AC motor big words

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HeadsUp
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AC motor big words

Post by HeadsUp » Thu, 12 Mar 2009, 20:03

i looked at some 3 ph motors , which are labelled in their spec sheet as ;


Motor (VAC) - 22/15x3 kW

22 kW peak , 15 kW continuous ?

what does the " x 3 " mean ?


it is from a lathe spec sheet , and mentions a 22 minute duty cycle , but no percentage , maybe its 22 minute continuous at 22 kW ?

max 5,000 min-1
22/15x3 kW
350 N•m (257 ft-lbf)

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Richo
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Post by Richo » Thu, 12 Mar 2009, 21:16

maybe give us a link.
Unlikely a lathe is going to be using 15kW continuous.
Maybe more like the 3kW at 22min on 15min off?
So the short answer is NO but the long answer is YES.
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Post by HeadsUp » Thu, 12 Mar 2009, 23:07


http://www.okumaaustralia.com.au/produc ... B4000%20EX

there is a list from small to large lathes , 7 kW to 50 kW , click on the lathe model , then click the PDF , it will show spindle motor kW

this is the current model series , many of which have a hollow shaft direct drive motor , the older ones had standalone motors with belt drive.

edited: many CNC lathes will run all day , using auto bar feeders , program the machine from the office , walk down and check a sample and employ a 17 year old kid to drive a forklift replacing the finished product feed bin every 3 hours.   

i dont expect a current model motor to be cheap , but second or third generations back there could be good technology and cheap second hand stock.

thankyou.
Last edited by HeadsUp on Thu, 12 Mar 2009, 12:23, edited 1 time in total.

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Richo
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Post by Richo » Fri, 13 Mar 2009, 07:32

Mmm Interesting.

A gearbox helps reduce the peak power requirements.
For example using about 85kW peak motor will get a BMW to 100 under 8 secs using a gear box.
Using the motor direct drive it would be about 15 seconds (Slower than the original car).
To achive the same results without the gearbox I need more like 140kW peak motor power.

The 30kW lathe motor has a sync RPM of about 445RPM and 700Nm.
The 30kW is fine for continuous but you will need more for acceleration.
Lets say you reconfigured the motor (rewind) and got it to produce 90kW.
Thats 700Nm out to 1335RPM.
On the BMW this would peak out at 35kph.
After that the acceleration would drop off.
And would take about 19sec to get to 100kph.
Which is reasonably slow - nearly twice as slow as the original ICE.

Assuming that these lathes run from 415V 3-phase.
You would still need to modify the motor to get the peak power.
ie rewind for about 120V ac.
Being a spindle motor for a lathe with a hollow centre you would also have to provide a custom shaft to couple to the diff. (140mm dia)

It would be similar to doing an eV conversion with a 16-pole Induction motor without being supplied a shaft.
Sounds like a lot of work.

btw I couldn't find the reference to the x3.
So I don't know what it is for.
But it would be 22kW for 30min or 15kW continuous.
So the short answer is NO but the long answer is YES.
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Post by HeadsUp » Fri, 13 Mar 2009, 07:42

beautiful . thankyou kindly

agree that the hollow shafts would add extra weight and machining , but the older generation were plain keyed shaft

funny if i email the Okuma tech department , they might say " sorry ... sir the x3 is a typo "

Image

thanks Richo.

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Post by Richo » Fri, 13 Mar 2009, 07:55

Yep typo.
It's good to see you are thinking outside the box for suitable parts.
Don't get me wrong - It would work
it's just a question of cost and extra effort to get it to work.
If the weight of the motor is under 120kg you could have a motor with massive potential ie 200kW+.
But still a lot of changes to work properly.
And no guarantees of working or performance.
So the short answer is NO but the long answer is YES.
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Post by weber » Fri, 13 Mar 2009, 08:44

Richo wrote:A gearbox helps reduce the peak power requirements.
For example using about 85kW peak motor will get a BMW to 100 under 8 secs using a gear box.
Using the motor direct drive it would be about 15 seconds (Slower than the original car).
To achive the same results without the gearbox I need more like 140kW peak motor power.


You would need a motor capable of 140 kW peak, but would you actually need to _use_ that peak? Couldn't you still have a VF drive and battery that were only capable of the 85 kW, thereby shaving that peak, and still do quite well?

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Post by antiscab » Fri, 13 Mar 2009, 09:13

for direct drive you build your controller and motor to be so powerful that you have the same power available at low speed as you do at high speed.

This means the setup is capable of *far* more power than the batteries can put out.

you cant get away with a smaller vfd, as you need the higher motor side amps, to drive the bigger motor, to get the higher torque needed to get the same power at lower rpm.

instead of only needing that 85kw as a peak value, with direct drive, you need it as an *average* value.

the funny thing is, a gearbox limits you to a lower power motor, so it removes any upgrade potential.

