RX400H transaxle

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Post by coulomb » Tue, 05 Jun 2012, 17:01

T2 wrote: Although I have rejected the idea of a Prius electric-only conversion in the past it was mainly because the electronic interface is not too constructor friendly, voltagewise that is. Then recently, I realized that a donor Prius may in fact bring something to the table after all if the constructor is prepared to discard the two motors, MG1 and MG2, together with their electronics package. A technology you cannot master is a liability not an advantage.

In essence the engine and then MG1 need to be removed first up.
Next, the planet carrier/gear cage has to be mechanically restrained somehow so that it is prevented from rotating relative to the chassis.
An induction motor as specified should then be mated into the sun gear of the HSD planetary in place of MG1.

Doing this enables the HSD planetary to deliver a reduction ratio between the 30t sun gear and 78t ring gear of 2.6 : 1.
The ring gear of the HSD couples to the front wheel axle through a conventional geartrain and differential with a cumulative ratio of 4.11 (PRIUS MY2004-9) Combined with the HSD planetary ratio this gives an overall ratio of 10.7 : 1 which is in the ballpark for a non compromised design.
Interesting. In the above, you don't mention removing MG2. Maybe it could be left there, and the inverter and boost converter retained, so that MG2 could be used as a 20 kW boost motor? Or maybe used mainly for regen, and a series DC could be used as the traction motor to reduce costs. One that would handle a ~ 220 VDC nominal pack would be good.

Though it's a bit of a waste of weight to have a 50 kW capable motor only delivering 20 kW (or maybe 25 kW, the limit of the boost converter).

Also, I suspect that it won't be all that convenient to connect a large motor where MG1 was, but I haven't considered the details.
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Post by T2 » Thu, 07 Jun 2012, 17:49


- PlanB   I don't have the where with all to rejig Prius transmissions,
- Coulomb Also, I suspect that it won't be all that convenient to connect a large motor where MG1 was, but I haven't considered the details.

The general consensus is fitting the motor could be tricky - but isn't the adapter plate a problem elsewhere with all constructors ?

But in this case you have exactly the ratio you need with the guarantee that it is built to accept 10,000rpm most other gearboxes will have a problem with that.

- Coulomb you don't mention removing MG2. Maybe it could be left there]

    I totally agree.    One thing more - either the resolver on MG2 or the induced voltage on MG2 stator could be used as a position reference for the induction motor. Not saying that absolute position is necessary just incremental movement so that actual rotor slip can be determined by the controller.

Coulomb, BTW before we go any further may I remind you that the following comes from your idea that I picked up from your Nov 14th 2011 post on the "how to convert a hybrid" May be I should repost this to that particular Topic ?

Now let me run you through a typical design the way I would do it.

I've been exploring what the Wave-Sculptor could do for us here assuming we can supply 120Vdc at 383 Amps which would be using 100A modules at the 4C rate. This supply would allow the W- S to supply a max AC voltage of 75Vac by my calculation ignoring onstate voltage losses.

We require 220Hz at this point so the motor will be wound for 75/220 or 0.33V/Hz.

Now returning to the world of 60Hz 1800 rpm to which we have become so indoctrinated.

At 60Hz our (0.33V/Hz) motor will require 60 times 0.33 equals 20Vac on its terminals

Let us assume our motor's breakdown torque (BD) is 300% Full Load Current and equals the absolute maximum phase current the W-S can supply i.e. 300 Amps. So the english of which is, we need a motor which has most of the time a 100Amp FLC rating.

Standard rating for motors is to withstand a max 40 deg C ambient. That's mighty generous for the ambient temperatures where some of us live, I personally don't believe in buying any more motor than I can get away with, particularly when I am picking up the tab.    

Still in the real world of 60Hz 1800 rpm, power of motor needs to be root3 times 20volts times 100 amps = 3.5Kw (5HP)

I perused Marathon Electric's website for their 1800rpm 60Hz Inverter/duty motors - and was steered towards their Black Max range.

Turns out the 3.5Kw comes in a 184 Frame size weighing in at 125lbs and rated at 14.9lbs-ft or 45 lbs-ft (60N-m) with 300% overcurrent.

Interestingly I see that the BD torque reaches out to 470% where the motor allegedly can supply 70lbs-ft but not unfortunately with the W-S and a 0.33V/Hz motor. And for that matter because of power factor limitations even the 45lbs-ft may be hard to attain. Not that I'd be too concerned because even 60N-m at 6600rpm is 41.5Kw (55.6Hp).

How did 5Hp become 55.6Hp ? Well that's what high rpms and overcurrent will do, oh and rewinding for a V/Hz of 0.33 in place of Marathon's 7.6 (460v/60hz).

