Understanding the Tesla Model S Front Motor

Join me for another deep dive to see the details of the 17,500 RPM front motor and drive unit from a 2014-2018 Tesla Model S AWD. See all four motor rotors from the Tesla Model S and Model 3. The video is divided into four sections showing: 1. The motor and gears. 2. The high-performance bearings. 3. The lubrication system. and 4. The electrical system.

TIMELINE:
0:00 Start
0:11 Model S, X, and 3 electric motor combinations
1:30 RWD Model S and X motors
1:37 AWD Model S and X motors
1:54 Performance AWD Model S and X motors
2:28 RWD and AWD Model 3 motors
3:10 MUST SEE Close up photos of all four motors
3:44 Video Section 1 - Gears and Rotor
3:56 Gear housing components
4:49 Comparison of differential with a rear performance motor
5:53 MUST SEE Why are the bearings and gears so big?
7:36 The front differential case speed at 250 km/h (155 mph) = 1877 RPM
7:54 MUST SEE Different tire sizes and different gear ratios
9:00 Installation of the front differential case with a 79 tooth ring gear (Prime Number)
9:22 The Counter Shaft with 21 (Factors 3, 7) pinion gear teeth. 79/21 = 3.7619:1 Gear ratio from countershaft to the differential case
10:41 The countershaft speed at 250 km/h (155 mph) = 7063 RPM
11:08 The motor rotor shaft and drive gear with 31 teeth (Prime Number)
11:35 MUST SEE Comparison of the front rotor to the rear performance rotor
12:56 Maximum torque at a vehicle speed comparison
15:36 Motor rotor speed sensor and reluctor wheel
16:49 MUST SEE SKF Ceramic Bearing (Silicon Nitride) on the rotor
17:43 The rotor is in a wet environment and cooled by the transmission fluid
18:33 MUST SEE Rotor shaft grounding rings with conductive filaments from (AEGIS?)
19:37 Shaft grounding protects bearings from damage from electrical current
20:10 The Rotor Shaft with 31 gear teeth drives the 77 (Factors 7, 11) tooth counter gear. 77/31 = 2.4839:1 Gear ratio.
20:52 See all three gears in the reduction gearbox with an overall gear reduction of (79/21) x (77/31) = 9.3441:1
21:26 The differential and the axle half shaft and jackshaft to reduce torque steer
22:23 Video Section 2 - Specialized Bearings
22:58 How Tesla run bearings at higher speeds than their limiting speeds with lubrication
23:07 Video Section 3 - Specialized Lubrication for bearings
23:34 The 20 tooth oil pump gear is overdriven by the differential ring gear 20/79 = 0.2531:1 gear ratio (3.95 times faster than the ring gear)
24:18 The transmission fluid drain and fill plugs
24:39 The fluid refill procedure
25:45 MUST SEE The proper fluids for the front-drive unit (Mobile SHC 629 and Dexron VI)
28:00 The path of the pressurized transmission fluid to six destinations
28:09 1. Lubrication and cooling to the motor gear and conductive bearing
29:08 2. Through the fluid-to-coolant heat exchanger to remove or add heat
31:04 3. Cool fluid is sprayed on the stator frame and right side windings for cooling through a sparge pipe
32:24 4. Cool fluid is sprayed on the non-conductive bearing and the right side of the rotor
32:58 5. Cool fluid is dripped on the stator frame and left side windings
32:47 6. Cool fluid is sprayed on the left side of the rotor
33:48 Transmission fluid fill capacities
34:42 Video Section 4 - Electrical Components
34:50 MUST SEE The three-phase, four-pole, 48 slot stator
35:55 The milli-ohm resistance of the stator windings with a Hioki RM3548 Resistance Meter
36:48 High-Performance induction motors versus high-efficiency Internal Permanent Magnet Synchronous Reluctance Motors (IPM-SynRM)
39:30 The inverter and its connection to the stator
41:42 The stator temperature sensor
42:40 How the stator frame is mounted with the stator housing
45:18 Thank you for your donations

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Weber State University (WSU) Davis Campus - Automotive Technology Department - Advanced Vehicles Lab. A technical description and operational demonstration of the Tesla Model S Front Drive Unit (FDU).

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[Dogpool]

People are paying many $ bills to get a teaching from this dude. We up here getting arguably a better experience then the class room in some ways, for free(ish). Awesome time we live in.

[geik]

If all teachers in the school system had been as good as you at explaining, .... Thank you professor

[ruhfsge]

This guy is the absolute best. I have watched his amazing videos and was able to pass my L3. Thank you so much!

[OkinSold]

Was waiting for this one! You are an excellent teacher!

[jean-clauded]

I'm very impressed with the level of knowledge transfer, and honesty when he says details about things he doesn't know. I wish when I had go to school, I had more professors like this that were driven for a quest for knowledge and not their ego or reputation. He also understands, as shown in these videos, that he could know everything in the world, but if he doesn't share it, that knowledge is useless.
In his case, he shares what he knows, and honestly wants people to help him learn even more where he may not know something in as far a depth as he would like.

