Check Out Tesla Model 3/Model Y's Modular Electric Drive Units

The overview of electric motors, gears, inverters and auxiliary components reveal smart engineering.

Tesla’s electric cars and drive units, in particular, are considered one of the best and most efficient in the industry. Today we will take a closer look at the Tesla Model 3 and Tesla Model Y drive units with Professor John D. Kelly from the Weber State University (WSU) Davis Campus – Automotive Technology Department – Advanced Vehicles Lab.

Those cars are closely related to each other and share a fair number of key EV components.

The integrated drive units in Model 3/Y consist of an electric motor, a set of gears (single-speed), an inverter/controller as well as auxiliary elements like an oil pump, oil filter and heat exchanger.

Rear – IPM-SynRM, Front – induction motor

The front and rear electric motors are different. The rear electric motor is an Internal Permanent Magnet Synchronous Reluctance Motor (IPM-SynRM), while the front electric motor is an induction motor (with cooper core or aluminum core seen in one of the Model Y – probably in the entry-level version only).

The reason for having two different types of motors lies in higher efficiency. The permanent magnet motor is highly efficient and in use most of the time (its rare idle losses are acceptable). The induction motor in the front, on the other hand, provides additional power or regen, and while idle it’s simply free-spinning. That’s a perfect combination.

Another approach would be to have two permanent magnet motors, but at least one of them would have to be mechanically disconnected from the wheels. Two induction motors probably would not be as efficient as a combination of two permanent magnet motors (with a mechanical disconnector for one of them) or two different types.

Modular approach

WeberAuto‘s presentation reveals that Tesla’s approach is highly modular and many parts in drive units are interchangeable, regardless of the type of the motor and its position.

The rotors (permanent magnet or induction motor) can be basically swapped and combined with the same set of gears (the overall gear ratio is 9.0363:1, which allows 262 km/h or 163 mph at 18,447 rpm).

The three-phase stator and inverter appear to be matched to each other (the same part numbers), but it’s not clear whether the stators are the same in all motor types (they could be and their might be some nuances). The inverters most likely are not the same, and for sure they work differently depending on a different rotor type (each motor type is controlled differently).

Anyway, the parts are very similar dimension-wise (mounting points), which is a smart move to lower costs, simplify production and logistics.

There will be a following episode on the Model 3/Y episodes and hopefully, at some point, we will see a presentation of Tesla Model S Plaid motors.

Corrections:
1. I swapped the definition of a Hunting gear set with a Non-Hunting gear set.

TIMELINE:
0:00 Introduction
0:27 The rear motor of the Model 3 and Y
1:08 The input shaft with 31 teeth
2:00 the input shaft SKF bearings for a rotor speed of 18,447 at 262 km/h (163 mph)
2:40 The countershaft and gear with 81 teeth
3:00 The input shaft to the countershaft gear ratio of 81/31 = 2.6129:1
3:10 The countershaft pinion gear with 24 teeth
3:15 The ring gear and differential case with 83 teeth
4:30 The countershaft to ring gear ratio of 83/24 = 3.4583:1
4:43 The overall gear ratio = (81/31) x (83/24) = 9.0363:1
5:03 The published gear ratio is incorrect
5:48 The CV half-shafts connect to the differential side gears
6:46 MUST SEE: two cool Permanent Magnet rotor demonstrations
8:05 The modular design of the motor shafts and rotors
8:25 MUST SEE: Watch as a rear motor is changed into a front motor
10:32 The differences in the modular motors
11:35 See what a permanent magnet does to the Induction Rotor
11:55 An aluminum core front induction rotor on the Model Y
12:13 There are at least three different rotors for the Models 3 and Y
13:54 See the rear motor inverter and where it attaches to the rear housing
14:45 The matching part numbers of the rear inverter and the stator (A matched set)
15:15 The three different power and torque levels of the Model 3 and Model Y
16:15 MUST SEE: See the front motor inverter attached to the rear housing!
17:37 the common bolt pattern and opening for the stator housings
18:30 The oil-cooled stator and ATF-9 fluid
18:47 The interchangeable transmission heat exchanger
19:13 The interchangeable variable speed electric oil pump
20:25 The interchangeable spin-on oil filter
21:06 What is not interchangeable between models
21:20 The rear drive-unit is mounted parallel with the ground
22:20 The front drive-unit is mounted upside down and on an angle
23:05 The matching part numbers of the front inverter and the stator (A matched set)
26:30 Additional EV training opportunities at https://www.weber.edu/evtraining
26:58 Video summary and donation opportunity

The previous episodes this year were about the Tesla Model S (the retired version):

https://www.youtube.com/embed/FVVT3FD30eYhttps://www.youtube.com/embed/OSL_935l568https://www.youtube.com/embed/MQV3D8F6gvw
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