Performance and cost between DC and AC -EV's

Technical discussion on converting internal combustion to electric
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woody
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Performance and cost between DC and AC -EV's

Post by woody »

Rattrap wrote: woody is there a reason why u are comparing the AC as direct drive? Are AC systems better suited to direct drive?
The industrial ones are, the easy to get, suitable motors are rated around 11-15kW, 4 pole which means peak torque of 200-300 Nm which is only suitable for direct drive in the small car I am thinking of. (it would break the gearbox I suspect). It makes sense to leave the gearbox out as the motor puts out almost as much torque as the original car does through first gear (so it will be as zippy, but won't break the diff!)

The DC direct drive option isn't an option at the moment, as Zeva has proved the Available controllers (Kelly, Curtis) aren't suitable for direct drive :-)
Gow864 wrote:Woody An excellent example of how numbers can be scewed to suit.
I'm not skewing them on purpose. It's just how the numbers fell :-)
Gow864 wrote: How about using prices of equipment designed for an EV? In reality I would imagine very few converters would be using industrial AC motors and second hand VFD's I think that this is the domain of the expert.
I only know of 7 AC car converters in Australia at the moment: 4 (acmotor, a4x4kiwi, Johny, Sparky Brother) are doing Industrial AC, 2 (Paul Gellatly, Ross Blade I.E. bev.com.au are using Azure), 1 (miked) is using MES-DEA stuff from metric mind.

My sample is not big enough to say that the majority are going one way or the other.

The industrial stuff is well documented, suitable for cars (accellerator = torque control), and has many handy features (e.g. a4x4kiwi has set up his drive to provide a pulse to drive his factory hilux speedometer).

It's not as simple as the curtis, neither is the zilla, or the kelly.
Gow864 wrote: Maybe it would be a good excersize to build (theoretically) comparable AC and DC systems using NEW equipment sold for the purpose of EV. This could be good for everyone. Maybe a thread containing suggested setups approximate costs and performances (if that can be done)
I'm just going with what I know. Unfortunately all the Australian distributors of stuff have pulled the prices from their websites until the currency decides what it's going to do :-)

The Azure AC55 (comprable to a 4 pole 11kW industrial) was about AU$9000 before th dollar piked.

The Telemecanique 82kW (peak) industrial drive is list price US$7762.

I don't know how much a discount you can get from the list price :-)
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Performance and cost between DC and AC -EV's

Post by zeva »

woody wrote: The DC direct drive option isn't an option at the moment, as Zeva has proved the Available controllers (Kelly, Curtis) aren't suitable for direct drive :-)

The Curtis would probably be OK with a 9" motor direct drive since its resistance & inductance is higher than the Warp 11 in the MX5, but a Warp 9 will only give you about 180Nm of torque at 500A, which is a bit low for DD unless you have a very small car and/or a very high diff ratio!

Really you do need a 1000A controller for a typical car if you want DD with a DC motor. In the absence of CafeElectric, Logisystems is currently the only player on the market to offer such a beast AFAIK.
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Performance and cost between DC and AC -EV's

Post by Goombi »

Lets do a small test: motor coupled to a 5:1 diff will turn 5 times from standstill in order to turn the wheel once and the 15 inch wheel has travelled 2 meters distance. (From here you can make your own calculations and assesment) If you force a 500-1000 amp to the motor I will bet you you will snap the pinion or strip the gears.
One case not log ago was driven in 5 th gear gearbox, Not being satisfied with with the sluggish performance Higher amperage was forced in the motor and the gearbox evaporated..I could rename the Controller to --- electric Torque converter--- The way many controllers are designed are purpose built for speciffic motors and output.
There are no bad controllers. ( talking about DC) What i would like to see is overdive input into controllers automatic or manual controlled extra 20% more amps.The moral of this exercise, all components have to be designed and be compatible for a specific job. and have to best match the   controller=motor=gearbox=diff = and the wheel size relationship.In the DC department , you have clear options. what voltage what Kw and the components are there-- and matched.
The complex US market and the competition amongst the Motor and controllers suppliers does not help anyone a I think the prices are rigged and lots is made in China.The waiting list for components makes the prices rise all the time. in fact the US prices have made a conversion a dicey investment.
I am not sure about this one :]
How fast will a ac motor turn being directly coupled to 5:1 diff reaching 100km/h ?? I am NOT looking for ,how quickly is the car going to do 100km/h !
I know already that the motor turns 5 time to move the car 2 meters wow that has to have some torque especially if you pushing 1.5 tone vehicle up the hill...
To operate a vehicle with el motor has to be close to what it was designed for and what the ICE was doing.. Overloading diff and geargox
by more then 35% will result in brakedown. I have built a good matching EV The gearbox is not overloaded the motor is running cool the distance travelled is perfect-- the speed is on par with other city traffic.. (almost-but sometime better) but satisfactory.
I could have only dreamt about a almost perfect combination of a commuter car. And it is such a quiet achiever...

