Upcoming M3P hairpin motor question

[Sam1]

Hoping someone with a background in motor tech can share some info on this. I watched a few youtube videos concerning the differences between traditional windings and hairpin wiring tech. Porsche claims that the hairpin can produce more torque, and holds sustained power better than traditional windings. Does anyone know +/- the estimates of what the hairpin wiring would do compared to a motor with traditional windings - with all other specs similar?

Also, since the plaid essentially uses model 3 motors on the rear, is it possible that the new motor being discussed, will be a cheaper variation of those motors?

 

[jkeyser14]

The difference is mostly ~1-2% less heat due to increased copper volume in the same space. Tesla could either keep the current in each winding the same which would make the car 1-2% more efficient, or they could increase current output by 1-2% which would increase torque.

The Model 3 already has enough torque to break the wheels free (software limited), so Tesla will likely use the new windings for a few extra percent efficiency.

 

[gearchruncher]

The difference is mostly ~1-2% less heat due to increased copper volume in the same space. Tesla could either keep the current in each winding the same which would make the car 1-2% more efficient, or they could increase current output by 1-2% which would increase torque.

This makes no sense to me. Why can't they do both? Why wouldn't it both be more efficient at highway cruise while also allowing 2% more max torque?

You can't "keep the current in the winding the same"- this is literally what your foot does on the throttle. This varies constantly. The question is for a given current, what torque do you get. If you get more torque per amp, then you are both more efficient and have a higher max power if you make no changes to your motor controller.

 

[jkeyser14]

This makes no sense to me. Why can't they do both? Why wouldn't it both be more efficient at highway cruise while also allowing 2% more max torque?

You can't "keep the current in the winding the same"- this is literally what your foot does on the throttle. This varies constantly. The question is for a given current, what torque do you get. If you get more torque per amp, then you are both more efficient and have a higher max power if you make no changes to your motor controller.

Tesla's motor controller software is what controls the amount of current going to the motor (not your foot). The motor controller listens to the pedal as an input, but Tesla software decides what duty cycle to PWM the Mosfets with inside of the motor controller. That duty cycle is what limits current to the motor.

So Tesla can keep the motor controller code the exact same as it is now, which would increase current and therefore torque output due to less winding resistance in the hairpin motor (more copper = lower resistance = higher amperage for the same amount of heat generated). Or Tesla can reduce the PWM duty cycle and get increased efficiency for the same current (current = torque) as before.

As to why they can't do both, they could but the majority of the heat is generated at high power levels which tend to correspond with highway driving which is where you typically want the added efficiency. So doing both would minimally improve range at very low speeds while giving barely noticeable added torque at high speeds. I doubt most drivers would notice 1%. However, they will notice 1-2% added range in marketing materials.

 

[gearchruncher]

So Tesla can keep the motor controller code the exact same as it is now, which would increase current and therefore torque output due to less winding resistance in the hairpin motor (more copper = lower resistance = higher amperage for the same amount of heat generated). Or Tesla can reduce the PWM duty cycle and get increased efficiency for the same current (current = torque) as before.

So you get more torque than before. Which means the car goes faster. Which means you back of the pedal a bit to actually go the speed you want. Your foot is just as much a part of the control system as anything else, as the human is trying to hit a speed target.

Tesla software decides what duty cycle to PWM the Mosfets with inside of the motor controller. That duty cycle is what limits current to the motor.

This is a very amateur version of what a modern AC motor controller does. The current in all phases is changing constantly, and uses a current feedback method. It's not a blind PWM controller.

As to why they can't do both, they could but the majority of the heat is generated at high power levels which tend to correspond with highway driving which is where you typically want the added efficiency. So doing both would minimally improve range at very low speeds while giving barely noticeable added torque at high speeds. I doubt most drivers would notice 1%. However, they will notice 1-2% added range in marketing materials.

Heat is generated in highway driving? These are 375kW cars. 220wh/mi at 60 MPH is only about 13kW. The power needed on the highway is nothing.

You're still not explaining why 2% extra efficiency (current to torque) is not exactly the same as 2% more peak torque.

 

[jkeyser14]

>You're still not explaining why 2% extra efficiency (current to torque) is not exactly the same as 2% more peak torque.

Because Tesla software limits torque (max current).

 

[gearchruncher]

Because Tesla software limits torque (max current).

So you're saying that Tesla has updated the controller to output 2% less current in order to keep the torque identical to before? They aren't taking any advantage of the higher efficiency of the motor at full power, even though this would take less work?

You're also claiming 2% increase in range is the primary advantage? Yet they are only doing this on the PERFORMANCE configuration? Meanwhile, Porsche uses hairpin winding in the Taycan and claims the advantage is higher power density and much easier cooling, with no mention of cruise efficiency.

Where is your data coming from?

 

[Ingineer]

I did a teardown of the new hairpin motor:

I posit that the hairpin will indeed allow for higher peak power, but the efficiency is probably close to a wash due to the higher skin-effect losses in the hairpin vs. conventional windings.

Yes, there is a lot of power "on the table" in this design, note the Plaid essentially uses the same parts as the older Model 3 design. (adapted for higher top speed) There are a lot of reasons to limit power, we have to consider the battery pack, powertrain longevity, chassis traction limits, and finally marketing. They don't want a performance Model 3 showing up their expensive flagship Model S.

 

[brkaus]

They don't want a performance Model 3 showing up their expensive flagship Model S.

And I’m sure they don’t want the drivetrain problems they are experiencing with the S/X either. Just because the motor can, doesn’t mean it should.

 

[DownshiftDre]

I did a teardown of the new hairpin motor:

I posit that the hairpin will indeed allow for higher peak power, but the efficiency is probably close to a wash due to the higher skin-effect losses in the hairpin vs. conventional windings.

Yes, there is a lot of power "on the table" in this design, note the Plaid essentially uses the same parts as the older Model 3 design. (adapted for higher top speed) There are a lot of reasons to limit power, we have to consider the battery pack, powertrain longevity, chassis traction limits, and finally marketing. They don't want a performance Model 3 showing up their expensive flagship Model S.

Nice video. Thank you. You mentioned in video this is on Model Y. Which years and models? Any other Tesla vehicles this Gen 4 version of powetrain is used on?

 

[jackmott]

Just remember an efficiency improvement on something that is already deep in the 90%s on efficiency won't be a big deal.
Better than nothing though!

 

[Ingineer]

The main reason Tesla is going to hairpin is COST and manufacturing speed (also cost).