Will a 5Hp motor producing 10Hp cruising @ 60MPH burn out ? Well doing it the easy way 10Hp represents 62.5 amps of battery current at 120Vdc.

Didn't our rewind specify 100 amps FLC ?    You tell me.
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Post by Tritium_James » Thu, 07 Jun 2012, 19:27

I've said this before, but here it is again: breakdown torque is *irrelevant* when you're running from a VFD. For example, the SEW motor we have extensive test data on (DRE132MC4) is listed with a nominal torque of 48.7Nm, and a breakdown torque ratio of 3.2.

But we know from dyno testing that we can get 240Nm out of it for a couple of minutes, which is a ratio of 4.9. And that's with the controller 300Arms being the limiting factor, there's no sign that the motor is approaching any significant limit at that point.

So I think you'll find you can push things even further than you expect...

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Post by T2 » Fri, 08 Jun 2012, 08:34

breakdown torque is *irrelevant* when you're running from a VFD.

Unfortunately that torque value is the only figure that is publicly available to provide an indication of the outer reaches of the performance envelope.

As you are aware for automotive designs we need that overcurrent information more than most because of the desirability for 500% overcurrent during short term acceleration.

Maybe what we need from the motor manufacturer is a 30 sec current/torque rating along with a thermal time constant. Then maybe results similar to your private dyno tests could enter the picture.

Certainly we need to get the story out there so that constructors can be saved the expense of over engineered systems at least in the motor department.



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Post by T2 » Fri, 08 Jun 2012, 13:42

- T_J
I went on the SEW EURODRIVE website this afternoon to examine the DRE 132MC4 specs since you mentioned it. I realize this motor is intended for another application but I was pretty sure you wouldn't have it in stock form either.
For the benefit of other readers who may be interested this motor is rated 7.5 Kw 400Vac 50Hz 4 pole 14.8 Amps.

However the motor that was on your dyno took 500% overcurrent within the 300Amp drive limitation. So I guess we can assume this particular machine has a nominal FLC of 60 Amps.

Since this is four times the FLC of the standard 400Vac motor as noted above, I assume you have had the motor rewound for 100Vac 50Hz ?

Even so, this motor would be unsuitable with a V/Hz of 2.0 for the Prius' MG1 replacement, as this value is six times larger than optimal, that's assuming it was anticipated for 120Vdc operation.
Even the use of a 360Vdc supply would still only place base speed at around 3300 rpm which is OK for a manual transmission but in the case of the Prius transaxle this corresponds to a speed of approximately 20mph which is rather low and of course a compromised power/speed envelope is something one wants to avoid. Doesn't one ? !! Excuse the levity but I've been trying to get this post out for three hours.

For that reason, T_J, I was wondering if you have had any fractional V/Hz machines running on the W-S ?
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Post by Tritium_James » Fri, 08 Jun 2012, 16:28

Yes, we get it from the factory wound for 100V - it's a standard configuration for the Japanese market I think.

There's certainly nothing off the shelf wound at lower voltages than this, the 100V/50Hz was the lowest option SEW offered.

Well, base speed might be low, but you'd be getting lots of torque up to 20mph! :)

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Post by T2 » Sat, 09 Jun 2012, 11:16

Well, base speed might be low, but you'd be getting lots of torque up to 20mph! :)
but that's only IF you run from 360Vdc.

Which I interpret to the answer of my original question as a NO.

However some of your target audience, and that includes myself sitting on the fence right now, may not wish to be saddled with the extra labor of making connections to 3 times the number of cells and installing the battery management system that would also be 3 times the cost and complexity than if we were just dealing with a lesser 120Vdc system. Any insistence on voltages above that may turn out to be a barrier to entry for this particular market segment and while I accept that there are those out there with the money, time and ability to run high voltage schemes I don't believe they are the norm.

OTOH I have come to realize, by doing much reading around these past years of other peoples' experiences with alternative equipment, that a 300AMP W-S drive is still a viable proposition at its price point even when considered for operation at only one third of its design input voltage.
I believe there will be numbers of NHW11 Prius vehicles becoming available soon which would be ripe for conversion to full electric. It's possible that they would set a price/performance not achievable elsewhere using a W-S 300Amp drive plus a 120Vdc supply in conjunction with a 3.5Kw motor wound for 0.33V/Hz as I have been stipulating.
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Post by antiscab » Sat, 09 Jun 2012, 21:22

T2 wrote: Well, base speed might be low, but you'd be getting lots of torque up to 20mph! :)
but that's only IF you run from 360Vdc.