Last edited by Goombi on Tue, 16 Dec 2008, 05:54, edited 1 time in total.
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Performance and cost between DC and AC -EV's

Post by fuzzy-hair-man »

Goombi wrote:How fast will a ac motor turn being directly coupled to 5:1 diff reaching 100km/h ?? I am NOT looking for ,how quickly is the car going to do 100km/h !


100km/hr = 100,000 metres / hr = 1666.667 metres / min

1666.667 metres / min with a 2 metre circumference wheel = 833.33 wheel rotations / minute

As we are using a 5:1 diff the motor rotates 5 times to 1 wheel rotation so:

5 x 833.33 = 4166.6667 rpm @ 100km/hr
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Post by woody »

zeva wrote:
woody wrote: The DC direct drive option isn't an option at the moment, as Zeva has proved the Available controllers (Kelly, Curtis) aren't suitable for direct drive :-)

The Curtis would probably be OK with a 9" motor direct drive since its resistance & inductance is higher than the Warp 11 in the MX5, but a Warp 9 will only give you about 180Nm of torque at 500A, which is a bit low for DD unless you have a very small car and/or a very high diff ratio!
The Cortina is light (~900kg lithium EV), high diff ratio (4.4:1), small wheels (165/70R13) = 4160rpm @ 100kph. I don't know the curves of a DC motor, but if I could get 180Nm all the way to 4160RPM, it would do 0-100 in 10.25 (which is stock MX5 territory for those playing along at home). 180Nm @ 4160rpm is 78.4kW or 500A at 160V, so probably a bit optimistic there, but still very "zippy".
zeva wrote: Really you do need a 1000A controller for a typical car if you want DD with a DC motor. In the absence of CafeElectric, Logisystems is currently the only player on the market to offer such a beast AFAIK.
Logisystems Manual wrote:This is an extremely high performance controller ... may tear the drive wheels and anything else completely off the vehicle. ... Start with low settings and work up to your preferred performance level.
Part of me is scared, part of me just wants one :-)

Here some wording for the Zeva manual: "If you turn this all the way up, it may tear a hole in the fabric of time and space and destroy the universe".

So 1000 amps = 360Nm Warp 9?

360Nm is peak ICE Nm * first gear ratio i.e. I won't break things direct drive.

Ah, if only I had a fleet of Cortinas to convert.
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Post by woody »

Goombi wrote: Lets do a small test: motor coupled to a 5:1 diff will turn 5 times from standstill in order to turn the wheel once and the 15 inch wheel has travelled 2 meters distance. (From here you can make your own calculations and assesment) If you force a 500-1000 amp to the motor I will bet you you will snap the pinion or strip the gears.
I'm assuming this is the RAV4 diff? I don't think you will snap it with a 8.5 inch motor or even a warp 9 - the torque coming out of a warp 9 will not be more than coming out of the gearbox in 1st gear.

