DS-FEB23-PG55_Layout 1 16/02/2023 10:00 Page 1
GEARS & GEARBOXES
FEATURE
GEARING UP FOR MICRO AND URBAN AIR MOBILITY
With micromobility and urban air mobility gaining popularity around the world, David Latimer, CEO of Magnomatics, looks at the role innovative magnetically geared motors play in these growing markets
E
merging technologies and the quest for sustainability mean that the transportation landscape is ever evolving
and, in recent years, several interesting mobility solutions have been appearing. Urban air mobility (UAM) – or flying cars – is
no longer the stuff of science fiction. In fact, the reality is much closer than many realise, with some industry players citing plans to start operating as early as 2024. While the concept is exciting, these new
aircraft bring with them many challenges. Not only do they need to operate in complex airspace and over congested urban areas, which means the need for reliability and redundancy is critical, but there is also a strong drive for zero emissions and very low noise. One common feature is that all these aircraft use multiple electric motors. The route to power density in electric machines has historically been to operate permanent magnet motors (PM) at higher speeds, often in excess of 10,000 rpm. To become useful for air mobility aircraft, these speeds need to be geared down by as much as seven times. Conventionally, this introduces the requirement for a mechanical gearbox, raising the issues of reliability, wear, maintenance, and noise.
NASA, which has been at the heart of UAM development, identified magnetic gears as being a potential technology for electric aircraft, and in 2018 embarked on a programme described in their paper Magnetic Gearing Research for Electrified Aircraft Propulsion. Their original focus was on pure magnetic gears, but in the 2020 paper Outer Stator Magnetically Geared Motors for Urban Air Mobility Vehicles they stated that the concentric combination of a magnetic gear and a permanent magnet motor would be ideal for UAM aircraft, concluding that a magnetically geared motor was a highly effective solution to avoid the pitfalls of a mechanically geared high-speed electric motor.
DRIVING MICROMOBILITY There has also been an explosion in the popularity of micromobility solutions such as
Magnomatics’ patented Pseudo Direct Drive (PDD)
aircraft and for personal micromobility vehicles. The company’s patented Pseudo Direct Drive (PDD) – which is designed to overcome the torque limitations of conventional direct drive electrical machines – consists of a magnetic gear mounted inside a stator. The outer magnetics of the magnetic gear are attached to the inner bore of the stator, and copper windings in the stator are used to drive the inner rotor of the magnetic gear. This is a relatively high-speed electric motor
e-bicycles and e-scooters in the past few years. While traditional micromobility solutions such as conventional bicycles have been used for decades, the primary factor behind the current micromobility trend is electrification. Thanks to advances in technology, complete electric powertrains can be easily integrated into micromobility platforms. A vital consideration, however, is how efficient micromobility solutions are. For many e-bicycles and e-scooters, powertrains have already become commodities. In this instance the priority is cost, not efficiency.
However, low efficiency reduces payload and
range, which means more charging. This contradicts the
objective of introducing micromobility solutions, namely lower energy use.
POWERING MOBILITY SOLUTIONS While both micromobility and UAM systems are inherently complex, their performance can be significantly improved with intelligent system- level design. Magnetically geared motors are a key enabling technology for these solutions to ensure efficiency. Magnomatics’ revolutionary magnetic gears have been implemented in a range of innovative industry solutions, including offshore wind, marine propulsion and light rail. Having achieved success at large scale the company has turned its attention to much smaller machines, including drives for UAM
with a relatively low load, which results in low currents and hence, low temperatures. This in turn brings great efficiency, long life, and prevents demagnetisation of the outer magnet array. The torque in the inner rotor is then geared up in the novel polepiece rotor, typically by between 5 and 10:1. The result is a very compact and highly efficient electric motor, which is perfect for the micromobility and UAM markets. The benefits of innovative magnetically geared
motors such as PDD against conventional generator technology, particularly for these markets, are drastic reductions in motor size, no minimum cooling requirements, and reduced maintenance requirements. Efficiency is also improved as there are no gearbox losses and, of course, gear wear is eliminated altogether. Ultimately, the lower mass and compactness of the PDD generator, when combined with partial load superior efficiency, low speed, high torque technology and improved reliability, makes it ideal for meeting the requirements of the broad range of micromobility and UAM solutions being developed.
Magnomatics
www.magnomatics.com
David Latimer FEBRUARY 2023 DESIGN SOLUTIONS 55
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