2 Speed Gearbox

[coulomb]

Incidentally, this system is actually how the Prius transmission works, but instead of a CVT adjusting the diff "ratio" is has the two motor / generators - which gives it a soft connection and allows more flexibility.

Right. Any time you think you need to "waste" power, put a generator there instead and regen back into the pack. The downside is the extra motor and electronics that is needed. So a Prius actually has a fair bit: a 50 kW and 30 kW (Gen II) "AC" controller (switched DC?), and a 20-25 kW bidirectional boost converter as well (200 V battery to/from the 500 V DC bus).

[Johny]

The differential planetary gears were not designed to take full power nor run at speed for any length of time. The bearings/bushes will burn out. Ask some of the burn out boys which part of the diff blows up!

[EV2Go]

Only pussies run planetary gears in diff, it a full spool or its nothing! Even mini spools are for wimps

[Johny]

Sparky, I really think you should check out whether a 2 pole can be rewound to a 4 pole then consider a 380/200 or 415/240 volt rewind (or other optimised voltage based on simulations we can run). It gets around all your problems.

[woody]

I think a 4 pole rewinding would result in the same torque, so you'd have a 7.5kW 4 pole. (But it's worth asking anyway)

With a 2 pole 15kW, 400V/690V you already have the same at as 4 pole 7.5kW 200V/346V. I don't think you'll be able to direct drive except maybe through the transfer case.

[Johny]

woody, do you think that the rotor is different? (I don't know - just asking)

[Johny]

Just checking back. A dahlander wound motor gave noticably less torque than a fixed pole motor but nothing like half (maybe 10% to 25% less).

The data on dahlander wound motors suggest that the rotor is the same for a 2 or 4 pole. So a rewind of a 15kW from 2 to 4 pole (assuming it's possible without massive change to the stator laminations) should result in twice the torque.

Go the lower voltage and he has acmotor's power + 20%. He has the VFD to reasonably support it.

[woody]

Hmm, trying to back myself up here...

The 2 types of dahlanders - constant torque + fan

Both switch from series to parallel and star to delta at the same time as doubling or halving the poles.



I think constant torque dahlander is:
Slow: 4 pole, series, delta
Fast: 2 pole, parallel, star
Which gives more torque in slow than fast by about 50%.

Fan dahlander must be:
Slow: 4 pole, series, star
Fast: 2 pole, parallel, delta
Gives heaps more torque in fast (about 3.5 times)

From a simplistic level, to get more torque, you need more magnetism.

As it is, a single speed motor is beginning to saturate when running at nameplate V/F ratio. So you are getting the maximum efficient torque.

Any pole count changing and rewinding is not going to change the stator magnetic saturation point, it will just change the V & F to get there.

The dahlanders are just undermagnetising in their low torque config. Handy if you haven't got a VFD

[Johny]

I understand where you are going now. I remember now when we did the whole dahlander thing.

Ok. So where does that leave us with rewinding a 2 pole to a 4 pole?
I think someone with a friendly rewinder - someone who has just given a rewinder some money (hint), should dive in on this and find out.

"Can a 2 pole 15kW motor be rewound (easily) to a 4 pole and will it give twice the torque at half the (old) speed?".

I'll stop hijacking yet another thread now...

[coulomb]

So a rewind of a 15kW from 2 to 4 pole (assuming it's possible without massive change to the stator laminations) should result in twice the torque.

Interesting. So that possibly explains why 4-pole motors are generally better value than 2-pole motors of about the same physical size; they've "already rewound" for 4-pole for you.

So then why aren't 6 and 8 pole motors even better I wonder? There must be something about 4 poles (perhaps like 3 phases) that is inherently more efficient somehow. Or perhaps it's something as mundane as not being able to fit the copper in for the extra phases.

If it's just a matter of not having an industrial application, well 16-pole (!) motors would be ideal for direct-to-wheel drive (like a 4-pole motor with a 4:1 reduction built-in). Of course, you'd need something to allow cornering etc. But two to four 16-pole motors with 2-4 smaller controllers (at least the back ends of the controllers) would eliminate all gearing. The one front end could calculate what to tell the four back ends to do to get the front to back torque (including dynamic braking) and steering right.

[woody]

I think you're getting away from reality here - a 15kW 4 pole has twice the torque of a 15kW 2 pole, but it's much bigger and heavier. It's just 15kW @ 1/2 the speed is twice the torque.
Looking at the catalogue motors, the breakdown torque per kg is roughly constant 3-4Nm/kg for Ali framed across all industrial induction motors, independant of pole count...

[Squiggles]

Only pussies run planetary gears in diff, it a full spool or its nothing! Even mini spools are for wimps

I take it you don't go around corners then!

[Johny]

Huh?

15kW ABB 2 pole 3GAA 131 316-••E, Torque 49.4, Tmax/Tn = 4.0. 81kg, 2900 RPM

15kW ABB 4 pole 3GAA 132 316-••E, Torque 97.8, Tmax/Tn = 4.0. 92kg, 1465 RPM

The 4 pole spins half as fast as the 2 pole but has twice the torque.
Are we on the same page woody?
Am I losing it?

[EV2Go]

a crap load of power takes care of that (just not tyre friendly).

Used to known a few people that ran spools and mini spools on the street in the past. Tends to feather the tyres badly, but generally they have a limited life span anyway with the sort of cars they were in.

I'm talking the sort of cars where the blower hangs out the bonnet.

[Squiggles]

And the families of the innocent people they murder never recover.

[Squiggles]

Huh?

15kW ABB 2 pole 3GAA 131 316-••E, Torque 49.4, Tmax/Tn = 4.0. 81kg, 2900 RPM

15kW ABB 4 pole 3GAA 132 316-••E, Torque 97.8, Tmax/Tn = 4.0. 92kg, 1465 RPM

The 4 pole spins half as fast as the 2 pole but has twice the torque.
Are we on the same page woody?
Am I losing it?

Isn't twice the poles = twice the torque fairly logical. Twice the magnets, twice the flux.....

[Johny]

Isn't twice the poles = twice the torque fairly logical. Twice the magnets, twice the flux.....

Yes, no problem there. Just confused as to why woody says

....
Looking at the catalogue motors, the breakdown torque per kg is roughly constant 3-4Nm/kg for Ali framed across all industrial induction motors, independant of pole count...

[Squiggles]

Isn't twice the poles = twice the torque fairly logical. Twice the magnets, twice the flux.....

Yes, no problem there. Just confused as to why woody says

....
Looking at the catalogue motors, the breakdown torque per kg is roughly constant 3-4Nm/kg for Ali framed across all industrial induction motors, independant of pole count...

Twice the poles twice the mass....surely not!

[Sparky Brother]

[quote="EV2Go"] a crap load of power takes care of that (just not tyre friendly).

I think back there in the TAFE you slept over when they were teaching the subject on the priciples of the Differential action. Yes the real experts will agree there are losses in any gearing set but let`s be serious whatever power doesn`t get transferred through the left wheel gives a good result at the right wheel.

I think the spools could be a step back to the Dark Ages

[EV2Go]

Yeah I’m only taking the piss , most street cars will get away with a well set up limo, very few street car (or even pseudo race / street cars) aren't going to break a quality limo. While it’s not impossible they have come a long way in the last 20 years.

[woody]

Unhijacking - the 2 pole / 4 pole discussion is over here...

[Speedily]

maybe a lenco would work lenco

[Johny]

They look expensive

[Speedily]

You get what you pay for, ebay or or 3speed

[EV2Go]

Seems the hunt is back on... going with 3.10 diff gears and 16" rims I think I am going to need a second gear for around town.