In wheel motors & inverter with 20% increase in efficiency

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janosch
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In wheel motors & inverter with 20% increase in efficiency

Post by janosch »

Check this out and tell me what you think.

Essentially they are saying current EV motors are not optimised for the conditions they are run in most times, and they figured out a way to do so.

They also claim that doing away with the diff/gearbox helps a lot, which makes a lot of sense, would like to see this deployed in a real vehicle.
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Re: In wheel motors & inverter with 20% increase in efficiency

Post by SuperV8 »

The problem with removing the gear reduction is that electric motor torque scales with mass of electric motors.
You need high torque and low speed for directly driving the wheels = heavy electric motor/ all of which is un-sprung weight which is very bad for vehicle driving dynamics/refinement.
Having sensitive/expensive motors inboard with driveshafts is much better from a durability point of view - and for vehicle driving dynamics/refinement point of view.
They mention about deleting the rear brakes in part of their weight saving calculation! which are actually legally required in most countries of the world.

From their own figures - 30hp max! this wouldn't pull the skin of a rice pudding!
Key Features:
‣ 300 Nm peak torque
‣ 22 kW peak power
‣ Up to 60 V battery supply
‣ 93.8 % overall efficiency
‣ 13 kg weight
‣ CAN-Interface for torque &
speed control
‣ Inaudible noise emissions
‣ Best-in-class economics
‣ Enables concepts without
mechanical rear brake
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Re: In wheel motors & inverter with 20% increase in efficiency

Post by SuperV8 »

SuperV8 wrote: Fri Feb 03, 2023 2:07 pm The problem with removing the gear reduction is that electric motor torque scales with mass of electric motors.
You need high torque and low speed for directly driving the wheels = heavy electric motor/ all of which is un-sprung weight which is very bad for vehicle driving dynamics/refinement.
Having sensitive/expensive motors inboard with driveshafts is much better from a durability point of view - and for vehicle driving dynamics/refinement point of view.
They mention about deleting the rear brakes in part of their weight saving calculation! which are actually legally required in most countries of the world.

From their own figures - 30hp max! this wouldn't pull the skin of a rice pudding!
edit#
Just seen their the spec of their other motor; the 1200 - good power - and ok torque if your using one on each wheel - but 30kg extra of un sprung weight - wow!
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Re: In wheel motors & inverter with 20% increase in efficiency

Post by janosch »

I think it is a very interesting idea, and the first time I saw in-wheel motors with enough torque.

The un-sprung weight issue I heard about before and need to look up how severe it is. Sure for a race car it will be rubbish, but is it good enough for a van for example?

Further, in their calculation they moved the efficient region of the motor itself which is great, I wonder how a software diff would behave or if you incur any other new losses that are not mentioned. And yeah, leave the mechanical disk brakes on!
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Re: In wheel motors & inverter with 20% increase in efficiency

Post by Ev8 »

So on the unsprung weigh front I believe it’s more of a ratio thing, I don’t know where the sweet spot is supposed to be but I know big unsprung weight on a light car = bad the same unsprung weight on a heavy car not so much….
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Re: In wheel motors & inverter with 20% increase in efficiency

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Ev8 wrote: Mon Feb 06, 2023 4:30 pm So on the unsprung weigh front I believe it’s more of a ratio thing, I don’t know where the sweet spot is supposed to be but I know big unsprung weight on a light car = bad the same unsprung weight on a heavy car not so much….
Using my Seat Leon for a thought experiment:
It has a common 225 45 17 tyre/alloy wheel which is around 20kg.
Add in an 8kg disc, a few kilos for the caliper and knuckle & 50% of the driveshaft/wishbone I think you're around 35kg unsprung weight.
If you hit a 2g bump that is 700N force the dampers & suspension has to deal with.

If I now bolt on a 30kg hub motor (You can delete the drive shaft/hub bearing - but you would also need to strengthen up the suspension so I would think this will be negligible) the suspension now has to deal with 1300N force! 85% more force will need stiffer springs and dampers to control this.

The faster you go and the bumpier the road the worse this is.
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