100kph @ 2m circumference = 50,000 rph = wheel rpm 866rpm * 5 = 4166rpm, same as my Cortina. What are you putting this diff under?
Goombi wrote: One case not log ago was driven in 5 th gear gearbox, Not being satisfied with with the sluggish performance Higher amperage was forced in the motor and the gearbox evaporated..I could rename the Controller to --- electric Torque converter--- The way many controllers are designed are purpose built for speciffic motors and output.
I'm not really following what you saying here. Yes the electric motors have higher torque than the gearboxes are designed for, but not higher than the tailshafts and diffs are - which is one reason why direct drive is favourable with big motors.

One reason I like to do some calculations is that I don't have the spare cash to evaporate gearboxes :-)
Goombi wrote: There are no bad controllers. ( talking about DC) What i would like to see is overdive input into controllers automatic or manual controlled extra 20% more amps.The moral of this exercise, all components have to be designed and be compatible for a specific job. and have to best match the   controller=motor=gearbox=diff = and the wheel size relationship.
Yes the Curtis doesn't have a any adjustment. The Zillas have lots.

There are lots of features which would be handy in controllers, canbus to drive modern car electronics.
The AC industrial ones are very programmable since that is useful in their usual setting in industry.
Goombi wrote:In the DC department , you have clear options. what voltage what Kw and the components are there-- and matched.
The complex US market and the competition amongst the Motor and controllers suppliers does not help anyone a I think the prices are rigged and lots is made in China.The waiting list for components makes the prices rise all the time. in fact the US prices have made a conversion a dicey investment.
I am not sure about this one :]
I don't think it's a sure thing investment just yet, the batteries are a much bigger cost than the electricity. The motor + controller in theory will last a very long time, so their cost/km fades after many kilometres have been driven. If your motor/controller makes your batteries last longer (more efficient, nicer treatment) then they will pay for themselves quicker.
Goombi wrote: How fast will a ac motor turn being directly coupled to 5:1 diff reaching 100km/h ??
With your 2m circumference wheels, 4166rpm.
Goombi wrote: I am NOT looking for ,how quickly is the car going to do 100km/h !
I know already that the motor turns 5 time to move the car 2 meters wow that has to have some torque especially if you pushing 1.5 tone vehicle up the hill...
Your 2m wheels have a 2/Pi/2 =~ 1/3m radius. So Torque from the motor, say 180Nm is multiplied by the diff (5:1) = 900Nm and the wheels (divide by radius) = 2700N of force. For your 1.5 tonne vehicle, 15000N to pull it up a cliff. You can go up a hill of 27 in 150 i.e. 1 in 5.5 which is pretty steep (18% grade).

As for acceleration, it would be leisurely (0-60 in 10s).
Goombi wrote: To operate a vehicle with el motor has to be close to what it was designed for and what the ICE was doing.. Overloading diff and geargox
by more then 35% will result in brakedown.
Agreed. This is why I'm doing my sums.
Goombi wrote:I have built a good matching EV The gearbox is not overloaded the motor is running cool the distance travelled is perfect-- the speed is on par with other city traffic.. (almost-but sometime better) but satisfactory.
I could have only dreamt about a almost perfect combination of a commuter car. And it is such a quiet achiever...
The gearbox makes the drivetrain very versatile. It can even cope with the horrible ICE :-) There are losses though, which is why direct drive can be better if you have a suitable motor & controller.

With a gearbox, if you get it wrong, you just change gear (seconds). With direct drive, if you get it wrong, you have to change the diff, or the wheels, or put the gearbox back in :-)
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Post by Johny »

Hi guys. I've avoided wading into this thread until now but it seems to have settled down a bit.
This is my story - and I'm stickin' to it!

Back around June this year I started getting the EV bug and began to look into how I could convert my already registered 1960's English car to electric. The wife didn't fall down dead when I suggested that this was a way to get our classic back on the road (I had been about to totally restore the petrol motor in it).

Since it was an automatic and I had already found out that fitting a manual, even though I had the pedals and hydraulics, was not an easy task due to the fact that the car had not been made with the gearbox mounts for a manual - I decided to look into direct drive.

