- Munro & Associates tear down a pair of electrical motors from Normal Motors and Tesla.
- What their engineers discovered are two utterly totally different approaches to cooling.
- One prioritizes simplicity, whereas the opposite squeezes out effectivity utilizing some stunning engineering.
Cooling an electrical motor looks like a science that we have had down for years. Simply throw some liquid antifreeze by means of some tubes, make certain air is blowing by means of a sufficiently sized radiator and every little thing is okay. However there is a tremendous science that goes into ensuring every element is cooled to simply the correct amount and in the precise locations.
Lately, Sandy Munro’s engineering agency, Munro & Associates, determined to tear down two electrical traction motors. One is from a Tesla Cybertruck and the opposite is from a Chevrolet Equinox—which means that we’re getting a style of Silicon Valley’s newest and biggest, in addition to Detroit’s tackle making an reasonably priced electrical powertrain. The variations present that the automakers have wildly totally different methods for cooling their drive motors.
Tesla Cybertruck electrical motor internals
Picture by: Munro & Associates Youtube Channel
The technical explainer of the 2 motors is given by Munro’s Paul Turnbull. He exhibits off the internals of each motors, in addition to the assorted elements wanted to chill them, and notes the trade-offs between the 2 platforms.
Let’s begin with GM’s method to cooling the motor. Turnbull explains that GM’s brilliance is within the simplicity of the way it achieves cooling—quite than use advanced plumbing and pumps, GM makes use of the motor itself as type of an ingenious gear system to fling oil upwards into forged channels that then use gravity to rain down over the motor. This cools the windings, magnets, and forged steel .
This methodology is affordable to engineer and easy as a result of there are fewer transferring elements to fail. It additionally does not require sapping extra energy from the automobile’s battery to run any exterior cooling {hardware} (extra on this in a second with Tesla’s method). It is also an previous trick that Toyota used greater than a decade in the past within the Prius C.
However this intelligent setup has limits. It is depending on the motor velocity, mainly self-throttling oil if you’re flying down the freeway however not a lot when the motor is stationary in site visitors. And should you’re on a steep hill or thrashing round a observe, the system’s “rainfall” methodology of cooling can shift off track, which could not be splendid for an electrical motor that may spin at velocity of round 10,000 RPM.
Tesla, alternatively, makes use of a extra exact methodology of cooling. It makes use of a high-pressure pump to pressure oil into channels the place it flows over particular parts like {the electrical} windings and magnets to maintain them good and funky. This method to cooling can be why Tesla can use cheaper neodymium magnets in its powertrains quite than uncommon earth metals.
By not over-cooling the motor itself (however quite exactly making use of the oil to the factors the place temperature issues probably the most), Tesla’s method implies that the motor’s casing stays at the next temperature regardless of its cooler internals. This will increase {the electrical} resistance of the case and reduces the formation of eddy currents.
Eddy currents, for many who do not know, are mainly tiny whirlpools of electrical energy that happen because the magnetic fields from an EV motor adjustments whereas it spins. This is not an issue distinctive to EVs in any respect, however we’re speaking about it immediately as a result of EVs use magnets to energy the drive motors. Each time the magnetic subject flips throughout the motor because it turns, tiny loops of undesirable electrical energy are stirred up and bleed into the steel encasing parts. These small fields create additional warmth and waste power—mainly inflicting an effectivity drawback that may be decreased by holding the motor’s casing hotter and naturally growing its resistance to electrical energy.
The trade-off is that the pump eats power from the battery simply to maintain issues cool. However so does the bodily resistance created utilizing GM’s methodology. It is a little more advanced, although, as additional machining is required for the particular passages in Tesla’s motor, plus additional elements, plumbing and the pump itself.
In brief: GM is trusting physics whereas Tesla is trusting plumping. However in a roundabout manner, the extra advanced manner—Tesla’s manner—is extra technologically groundbreaking. It permits the model to chop prices inside the motor because of some funky electrical wizardry and squeeze out each additional ounce of efficiency.
Each methods are good, and each methods actually work. If nothing else, it is proof that there are many methods to go about reaching the identical activity within the EV world utilizing wildly totally different strategies. The query is: does the automaker prioritize effectivity or simplicity? That is what shapes the answer.
