Weber and Coulomb's MX-5

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woody
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Post by woody »

Travers - the mx5 will have a clutch, but yes, I'm not sure how that's going to work.
weber wrote: The amount of current imbalance between the windings looks worrying, if that's what this means. And it doesn't say (OK) next to them.
5 tests and 5 "Ok"s looks fine to me. I don't know if 8% variation in winding current is good or bad, but ABB think it's "(Ok)"
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Post by coulomb »

I think it's one functional test, hence only one OK. Presumably it's supplied in star configuration, and they applied nominally 400 V to the motor. For whatever reason, presumably something to do with their test setup, they decided to only give it about a 35% load (hence the low ~15 A current draw). They are reporting the voltage because otherwise their exact mains voltage might have some effect on the test, so the voltage isn't an output. (Unless they tested it as a generator, but then the speed would not be an output either).
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Post by Johny »

I think they state the voltage because they can not control it totally.
The current looks like the no-load current.

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Post by coulomb »

Johny wrote: The current looks like the no-load current.

I don't think so. Full load power factor is 0.88, so it will use (1-0.88) x 41 A = 5 A (per phase) magnetising current at full load. So surely ~15 A per phase is with a significant load.

Also, with no load, I would expect the speed to be closer to 3000 RPM; 2900 is most of the way from 3000 to the full load speed of 2895, so I'd say it's loaded.

It would have been nice if they specified the mechanical load on the test ticket.

Edit: this is bad maths. See below.
Last edited by coulomb on Wed, 27 Jan 2010, 06:28, edited 1 time in total.
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Post by Johny »

My reasoning is based on a typical 11kW drawing around 7 Amps per phase no load. Fair enough about RPM though.

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Post by weber »

Hi Travers. What you say is correct, and as Woody mentioned, we are keeping the clutch. Part of the reason is that we want unskilled people who are used to driving a (manual) ICE vehicle to be able to hop in and drive this vehicle safely first time.

You don't really need to have a clutch to have an idle mode for power steering and aircon. You just need to be able to put it in neutral. But the clutch makes it a lot more convenient.

Our controller, an industrial VF drive, is highly programmable, with lots of digital inputs. The gearbox already tells us when it's in neutral, and we can put a switch on the clutch and monitor the aircon's magnetic clutch. So we should be able to implement idle mode any way we want.

We can arrange it so if it is in gear and the clutch is engaged and there is no accellerator, then the motor will do zero revs. Too bad about the P/S or A/C. Then you can just hit the accellerator to go.

But if you're at the lights with the clutch held in, or if you're parked and in neutral, then it can idle to run the A/C if it's on. We could add a switch to say if we want P/S in cases where the A/C is off.

This is all theory. Anyone forsee any problems with these ideas?
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Post by weber »

woody wrote:5 tests and 5 "Ok"s looks fine to me.
Good point.
I don't know if 8% variation in winding current is good or bad, but ABB think it's "(Ok)"

Right. But you'd think they would have miscounted a turn or something to be that far out, and you'd think it would result in significant torque harmonics. Maybe it's just as well we will have a flywheel, although somewhat lightened.
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Post by woody »

weber wrote:Anyone forsee any problems with these ideas?
I've been driving ancient (1960s) cars as my primary transport since I was 18. None of these have power steering. The only time I've wanted power steering is when you are stopped on bitumen. This is 90% of the time when you are reverse parking.

For you this will mean you'll slip the clutch as per normal manual car reverse parking. I'd like a "Parking" mode or button which would tell the controller to idle at 800rpm with just enough torque to spin the PS pump. Dropping the clutch or hitting the brake would stall.

I've also driven a few cars with broken power steering. This is horrible - I'm not a body builder, but I'm no lightweight - a VR commodore with no PS fluid is back breaking labour to steer even when moving. The ratios are all different.

I would try an MX-5 with manual steering and see if you can live with it, I find you can usually move slowly when parking, which makes the steering light.

cheers,
Woody
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Post by weber »

You may remember how we ordered our motor with foot and flange, but it was delivered without the flange. Then they sent us a flanged end cover and we thought our troubles were over...