Many websites later, including quite a few emails with, Jim Husted, the guy who customises the motors for White Zombie and Kilocycle, I had been convinced that the only way I could direct drive this car (total weight would be around 1200kg) would be with either a Transwarp 13 (Jim thought a 11 inch would still not handle take-off from stall) or a pair of 8 inch motors very similar to the White Zombie (drag racing Datsun) setup. The two motors allow you to lower the starting current by running them in series during take-off then switching to parallel for higher speed (this has a strange parallel in AC motor land).

The other issue was that I would need at least a 1000 Amp controller - preferably 2000 Amp which meant the Zilla. At $5000 (US) for the 2000Amp and about $6000 for the motors, this was already beyond my budget for the whole elctric system. I told him I just wanted to drive to work - not have the fastest drag EV in Australia.

Around about then 2 things happened. I stumbled across Red Suzi's entry on evalbum (and then this forum) and I noticed that a number of evalbum cars were AC motor powered.
I fairly quickly discovered that the AC powered EVs mostly used really expensive commercial controllers and had even emailed HiTor about their offering and got an even bigger price shock.
Back to Red Suzi. Having had lots of experience in industrial DC drives (controllers), and having watched the total ingress of AC drives and motors into industrial areas previously dominated by DC motors and drives, I felt I had enough knowledge to at least pursue this as an option.

The AC motor, in rear wheel direct drive, has a few advantages over a DC motor in the same setup. Using an industrial 415 volt 3 phase motor means the current is lower during start off Torque. While new AC controllers are indeed expensive, their are Chinese options, just as Goombi has found for DC controllers. I spent a lot of time and energy tracking down prices of virtually every AC controller that was possible to get in, or to, Australia. The posts are here somewhere.

Once the decision to "go AC" was made, the motor and controller became a really complicated area to decide. There are the main compromises of weight, starting torque and maximum speed - hence the threads containing lots of spreadsheets and calculations. I think I have bought the right controller but the proof will be in the "eating". I have a motor waiting for me in a store in South Melbourne but is it the right one???

Industrial AC and controller isn't for everyone, I hit little problems constantly - for instance I won't have a speedo cable so I'm re-engineering my dashboard for total digital displays - something I can do because it's my job.

There are times when I start to wander down the easier DC path, then the gearbox and/or controller issues rear up and I jump back - but for some of us EVers, it's the more interesting way to go - and for me it will be less expensive than a similar DC option.

We are ALL EVers. I read many posts with envy and relish every word on threads written by those who are already driving their hard one prizes. I don't care whether the electrons dart back and forth or just flow in one direction...
Good luck to all of us.



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Post by sparau »

Hi all :)

Interesting reading. Do you think it would be wise or perhaps highly helpful to try and make a list of compatable controllers / motors / batteries for people without the experience in the area to work with? (and please forgive me if i have missed one already existing)

The goal of furthering EV's it appears to me is to make it possible for the comparitive novice to put one together (eg *me* - little electronics/electrical knowledge, computer programmer with fair mechanical experience).

The end goal to make an Open Source set of blueprints for putting one together yourself in the safest way.

Lets say some categories:

1: Car 650-900kg - gearbox drive - DC

Moderate performance = 7" DC - curtis? - TS 96v 30*60ah (180A safely) lithium pack
Medium performance = 9" warp 9 - curtis - TS 144v 45*90ah (270A safely) lithium pack
High performance = warp 9 - zilla? curtis? - 160v - TS 50*160ah (480A safely) lithium pack

2: Car 650-900Kg - direct drive DC
3: Car 650-900Kg - gearbox AC

etc. etc.

