The start of the end of the combustion engine era, a glimpse into the future with Tesla
Current Combustion Engines
For a long time, around ten ago I remember thinking to myself, before I even got into college, that the combustion engine was something that had to be replaced. This happened back in the 2008-2010 period when in NY gas prices were over 4$. The reason that I thought this was that the efficiency of the combustion engines were only 30%. Today, their efficiency hasn't gotten much better, we are now boasting a 35-40% efficiency, for gasoline and 40-45% for diesel. While incremental improvements are to be expected with technology the only question that I begged was why can't we scrap what we know and start from scratch? My approach to this problem stems from my engineering background, and probably very common in the field. When software engineers don't like something, we tend to ask why don't we start from scratch and build with an infrastructure first mentality. That's what Tesla did, and they effectively refactored the engine.
The Quick Summary
The rest of this article will be pretty technical, and a little lengthy. I will do my best to outline what each piece of technology means, but this is summary intended for non-technical persons, or if you want to bail out early.
Tesla perfected the PMSRM; Permanent Magnet Switched Reluctance Motor. It was an engine that was first conceptualized and in 1838 (50 years before Tesla). Motor companies have avoided this technology due to torque ripple. Torque ripple means that the power generated by the engine fluctuates. By using rare earth metals Tesla, in short, solved this and thus created a lighter smaller more efficient engine that uses fewer parts.
Where did they start? The Induction Motor (Pre-Model 3)
Tesla's name is credited to the 19th Serbian-American inventor, electrical engineer, mechanical engineer, and futurist. Nikon Tesla is best known for his contributions to the design of the modern alternating current (AC) electricity supply. When Tesla first started making their cars, their engines had a 3-phase AC Motor. Another critical technology was the portable inverter. First invented in 1990 by Alan Cocconi), a device that turns the direct current (DC) in an electric car’s battery into the alternating current (AC). Using Nikon Tesla's motor designs and a portable inverter, Tesla started to make their first engines.
Pros of the Tesla induction motor:
- Doesn’t require any expensive permanent magnets
- Uses cheaper electromagnets
- PM-free induction
- Costly and difficult-to-cast rotor fashioned from pure copper
- The rotor tends to get hot and can even overheat (wasted energy)
- In-efficient at low speeds
How it works
A large magnetic field is generated from the stationary portion of the motor, which in turn, induces an opposing magnetic field on the highly conductive copper rotor. When the two opposite magnetic fields interact: they pull toward each other. When the two opposing magnetic fields generated inside the motor of one of their cars collide, it produces an insane amount of power and takes off faster than some of the fastest supercars.
The induction motor is still a great engine. In comparison to the newer engine in the Model 3, we can see the change in technology and the innovation that Tesla has done to put their best product forward.
How Tesla refactored the Engine
Tesla scrapped the induction engine and opted for a permanent magnet engine, and wait didn't I say that was a benefit of the induction motor by not using one?
So, as you know, our Model 3 has a permanent magnet machine now. This is because for the specification of the performance and efficiency, the permanent magnet machine better solved our cost minimization function, and it was optimal for the range and performance target. - Tesla’s Chief Motor Designer, Konstantinos Laskaris
Yes, I did, but that was because they would be costly, but this motor is cheaper than before and uses 25% fewer parts so let's dive into how they pulled this off.
Let's start with an expert, enter engineering teardown master “Ingineerix.” In February 2018, Ingineerix posted a series of videos exploring the innermost secrets of the Model 3. In a video titled “The Dark Side,” he explores the underside of the car and more specifically the motor. It was here he that revealed that the car has a “Switched Reluctance motor, using permanent magnets.”
“Tesla calls it a PMSRM, Permanent Magnet Switched Reluctance Motor. It’s a new type, and very hard to get right, but Tesla did it!” - Ingineerix
The Simple Concept
If you have a magnet and a piece of iron, the magnet will pull the iron towards it. If you turn on and off the electromagnets and that iron is on a rotor, it will begin to turn. That is a Switched Reluctance Machine.
Take what you learned above about the Pre-Model 3 engine, a phenomenal engine that produces an insane amount of power and speed. Now you are given the challenge to make it lighter, smaller and not compromise on that same record-breaking speed.
To succeed at this daunting task you would have to look back even further than 1892, the year Nikola Tesla invented the induction motor. You'll have to go back 50 years further to 1838 when the first reluctance machine was made. The reluctance machine is simple, compact, inexpensive, but suffers from Torque Ripple an infrequency in the amount of power generated.
The Reluctance Machine
The reluctance motor is difficult to control; it's RPM, rotor position among a few of the difficulties of working with it. With modern day control systems, and power electronics Tesla overcame these challenges, but torque ripple remained the underlying problem. However, in 2011 a researcher found that if you embed small rare-earth metals in the motor alongside the existing electro-magnets the fluctuations would be smoothed out and a 30% increase in efficiency as well!
You are now able to remove the expensive copper rotor, replacing it with a smaller, cheaper one, saving money and weight. The rare-earth metals are costly sure but offset by that old rotor's cost. A more powerful and efficient motor, one that is also smaller and cheaper!
A Final Comparison of the Model 3 engine to a combustion engine.
As stated before the current combustion engine, at best can get a power efficiency of 40% on gasoline and 50% on diesel. The pre Model 3 induction motor has an efficiency of 82%, and with the new permanent magnetic switch reluctance motor, that is speculated to be about 90%! While this may seem like a small incremental increase, the new engine boasts fewer parts, more power and is cheaper to manufacture. Nothing can be 100% efficient as heat (energy) gets released while it travels, but this new engine is much better by a far margin. We should see ourselves moving away from the old combustion engine to something much more reliable and efficient. As technological advancements affect every industry, we can only ask ourselves what's next?