*snip*

I believe there will be numbers of NHW11 Prius vehicles becoming available soon which would be ripe for conversion to full electric. It's possible that they would set a price/performance not achievable elsewhere using a W-S 300Amp drive plus a 120Vdc supply in conjunction with a 3.5Kw motor wound for 0.33V/Hz as I have been stipulating.


A NHW11 prius won't work without a battery voltage around 300V.
That is, the transmission won't work and nor will the original DC-DC.

If you are going to the trouble of changing the transmission and all the other hybrid related parts, you are far better going with a toyota echo, which is essentially the same body.

If you are starting out with a hybrid, going AC is probably a waste of time, as the transmission is already capable of doing regen.

There are plenty of DC motors and controllers that do 300v nominal

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Post by T2 » Sun, 10 Jun 2012, 09:20

I am going to move my posts to the Technical and Conversion area "How to convert a Hybrid" discussion

Originally PlanB queried "why they went for a 650v winding on a 288v battery pack" and I wanted to make him aware of the Upconverter which is located in the (PEM) power electronics module together with three other motor inverters. Its purpose is to significantly extend the power/speed range of the HSD system.
It just so happens that if you choose the right V/Hz for an induction motor you can practically achieve the same thing without one.
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Post by Tritium_James » Sun, 10 Jun 2012, 16:11

T2 wrote:It just so happens that if you choose the right V/Hz for an induction motor you can practically achieve the same thing without one.


I'm not so sure you can. You're going to be running at a relatively high frequency (10000rpm / 4 pole = 330Hz) from a low voltage, the power factor is going to be lousy. I don't think you'll be able to actually get the real power you want into the motor.

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Post by PlanB » Sun, 10 Jun 2012, 16:44

tnks for your posts T2, I was aware of the presence of the Lexus voltage doubler, what I didn't understand was why it was there in there first place. If you're a big company like Toyota why wouldn't you just design a motor from scratch to suit your battery pack & skip the doubler? I guess there is a lot more going on in these systems than meets the eye? Ryan said he thought the up converter might actually be variable which surprised me greatly because I would have thought you could get all the control you want from the VFD?

TJ did you get my PM? Any chance of some detail on the Sew? What RPM range would you see it running over at in an EV? Does a 4 pole have lumpy torque at low RPM?

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Post by Tritium_James » Mon, 11 Jun 2012, 01:05

Didn't see the PM, sorry! Read it now... send me an email so I can send you the data I have.

Max speed is rated to 6000rpm, though you could probably balance it to go faster, but torque is dropping off rapidly at that point and it's probably not worth much more to spin it faster. Base speed (peak power) with a pack at 380V is 2700rpm. The torque is smooth over the entire rev range.

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Post by coulomb » Mon, 11 Jun 2012, 15:37

PlanB wrote: Ryan said he thought the up converter might actually be variable which surprised me greatly because I would have thought you could get all the control you want from the VFD?

The Prius does the same thing; it varies the DC bus from around 240 Vdc (straight through) to something like 500 V (from poor memory). Later models go to 650 V. They seem to do this to get better efficiency.
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Post by PlanB » Tue, 12 Jun 2012, 17:27

AC electric traction is proving to be much more interesting than I thought. TJ do you have any comments on this scheme of varying the supply voltage to a VFD? Is this universal amongst manufacturers or just a Toyota thing? I'm trying to fit this jigsaw piece in with Coulomb's/T2s discussions in 'How to convert a hybrid' but can't seem to make it fit in my mind. Maybe that's because a jigsaw piece can't be a good fit in a can of worms?
This debate on motor types reminds me of what went on a hundred years ago with the development of the ICE starter motor. The naysayers said it couldn't be done but the key was non continuous rating. Seems to me that the motor that can cope best with over torquing for short bursts of acceleration is going to be the winner? In which case my beautiful little IPM transaxle is never going to cut it because over current is going to depolarise the magnets?
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Post by Tritium_James » Tue, 12 Jun 2012, 18:59

Supplying variable voltage to the VFD allows you to reduce switching losses in the VFD since switching losses are approximately proportional to voltage. So if you don't need the full DC voltage available, because the motor is only going slow, then you cut your losses by only supplying the voltage necessary.

BUT, you now have extra losses due to the boost converter, which has added another power processing stage between the battery and motor. The calculation on the tradeoff between the two is highly dependent on expected duty cycles, operating speeds, etc, etc and isn't a trivial amount of work.

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Post by coulomb » Tue, 12 Jun 2012, 19:22

PlanB wrote: Seems to me that the motor that can cope best with over torquing for short bursts of acceleration is going to be the winner? In which case my beautiful little IPM transaxle is never going to cut it because over current is going to depolarise the magnets?