Just a thought.
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Post by Goombi »

Thanks for calculating the distance and speed of the Motor coupled direct to diff. Fuzzy and woody came with the same answer.
4166= 100km/h That is a fair speed but not impossible from AC motor. What would it use in AMPS at this speed??? and where does the curve start to drop? Where most power is needed between 60 and 100Km/h the power drops and the amp consumption will increase furiously.
The range between 0 and 100km/h is a fair bit to ask from a directly coupled motor. The speed 4166rpm in my opinion will do a comfortable existance with a even a 3 speed gearbox. and run top speed at comfortable 2500rpm with plenty of oomph ...
Most DC motors will reach 3000 tops that means top speed coupled directly is around 60-65 km/h... Not good..
Example: when driving in town in 3 rd gear and coming to a hill i see the amps jump up change into 2 nd and the speed slows marginally and the amps fall well down. My thrd gear will run up to 65 km/h using 120 amps if favourable i switch to 5 th gear my amps drop to 50-60 and increase the speed--- and get caught speeding Ahhhrrrr

Sparou,
You have to decide which way you will go-- AC or DC There is a lot of information in this chat room just go through some older lisings
Cheers and welcome
Last edited by Goombi on Tue, 16 Dec 2008, 12:27, edited 1 time in total.
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Post by woody »

Goombi wrote: Thanks for calculating the distance and speed of the Motor coupled direct to diff. Fuzzy and woody came with the same answer.
Yes that was nice.
Goombi wrote: 4166= 100km/h That is a fair speed but not impossible from AC motor. What would it use in AMPS at this speed???
For an AC motor, up to about 70% of peak torque, AMPs is proportional to torque.
Beyond that it goes up, peak torque is about triple nominal torque for quadruple AMPs.

Like DC, voltage goes up for speed.

Looking at my ideal setup (18.5kW ABB 4 pole rewound for 220 volts with 80kW 144A controller), this would be 132Amps per phase on the motor, 110A from the batteries, giving me 139Nm at that rpm.

The peak torque would be 267Nm from 0 to 70kmph (2911 rpm), this is limited by the controller current limit of 144A per motor phase.
Goombi wrote:and where does the curve start to drop?
It drops when you run out of voltage. A standard australian delivered 4 pole motor
like acmotor is using starts to drop off just before 1500rpm.

When you rewind a motor, you trade volts for amps, so rewinding at 200V instead of 400V, you need double the current for the same torque, but that torque drops off just before 3000rpm, instead of 1500rpm.
Goombi wrote:Where most power is needed between 60 and 100Km/h the power drops and the amp consumption will increase furiously.
Are you talking about motor current or battery current?

In AC land, the current drops off too after this point, you are "over the hill" you've run out of voltage and each increase in speed will proportionally decrease the power available and used.
Goombi wrote: The range between 0 and 100km/h is a fair bit to ask from a directly coupled motor. The speed 4166rpm in my opinion will do a comfortable existance with a even a 3 speed gearbox. and run top speed at comfortable 2500rpm with plenty of oomph ...
Most DC motors will reach 3000 tops that means top speed coupled directly is around 60-65 km/h... Not good..
Example: when driving in town in 3 rd gear and coming to a hill i see the amps jump up change into 2 nd and the speed slows marginally and the amps fall well down. My thrd gear will run up to 65 km/h using 120 amps if favourable i switch to 5 th gear my amps drop to 50-60 and increase the speed--- and get caught speeding Ahhhrrrr
I guess this is motor amps then. At a higher RPM for the same power you are using less motor amps, but more volts. Should be more efficient :-)

Yes 0-100km/h is a fair bit to ask. The motor I am wanting is a 108kg 160 frame (~13 inch), and the controller is 45 kg, so there's a fair bit of mass produced engineering in there to handle the task.

Yes the AC stuff is not purpose built, but because it's mass produced to be adaptable to different tasks (conveyers, fans, pumps, lathes, winders), it is:
1) adaptable to EV use. (Treat the road as a conveyor belt?)
2) better value for money due to economies of scale
3) better tested due to large market
4) available 2nd hand.

cheers,
Woody
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Post by Goombi »

" When one runs out of Voltage" The AC conversion tranfere AMPs and Volts from DC battery power to AC converter come Controller (percentual losses for this tranfer) Every exchange is costly-- how much?
If the 120 volt dc (1000 amp)goes through to controller and into a AC motor 270 volt --re-wound motor-- how many amps will also pass through to the motor? or will be available ..same? 1/2? double?

