applications. Our machines are optimized for low speed high torque applications as well as high speed high power application. Below is an example wind turbine configuration with the DDU SRG.


Below are featured benefits of a DDU SRG based wind turbine.

DDU SRG Based Wind Turbine Benefits


Machine Capital Cost MRO TOTAL COST
GB DFIG Low High Moderate
PMG DD Very High Low Moderate to High
EESG +Moderate High Moderate to High
SRG +Moderate Low Moderate
*DDU SRG Low Low Low

*DDU SRG generates power without cogging torque and without requiring complex controls and software!

Traditional techniques use symmetrical winding patterns that create diametric 'd' and 'q' axis separated by some angular displacement about a common orthogonal axis optimized for saliency ratios greater than 7. DDU SRG is the 21st century Faraday machine. See the astonishing difference below.