Your IPM transaxle will already be assuming a low duty cycle for its peak power rating. If you keep the temperature reasonable, I don't think you need to be concerned about depolarising the magnets.
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Post by PlanB » Tue, 12 Jun 2012, 21:39

I don't know Mike, I just can't seem to get any figures on this EV torque thing that I'm happy with. The RX400H starting torque is 130Nm which is 892Nm to the wheels after it's 6.86:1 internal gearing. But Ryan reckons it's not enough for his 1 tonne vehicle with really sluggish hill starts.
TJs 132 frame Sew can peak up to 240Nm but if I use it with an MX5 4.1:1 diff that's only 984nm, just 10% more. To get a 50% torque improvement (1338Nm) I'd need 5.6:1 gearing. But even if I could get that it wouldn't be easy to secret 63kg of Eurodrive up the back of an MX.



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Post by Tritium_James » Tue, 12 Jun 2012, 22:54

Not surprising it's sluggish with that torque. We've got 1750Nm at the wheels in the Civic (500Nm Ultramotive Carbon + 3.5:1 fixed reduction) and it's quite OK but nothing spectacular. A 'normal' car in 1st is probably more like 2500-3000Nm.

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Post by Johny » Tue, 12 Jun 2012, 22:59

What does the Civic weigh TJ?

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Post by Tritium_James » Wed, 13 Jun 2012, 14:09

About 1400kg.

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Post by T2 » Wed, 13 Jun 2012, 15:20

Infering to the possible use of an Upconverter with an induction motor I wrote "It just so happens that if you choose the right V/Hz for an induction motor you can practically achieve the same thing without one."

T-J replied I'm not so sure you can. You're going to be running at a relatively high frequency (10000rpm / 4 pole = 330Hz) from a low voltage, the power factor is going to be lousy. I don't think you'll be able to actually get the real power you want into the motor.

I have to ask where this fixation against 120Vdc low voltage systems and high frequencies stems from ?

Consider an equivalent sized 0.5V/F motor in place of your Japan market 100Vac 50Hz 2.0V/hz machine. This hypothetical machine will have one quarter of the turns and therefore only one sixteenth of the stator inductance. I don't think the effect of power factor is going to intrude even when approaching 400Hz excitations. OTOH I can see your machine would have those problems and well before 500HZ.
      
For an extreme example I notice the motor on the Tesla roadster has a base speed around 7200rpm that in conjunction with the application of 206Vac suggests a V/F of 0.8. In this design the motor runs through to 480Hz at top speed.

I suggest any doubts you may have regarding power factor constraints will be quelled when you finally get around to putting a fractional V/F machine on your own rig and seeing for yourself.
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Post by PlanB » Wed, 13 Jun 2012, 15:29

So 1750/1400 = 1.25Nm/kg power-to-weight on the Civic, so if I could get a 5.2:1 diff with the Sew (5.2 x 240 = 1248) on a 1tonne post conversion vehicle I could at least get 'quite OK but nothing spectacular' performance.

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Post by Johny » Wed, 13 Jun 2012, 16:38

Lets compare that to the Nissan Leaf. Generally this car has been reviewed as having good power and acceleration.
Motor torque 280NM.
Final drive 7.9377:1
Curiously if your delve you find the the motor torque is actually 280NM from 0 to 2730RPM which equated to around 40kmh.
Why is it then that folk say it's so good?
Because lots of torque at low speed is what they are used to from ICE world (IMO).
This graph of power vs speed supports the torque "knee" at around 2730RPM.
Leaf 2 Dyno runs.
Image
The Leaf weighs 1530kg
So while the Leafs 2222/1530 => 1.45 power-to-weight looks good, it only pertains to up to 40kmh. After that the torque must be dropping off or the power wouldn't be basically flat.

Edit: Replaced link with image
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Post by PlanB » Wed, 13 Jun 2012, 18:07

I take your point T2 about 400 Hz fractional V/F motors & low voltage battery packs. TJs mention that switching losses are voltage proportional & the step up Toyota inverters prove the point. I don't know that there is a fixation against the idea it's just that I don't see any available motors other than Tesla/UQM exotica. Do you know of anything available in EV sizing? All the aircraft stuff I've looked at (wing flap motors & the like) are all way to small.

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Post by coulomb » Wed, 13 Jun 2012, 20:03

Johny wrote: This graph of power vs speed supports the torque "knee" at around 2730RPM.
Leaf 2 Dyno runs

Johny, I'm getting a protection error on that link. Can you check a box or something that says others can read it, please?
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