Why two motor types in CyberBeast?

[Scott Beall]

I’m wondering why the Beast has two permanent magnet motors in the rear and an induction motor in the front.

As I gather from posts here on the forum, induction motors have a “back EMF” force that doesn’t allow them to “free spin” without power. I think permanent magnet motors will free spin.

The Semi gets its great range by having the rear motors shut off (via a clutch) during cruise. The rears for acceleration (mostly).

Could it be that the Beast is meant to operate the same way, but without the clutch and with software to shut off the two rear motors at cruise and just let them free-spin while relying on the front motor? Could we see this as a software upgrade in the future?

It seems odd that the only functional difference between AWD and Beast is the acceleration. And there is a published range loss as a cost. There HAS to be more for $20K.

Maybe I’m just trying to justify buying the Beast…

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[FarAway]

This was briefly touched on in one of the videos, either the Haggerty or Top Gear, I don't recall which.

 

[cvalue13]

I’m wondering why the Beast has two permanent magnet motors in the rear and an induction motor in the front.

I believe this info that the rears are perm mag is coming from the EPA data, then spreading like gospel on the xwitter cesspool


I also believe the EPA data submission is in error

Not the only reason I believe this, but a pretty good indication

 

[Scott Beall]

Forgot to finish the thought.
...If that's the case, maybe we'll see a range increase in the Beast. It might be a factor in why FSD isn't fully baked in the CT yet.

 

[JBee]

I’m wondering why the Beast has two permanent magnet motors in the rear and an induction motor in the front.

As I gather from posts here on the forum, induction motors have a “back EMF” force that doesn’t allow them to “free spin” without power. I think permanent magnet motors will free spin.

The Semi gets its great range by having the rear motors shut off (via a clutch) during cruise. The rears for acceleration (mostly).

Could it be that the Beast is meant to operate the same way, but without the clutch and with software to shut off the two rear motors at cruise and just let them free-spin while relying on the front motor? Could we see this as a software upgrade in the future?

It seems odd that the only functional difference between AWD and Beast is the acceleration. And there is a published range loss as a cost. There HAS to be more for $20K.

Maybe I’m just trying to justify buying the Beast…

So that's actually the other way around.

A Permanent Magnet motor has a "permanent" magnetic field which when rotating induces a current in the coil windings of the stator and causes a back EMF that tries to slow down the rotor. This also generates a current that needs to be dissipated, for example to charge the battery.

An induction motor does not have any permanent magnetic field, because the rotor uses windings that "induce" a magnetic field. Hence the name.

So in the case of the beast, the two rear motors are induction and are turned off during highway cruise and low power settings. This way the PM, that also has a higher efficiency than the induction motors, can drive the vehicle at the best possible efficiency. Like this the turning off is done without a clutch as well meaning less parts.

As for the price difference, the Beast has some other smaller extras like trim, but otherwise the premium is primarily for the extra motor. Which btw does torque vectoring in the rear as well, instead of using a diff lock.

 

[Deleted member 17810]

I believe this info that the rears are perm mag is coming from the EPA data, then spreading like gospel on the xwitter cesspool


I also believe the EPA data submission is in error

Not the only reason I believe this, but a pretty good indication

Counterpoint: exosekelton

 

[Tiberius]

Should point out that the Tesla EPA submission shows all three motors are permanent magnet, one part of Tesla isn't talking to the other

 

[hooptycam]

Forgot to finish the thought.
...If that's the case, maybe we'll see a range increase in the Beast. It might be a factor in why FSD isn't fully baked in the CT yet.

Really? FSD is not baked in? That’s insane.

 

[ED_SFO]

So that's actually the other way around.

A Permanent Magnet motor has a "permanent" magnetic field which when rotating induces a current in the coil windings of the stator and causes a back EMF that tries to slow down the rotor. This also generates a current that needs to be dissipated, for example to charge the battery.

An induction motor does not have any permanent magnetic field, because the rotor uses windings that "induce" a magnetic field. Hence the name.

So in the case of the beast, the two rear motors are induction and are turned off during highway cruise and low power settings. This way the PM, that also has a higher efficiency than the induction motors, can drive the vehicle at the best possible efficiency. Like this the turning off is done without a clutch as well meaning less parts.

As for the price difference, the Beast has some other smaller extras like trim, but otherwise the premium is primarily for the extra motor. Which btw does torque vectoring in the rear as well, instead of using a diff lock.

This is pretty much the best answer.. the engineer I spoke with said that to get the best efficiency having induction in the rear was the best scenario with also being cheaper to manufacturer. I wonder if the semi will eventually do this vs having the clutch system they currently have.

On the note about the EPA application...it also states the battery pack is 150kw. When Elon said 123kw battery is that the current usable? Seems like a lot more range is unlockable in a future update.

 

[swengl]

Minimizing rare earth elements used is another reason for the single permanent magnet motor. The permanent magnet motor uses more rare earth elements. Rivian uses 4 permanent magets in their motors, Tesla uses on 1 (for the Beast only).

 

[Scott Beall]

So in the case of the beast, the two rear motors are induction and are turned off during highway cruise and low power settings. This way the PM, that also has a higher efficiency than the induction motors, can drive the vehicle at the best possible efficiency. Like this the turning off is done without a clutch as well meaning less parts.

Thanks @JBee!
So if it gains this efficiency, why doesn't the Beast get longer range than the AWD? It's only heavier by the weight of one motor. The range difference doesn't make sense to me.

 

[HaulingAss]

Thanks @JBee!
So if it gains this efficiency, why doesn't the Beast get longer range than the AWD? It's only heavier by the weight of one motor. The range difference doesn't make sense to me.

Because the dual motor Cybertruck uses the induction motor in the front and the permanent magnet motor in the rear. So the dual motor is effectively RWD at cruise while the Beast is FWD at cruise.

 

[Scott Beall]

Really? FSD is not baked in? That’s insane.

Speculation here on the forum is that since FSD wasn't mentioned at the delivery that it's not ready in Cybertruck. That's just speculation so far I think. If it's true, I wonder how many hours of video Tesla will need in order for their AI to make FSD work. Another reason to hope for a steep ramp up in production.

 

[scottf200]

I’m wondering why the Beast has two permanent magnet motors in the rear and an induction motor in the front.

FYI, Tesla has had combinations already. See the chart I put together.

One aspect: It does appear that permanent versions allow them to regen down to 0 MPH. My 2017 Model X with two inductions does not (regens to like 3 MPH).

 

[hooptycam]

Speculation here on the forum is that since FSD wasn't mentioned at the delivery that it's not ready in Cybertruck. That's just speculation so far I think. If it's true, I wonder how many hours of video Tesla will need in order for their AI to make FSD work. Another reason to hope for a steep ramp up in production.

I just assumed it was a given.

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