Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[MPaulHolmes]

They go down to a LEM 50, which would be a LEM 25 with a single loop of wire. Its just that I just got done spending like $200 on 6 of those. haha. The LEM 50 has a range of -150Amp to 150Amp. But I don't know if it stays linear through that whole range. -100 to 100 would be a safer bet. It also needs leeway for startup surges not tripping the hardware overcurrent. A LEM 150 might be good. Then, the hardware overcurrent wouldn't trip until +/-300amp (that's the resistor values I picked. For it to trip at double the lem rating). The resolution would be around 128 ticks of the A/D corresponds to 150amp. I think I'll get a couple LEM 50's for testing. Actually, one of the beta testers has a rewound motor for a lower voltage, which would mean a high current anyway, so at least his LEMs aren't a problem. And depending on thingstodo's motor choice, I could get different LEMs for him to suit the motor. I can always use the leftover LEM 300s for other stuff later. Those are what I used in the DC controllers.

I think spread spectrum switching will work really well. It's working in a beta tester's DC controller up in Olympia, WA.

EDIT: That's a good idea about squarifying (I declare that to be a word!) the wires. I have a sheet metal bending machine that I can squish stuff with. Actually, if I squash them flat I bet I could get 3 #6 loops.

[freebeard]

Originally Posted by thingstodo

I agree that this would make an AWESOME drivetrain for an EV. And I like the simple interface - 3 wires in, motion out. Whatever is bolted to this drivetrain will move as commanded.

It is the part I'd been waiting for since I saw that Oztralian Porsche part. I think it will be about matching the rear tire diameter to the aerodynamic drag of the vehicle. And maybe drilling and tapping for external oil flow.

[e*clipse]

I've been mulling over the external oil options for the motor. I have to admit, I don't have any experience with these, but it seemed that Toyota's solution (use the gears as a pump) was very reliable, but maybe not the most effective. I think Tilton makes an external pump, other than that, I'm not familiar with other brands.

It seems some sort of gear pump would be a good start; in fact I've been drawn to the "gearotor" type pumps for very reliable options. This leaves how to power the pump... can anyone see a way to power a pump from an internal PTO? If there was some sort of shaft-driven setup (like IC car engines) running off the motor shaft, power and lubrication would be very reliable. After all, if the motor wasn't turning, the oil pump wouldn't be either.

OTOH, there may be some nearly 100% reliable brushless motors . . for example there are some very interesting racing fuel pumps out there. Perhaps others on this list know of some options?

It seems once the issue of how to circulate the oil is resolved, the rest (of the cooling/lubrication) would be relatively straight forward.

Perhaps it would be possible to tease a little higher max RPM out of the motor with the controller by working with the field weakening and input voltage. Better cooling and lubrication would also help squeeze a bit more performance out. In other words, I think we have some options (that I certainly want to play with) other than just final gearing.

- E*clipse

Originally Posted by freebeard

It is the part I'd been waiting for since I saw that Oztralian Porsche part. I think it will be about matching the rear tire diameter to the aerodynamic drag of the vehicle. And maybe drilling and tapping for external oil flow.

[thingstodo]

Originally Posted by MPaulHolmes

I can only get 1 loop around the lem with #4 or #6 welding cable, so I guess I have to be happy with a "lem 150". Although 8 gauge would work.

For a short and SUPERVISED test, like your 10 second stall test, you may get away with a smaller wire for the short bit of wire you are stringing through your LEM.

I cannot stress enough that this is ONLY FOR A SHORT AND SUPERVISED TEST!

Here's why I think that ...

I have recently done a bit of my own testing - how much current can a #18 wire (copper stranded wire, tinned) take before it melts? Rated 16 amps for chassis wiring (low voltage) according to the table I used. I believe that is a continuous rating.

The answer was quite shocking to me:
- 80 amps (5X rated current), the insulation burned off after 10 or 20 seconds
- 225 amps (14X rated current), the tin coating on the wires melted at about 60 seconds
- I was not able to melt the copper! My setup only went up to 280 amps (17.5X) for a couple of minutes.

The piece of wire under test was about 6 inches long, strung between 2 insulators, sitting on concrete.

The test was a failure. I wanted the wire to act as a fuse, so that during my battery testing I did not have to put big, expensive fuses for each battery connection.

