electric motor tech

There are a few pictures at http://priuschat.com/forums/gen-iii...79-does-2010-drive-system-work-backwards.html. I have some higher res (8 mp) ones that I took at Prius Connection SF and if you let met know of a site where I can upload (and you can view) unreduced photos for free, let me know. (Need a pro account on Flickr for that.)

There are a few details in the PDF at http://priuschat.com/forums/gen-iii-2010-prius-main-forum/60002-prius-technology-video.html.

I don't see any brushes and think that MG1 and MG2 on every generation of Prius have always been brushless. There are plenty of brushless motors out there. Go look at any fan.

There's some more info if you search for "trans" at Prius links. Most of it is for previous gens though.

I don't know of any maintenance needed on the power split device other than fluid changes.

 

As far as I am aware, all hybrid vehicles use 3 phase ac induction motors that are brushless. The bearings have not been an issue in the 10 years they have been on the road. Most problems have been related to shorted stator windings.

 

There are no brushes. The Prius uses a permanent magnet AC electric motor. An A/C motor uses many coils on the outer ring of the motor to spin a magnet connected to a drive shaft. A microprocessor sends energy to each coil one after another that makes the drive shaft spin one way or the other.

This makes it easy to spin the motor both ways and the only parts that can wear out are the bearings to hold the drive shaft in place. The real name of the drive shaft with the magnetics is a rotor. Here is a good link that shows the basics.

AC motors

 

It's not an inductive AC motor, per se. Inductive AC motors use induction to cause current in the rotor. The rotor current makes it an electromagnet that interacts with the stator electromagnets.

The Prius uses permanent magnets in the rotor, so there are no rotor windings to induce current in. The stator gets 3-phase AC power from the invertor (or generates 3-phase AC power) at varying frequencies. Induction AC motors have low starting torque (from 0-speed), so they'd be a bad idea anyway. Since no current is supplied to the rotor, there are no brushes. The only parts to wear out are the bearings.

In the terms of the motor business, it's a permanent magnet AC motor powered by a variable frequency drive. The amazing thing is how they got two VFD's (totaling over 100 hp) in a box the size of a 12-pack.

 

Wouldn't permanent magnets looses it magnetism over time?

Well, come to think of it. Hi-fi speakers use permanent magnets too. The set of speakers in my family room was purchased almost 30 years ago and they still sound fantastic!

I'm just wondering how can permanent magnets last so long? When a magnet attracts and moves another metallic object, isn't it actually having "work done" and erergy used up from it? How can permanent magnets seemingly last forever? Isn't this against the law of physics?

 

Adding to this, the type of motor used in the Prius is a hybrid synchronous permanent magnet motor. The "hybrid" part of the name means that the motor works as both a permanent magnet motor and as an induction motor. At lower power levels the permanent magnet dominates, providing more efficiency. At higher power levels induction becomes more important. This allows for higher power levels when needed, while still maintaining good efficiency for most driving.

No, it doesn't violate any physical laws. Think about this for a minute. Anything you pull away from a magnet had to be put close to the magnet in the first place. The object being pulled gives up potential energy as it is lowered into the magnet. It gains potential energy as it is pulled away. The gains and losses are exactly equal.

Some permanent magnets do lose magnetism over time. This is not because of conservation of energy, but because of physical changes in the material. For example, heating many magnetic materials will allow their particles to twist and cancel out the internal magnetic fields.

Tom

 

So a permanent magnet is like a mini planet with gravitational fields, but it's not spherical because of the opposite poles. Thanks.

 

On a lighter note, are "Chic magnets" some kind of permanent magnets, and their magnetism deteriates over timer too?

 

It could be spherical, but it's not required. Likewise planets are only spherical because of their large mass. With enough mass, gravitational pull overcomes the physical strength of a planet's material, and it is pulled into a sphere. Small planetoid objects, such as asteroids, are often lumpy and irregular, lacking enough mass to squish themselves into a sphere.

Tom

 

No I mean the imaginery lines of gravitaional fields are spherical cause they are all pointing towards the centre of gravity of the object, regardless of the shape of the object; while the lines of magnetic fields are not spherical, somewhat butterfly like (looking at a 2D point of view) going from north pole to south pole of the magnet, even if the physical shape of the magnet is a sphere.

 

Ah, gotcha. Gravity, as far as we know, is a monopole. That makes for some weird things. Magnets, as you point out, have two poles, so we get looping flux lines.

Tom

 

The usual published half life for neodymium iron boron alloy magnets is about 2000 years. Each year the magnet loses about .035% of it's remaining magnetism.

-mort

 

My Prius might need new brakes by then.

Tom

 

Years ago I was dreaming of designing my own EV/hybrid car. My thinking was that the ICE charges the battery and the motors drive the wheels, like the Chevy volt.

Except that all the 4 wheels have MG's mounted directly on them. So 4 wheel drive all the time, no gearing friction loses. All drive by wire. Full size spare wheel with spare MG mounted.

And one more crazy concept: no steering mechanism other than electronic control of differential speed of left and right wheels. You turn right by making the left wheels run faster than the right ones, and vice versa. You can even make the car spin around on the spot with left wheels forward and right wheels reverse.

Engine can be very small like a 1L atkinson cycle, running all by it's own will even when parked. All it does is charge the batteries.

The batteries are modular rectangular bars lying in a sub-floor between the ground and the cabin, all shaped like long gold bars sliding in from the side after flipping open a long but narrow door. You can even plug it in at night.

This was my idea back in the 90's before the Prius was born.
Am I crazy or is this feasible?

 

You get most of the benefits from a motor in each of the front wheels and and one driving the rear axle. Porsche uses this configuration in their hybrid. You can of course use 4 mgs instead of 3. In small airplanes you turn by braking on one wheel which rotates the other on it. You would want to change the tire angles though otherwise you would have great tire wear. You don't want to mount the mg to the wheel but on the car, the brake should be here as well. This makes it much easier and lighter to change a tire and removes the hassle of wires etc. I don't think steer by wire is legal in the us, but there have been prototypes built.

Lithium polymer batteries can be thin and conform to just about any shape. Putting them in a sub floor and under seats seems perfectly logical. You will want to have some sort of air or liquid cooling.

You probably want to turbocharge and direct inject that motor. Ford will soon produce a 3cylinder 1L DI turbo that can produce 120hp. Nissan will soon produce a 3 cylinder 1.2L DI miller cycle (atkinson supercharged) engine. So the small light engines for your generators are there. Even the 3 cylinder 1L atkinson cycle engine from the original insight might meet your requirements.

 

Ok. I put up the few pics I took at Prius Connection SF in March 2009 at Picasa Web Albums - cwerdna - Prius Connect.... It includes some pics of the PSD. We got to drive the 2010 Prius a few months before became available to the public. Big thanks to Toyota!

Enjoy!

 

It is called Interior Permanent Magnet (IPM) motor.
High-efficiency IPM motor | Energy-saving technology of Daikin | Daikin Industries

Ken@Japan

 

Thanks ken. So its partially synchronous and partially induction? Do you know how much mg2 weighs and what the efficiency is?