Red Suzi

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Post by Electrocycle » Wed, 04 Nov 2009, 12:41

I would have thought you could have a 2 pole rewound as any number of poles you want - depending on the number of slots in the stator.
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Post by woody » Fri, 12 Feb 2010, 19:29

Another Red Suzi Conversion.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

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Post by macvouty » Mon, 03 May 2010, 23:01

gday, i'm looking at converting to a 4WD EV, and I was really interested to see what you've done with the Sierra. (Thinking of a Sierra ute myself, as I don't think 4WDs get much lighter than that!) I'm up in Perth for the week and was wondering if there'd be a chance of having a chat and a look? I've never done an EV conversion, so I need as much inspiration as I can get! Anyway, if that sounds alright to you, feel free to drop me a text/call on 0418 242 979.

cheers
Charlie.

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Post by T2 » Thu, 13 May 2010, 17:10

ACMOTOR - Great work well done!! But I have some queries if you have the time.

Too bad I am late to the party. But it so happens I have lying around a DANFOSS product catalog which devotes 69 pages to the VLT 5000 series, I therefore became more interested in how you might or might not be abusing this animal.

So, for people too busy to spend time navigating Danfoss' website, including myself, I thought I'd put the facts about your controller from their Product Catalog in one place here.
It appears we are discussing the VLT5042 H.O. version (High Overload)
And as I understand from pg D20, and in case others were wondering :
This is a 30Hp controller requiring a 380-440AC supply input.
With the H.O. version providing a one minute 160% overcurrent capability allowing a nominal 61.0 amps to increase to 97.6A
In the vehicle it is fed from a 576Vdc ~ 12kw battery pack which droops 72V under a 60A load.Therefore the controller can only provide 306Vac at that time. Of course that isn't too important until the motor V/F factor times the current frequency hits 306Vac voltage wall.
======================================================================
Here are the questions I have,

- why doesn't your drive complain about input phase loss ?
I ask because I am in the act of spoofing a drive right now.

- Why doesn't 1.732 X 415v X 22.17A = 11kw ?
clearly everyone (and myself) seems to be using 415v, 22.17A and the new line voltage to compute what the expected new value of line current should be (For inputting to the controller's memory). Explain please.

- burying the controller into current limit is something you wanted to see. Frankly, I don't think that's so hot. You stated on Sept 1st 2009 that in 346 STAR the real life test that the motor current sits flat from 10km/hr onwards. If towards the end of an accel profile that's OK with me - but from 10km/hr onwards ?

- Finally the 350A controller with the 10.5 : 1 ratio screams success, but no comments from you ?

- wouldn't 100v connection with 10.5 ratio and the Danfoss be something to see ?

- Does the Danfoss have provision to specify a current limit on its input, like setting it at 60 amps say, so you can have as much of that 97.6 amps line current in the motor until the motor voltage rises causing its total power demand to equal [60 x( 576-72)] after which the 97.6 amps is gradually reduced as the motor accelerates to avoid damaging the power supply. Enquiring minds.......?
T2

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Post by acmotor » Thu, 13 May 2010, 18:44

Hi T2,
VLT 5042 is 30kW (40HP) nom. shaft output not 30HP, and as you note, it is the drive current that counts.

Input phase loss..... This drive is designed to operate from DC bus sharing connection (without 3 phase mains present). It cannot tell that there is a mains loss except by excess ripple on the DC bus as would occur if one phase was lost.
This EB (extended braking) version also accepts higher ripple as it will work with large regen and DC bus voltage 470 to 810V with braking resistor comming in at 750V.
Few VFDs can't be operated by DC direct to the bus (with inrush control added if the input rectifier is half SCR type)

Check out the induction motor threads on this forum.
1.732 X 415v X 22.17A = 11kw ???   well it does if you include the power factor and motor efficiency. You have calculated the kVA to the motor. The 11kW motor nameplate number is the actual mechanical shaft output of the motor at that input kVA.
So 1.732 X 415v X 22.17A x (pf maybe).8 x (efficiency maybe) .87 = 11kW

Continuous torque with AC motors in EVs is the good part. For continuous torque you need continuous current. The 97.5A current is a safe industrial limit for the controller and well withing the 60 second rating for the motor were it used in DOL mode so there is no isssue.
An IM can hold full overload torque at zero RPM for some time (60 seconds) better still with external fan. It is the same current at all RPM so the low speed is not an issue. The stator field is rotating at a 100 or more RPM due to the IM design slip. A difference here with say series DC motors is that if the are at zero RPM and high current then the armature winding is at risk from overheating as the current is not being shared in time around a rotating armature.   