How low can the DC voltage (120 vdc)drop for the ac motor to also stop
There must a critical area where the whole system seizes.
If the voltage drops to 90 volt what will happen?
and yet there is plenty of amps still in the batteries The lack of voltage to controller does not allow the tranformer to create energy for the motor. or well below in order to perform. This AC is rather a complex system which is not fully understood by most anyone.. If someone were to offer a controller and motor perfect combination that it will be compatible and fail proof then perhaps i will take more interest. THERE HAS TO BE ONLY ONE TYPE OF AC NO EXTRA THIS AND NO EXTRA THAT SIMPLE ONE OFF-- PERFECT. But wood would not like to have the same one as acmotor ohh no no thats no competition LOL LOL Image Image
Last edited by Goombi on Tue, 16 Dec 2008, 14:26, edited 1 time in total.
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Post by zeva »

Goombi wrote: Most DC motors will reach 3000 tops that means top speed coupled directly is around 60-65 km/h... Not good..

While many DCs out there are indeed rated to around 3000rpm, NetGain's 9" motors are rated to 5500rpm - so you'd be exceeding the speed limit of any road in Australia! (The 7s are a little higher still, and the 11s are a little lower. I'm pretty sure the Advanced DC 8" and 9" motors are similar.)
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Post by Goombi »

Who wants a high speed whistling motor 3000rpm is plenty for reasonable distance travel. You do realise the higher the revs the shorter the life of your batteries and your motor... I am 72 and Like to drive my 3000 rpm EV in another 15 years and it will..-- Positive!!!
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Post by Goombi »

Someone had problem with insurance I tought i get mine done no problem

SUNCORP-METWAY they own aami, promina and 7 others..
My insurance is third party accident--- 120$ per year
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Post by zeva »

Goombi wrote: Who wants a high speed whistling motor 3000rpm is plenty for reasonable distance travel. You do realise the higher the revs the shorter the life of your batteries and your motor... I am 72 and Like to drive my 3000 rpm EV in another 15 years and it will..-- Positive!!!

Oh sure.. I just didn't want that 3000rpm figure causing people to preclude DC motors when considering a DD conversion!

(FWIW I calculated the RPM of the Warp 11 in my MX5 to be ~2300rpm at 60km/h, which is conveniently right around the motor's peak efficiency. 3000rpm would get me just short of 80km/h - a bit low for those of us frequenting highways. The national speed limit of 110km/h requires 4200rpm from the motor in my EV.)
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Post by Goombi »

Ian, I like your conversion and the speed max is simmilar to mine and
I realised from previous post that you have only shown alternatives to 3000rpm motors and the DD system You must have a reason for choosing 3000rpm Motor for your MX5. I think the speed is comfortable..
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Post by AMPrentice »

Just in case no one figured out who makes a commercial DC drive car,
not in large numbers a whole 2!! so far but the Tango comes to mind.
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Post by sparau »

Goombi wrote:Sparou,
You have to decide which way you will go-- AC or DC There is a lot of information in this chat room just go through some older lisings
Cheers and welcome


Fair call - i have gone through a lot of posts - it's just that many of them contain contradictory or argumentitive information, it can be hard to compile in your head hundreds of posts - no dissing anyone, there clearly are a lot of very knowlegeable people here.

My point being that it would be worthwhile to find common ground and lay out a good guide for conversions of different vehicles for different purposes (not necessarily perfect, just good and safe would be cool).

I am a computer programmer and am amazed at what can be achieved via community effort (love open source projects) and while a forum alone is not the perfect method to manage this it is a start. Next would be working out what tools can be used to map out the possibilities.
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Post by antiscab »

Goombi wrote: Who wants a high speed whistling motor 3000rpm is plenty for reasonable distance travel. You do realise the higher the revs the shorter the life of your batteries and your motor... I am 72 and Like to drive my 3000 rpm EV in another 15 years and it will..-- Positive!!!


high rpm might shorten the life of the bearings (and maybe brushes?) in your motor,
However it will *increase* the life of your batteries and controller.
it may even increase the life of your motors insulation.

your motor controller is more efficient at higher duty cycles (ie when the motor voltage and pack voltage are closer together).
your motor will be more able to disipate heat at higher rpm.
your batteries will see less ripple at higher controller duty cycle.

