Why is the Prius's 2 motor generators more reliable than an alternator?

that doesn't sound right to me. alternators are pretty reliable. but the motor generators are the heart of the hybrid system, and have to be hyper reliable, because replacing them is no mean feat, and vastly more expensive than an alternator.

otoh, it would not surprise me if toyota is continually decontenting the ecvt, now that they know it was originally over engineered, and they can save some money going forward.
they just need to get most of them past warranty

 

Alternators have brushes that wear out, are more exposed to contaminants, and are relatively cheaply constructed.

 

Because it must be, as it is part of the core propulsion system. Considering its cost and difficulty to replace, ordinary alternator failure rates would turn this hybrid into a marketing disaster.

Thus, it is better engineered and protected from the outside environment.

 

Back when you had an alternator, it was hung off a bracket and had some pulley pulling on it from the end.

If you watch the WeberAuto videos, you see very well supported M/Gs with precision bearings. So the stresses are less and motors last longer.

He does not mention all the bearings, but the video shows them. He mentions a couple of ball bearings, I saw what I think of as Timken bearings.




In contrast, many alternators are on a long (flimsy?) arm and rotate a pulley at one end, pretty much unsupported.



(this alternator is painted red, perhaps by the same individuals trying to sell red solenoids)

 

And are not liquid cooled.