Yep, 350A controller would be great.
3 limits....
Battery current
controller size
$$$$$$
Don't worry, the Rodeo with lithium, 75kW VFD and 22kW motor will be interesting.
The wavesculpter 3 phase controller would be interesting. Need a lower motor voltage though.

100V motor, 10.5:1 and the VLT5042 would be too current limited.
At present I am running in 200V connection and 10.5:1 with VFD going to 200Hz.

This VFD does not have the option to limit via DC bus current number but can limit estimated motor kW. (I haven't done so)
There are many options as you can see in the docs.

Hope that helps.

PS hey Charlie, I only just saw your post.
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Post by T2 » Tue, 18 May 2010, 09:57

-acmotor
IMO your machine isn't quite getting the performance of which it might be capable.

You seem to have done a lot of the right things so I did an evaluation of the Impact's system in greater depth than I had bothered before, to see what I could learn.

Their Pb-acid Battery system is one third larger but they are caning it to the extent of 90Kw compared to the 30Kw of yours.
They generate 162.5Vac at base speed, from max of 196Vac. Yours is 306Vac.
They feed 318 amps to your 97.6 amps. Their V/Hz is 0.74, yours would be 4.0. I would reckon you lose 30 amps of torque in the rear diff hypoid and gearbox otherwise your initial take off, on paper, is better than the Impact.

This post has been written I'm writing this summation last. So the price of rice is I think that your motor has to be connected in 100volt delta before you relinquish this design. You have it geared 10.5:1 which brings the current down. I suggest ATF in the transmission or Mobil 1 synthetic. I would suggest it worthwhile to upgrade to a 200Amp controller.

I've computed the maximum motor line voltage for the Danfoss on your system to be 306Vac, that places base speed for a 100 volt (the delta) winding at 4500rpm (56Km/hr with your gearing) i.e. 60Km/hr. A speed reference signal is required as an input, beginning at 40km/hr, that must start to reduce the current limit in stages as base speed is approached so as to prevent the battery seeing more than 100 amps of draw or whatever you decide. Some drives may have logic blocks to do that internally. You must know better than I. I respectfully suggest that this would make Red Suzi an even more interesting ride than it is now.

GM's 1990 IMPACT TWIN Drive system
Power        57 Hp (42.5Kw) each induction motor
Input to motor     (44.76Kw) est.
Amps                 159 A (per motor)
Volts               162.5Vac @ 220Hz base speed
Volts/Hz             0.74
Torque               47lbs-ft to base speed
Base speed        6600rpm 42mph    220Hz
Quoted (video)     9500rpm 60mph   ~320Hz
Max speed                  75 mph
Effcy                  90-95%
Voltage             400 ? (196Vac from 320Vdc)
Amps               159 A (per motor)
Frequency        500Hz max - infers 4-pole machines
Planetary ratio     10.5:1
Battery pack     32 x 10v lead acid 42A-Hr 13.6Kwhr 870lbs
Rims 14"
Tires P165-65

Note base speed output of 162.5Vac only requires a 265Vdc bus
however the bus is unlikely to droop 55v on ~ 300A with AC-Delco Pb-acid
Assume 300Amp draw at 300Vdc to provide ~ 90Kw , Vm=162.5Vac   Im =159A ( x2 )

-johnny Posted this : 06 August 2009 at 9:36am
I've assumed 50 x 12V 20Ah SLA, Red Suzi weight - diff etc. If might have not got it exactly right but it looks pretty close to what I'd expect.

Delta V 0-60km/hr 60-100km/hr
150     10.7     9.75
173      9.24    9.4
190      8.4    10.7
200      8.0    12.25
220      7.44   16.75

The 60 Amp draw from the 12Kwhr pack seems low compared to the 300 Amps drawn by the IMPACT from its 13.6Kwhr pack

Introspection of 200 and 173 would imply that the 200Vac winding is running out of volts so its V/Hz is suffering -12.25s from 60-100km/hr.
The 173Vac winding is torque reduced as expected however its V/Hz is not impacted at the higher speeds           -9.4s from 60-100km/hr

Gearing is quioted 8krpm @100km/hr at 10.5 : 1 That is correct ?
We know max output of inverter at full load is 300Vac because of droop therefore the 200Vac motor winding starts to field weaken at 2250rpm which is 28km/hr. The 173Vac will be starting to field weaken at 300/173 x 1500 =2600rpm which is 32.5km/hr. This small increase of 4.5Km/hr in base speed trims nearly 3 seconds off of the 60-100Km/hr. This would imply that there seems to be a rapid drop off at twice base speed with all windings are deep in voltage saturation.

