In­sight: in-wheel mo­tors Bri­tish firm’s rad­i­cal tech

Tech firm’s Pro­tean Drive sys­tem, aimed at sav­ing weight and space, is set to roll out af­ter eight years in de­vel­op­ment


Anew in-wheel elec­tric mo­tor de­signed to make it eas­ier and quicker for man­u­fac­tur­ers to de­velop EVS is due to en­ter pro­duc­tion in 2018.

The weight-sav­ing tech­nol­ogy, called the Pro­tean Drive, has been un­der de­vel­op­ment by Farn­ham­based Pro­tean Elec­tric for the past eight years. “There are a num­ber of dif­fer­ent ap­pli­ca­tions for it,” ex­plained Pro­tean’s Gabriel Don­ald­son. “It can be used for two-wheeldrive EVS, to hy­bridise an ex­ist­ing ve­hi­cle or to con­vert a two-wheel-drive ve­hi­cle to four-wheel drive.”

The Pro­tean Drive is a com­pletely self-con­tained ‘smart ac­tu­a­tor’ that in­cludes a per­ma­nent mag­net and syn­chro­nous elec­tric mo­tor, as well as the elec­tron­ics needed to make it work. Each mo­tor pro­duces 81kw (109bhp) and 922lb ft, so a two-wheeldrive elec­tric ve­hi­cle could con­ceiv­ably pro­duce peak power and torque of 160kw (214bhp) and 1844lb ft.

Us­ing self-con­tained wheel mo­tors such as the Pro­tean Drive elim­i­nate trans­mis­sions and drive­shafts and free up space in the cen­tre of the car between the driven wheels. Ca­bling is min­imised – two ca­bles sup­ply­ing power and an­other smaller one used by the main ve­hi­cle com­puter to con­trol the mo­tor.

Don­ald­son says that, at 72kg, a pair of the mo­tors weighs 30kg less than the elec­tric driv­e­train of a BMW i3 (102kg). How­ever, the wheel mo­tors still weigh more than a con­ven­tional wheel.

With that in mind, the Pro­tean Drives were fit­ted to a Volk­swa­gen Golf, the sus­pen­sion of which was tuned by an in­de­pen­dent ve­hi­cle dy­nam­ics ex­pert. Ac­cord­ing to Don­ald­son, the ad­di­tional un­sprung weight was man­aged suc­cess­fully and the test car was made to han­dle as well as a stan­dard VW Golf GTE.

Elim­i­nat­ing trans­mis­sion re­duces fric­tion losses by 6-8% com­pared with a con­ven­tional two-wheel elec­tric drive sys­tem. The ex­tra ef­fi­ciency is a ben­e­fit dur­ing both ac­cel­er­a­tion and de­cel­er­a­tion, so more en­ergy is re­cov­ered dur­ing re­gen­er­a­tive brak­ing.

The Pro­tean Drive can be pro­duced to fit wheel sizes from 14in to more than 20in. It is cur­rently in pre-pro­duc­tion and will be built in China, ini­tially at the rate of five to ten units a week.

Although there are sig­nif­i­cant pack­ag­ing and ef­fi­ciency ben­e­fits, the tech­nol­ogy is more ex­pen­sive than a con­ven­tional elec­tric driv­e­train and work is con­tin­u­ing to make it more price-com­pet­i­tive. “Although there are com­mer­cial ben­e­fits in us­ing it,” says Don­ald­son, “no­body will pay more for it.” A Chi­nese ve­hi­cle man­u­fac­turer will be the first to adopt the tech­nol­ogy next year.

It can be used for 2WD EVS, to hy­bridise an ex­ist­ing ve­hi­cle or to con­vert a 2WD ve­hi­cle to 4WD

Mo­tor is mounted be­hind, and sends torque to, the wheel

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