Hitachi develops electric motor using SMC iron powder in new core design
With the upsurge in interest in electric motors used in hybrid and/or all-electric vehicles, efforts are underway to improve the efficiency of the motors whist at the same time making them progressively smaller and lighter.
According to Hitachi Metals Ltd in Japan this is made possible by the use of new magnetic materials such as rare earth NdFeB magnets and soft magnetic composite iron powders which have enabled significant breakthroughs in electric motor design.
Motor cores are typically made from laminated magnetic steel sheets and coils are wound around the laminated core to produce the electromagnetic effect. However, Hitachi states that by using SMC iron powders lower eddy current losses can be achieved and core and coil shapes can be produced thereby giving more flexibility in designing the motor core shape.
In a new permanent magnet motor developed by Hitachi, space is saved by sandwiching a coil between claw-shaped SMC iron cores. The company states that this design was selected based on 3-D magnetic field analysis. The resulting electric motor is significantly smaller than conventional motors and can be embedded in electric-powered systems.
More information visit: www.hitachi.com
Powder producers develop improved SMC Iron powders
In a separate development, Kobe Steel Ltd of Japan recently reported (Kobe Steel Technology Review, August 2010, pp79-83), that it has developed a new SMC iron powder with iron losses in dust cores of 28.6 W/kg compared with 50.4 W/kg in conventional SMC iron powder and comparable to electrical sheet (35.5 W/kg). The coercivity was also reduced to 134 A/m in the new material compared with 243 A/m in the conventional SMC iron powder. The company expects that the size and weight of magnetic parts used in electric motor cores can be reduced.
Daido Steel Ltd also in Japan has been collaborating with Toyota Motor Corp to develop a powder magnetic core with reduced core loss used in a reactor within the power booster of hybrid cars. The power booster raises the voltage of batteries to increase the torque of the electric motor driving the vehicle. The significant decrease in core loss was achieved by using an Fe-Si water atomised powder having pseudo spherical shape in combination with a new insulating resin used to coat the SMC iron powder which be annealed at 700oC or higher. In addition to lower core loss of the SMC Fe-Si material, the reactor can be produced to net shape. Daido Steel states that reactors incorporating its SMC iron powder are used in hybrid cars currently on the market. The company received an award from the Japan Powder Metallurgy Association for this development in 2009.
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