A theoretical 150Vac winding should have a higher base speed of 3000 rpm 37km/hr . At 60km/hr and well above its base speed it should be the most powerful configuration since in a voltage starved world it has the lowest V/Hz yet 9.75s makes it less powerful than the 9.4s acheived by the 173Vac winding.

Can that be explained ? I think there is a problem with the spread sheet.

In real life testing does 173 and 200 prove the computed figures I read somewhere that you had close agreement with theory and practice.

Has the 100Vac been tried to see whether it improves the 60-100km/hr figures ? Sure its 0- 60km/hr may prove undriveable in traffic.

johnny you posted in reply to acmotor :
The 150 volt line (winding config) is rated speed at 83km/hr in Red Suzi. [This sentence should have been in italics not at bottom page ?]

Wouldn't 83km/hr with 10.5 ratio be 6600rpm (coincidentally same as IMPACT) and at 220Hz ? I was with the understanding that all our ratings with a 4 pole motor refer back to 50Hz when you're talking to the rewinder guy - I'm assuming - therefore 1500rpm is the reference speed for winding voltage. It sets the V/Hz factor. The actual base speed is the inverter maximum voltage based on that figure. Of course that is providing you are willing to let the motor see that voltage. With Red Suzi that won't be a problem since all configs of the motor are for high voltage. For example the 100volt winding is 4V/Hz, in comparison the IMPACT motors are 0.74V/Hz.

Well those are my thoughts and like a gift bottle of brandied cherries, I hope you appreciate the spirit in which they were given.
The 150 volt line (winding config) is rated speed at 83km/hr in Red Suzi.
T2

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Post by Johny » Tue, 18 May 2010, 15:32

T2 wrote:In the vehicle it is fed from a 576Vdc ~ 12kw battery pack which droops 72V under a 60A load.Therefore the controller can only provide 306Vac at that time.
I make it 361 VAC under load.
BTW T2. You are flogging a dead horse a bit here. acmotor used Red Suzi to prove some important details and is now working on his next EV. As far as I know Red Suzi was not intended as a "final product" (well not now anyway) - more a proving ground. acmotor has provided some excellent real-world data from it that helps a lot of us that may only get one crack at it.

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Post by woody » Tue, 18 May 2010, 17:26

T2 wrote: A theoretical 150Vac winding should have a higher base speed of 3000 rpm 37km/hr . At 60km/hr and well above its base speed it should be the most powerful configuration since in a voltage starved world it has the lowest V/Hz yet 9.75s makes it less powerful than the 9.4s acheived by the 173Vac winding.

Can that be explained ? I think there is a problem with the spread sheet.
Hi T2,

The result of lower voltage winding is that you need higher current for the same torque.

So with a 100amp controller, the peak torque is lower with Red Suzi's motor now that the voltage is lower.

PM me your email address and I'll send you the offending spreadsheet :-)

cheers,
Woody
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Post by Johny » Tue, 18 May 2010, 17:35

T2, once you get woody's SS you will find that it's a huge game of conflicting real-world compromises. If controllers had infinite current there would be no question - set the v/f and base speed for the maximum speed you want the vehicle to go.
But given that controllers have current limitations, we try to choose a reasonable high speed for base speed (I choose 80kmh) that doesn't place the controller in too much current limit at lower speeds.

In my case the controller can do 89 Amps but I have plans for upping this to 150 Amps so the compromise was to try to pick a middle ground that had the vehicle usable until my new controller is ready. So, I'll be controller limited for a while.

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Post by T2 » Thu, 20 May 2010, 16:31

I make it 361 VAC under load.
OK johny, I took 576-72Vdc
          Then divided by root 2
....   To give rms value between legs that are 180 deg apart
          Then multiplied by (root 3)/2 i.e. 0.866
....   To correct for 120 deg between legs
             I get 306Vac

but then since the output waveform for motors is not sine
but usually sine + 1/6th 3rd harmonic Esinwt-(1/6)Esin(wt+2pi/3)
I wonder whether that 0.866 is fully valid ?

I am going to PM Woody for that data but will let this rest in the meantime.
Have one question : Any chance we could be specifying motors that may be oversized ?