I ended up using cat6 cable (solid core #24, 6 inch length) as a fuse. I was not able to verify the specific current where the #24 failed ... but it was below 225A and that was OK for my battery testing. It was there in case I shorted something and thankfully I did not

[thingstodo]

Originally Posted by e*clipse

The Multimeter is a Fluke 179. If I measure a 1K resistor, I'll get a result like 0.997kOhms. A very low resistance like the motor windings is simply 0.3 Ohms.

OK - when a meter is down around it's least significant digit, the accuracy may not be very good. The resistance is likely between 0.2 and 0.4 ohms.

Regarding carrier frequency, one issue is simply audible noise. One way to avoid an audible whine is to move the carrier frequency above the human hearing frequency range, like 18 kHz or 20 kHz. (probably lower for those of us who went to too many rock concerts...)

Paul had a great discussion about a "moving" carrier frequency on the EV tech list. If done correctly, this can result in a much less annoying variable hiss - type sound. I would definitely say Paul is a much more qualified person to answer those issues.

I was wondering if you knew what Toyota has used as a carrier.

I had a thought about that while watching one of the Star Trek movies ... the low thrum that the sub-woofer shakes the house with when the enterprise is moving away from it's berth .... it would take a bunch of memory and perhaps some code to superimpose such low frequencies over the carrier, but NO ONE would complain that they could not hear my EV![/QUOTE]

[freebeard]

I was thinking if it was matched to my tinnitus, I'd never hear it.

Drive the pump with a sprocket on the CV joint?

[Astro]

Originally Posted by e*clipse

...
One detail that isn't apparent from the cutaway (because it's in the cutaway part) is how the oil moves in the system. It's a pretty important detail, because the motor is cooled by the gearbox oil. Basically, the oil is "pumped" by the big gear connected to the differential between the gear teeth and the gearbox case up into a small holding container. (cut away) The oil then dribbles down by gravity into other containers (cut away) that have holes to dribble oil onto the various bearings and gears. See that opening on the near side of the motor's shaft? The motor shaft is hollow, and oil is pumped (I guess) by the rotating shaft out holes in the shaft, where it sprays over the motor stator coils. That's what cools (or at least distributes the heat) from the motor.

So, if you plan to use this in a stock set-up, you ****have to***** run it with the motor forward of the differential. That's the only way the "oil pump" will work. In my Eclipse, I can do this in the front no problem, but I'm going to have to modify it with an external pump or something in the rear, because these will only fit "backwards."...

I was looking at the pictures of the cutaway housing and the complete housings. I can see how the large gear on the final drive shaft picks up the oil and hurls it up and over towards the intermediate drive shaft. I can also see the scoop/funnel that catches that oil and feeds it into the inside of the motor shaft.
So the problem is that if the housing needs to be mounted backwards due to space resrictions then its normal gear directions are reversed. Essentially the whole thing is driven in reverse. Which means the large gear on the final drive shaft rotates the opposite direction going down into the oil and flicking it forward off the lower edge of the gear. So no oil gets into the funnel bit of the housing and therefore no oil to cool the motor.
Hopefully that is a accurate description of the issue, if not then please ignore the following suggestion.

I was looking at the intermediate shaft and it sits so low compared to the other two shafts that it's gears should be making good contact with the oil. With the motor going in reverse the large gear on the intermediate shaft will now rotate in a direction where it will pick up oil and hurl it up over the top of the gear and forward towards the motor shaft.

Question: Would it be possible to dremmel out a section of the funnel part of the housing so that the oil splashed/thrown from the large gear on the intermediate shaft ended up in the funnel?

Edit: Actually i may have answered my own question. I saw some more photos on eBay from different angles and it doesn't look possible to go from the intermediate gear to the oil collection funnel. Oh well, maybe somebody else can figure a way of getting the oil to move without having to resort to an external pump.

[thingstodo]

Originally Posted by freebeard

I was thinking if it was matched to my tinnitus, I'd never hear it.

It would be tough for anyone else to match the ringing in your ears

Drive the pump with a sprocket on the CV joint?

Chain drive? A few technical issues to solve, but it should work. Is this a prototyping solution or would this be permanent?