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Post by Richo » Fri, 13 Mar 2009, 09:23

Assuming it was the bigger motor - sure.
Having a bigger motor is more efficient too Image
Plus no gearbox for lower losses and things to break Image
Prob may not even need to rewind it either.
Just buy and put in.

A lot more simple than trying to get a lathe motor to work Image

Know of any cheap ali 180-frame motors?
So the short answer is NO but the long answer is YES.
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Post by weber » Fri, 13 Mar 2009, 09:27

antiscab wrote:you cant get away with a smaller vfd, as you need the higher motor side amps, to drive the bigger motor, to get the higher torque needed to get the same power at lower rpm.


But at lower rpm, you have some volts to spare, so you trade them for reduced amps by switching your motor from delta to star. Then you require only 0.58 of the current but must put in 1.73 times the voltage. Does that get you down to an 85 kW VF drive with your 140 kW motor and still give max torque at low revs?

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Post by Richo » Fri, 13 Mar 2009, 09:33

antiscab wrote:the funny thing is, a gearbox limits you to a lower power motor, so it removes any upgrade potential.


Not if you buy 1 small one to go on the box.
Then later buy another exactly the same.
Ditch the box couple the two together lengthways.
Now you have decent direct drive.

The numbers work.

But really who wants a box?

when you can play with these...
So the short answer is NO but the long answer is YES.
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Post by acmotor » Sat, 14 Mar 2009, 06:49

Don't show Andrew ! Image
iMiEV MY12     105,131km in pure Electric and loving it !

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Post by Nutz » Sun, 26 Apr 2009, 06:17

Can somone translate the info in this for me and let me know if it is big enough for an EV? It has agreat retro look for my old Mazda.
http://cgi.ebay.com.au/ws/eBayISAPI.dll ... 2759.l1259
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Post by woody » Sun, 26 Apr 2009, 06:35

Sure. 1/3HP = 0.25kW. Would only be enough power to run the demister fan unfortunately. :-(

You'll be looking for a 15-20 HP (11-15kW) 4 pole (~1450rpm) 3 phase motor, which will weight 60-100kg.

Controller you'll want 22kW (cruisy) or more (55 - 75kW is high performance) 3 phase which will be 10-75kg.

Voltage will probably be ~400V AC in australia which will need 600V DC batteries.

3 phase 240V AC is US/Japan spec, but more weight per kW.

For retro, you can fake it if you want :-)

cheers,
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Post by acmotor » Sun, 26 Apr 2009, 06:45

Sorry Nutz, that motor is not even retro. Scrap copper value only.
The seller is smooth with his words, maybe he'll find a buyer !

It is amazingly heavy at 20kg for 1/3 hp. (250W , 0.25kW)

You need a motor with 100x times that power for an EV.

Single phase motors are really not an option for EVs. Their power to weight is very low and efficiency poor. The main problem is their lack of starting torque compared with 3 phase motors. Image

edit: nice overlap there woody !
Last edited by acmotor on Sat, 25 Apr 2009, 20:48, edited 1 time in total.
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Post by Nutz » Sun, 26 Apr 2009, 18:01

Voltage will probably be ~400V AC in australia which will need 600V DC batteries.

--Gulp, that's 50 x 12 volt lead acid or 200 x 3v Thundrerskys...at least you would not have to use the 90amp hour ones.

3 phase 240V AC is US/Japan spec, but more weight per kW.

--Would this be greater than the weight offset by halving the battries?
Last edited by Nutz on Sun, 26 Apr 2009, 08:04, edited 1 time in total.
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Post by HeadsUp » Sun, 26 Apr 2009, 18:31

The Brusa controllers are 120 - 480 VDC

whether you have 200 x 40 AH batteries , or 100 x 80 AH , you still only get driving range from the kW/hrs of battery you have on board , and battery cost is the same per amp hour if using TS batteries.
you would however save money with having lower battery pack total voltage by requiring fewer BMS units ,fewer cabling connections , and battery charger requirements may also be a bit lighter

http://www.brusa.biz/products/e_dmc514378.htm

looks like very nice quality device on paper , but currently too expensive for the likes of us ,obviously its more logical for them to focus on selling packages of 50,000 units per order to Volkswagen , BMW mini , Renault etc

Azure also looks like a nice package , but again , the pricing is not there.

-----------------------------------------------------------
from Blade Electric Vehicles
AC24LS motor for US$2895
DMOC445 controller for US$3495
AT1200 gearbox for US$1695.

For larger applications;
AC55 for US $3495
AC90 for US$4695.


some people here have built perfectly good EV's using Danfoss controllers ( approximately $ AUD 2500 controller , and a 415 v 3 ph motor $ 1100 - 1500 )

for a decent range , my calculations come up with around 28 kW/hr of battery which will bite a hole in your bum where your wallet used to be to the tune of around $14,000

hope that helps

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