[StanAnderson-yghj]

WOW, Professor Kelly is a wealth of information. He does an excellent job of explaining the inner workings of Teslas. Great job Professor.

[petermolnar]

Thank you Professor Kelly for your efforts to keep us informed! They are much appreciated!

[tony]

Great videos.
The high performance motors are induction machines to get around the problem of back EMF caused output power loss at higher speeds.
Comes down to a tradeoff:
Constant power over the full operational span at the cost of increased overall energy losses, or higher efficiency for decreased output power as speed increases?

A magnet moving past a field creates a voltage proportional to the magnet strength and speed (back emf). A permanent magnet always has a strong magnetic field in the rotor. So, at some speed, the back emf exceeds the bus (battery) voltage and no more torque can be generated (flux weakening can help this, but eventually, no useful work can be done). But, because no rotor magnetization current is needed, PM based motors are much more efficient. None of the current in the motor is spent creating a magnetic field in the rotor. No rotor losses.
For induction machines, the rotor acts as the secondary of a transformer. The current induced in the rotor (from the stator, primary) creates the rotor magnetic field that can then be used to create torque (via a process described as slip). This means the current in the rotor can be controlled. Because the current in the rotor can be controlled, the back emf can be controlled. Because the magnetic field in the rotor is controllable, constant mechanical power can be output until the variable frequency drive (VFD, converter) can no longer output higher frequencies. The penalty is rotor loses. Because there is current flowing in the rotor, induced by the stator, this power is lost in the form of rotor current (resistance of the rotor circuit). You have to pay, in terms of input electrical power, to create the rotor magnetization, therefore, less overall efficiency. But, constant mechanical power for the full operational frequency of the VFD.

You can see this by spinning a motor by itself. A PM motor will generate a voltage as it freewheels, DMM between any two leads. (No current, because there's no circuit. Completing the circuit will make it a generator and the PM motor will act as a brake)
An induction machine won't. (There will be a small residual voltage if it's an iron core, because of residual rotor margination, but not much)
Applying a constant (DC) current to the windings of an induction machine (current limited power supply between one of the phase pairs, be sure to limit the power to something that won't damage the stator by too much heat), and spinning the rotor will make it feel like it turning thru peanut butter, the shaft will get stiffer as you try and spin it faster.
Doing the same to a PM machine will make it 'cog' or make it unable to spin (by hand) at all. Be carefully at startup. It may turn very quickly with great force when current is first applied.
If it's an IPM machine, there might be some cogging due to the motor saliency, e.g. the Nissan Leaf does this.

I hope this was understandable and useful.

[WouterB]

Long video? Yes. But if you want to explain something right down to the details, time has to be taken.

Thanks for another insightful and clearly explained bit of Tesla technique!

[mikel]

Another excellent presentation.
Thank you, professor !

[sene-teckkservicesltd.]

Thank you Professor Kelly. You have made it possible for those of us in the developing world (I am in Ghana) to also learn and have an understanding of the new tech underneath the EV drivetrains. These videos are an absolute germ and it is my hope that we can all contribute to ensure its sustenance. Thank you once again.

[chuvvyyk]

This is the most comprehensive video about tesla motor! Thank you very much!

[tonybryan]

Thank you (again!) professor for another illuminating session on the Tesla system.
I know that there are many, many hours (days or weeks) of research and disassembly/re-assembly, editing and other real, unseen work that goes into your presentations.
Thank you so much for these condensed, easy-to-understand tutorials on these very complex systems.
Great nutrition for curious minds!

[Skarkroe]

Been watching since the 2nd Gen Volt videos. Now with a CyberTruck pre-order I’m enjoying the detailed dives into Tesla’s tech. Thank you so much for producing these!

[bergssprangare]

The best explanation of the Tesla motor set on Internet. Thank you

[Martin-seij]

i can only imagine the hours that have gone in to clean all these parts. You are opening my eyes to the amazing engineering that goes into these cars. Who would know your front wheels are a different size than the back, I'm sure owners would just rotate the tires thinking them the same?

[victorhoe]

Professor John Kelly, I was once an Electronics Tech at Weber State College, working for Sid Jensen back in 1969 through 1973. I wish I am younger to attend your classes on line or in person. I am a life long techie and find your teaching as excellent. The circular lecture hall was brand new in 1969.

I did a Google Map of Weber State University, showing Engineering Technology Centre with what seems tobe new construction of Engineering Tech buildings.

[jamesbruce]

As you drive down the road it puts the induction motor in 'torque sleep' mode (0 torque). It uses the PM motor only to drive the car. At some point in the application of the accelerator it starts using moth motors.
I think torque sleep puts enough power to the induction motor so the output torque is 0 reducing drag and increasing efficiency.

[katout]

Phenomenal reverse engineering presentation on a variety of Tesla electric motors and gears. Thank you for creating these extremely informative technical video's.

[Bassotronics]

I thought those vehicle motors were much bigger.
259 hp on that little motor is amazing!