Traction Applications


Two-slice SEMA wheel motor concept

The high torque capability of SEMA technology makes it a candidate for direct-drive propulsion of electric and hybrid-electric vehicles. At this time, a number of fixed gear reduction traction systems have been studied for use in series hybrids, including in-wheel motors for heavier vehicles (4,000–6,000 kg vehicle weight). The leading candidate for traction systems based on current SEMA technology is an ironless, or partially iron-core, SEMA motor paired with Oak Ridge National Laboratory’s Dual-Mode Inverter Control (DMIC) inverter system. This pairing offers the high efficiency of ironless SEMA technology with a high constant-power speed range (CPSR) afforded by the DMIC. The resulting system can utilize a smaller motor due to the lower thermal demands and requires a lower primary switch current rating due to the elimination of circulating currents in the motor winding. CPSR ratios in excess of 10:1 are possible with the SEMA/DMIC pairing. A number of automotive research projects are currently underway at Lynx to commercialize SEMA motors for use in vehicle traction applications.

Electric-Assisted Power Steering

The elimination of the need for power steering fluid is a benefit from both a maintenance and environmental perspective. SEMA motors are well suited to both the electro-hydraulic and electric-motor steering-assist systems being planned by many manufacturers. This torque servo application benefits greatly from the high bandwidth and peak torque attainable by SEMA-based motors.

Air-Conditioning or Fuel-Cell Compressor Motors

A SEMA motor electric drive is well suited to direct-drive compressor applications. The high torque-to-inertia ratio possible using a SEMA system is particularly well suited to the high transient load capabilities required by future fuel cell compressors. At this time, a family of motors intended for use in air-handling and compressor applications is under development with commercial partners and government-sponsored research projects.