A direct-drive mechanism is where the transmitting of torque from an electric motor to the output device (such as the driven wheels of a car) occurs without any gearing reductions.[1][2][3]
Design
The main benefits of a direct-drive system are increased efficiency (due to reduced power losses from the drivetrain components) and being a simpler design with fewer moving parts.
The main drawback is that a special type of electric motor is often needed to provide high torque outputs at low rpm. Compared with a multi-speed transmission, the motor is usually operating in its optimal power band for a smaller range of output speeds for the system (e.g., road speeds in the case of a motor vehicle).
Direct-drive mechanisms also need a more precise control mechanism. High-speed motors with speed reduction have relatively high inertia, which helps smooth the output motion. Most motors exhibit positional torque ripple known as cogging torque. In high-speed motors, this effect is usually negligible, as the frequency at which it occurs is too high to significantly affect system performance; direct-drive units will suffer more from this phenomenon unless additional inertia is added (i.e. by a flywheel) or the system uses feedback to actively counter the effect.
Applications
Direct-drive mechanisms are used in applications ranging from low speed operation (such as phonographs, telescope mounts and ski lifts, video game racing wheels and gearless wind turbines)[4][5][6] to high speeds (such as fans, computer hard drives, VCR heads, sewing machines, CNC machines and washing machines.
Some electric railway locomotives have used direct-drive mechanisms, such as the 1919 Milwaukee Road class EP-2 and the 2007 East Japan Railway Company E331. Several cars from the late 19th century used direct-drive wheel hub motors, as did some concept cars in the early 2000s; however, most modern electric cars use inboard motor(s), where drive is transferred to the wheels, via the axles.
See also
References
- ^ https://www.autoblog.com/2015/11/30/what-is-direct-drive-gear/
- ^ https://www.caranddriver.com/news/a28903274/porsche-taycan-transmission/
- ^ https://etmpower.com/learn-more/what-is-a-direct-drive-motor/#:~:text=Direct%20Drive%20motors%20are%20simply,to%20achieve%20the%20necessary%20torque.
- ^ "Fanatec Release Details On Their(sic) Direct Drive Wheel - Inside Sim Racing". 4 June 2017.
- ^ Patel, Prachi. "GE Grabs Gearless Wind Turbines". Technology Review (MIT). Retrieved 7 April 2011.
- ^ Dvorak, Paul. "Direct drive turbine needs no gearbox". Windpower Engineering. Retrieved 7 April 2011.