Matt
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Performance and cost between DC and AC -EV's

Post by Goombi »



Hi Matt
I have been reading many of your past posts. But this answer you gave is debatable and inconclusive...
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Performance and cost between DC and AC -EV's

Post by Rattrap »

sparau wrote:My point being that it would be worthwhile to find common ground and lay out a good guide for conversions of different vehicles for different purposes (not necessarily perfect, just good and safe would be cool).

I am a computer programmer and am amazed at what can be achieved via community effort (love open source projects) and while a forum alone is not the perfect method to manage this it is a start. Next would be working out what tools can be used to map out the possibilities.
Well said Sparau,
Over the last 6 mths that i've been a member here i've mostly just been skimming over all the many interesting posts here, glazing over what i don't understand & trying to absorb the few bits that i do but over the last week or 2 i've begun reading in depth & trying to get my head around it all & i can tell u now - MY HEAD HURTS!!!Image
I'm quite sure i'm not the only 1 who has felt that way at times.
A basic guide here on this forum would be a great place for new comers like me to start so that when threads get really technicial as this 1 has we have some sort of common reference to help us swim thru the figures.
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Performance and cost between DC and AC -EV's

Post by Goombi »

SPARAU-- you are in a wrong place -- why don't you start a new TOPIC
This discussion chat is about "Performance and cost between DC and AC -EV's" any discussion on this subject is most welcome.
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Performance and cost between DC and AC -EV's

Post by fuzzy-hair-man »

Goombi wrote:

Hi Matt
I have been reading many of your past posts. But this answer you gave is debatable and inconclusive...
The specs on the AC24LS I mentioned before show that it is getting towards it's most efficient at about 5000 - 6000 rpm so this would support what Matt said whether this efficientcy comes from the motor or the controller or both I wouldn't know.

Are high RPMs a problem? is there a reason to suggest that they will cause your electric motor to wear out prematurely? if the motor is built for those kind of revs I don't see a problem with using them but I know nothing about it.

I can see that there is far more to wear out on a ICE with high revs than on an electric motor, but is it a case of transfering a dislike of high revs from ICE to electric where it isn't really an issue?

It seems like it might be important because it seems like high revs are one of available the ways of going direct drive ie either you have a motor that has high torque and low revs and a normal (~3:1) diff or you have a motor with moderate torque and high revs and a diff or gearbox with a high ratio (10:1) if high revs are really a problem then it looks like you rule out one of these options.
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Performance and cost between DC and AC -EV's

Post by Johny »

Goombi is correct in one respect. High RPM will wear out a brushed DC motor faster and it's not proportional - the rate of wear increases more than simply as a multiple of RPM.
Not so with brushless motors (BDLC and AC) where the only wear factor related to RPM is bearing life which is generally rated at about 20,000 hours (that's over a million kilometers at 60 k/h).
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Performance and cost between DC and AC -EV's

Post by Goombi »

DD or not DD----With various diff sizes from 3-4-5-7-9-11:1
Take the 3:1 DD one would need a very large motor but could reach 100Km/h in around 3.600 rpm.
7:1 DD will need to move at 7200RPM or run the motor at 3600Rpm at 50 km/h.
Considering all ratio's Not very satisfactory..
Perhaps AC could do a better job but the the sheer rate between 0 and 100km/h will need some gear in between, so the motor can run at best capacity and power around 3.000rpm '
How about using 2 motors one to 50 km/h and then engage transfer case from 50-100 km/h.... how about 2 speed diff? ---that has a merrit---
2 speed diff has definitely a strong possibility ratio 6:1 and 2:1
6:1 will take you through the City traffic and 2:1 to the highway.
That could be a revolutionery concept adaptable for DC and AC with ease.
depending on ones preferences-- and suddenly DC and AC become good friends.
There are 2 speed diffs available for trucks from 4 tonne up.. nothing smaller.
Enough inventions for one day.....


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