EV Engineering News

TM4’s external rotor motor technology powers first electric bus in China

TM4 SUMO HD external rotor

A new 18-meter battery-electric bus is now plying the streets of Beijing. The Foton Harmony City BJ6180 carries up to 143 passengers, and features a lightweight monocoque structure with low-floor access.


The bus’s SUMO HD powertrain, built by TM4 Inc., is designed to interface with standard rear differentials with no need for an intermediate gearbox. The system features TM4’s external rotor motor technology (in which the rotor rotates on the outside of the stator), which delivers higher power density, high torque density, and better long-term reliability than a similar motor with an internal rotor, according to the company. 

The 336 kg LSM280 motor delivers 250 kW (peak) or 170 kW (continuous) power, and maximum torque of 3,500 N·m. The high number of poles and rounded magnet shape of the motor enables a lighter rotor and stator, and thinner magnets that use a smaller amount of magnetic material. Peak system efficiency is 95%.

The 215 kW/h lithium iron phosphate battery pack from Beijing Pride Energy Technology gives the bus a range of 62 miles, and can be recharged in two hours.

Advanced noise insulation technology reduces vehicle noise by six to eight decibels compared to other electric bus models, according to Foton AUV.


Source: TM4 via Green Car Congress

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