by Jack Rosebro
|The new prototype motor. Click to enlarge.|
General Electric engineers have successfully tested a prototype hybrid and electric vehicle motor with a peak power level of 55 kW and the ability to operate continuously at up to 105 °C (221 °F), using conventional transmission fluid as the motor’s sole cooling agent.
The motor—which GE says is 3 to 5% more efficient than existing motors—could potentially extend the range of a plug-in vehicle. It was developed as part of a $5.6-million US Department of Energy (DOE) project, and performs well over a range of bus voltages, from 200V to 650V.
The permanent-magnet motor uses a concentrated (solenoidal) winding, and is extremely compact, with a stator diameter of approximately 23.4 cm (9.2 inches), and a length, including end turns, of approximately 13 cm (5 inches). Power density is about twice that of today’s motors, according to GE.
The motor can use a transaxle’s fluid to cool both the rotor and the stator, producing a continuous 30kW of output over a range of 2,800 to 14,000 rpm at 105 °C.
Alternately, the motor can use a hybrid vehicle’s engine coolant to limit operating temperature, rather than a separate, dedicated coolant loop, GE Senior Engineer of Electric Machines Ayman El-Refaie noted that many current production motors are limited to a continuous temperature of 65 °C (149 °F).
GE also developed new high-resistivity magnets for the motor, which reduce magnetic losses and reduce or eliminate the need to use more costly segmented magnets.
General Electric has discussed licensing the motor technology with electric motor manufacturers as well as automakers, and hopes to see commercial application in the automotive sector by 2015.
“This technology is scalable and flexible enough that it can be leveraged in a number of capacities,” commented El-Refaie, noting that GE plans to explore additional potential product applications, including higher efficiency industrial motors, high-speed oil and gas compressor motors, and generators for aerospace applications.
Next steps include a four-year project, during which time GE engineers will seek to produce a motor with similar performance characteristics, yet with no rare-earth magnets.