[e*clipse]

On the lube issue, perhaps an internal chain?
On old lathes, there used to be chains drooping into the oil pan. The chain itself would carry the oil up to the bearings. That may not be enough oil, but it might work pretty well to run a chain off the motor shaft down to a pump in the oil pan.

On noise, the main issue is a continuous high frequency whine - it's pretty much universally agreed that constant high frequencies are annoying. Starting at 60hz and up.
If the frequency can be lowered and varied over time, people start to **like** it. Look at peoples' reaction to IC engine noise. If the high frequency noise is varied over time, it can be acceptable - I've heard people say they'd like the Jetson's "car" sound. Also, sirens are required at certain events to warn people of the racecar - see the EV class at Pike's Peak. Personally, I find the sirens annoying.
I think it would be a great "hot rod" or "upgrade" for EV's to have a plug-in chip that allowed any sound you want. Jetson's sound? - ok Startreck Enterprise sound? - ok Old school hot-rod? - ok. How fun!

[e*clipse]

Astro - Yes, that's exactly the problem.

Also, regarding the intermediate shaft, I went to my shop and re-assemble the geartrain to get a better look at things. Assumming that the bottom of the oilpan is designed to be level, then the oil drain/fill holes on the gearbox (vs the motor stator) side of the case pretty much define the oil level. If it's like most transmissions, then the oil should be filled up to the bottom of the "fill" hole. When static, The motor's shaft is just out of the oil and the intermediate shaft is submerged. I don't have any idea how much this oil level drops when the vehicle is moving.

There's very little space to put things (like I've suggested) like an internal chain drive or oil pump. It would take some real creativity to somehow fit a motorcycle gearotor pump (about the smallest pump I can think of) directly below the intermediate shaft.

So this leaves three possibilities:
An external pump pulling off the drain, which is right below the geabox-side output shaft. This could be driven in a variety of ways, but the concern I would have is how to protect it from all the dirt and grime that's always in that area.

The second possibility is to use an electric pump, and move the pump to a more protected place. Also, an electric pump could be direction independant, which would be nice if the motor ever needed relocation.

The third possibility is a bit of a longshot. It would require REAL knowledge of how gearpumps work, and the tolerances involved. If the design can be worked out, actually making the parts could be relatively easy. Basically the design calls the motor output gear and the intermediate shaft input gear the "gear pump." A flat plate would be fit between the motor output shaft, the intermediate shaft, and the case. This flat plate would form the gearpump's "input" side, and the would be a strategically placed hole to allow oil to flow into the space where the two gears seperate from each other. The gearbox forms the surfaces that (with the gears) moves the oil. The place just above the intermediate shaft is the high pressure point where the gears mesh. A hole could be cut into the space directly above it, which currently forms the oil reservoir. I'm trying to figure out how to attach that plate to something, yet allow disassembly. That plate might have to stand up to fairly high oil pressures.

I need to learn how to post pics around here. I could post some scribbles that would help illustrate these babbles...

Originally Posted by Astro

I was looking at the pictures of the cutaway housing and the complete housings. I can see how the large gear on the final drive shaft picks up the oil and hurls it up and over towards the intermediate drive shaft. I can also see the scoop/funnel that catches that oil and feeds it into the inside of the motor shaft.
So the problem is that if the housing needs to be mounted backwards due to space resrictions then its normal gear directions are reversed. Essentially the whole thing is driven in reverse. Which means the large gear on the final drive shaft rotates the opposite direction going down into the oil and flicking it forward off the lower edge of the gear. So no oil gets into the funnel bit of the housing and therefore no oil to cool the motor.
Hopefully that is a accurate description of the issue, if not then please ignore the following suggestion.

I was looking at the intermediate shaft and it sits so low compared to the other two shafts that it's gears should be making good contact with the oil. With the motor going in reverse the large gear on the intermediate shaft will now rotate in a direction where it will pick up oil and hurl it up over the top of the gear and forward towards the motor shaft.

Question: Would it be possible to dremmel out a section of the funnel part of the housing so that the oil splashed/thrown from the large gear on the intermediate shaft ended up in the funnel?

Edit: Actually i may have answered my own question. I saw some more photos on eBay from different angles and it doesn't look possible to go from the intermediate gear to the oil collection funnel. Oh well, maybe somebody else can figure a way of getting the oil to move without having to resort to an external pump.