I understand that motors are carefully specified here for their estimated size for continuous running but do many of us have battery packs that could actually burn out the motor if it were underrated. If the battery lasts only 1 hour then the motor thermal time constants may be long enough that even a 5Kw machine with the 10.5 ratio in Red Suzi would survive ? I accept there may be a significant rise in temp but not a dangerous overtemp condition. I've experienced hot DC motors in the past but they were nowhere near as efficient as the vector drive AC machines being used now.
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Post by Johny » Thu, 20 May 2010, 16:42

T2 wrote:Have one question : Any chance we could be specifying motors that may be oversized ?
a4x4kiwi's 15kW definitely needed force cooling in normal use and this blog at one stage used an under-sized motor AC that cooked.
There is also the issue of saturation that limits the power available from any motor.

Edit: anY motor
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Post by coulomb » Thu, 20 May 2010, 17:46

Johny wrote: ...this blog at one stage used an under-sized motor AC that cooked.
Actually, I believe that the author has since retracted his assessment of what died:
http://kermitthecar.blogspot.com/search ... -results=1

He found two dead IGBTs; he was using the controller without the bus capacitors! [edit: just snubbers.] Image    Even now, he seems to be wanting to use just one large capacitor, and I don't think he can get away with it unless he has amazing bus bars to that cap. Capacitor and switching device layout is one of the most important aspects of controller design. I guess he'll learn.
There is also the issue of saturation that limits the power available from any motor.

Yes, but that issue appears to be unsettled at this stage. TJ happened to be chatting to Weber and I about this last night after the meeting. Hopefully, we'll all know more in a few weeks, when TJ gets his 15 kW motor to test. Since the current at 350% of nominal torque on the "7.5 kW" motor that has DOL breakdown torque specified at 320% of nominal torque used only a few percent more than 350% of nominal current, it would appear that at least for that motor, saturation is nowhere near breakdown torque. Myself, I can't imagine that saturation will typically be very far away from breakdown torque, but it looks hopeful.

Another interesting result of TJ's recent experiment: it appears that external cooling will not affect peak power in any meaningful way. He had a thermistor right on a winding, and it hit some 85°C when the outer case will still just warm. As soon as the power was removed, the winding temperature started coming down, which is reassuring. Three minutes later, the outer case was at some 70°C, so the heat gets there eventually, but there is enough thermal lag that at least for this motor, external cooling won't affect the very short term peak power that the motor can handle. There is enough of an air gap between most of the windings and the case to ensure this. Perhaps 25% of the circumference of the stator is in direct contact with the outer case.

So the result of these is that we may be able to get a lot more power than we thought from a typical induction motor, but for a rather short period of time. When pushing the boundaries like this, a thermistor on the windings would appear to be mandatory. Motor windings will take insane temperatures, but you definitely don't want to exceed their ratings, and probably don't want to get too close routinely, due to the effects of all that expansion and contraction (at different rates) on the copper, insulation, and iron.
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Post by Johny » Thu, 20 May 2010, 19:19

I would have replied immediately but for some strange reason the forums block sometimes to Victoria (I think). Work and home can't get to them.
Anyway. I was aware of the VFD issues that kermit's builder had but the overheating motor (the 3.7kW) dated back earlier. Trouble is I can't find it anywhere???

I also await TJ's findings with interest.

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Post by woody » Thu, 20 May 2010, 19:31

coulomb wrote:
There is also the issue of saturation that limits the power available from any motor.

Yes, but that issue appears to be unsettled at this stage. TJ happened to be chatting to Weber and I about this last night after the meeting. Hopefully, we'll all know more in a few weeks, when TJ gets his 15 kW motor to test. Since the current at 350% of nominal torque on the "7.5 kW" motor that has DOL breakdown torque specified at 320% of nominal torque used only a few percent more than 350% of nominal current, it would appear that at least for that motor, saturation is nowhere near breakdown torque. Myself, I can't imagine that saturation will typically be very far away from breakdown torque, but it looks hopeful.
My understanding of magnetic saturation is different:
Up to a certain V/F ratio, there is zero magnetic saturation.
Above that V/F ratio, the iron gets permanently magnetised a bit, and this has to be reversed (hysteresis) which is one source of inefficiency. This is saturation.
The more you go above that V/F ratio, the more it gets permanently magnetised, and the less magnetic field you get for your current.

The nominal V/F ratio (e.g. 8V/Hz for a 400V @ 50Hz motor) is a little bit into saturation I think.