See if you can spot what's wrong in this picture, when I tell you that the calipers are set to the diameter of the bearing above them.

Image
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Post by Johny »

Oh dear!

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Post by weber »

For those curious about how this very-powerful-for-its-size 2-pole 132-frame (240 V delta) motor is wound, you can see in these photos that somewhere between 6 and 8 parallel wires go to each terminal.

Image

Image
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Post by coulomb »

In the photo above, the brown, red. and yellow cambric tubes go right up to the motor terminals. They have about 6 copper wires in each; it looks like each coil is in parallel already, making rewiring for lower voltage rather unlikely. Also, the wiring in this motor is absolutely packed.

The first clue that something was wrong about the flange came when we realised that the new flange has 3 bolt holes to hold the bearing in place; the old one had 4. The bolts thread into the plate with the four dimples immediately behind the bearing. The bearing is presumably a press fit to the shaft, so we were not keen on removing it and replacing it with the provided plate with 3 tapped holes.

The flange is amazingly light; it feels like it would weigh 250 g.
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Post by acmotor »

Wow, you got your money's worth in copper !!
Shoehorned hand winding. Nice bit of kit !
Those ABB ali casings are so much nicer than the old cast iron type.
2 pole motors have such full looking stator winding ends. What's the term for that wiring area ?
More pics please.... pull the rotor out too !
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Post by weber »

Here you can see the Coulomb & Weber cover puller (pat pend) in action. A scissor jack on the end of the shaft with wires going to the 4 cover bolt holes. It works a treat provided you don't plan to use the cover again. Image

Well it worked a treat at first. But we had forgotten something. It's out of sight in this photo. Out of sight out of mind you might say.

Image

We forgot the key was still in the shaft. Duh.
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Post by weber »

We also removed the plastic fan from the other end, where we hope to mount the pulley to drive the aircon and power steering (and maybe even alternator). The pat pend puller didn't work here, nor did any of the other non-destructive methods we tried.

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Post by acmotor »

Yep, the two retangular holes are for a two arm puller. Image
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Post by woody »

The ABB drawings for 132 SM B34 or B35 foot + flange show a rear output shaft of 70mm (80mm for the front) - did they forget this bit too? :-(
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Post by weber »

More photos you say. Here you go.

Image Image

Image Image

Let me know if you want higher resolution versions of any photos, or of particular regions in any photos.

Pull the rotor out you say. Well we've long ago packed up for the day, and we didn't do it because those bearing are a very tight fit in the end covers and we didn't fancy pulling another one if we didn't have to.

Can you make a case for what we might all learn from such an excercise?
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Post by weber »

woody wrote: The ABB drawings for 132 SM B34 or B35 foot + flange show a rear output shaft of 70mm (80mm for the front) - did they forget this bit too? :-(

We weren't expecting one and wouldn't have wanted it that long anyway. We don't have much room in which to mount the pulley (and shaft encoder). There's an anti-sway bar in the way.

I'm pretty sure an actual output shaft at the fan end, as opposed to just the stumpy fan shaft, is a variation you have to order specifically.

We have to be careful about the side-load from the belts, since the bearing at the fan end is not as strong as the one at the drive end. This is one reason I favour keeping the alternator. Its belt goes to the opposite side and might counterbalance the side-load of the aircon/power-steering belt a little.

[Edit: Spelling]
Last edited by weber on Tue, 26 Jan 2010, 18:20, edited 1 time in total.
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Post by weber »

One more photo. This shows the insides of the unflanged cover we were wrongly supplied with, and the flanged cover they sent to replace it. At least the unflanged one has the right sized (90 mm) bearing socket. The flanged one can only fit an 80 mm bearing. You can see the 4 hole vs. 3 hole bearing retainers in an earlier photo, and the 4 vs. 3 bolt holes for them here.

Image
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Post by coulomb »

coulomb wrote: I don't think so. Full load power factor is 0.88, so it will use (1-0.88) x 41 A = 5 A (per phase) magnetising current at full load. So surely ~15 A per phase is with a significant load.

Ahem. I was being lazy and ignored the vectorial subtraction. In fact it makes a lot of difference.

