Outrunners (or outer-rotor motors) are typically used where the intent is to maximize the radius to the rotor-stator gap, realizing that the stator is much bulkier than a surface-magnet rotor; burying the magnets in a bulkier rotor would negate that advantage.There are quite a lot of IPM inrunners, but I have never heard of an outrunner that is IPM. Why not? I admit that the motor bell would gain some weight in the process and maybe that's the main reason for not making IPM outrunners?
Direct-drive in-wheel motors are another mess entirely, but I'll note that a direct-drive motor runs at only wheel speed, while a normal geared motor runs at a significant multiple of that speed, making rotational inertia much more important.This can't be worse than the spinning mass of a hub motor!
Sometimes it's about rotational inertia, not just mass, and rotational inertia is about the radius where the mass is located. If a IPM inrunner rotor and a SPM outrunner rotor have the same mass and the same radius (to the rotor-stator gap), the outrunner will have much higher rotational inertia because that mass is at a larger radius.The mass of an IPM inrunner armature vs an SPM armature is probably pretty close to the same. There's no added spinning mass issues.
If they were not angled in, they would just be at the surface, and would be surface permanent magnets. If you look at the flux paths at various speeds - not just the mathematical models of motor performance - you would probably find that the interior magnets in a vee configuration are suited to producing reluctance torque at higher speed, which is what the "MTPA" discussion appears to be about. Be prepared to look at a lot of diagrams in a lot of articles...Most IPM inrunners have the magnets angled inwards in a V like this. Not all do, but this is very common. Does anyone know why?
OK. What are you building? What application is this for, to where an inrunner is suboptimal?Agreed hubs tend to suck. Good thing I never mentioned them other than as a bad example. LOL
The title of the web site is "electric cars", but there are plenty of people on here, myself included, not building cars or anything 4 wheeled. This web site is about EV's of any kind, not just cars despite the domain name.