From ABB specs, it's not very far, as if you run a 500V motor at 550V they expect 119% of breakdown torque, whereas you'd get 121% if magnetic saturation wasn't an issue.

cheers,
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Post by coulomb » Thu, 20 May 2010, 20:47

woody wrote: Above that V/F ratio, the iron gets permanently magnetised a bit, and this has to be reversed (hysteresis) which is one source of inefficiency. This is saturation.
The more you go above that V/F ratio, the more it gets permanently magnetised, and the less magnetic field you get for your current.

Yes, so the effect is like with DC (X% more current gives you a little less than X% more field strength). I was going to say that the cause is a little different, but really it's just the same, with hysteresis making it a little worse for AC (in a DC motor, you don't care about hysteresis much, as you don't reverse the field very often).

But you've got me to thinking as follows. If the DOL breakdown torque figures are real (not fudged for efficiency rating purposes), then the breakdown torque is at a motor current of approximately Tb/Tn times In (the ratio of breakdown to nominal torque, multiplied by the nominal current. If this is getting near saturation, then a few percent more current will be needed to overcome iron losses. The field current involved will presumably be this motor current multiplied by sqrt(1 - PF^2), i.e. the imaginary component of that motor current. [Edit: where PF is the power factor, i.e. the ratio of real motor current to total motor current.]

With DOL, you can't really get any more field current into that motor. Increasing the slip will just cause breakdown to occur, and the controller will "lose" the motor. So this is presumably the operating point where the motor is expected to have maximum field current; it would never see more field current than this when connected DOL (apart from when starting perhaps, but that's transitory). So the stator iron would be designed to have this point be a little into saturation, but not too much, so the motor is reasonably efficient at peak power. To get more than breakdown torque, the VFD is going to have to pump in more imaginary current, so there is more torque per real motor amp. This will put the motor field current at a level that arguably it's not designed for, further into saturation. Saturation curves are however usually fairly gentle, so the extra losses should not be extreme for torque amounts not too far in excess of breakdown.

My apologies if that sounds like the same argument I've made before; I'm still struggling a little understanding this, and I may have come to a similar conclusion via a different path.
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Post by acmotor » Fri, 21 May 2010, 02:51

All those posts !
Yes T2, red suzi is only getting about 1/3 of possible performance from the motor but neither the controller or batteries are up to anything more. Motor can supply 132kW at 6000RPM 200Hz 216Nm.

Red suzi's acceleration seems marginally better than the imiev from driving one the other day, at least up to 80kmph.

Coulomb, magnetic saturation in DC motors is much the same diminishing returns problem as AC motors, and hysteresis is also an issue with DC motors as the armature is required to reverse the same 4 times per revolution with a 4 pole DC motor. (true the field can be wound on boiler plate !(usually is!)).

Both types of motor need the switching silicon to deal with the inductance change as saturation is approached/entered/fully planted.

We were discussing this at the last Perth meet where a DC motor pushed into saturation presents less than the expected inductance for the buck converting controller to work with. Possibly causing one of the common modes of controller failure at low revs/high current. i.e. di/dt rising too fast due to reduced inductance.

Saturation due to v/f seems to be somewhere at least 20% higher than nominal motor voltage. Torque boost on Danfoss will go to 14V/Hz c.f 8 nominal and acceleration curves show result for the effort. % return is not quantified as yet.

I have run the 346V configuration at 415V in controller settings with no detectable change in performance but an increase in motor temp during cruise most likely due to saturation ? Things may be masked here due to controller current limit though.

Not to confuse stator current with v/f ratio of course. We know that up to at least 70% of Tmax the current and torque increase linearly. So there is no sign of saturation up to at least 2.5x current on most motors. If you are looking for a number for a good motor then chase a high Tmax/Tn.

I do not see that anything on the torque curve below the RPM of Tmax has anything to do with emotors in EVs. i.e. DOL parameters are of no interest. They are just that.... a designed ability to be able to start DOL without ringing the power station first controlled by rotor reactance and air gap.
DOL figures have (almost) nothing to do with motor efficiency at least they would not be fudged for any gain.

I agreee though that your thinking may answer some questions.

edit: the spelling mystaakes I did find
   
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Post by coulomb » Fri, 21 May 2010, 04:19

I should perhaps point out to some readers that most of the time when I say DOL I really mean "without a VFD", i.e. I'm totally uninterested in the first few seconds starting a motor Direct On Line, only when it's up to speed. Once the motor is up to speed and connected to the fixed frequency and voltage mains, basically the only influence you have over its behaviour is the mechanical load.
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Post by acmotor » Fri, 21 May 2010, 07:29

I'm glad you clarified that. Image
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