Electric Motor?

Electric Motor?

First, I just wanted to say that I placed my order this week and I am BEYOND excited! Second, where are the details on the electric motor? I've read a countless number of articles and watched dozens of videos on the Model S, but I simply can't find any information on the motor? Does anyone know what the lifespan is and whether or not it requires maintenance?

jbunn | April 28, 2013

Electric motors are generally long lived compared to their internal combustion engine cousins. Should it need replacement, it should also be much cheaper than an engine. Any maintenance will be done by the Tesla service center during one of your annual visits.

The motor is a 4 phase (I believe) variable frequency alternating current motor. It has no permanent magnets or rare metals. RPM of the motor is increased by the increasing the AC frequency to the motor. Very simple design that eliminates brushes, magnets, etc. I believe (again) that this motor design traces back to Nikola Tesla himself.

Glad you placed your order. I've put 3500 miles on mine and love it. I think you will be happy.

DJung | April 28, 2013

The motor is a 3 phase, 4 pole AC induction motor. from what i understand it is a copper coil being spun by the changing poles of the magnets. An AC induction motor is incredibly reliable. It's basically just magnets, copper, and rotor. I've heard the lifespan is very long and should far outlive the other components of the vehicle. I did hear on this forum a while back that it needs to be oiled after a LONG time the vehicle has been purchased

this video explains how it works:

DJung | April 28, 2013

^i guess it does not have magnets.

dbullard | April 28, 2013

Should last forever - industrial electric motors built in the '40s are still in use today.

The gear reduction/differential will need to have it's oil changed (just like a regular car's differential), but the motor itself has only one moving part.

Of course, the service plan pays for all maintenance... :)

Kleist | April 28, 2013

Start here reading here -
Tesla makes its own induction motors... not much that really wears.

tm | April 28, 2013

Awesome information everyone, thanks! Every time I tried searching something along the lines of "Tesla Model S electric motor", it kept bringing up Tesla's site/articles related to "Tesla Motors" haha. I wasn't sure whether or not Tesla uses new proprietary electric motor tech, as they've acquired a fairly long list of patents pertaining to the technologies used in the Model S.

Kleist | April 28, 2013
robkal007 | April 28, 2013

Our cars rest on the shoulders of a genius! See:
It has been 125 years since the first patent was filed. Probably the most interesting patent pertaining to our cars is liquid cooling the rotor. The Roadster can't sustain it's top speed for more than a few minutes because its air-cooled motor overheats and current is reduced, and yet we can charge up the Grapevine on Hwy 5 at 70 miles an hour without any difficulty. Nikola Tesla invented it - Teslamotors perfected it.

jat | April 28, 2013

@robkal007 - I think it is the battery and inverter temperature that is an issue more than the motor.

tm | April 28, 2013

Wow... Ready this page ( from @Kleist this morning. One word: AMAZING! The motor is so simple, yet so advance with its electromagnetic field and how its controlled.

jbm6207 | August 6, 2013

To confirm... the induction motor was patented but Nikola Tesla in 1888.

The Model S has a three phase, four pole induction motor. It is very simple in design, basically a cylindrical rotor inside a wound metal enclosure. The only moving part is the rotor. When voltage is applied to the terminals, the rotor rotates at a speed that is proportional to the frequency. So, if you were to plug the Model S motor into a three-phase voltage source within the United States, it would spin at approximately 1800 rpm (in the UK, it would spin at 1500 rpm).

The speed of the Model S is controlled by the applied frequency of the voltage through what is called a "variable frequency drive" or "variable speed drive". These are the same drives that are used in many industrial processes today. The direct current battery voltage (which is about 400 volts) is converted to three-phase alternating current using an inverter which is part of the variable speed drive.

The induction motor is a beautiful thing. It has maximum torque when the rotor is at stand still. The torque remains fairly constant until you reach synchronous speed (the speed at which the rotor turns at a given frequency).

The induction motor can also be operated as a generator. Nearly all wind generators are induction machines. As a motor, the rotor spins slightly slower than the frequency of the voltage that is applied. In order for the motor to become a generator, the rotor must spin slightly faster than the frequency of the applied voltage. That how the Model S is able to charge the battery when you let-off the accelerator.

One disadvantage is that the motor generates a lot of heat. When a motor gets hot, it has to be shut down or it will damage the rotor or the electrical windings. In most applications the motor is "turned-off" until it cools down. For a car, that is rather impractical. Although the Model S has a cooling system, there is a limited amount of heat it can absorb. I suspect that when motor (and/or battery) gets too hot, Tesla limits the power input into the motor to reduce heat dissipation, effectively making the car slower. This is probably why the Model S "slows down" on repeated 0-60 or 0-100 tests.