[eldis]

So last week I've became a proud owner of a Tesla drivetrain:

On the way home, we stopped by a Tesla superchager - the owner of the brand new white Tesla was quite surprised, to see a Peugeot with a Tesla drivetrain

By the looks of it, this motor indeed is the same one as in Tesla Model S. I have no idea if different battery in Model S means different motor, but most likely they are all the same (as power limiting factor is the battery).

The history of this motor is quite complicated. It came from Mercedes, where they were using it on a testbench. Most likely this motor never even seen a car The reason why Mercedes had it, is their new Mercedes B electric car. I presume that they couldn't be bothered with downsizing their licensed Tesla parts (they bought everything from Tesla, including the battery and charger), so Mercedes B motors are (most likely) Model S motors. If someone has the dimensions of Tesla Model S motor, please write them here. I would love to compare them.

I've bought the whole drivetrain - motor, single speed gearbox and the inverter. Since this is a factory test motor, most likely the firmware will not be compatible with Model S (it might be compatible with Mercedes B). In the best case it just spits bit more diagnostic information, but most likely having a Tesla capture will not spin it. This is okay, as my plan is to use my own motor controller to replace the "brain" of this beast. Over the past year, I've started to enjoy performing lobotomy to different inverters (link in my signature).

I'll be using this thread to give some information about this motor, and how to use it in your conversion.

 

[eldis]

Some more pictures:

 

[Woodsmith]

WOW!
What's you plan? What vehicle are you going to put it into?

It makes my latest acquisition, Beryl the EV, look a bit, ummm, rustic!

 

[eldis]

WOW!
What's you plan? What vehicle are you going to put it into?

It makes my latest acquisition, Beryl the EV, look a bit, ummm, rustic!

Well, I bought it just because it was cheap (unfortunately I promised the seller not to give the number, but I payed much less than EVTV did).
There are several candidates, but for now main ones are old Porsche or Lotus Esprit Mk1. Anyway, it will be an interesting conversion to do.

If numbers match Tesla Model S, we could be looking at 310kW 600Nm.

 

[kennybobby]

It looks like a slightly bigger motor than the Model S, maybe the Performance version, P85+.

 

[eldis]

So it Seems that kennybobby was right
This motor indeed is the high-end Tesla Model S motor.

I started with the inverter. The idea was to find a way to get out all the electronics and power parts to judge on what kind of power levels could I expect, and how difficult it will be to do the hardware hack of the Tesla inverter.

Main DC cables go off quite easily, just one screw on the orange plastic protector, hiding two massive bus bar screws (DC from the battery pack).

Now is the time to remove the whole aluminum cylinder protecting the inverter. You just have to go around and release ~8 screws. Some warranty had to be voided

Now just slide it off and observe the beauty (more like a beast, this is a 300kW 3 phase inverter!)

The nice triangular design is clearly visible (each side is one phase). The PCBs on top are IGBT drivers. You have to remove the top to access millions of screws that joins the inverter to the gearbox.

Orange cap on the gearbox assembly hides three phase bus bars that routes the power directly to the motor. They have to be removed as well.

Unplug the temperature probes and other wires that goes to the gearbox and motor assembly. Now nothing is preventing you from removing the whole inverter

Pay attention to the clever cooling cutouts, don't damage the sealing as you pull the inverter.

I've done a basic analysis of the circuits and interconnections between modules, checked the power parts and I'm pretty certain, that I can make it compatible with my UMC Drive controller. More on that some other day.

 

[aeroscott]

Great work,this is my first look.

Do you have a weight on the package?

 

[eldis]

Great work,this is my first look.

Do you have a weight on the package?

Thanks! I don't have an exact figure, but I would place this somewhere around 140kg (motor+inverter+gearbox). The power per kg ratio in Tesla is amazing.

 

[rochesterricer]

Great stuff, can't wait to see more!

 

[david85]

Its like watching you take apart a UFO. Love it!

 

[kennybobby]

Great photos, thanks for sharing. Looks like you have a fun project.

Would you be able to measure the resistance and inductance at the motor lugs, phase to phase? Maybe at DC, 60 or 120 Hz, 400 Hz, 1000 Hz?

Why is this important or of any interest? Because these electrical characteristics are used in the calculations made by the inverter to drive the motor using a Direct Torque Control (DTC) scheme, described in TM patents.

For a 3-phase, 4-pole wye motor with the poles wired 2s2p, and with 4 Turns per pole using 16 AWG copper wire 12-in-hand, i've done a rough calculation:

phase inductance ~ 493 nH
phase resistance ~ 5.3 mR

This gives an L/R time constant of 93 usec. If we use 3 tc to reach full current, then the inverter would need to generate a current waveform at about 895 Hz and the motor max speed ~ 26,858 rpm. With a 9.7:1 gearbox the theoretical max speed would be ~228 mph, but realistically the available motor power at that rpm wouldn't be enough to propel the car that fast.

