John in CR said:
The one on the left is a HubMonster. The latest one open with the high slot count definitely is not, and definitely not a motor for high speed. MidMonsters share the same design as HubMonster (slot/pole counts) and same high quality Japanese motor steel. That combination is what makes them capable of so much high peed than high slot/pole count motors, and it's what gives them so much higher efficiency. MidMonster is about 30% smaller and it's magnet ring is cast in an aluminum sheel.
High slot/pole motors are more common because they are cheaper to make for the same torque capacity, because the motor steel doesn't have to extend as far to the center. The tradeoff is more alternating polarity switches per revolution, so more heat from iron losses for the same rpm.
The 6 phase of the Monster family designs has the following benefits:
- More turns on each tooth for the same rpm, so higher inductance for same Kv |(easier on controllers.
- Current split between 2 controllers, so much much cheaper controllers can be used, less than half the cost for the same power.
- Takeoffs are smoother, so they work just fine and near silent with cheap trap controllers.
Hope that info helps settle things a bit.
John,
Thanks for all the good info!
It looks like the hubmonster so I thought it was one of the midmonsters since the shell looks so similar. It has really nice stators in it. They are better than any hub I've ever opened up.
If you have 2 motors on the same stator doesn't that effectively halve the number of transitions per motor? Why not take any high tooth count hub and rewind it as 2 motors?
This ought to work on any motor. I have an Alien Power 12090 outrunner. It has 24 stators in it. If I rewound it as 2 12 stator motors, the eRPM would be 1/2 as much per motor. I would have half as many transitions per motor per rotation right? The pole count per motor would be half of the total pole count. It's wound for 50kv right now. Getting an 18kw controller that runs at 100 volts and can keep up with the motor is a limiting factor. At 100 volts it's eRPM is 60,000. Rewinding it as 2 50kv motors would require 2 9kw controllers, but it's eRPM would be 30,000 at 100 volts. Maybe there's not enough iron here to make this work well? Am I getting the implications right?
Look at the magnets in this motor. Look at how big the stator is. I bet it has 30% more iron per tooth than the QS motor in the bottom picture. The magnets span 3 stator teeth. Doesn't that make this actually a low tooth count hub? I have no idea how it's wound. Typically 3 side by side teeth are the same phase with the center tooth wound backwards of the outer 2 teeth and the magnets are the same size as the teeth. How does that work on a single magnet with the center tooth wound reverse of the outer 2 teeth? I think it doesn't work at all and is immensely wasteful if done. Maybe all 3 teeth are wound the same direction so they can all present the same magnetic pole to the magnet? If that's the case, then this is a 3 phase, low tooth count motor right now. It has 48 stator teeth and 16 magnets. It has to be wound with 3 side by side teeth in the same phase and all wound the same direction.
It can be done, but why would anyone ever do this in a motor? A single magnet can be made with 3 magnetic domains in it. By why not just make 3 smaller magnets instead and place them side by side like in the below QSmotor? It is more logical that the magnets in this motor are a single magnetic domain. The inner face is a single north pole or a single south pole, not north/south/north on a single magnet face. That, IMHO, would be the only way to make a reverse wound center stator tooth work with a magnet that spans 3 teeth.
This is a multi-domain magnet. Each section on the film is the opposite pole. you are seeing 4 north and 4 south poles here. Hard drive magnets do this too. The magnet is actually 2 side by side magnets with the poles flipped. I was really surprised by a lot of magnets when I got this magnet film!
This is a 4kw QSmotor I have. This clearly has 1 magnet width per stator tooth. What you said about hi tooth count stators totally applies to this motor.