The proportion of reactive current will be sqrt(1 - (0.88)^2) = 0.475, so the full load reactive current is in fact about 0.475 * 41 = 19.5 A (per phase).

So ~15 A per phase could be the no-load current, and per Johny's observation, probably is. The RPM may not have been measured all that accurately, or rounded to the nearest 100 RPM.
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Post by woody »

weber wrote:
woody wrote: The ABB drawings for 132 SM B34 or B35 foot + flange show a rear output shaft of 70mm (80mm for the front) - did they forget this bit too? :-(

We weren't expecting one and wouldn't have wanted it that long anyway. We don't have much room in which to mount the pulley (and shaft encoder). There's an anti-sway bar in the way.

I'm pretty sure an actual output shaft at the fan end, as opposed to just the stumpy fan shaft, is a variation you have to order specifically.
Option number 69 is a shaft extension at both ends. I should've guessed rather than looked it up.

Cortina doesn't have anything to drive off the front end anyway, except an encoder. The current fan belt is crankshaft, water pump, generator (no - not alternator).
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Post by Nevilleh »

It looks really interesting and I'm sure that there's a lot of us eagerly awaiting some results!
If you really need power steering, why not fit an electric pump? I used one from a Toyota MR2 and it works really well. Built a little switch-mode controller to drop the volts down to 6 or so and it draws about 5A from the 12V battery. It cost me more to get the hydraulic fittings made to connect it up than I paid for the pump!

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Post by weber »

Nevilleh wrote:If you really need power steering, why not fit an electric pump? I used one from a Toyota MR2 and it works really well. Built a little switch-mode controller to drop the volts down to 6 or so and it draws about 5A from the 12V battery. It cost me more to get the hydraulic fittings made to connect it up than I paid for the pump!

To eliminate the need for belt drive we'd have to replace not only the P/S pump, but also the aircon compressor. That gets very expensive. Take a look at the price of compressor and controller from EVWorks.

So if we keep the belt-drive aircon, we might as well keep the belt-drive power steering and alternator.

I had an interesting call from Jeff Owen this morning. Jeff, with his converted Honda City, is a Brisbane EVer from way back. He's turned up to so many of our EV days and helped us out with so many great mechanical ideas that I think we might have to make him an honorary SI unit. I think we should call him "Newton". Image

Anyway, he suggested an arrangment that would solve two problems in one fell swoop. One problem being the mounting of the PS pump, aircon compressor and alternator on the front (non-drive end, fan end) of the motor for belt drive, and the other being the solid attachment of the gearbox to the motor.

The latter is a problem because in an MX-5 there is no gearbox mount to the chassis. The back of the gearbox is connected to the front of the diff with a large aluminium alloy beam called the Power Plant Frame (or PPF). Then the entire power train becomes a rigid assembly hung from 4 rubber mounts - the two engine mounts, and two diff mounts (the diff has "wings").

Now that we've seen the how light-weight the flange of the induction motor is, and how it's held to the motor case with 4 piddly little M6 bolts threaded into aluminium, and compared it to the ten or so M12 high tensile bolts that held the gearbox to the original ICE, we know this flange is only good for precision alignment, not for supporting the weight and g-forces on the gearbox.

Jeff's suggestion was a thick metal plate at the front (fan end) of the motor with say four M12 high tensile rods (threaded both ends) going up between the motor fins and passing through the holes in the motor flange (and any spacer ring) before being bolted through the gearbox adapter plate. So the whole cylindrical motor casing is in compression.

This front plate would also have suitable extensions on which to mount the aircon compressor etc.
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Post by Nevilleh »

Fair enough, I plan on using the original air-con compressor and have fitted the drive pulley for it although I haven't had a go at the mounting bracket yet. It has to be adjustable to get the belt tension right, of course. To fit the original power steering pump as well was a bit difficult and I don't have a clutch so I can't run the motors when stopped. Which would have meant no power steering when trying to park. I don't mind not running the air-con when stopped as there should be enough reserve to cope with short stops. I decided not to use the alternator for the same reasons and have modified a standard 20A battery charger to run from my 150V dc source to keep the 12v system running.

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