 

[eldis]

Great photos, thanks for sharing. Looks like you have a fun project.

Would you be able to measure the resistance and inductance at the motor lugs, phase to phase? Maybe at DC, 60 or 120 Hz, 400 Hz, 1000 Hz?

Why is this important or of any interest? Because these electrical characteristics are used in the calculations made by the inverter to drive the motor using a Direct Torque Control (DTC) scheme, described in TM patents.

For a 3-phase, 4-pole wye motor with the poles wired 2s2p, and with 4 Turns per pole using 16 AWG copper wire 12-in-hand, i've done a rough calculation:

phase inductance ~ 493 nH
phase resistance ~ 5.3 mR

This gives an L/R time constant of 93 usec. If we use 3 tc to reach full current, then the inverter would need to generate a current waveform at about 895 Hz and the motor max speed ~ 26,858 rpm. With a 9.7:1 gearbox the theoretical max speed would be ~228 mph, but realistically the available motor power at that rpm wouldn't be enough to propel the car that fast.

Great, I'm glad there are people seriously looking into the design of that motor as well I'll be more than happy to take those measurements for you. It will be next week, as the motor is in my friend's garage and I took home only the inverter. (I already have more than enough motors stored in my flat..)

 

[jhuebner]

Great stuff!

Encoder or no encoder?

 

[eldis]

Great stuff!

Encoder or no encoder?

There seems to be an encoder mounted on the side of the motor - not a resolver or anything like that. I still have to look into that section of the control, but there are no resolver digitizers onboard, so it is safe to presume Tesla is using standard optical/magnetic encoders.

kennybobby, the Direct Torque Control actually sounds about right, as I found very hardcore phase current measurement system in the inverter. Every other manufacturer uses hall effect sensors to measure the phase current (two or three), but Tesla designed a bus bar that has a small section made from less pure / more resistive material, and soldered a voltage drop sensor on top of it.

This configuration will be very precise (definitely better than 1% accuracy), but has to be quite difficult to manufacture just right, and every sensor like this is must be compensated for resistance error. You can see different coloration in the material, I would presume that this is due to laser trimming - they put the bus bar under test and cut in it using high power laser, to get the resistance just right. They went for this most likely because the DTC have high requirement on current measurement accuracy.

Someone might ask, why to go through all this trouble with laser trimming of the shunt, when we can easily compensate for it in software? That would perfectly fine in one-off equipment, but we are talking here about large scale automotive manufacturing. When you receive a batch of current sensors, someone would have to pick a bus bar, write it's calibration parameters in the firmware and upload that in the inverter. This creates delays, adds complexity and can lead to errors and problems during regular firmware updates pushed by Tesla.

 

[Duncan]

Damn but that looks like fun!

 

[aeroscott]

Looks like they are changing the resistance by over heating the bus. I had a fire in the engine compartment burning the insulation off the alternator power wire, so I taped it up but got a charging failure light. I was told to replace the over heated wire ,I did and it worked fine.

 

[kennybobby]

There seems to be an encoder mounted on the side of the motor - not a resolver or anything like that. I still have to look into that section of the control, but there are no resolver digitizers onboard, so it is safe to presume Tesla is using standard optical/magnetic encoders.

kennybobby, the Direct Torque Control actually sounds about right, as I found very hardcore phase current measurement system in the inverter. Every other manufacturer uses hall effect sensors to measure the phase current (two or three), but Tesla designed a bus bar that has a small section made from less pure / more resistive material, and soldered a voltage drop sensor on top of it.
...

Great catch in finding the phase current sensor and the explanation.

The patent for AWD (dual motors) describes how they use DTC and traction control to obtain the minimum power solution for the required torque. http://www.faqs.org/patents/app/20140257613

i didn't see anything that looked like an encoder on the motor pictures, but you're the only person to split one open and can answer that question--we are dying to know...

 

[eldis]

didn't see anything that looked like an encoder on the motor pictures, but you're the only person to split one open and can answer that question--we are dying to know...

This is what gave me the impression that there is indeed an encoder (looking on the motor side). Next time I see my motor, I'll track the wires and check where it goes and if it can be an encoder. My bet is on magnetic sensor like for the ABS system.

Tesla had to publish (by law) schematics and diagrams for the whole Tesla wiring and interconnection, unfortunately it is payed. If I need it desperately in the future, I will just have pay the access for few hours. But if it can be done without it, even better.

 

[Moltenmetal]

Watching this with great interest!

 

[Hollie Maea]

Thanks! I don't have an exact figure, but I would place this somewhere around 140kg (motor+inverter+gearbox). The power per kg ratio in Tesla is amazing.

That's pretty good for an induction machine. Can't quite compete with a good PMAC system, but impressive nonetheless.