Smart Solutions: A New Direct Current Electric Machine Design to Reduce Weight and Enhance Efficiency

The main use of brush direct current (DC) motors has traditionally been in variable speed applications. Although the introduction of variable-frequency systems shifted the market toward alternating current (AC) technologies, direct current (DC) solutions remain relevant, especially with solar power generation where DC operation can avoid inverters. However, the high cost of brush DC motors limits broader use, creating a need for designs with higher efficiency, lower cost, and simplified manufacturing. A promising solution is the direct current motor with a winding-free rotor (DCFR). This design eliminates commutating poles and compensating windings while maintaining high overload capacity, and it doesn't require expensive permanent magnets. Since all windings are stationary, the DCFR can operate with either a commutator or an electronic controller. Research results demonstrate clear advantages of the electronically controlled DCFR compared to a classic DC motor. With a rated power of 5.9 kilowatts and a nominal speed of 1490 revolutions per minute (rpm), the DCFR weighs only 60 kg versus 76 kg for the conventional design. Efficiency reaches 91.8%, compared to 85%. These improvements in efficiency, reduced weight, and lower material costs indicate that the DCFR design is highly suitable for both variable speed operations and solar energy applications.