# Benefit of different motors



## brian_ (Feb 7, 2017)

The motor type is not a significant limitation to power or torque for the same size of motor, in these applications. These manufacturers take different approaches to thermal management (mostly of the battery rather than the motor itself) and reliability, leading to different power ratings.

The Tesla motors provide an interesting comparison: the old models (S and X) have induction motors, but the Model 3 has a permanent magnet motor. They are different cars with likely differently sized motors, but they all have relatively high power ratings compared to most other brands.

No one is putting induction motors into new EV designs now (or in the last decade), so power output of PM motors doesn't seem to be an issue.


----------



## kennybobby (Aug 10, 2012)

It's my understanding that the power and torque of a motor are related to the size of the air gap between the stator and rotor, and the strength of the magnetic field in the gap. 

The various type motors you listed use different methods to create and route a path for the electromagnetic fields within the motor and across the gap.

A motor with larger gap is cheaper and easier to manufacture, but is less efficient due to the higher "resistance" of the path across a longer air gap. This "resistance" is known as magnetic reluctance.

To manufacture a motor with a smaller gap (that won't rub) requires higher stiffness and quality of bearings, and tighter tolerances on every aspect of alignment, all of which increases the cost.


----------



## brian_ (Feb 7, 2017)

kennybobby said:


> It's my understanding that the power and torque of a motor are related to the size of the air gap between the stator and rotor, and the strength of the magnetic field in the gap.
> 
> The various type motors you listed use different methods to create and route a path for the electromagnetic fields within the motor and across the gap.
> 
> ...


Good points. There are various configurations within the general types of "induction" or "PM", and those individual variations will matter more than the general type. For instance, permanent magnets can be mounted along the surface of the rotor or internally, for a very different flux path and resulting different motor performance. Within internal PM (IPM) rotors, leaving some holes in laminations adjusts the reluctance, making the motor a "hybrid" of PM and synchronous reluctance, and that's a routine thing to do now (certainly the BMW motors are this way).


----------



## SpeedRacer93 (Apr 22, 2018)

I may not have phrased my question quite right. Looking at some different documents on the OEM motors and it appears that they are all just about the same size rotor diameter and length (less bearings and outer cooling) and the same for the stator. (Tesla rotor and stator are 25 mm larger diameter ver Nissan but the lengths are with in 2 mm of each other)

Does it just come down to the type of machine and the volt and amps?

Tesla Model S is 1000+ amps 375 Volt (335kw 450 Nm, 400kw 600 Nm)
Tesla Model 3 is 550 amp 350 volt (192 kW - 430 Nm)
BMW is 375 amp 360 volt (135kw 270 Nm)
Nissan is 225 amp 360 volt (80kw 280 Nm)

I know there are some getting 230 Kw out of the Nissan Leaf machine using DIY Intervertors.

I know there is a difference between the number of slots and poles between the different machines and their construction differences (PM, HPM, etc).


----------



## brian_ (Feb 7, 2017)

SpeedRacer93 said:


> I may not have phrased my question quite right.


Different phrasing, same answer...



SpeedRacer93 said:


> Does it just come down to the type of machine and the volt and amps?


Tesla has bigger batteries so they can deliver more power to the motor, and apparently pushes their motors and batteries harder. The fundamental motor type (induction, PM...) doesn't seem like a significant factor.


----------



## CanadaLT28 (Oct 15, 2011)

SpeedRacer93 said:


> Nissan is 225 amp 360 volt (80kw 280 Nm)
> 
> I know there are some getting 230 Kw out of the Nissan Leaf machine using DIY Intervertors.
> 
> .



Do you have a link to someone doing the Leaf changes? I haven't been able to find anyone who done anything like this. Maybe I am just out of the loop. Hell, i can't even find a definitive answer to who I can use Volt packs with a Leaf BMS.


----------



## SpeedRacer93 (Apr 22, 2018)

CanadaLT28 said:


> Do you have a link to someone doing the Leaf changes? I haven't been able to find anyone who done anything like this. Maybe I am just out of the loop. Hell, i can't even find a definitive answer to who I can use Volt packs with a Leaf BMS.


Arlin Sansome on endless-sphere.com put a Nissan Leaf drivetrain in a CRX. He built and designed his own inverter using a Lebowski brain. He is upgrading the IGBTs to push the motor even harder. 

https://endless-sphere.com/forums/viewtopic.php?f=30&t=63982

https://endless-sphere.com/forums/viewtopic.php?f=31&t=92039


----------

