12 kw rc motor

[olaf-lampe]

sorry to say it arlo1 but i think your statment is not true.. KT (torque constant) is inversely proportional to KV. the delta/wye difference is sqrt3 (1.73).

the output watts for both motors would be the same (if the efficiency is the same)
but the delta motor has 1,73 times more rpm than the wye motor
the wye motar has 1,73 times more torque than the delta motor

Nope it is 100% correct!
As quoted by luke.
" For the same battery amps and battery volts its identical. But Delta puts 1.7 times more load on the FETs"
So WYE does not give you 1.73 times more torque it just makes it 1.73 times eiser on the FETs!

Nieles is right.
Why else would a wye motor have the same efficiency but deliver lower rpm? Same battery current leads to longer duty cycle for the FETs in wye, thats why switching losses and overcurrent stress is lower in wye. The inductivity is higher in wye, thats why the current slope is less steep: it takes longer to reach current cutoff limit.
If I only could explain it better
-Olaf

-Olaf

 

[nieles]

Nope it is 100% correct!
As quoted by luke.
" For the same battery amps and battery volts its identical. But Delta puts 1.7 times more load on the FETs"
So WYE does not give you 1.73 times more torque it just makes it 1.73 times eiser on the FETs!

okay sorry for questioning you!

for my understanding; can you confirm/deny this:

2 motors with different KV an KT (both a delta wind) both produce the same torque at the same battery voltage/current.
but the controller has an easier time controlling the motor with the lower KV.

what about this situation:

motor 1: delta wound with battery volage: 50V battery current: 50A
motor 2: wye wound with battery voltage: 86,5 (50*1,73) battery current: 50A

both motors have the same amount of windings.

is the torque higher or the same?
(i really would like to understand this, so that is why i am asking)

Niels

 

[Arlo1]

Nope it is 100% correct!
As quoted by luke.
" For the same battery amps and battery volts its identical. But Delta puts 1.7 times more load on the FETs"
So WYE does not give you 1.73 times more torque it just makes it 1.73 times eiser on the FETs!

okay sorry for questioning you!

for my understanding; can you confirm/deny this:

2 motors with different KV an KT (both a delta wind) both produce the same torque at the same battery voltage/current.
but the controller has an easier time controlling the motor with the lower KV.

what about this situation:

motor 1: delta wound with battery volage: 50V battery current: 50A
motor 2: wye wound with battery voltage: 86,5 (50*1,73) battery current: 50A

both motors have the same amount of windings.

is the torque higher or the same?
(i really would like to understand this, so that is why i am asking)

Niels

These are more questions for guys like luke or ryan. From your situation motor 2 would produce more torque and HP the max rpm would be the same because you upped the voltage to make up for it so then as long as you are not to close to saturation it would be simply 1.73 times as much torque because thats how much more wattage you are putting into the motor!

 

[Arlo1]

SO to post this clearly.
Delta and WYE with the same amount of copper fill with the same battery amps and battery volts will give you the same Torque output
Series and Parallel windings with the same amount of copper fill with the same battery amps and battery volts will give you the same Torque output
Steveo and Dr Bass both tired both of those tests on bikes on the road and found Luke (live for physics) was right in saying what I just posted!

 

[Biff]

Arlo is Correct, but everyone else is also correct. For a given battery voltage and current your motor should produce the same output power regardless of delta or wye connection, since battery amps/volts is power, and battery Volts doesn't change with RPM, and output torque and RPM is also power, they must be equal (assuming 100% efficiency), so your controller can spin your motor at whatever RPM/torque it wants to get the same output power, so in theory it doesn't matter if your motor is wye or delta if the required motor current/voltage to produce the desired torque/rpm is within the range of the controller, your controller can do that for you.

However what everyone else is talking about is motor volts and amps. And they are correct. Changing between Wye and delta swiches the Kv for the motor, therefore if you switch from delta to wye but keep the same motor input current and voltage you will get 1.73x the torque at 1/1.73 x the RPM (same power), The Battery Voltage will still be the same therefore the battery current won't change either, since you still want the same amount of power from the battery. Now if you wanted to keep the same shaft torque and RPM when you switch from Delta to WYE, your Motor volts would have to increase by 1.73x and your motor current would decrease by 1/1.73x (provided your controller can operate at that voltage and current), but since the motor power doesn't change, your battery power also doesn't change therefore your battery voltage and current remain the same.

Hope that clears it up, you are all right, just talking about different things.

-ryan
*edit to add some clarity

 

[nieles]

thanks for clearing that up.

but to answer the the "question" from crap.

if we are limiting battery current there will be no performance gained

correct?

what about if we limit the phase current?

 

[Biff]

thanks for clearing that up.

but to answer the the "question" from crap.

if we are limiting battery current there will be no performance gained

correct?

Generally that is true, but there are lots of things to consider, what is performance? Is it peak torque, top speed. Changing the winding changes the controllers ability to deliver power at different speeds, that can somewhat be overcome with adjusting gear ratios.

Quite often performance is measured by top speed, a current limit on your battery spesifes a maximum power, maximum power will translate to a maximum speed (the speed at which rolling resistance and drag add up to the power the battery can provide) if the system is geared to get you to that point.

what about if we limit the phase current?

If phase current is the limitation (controller or motor limitation), you probably want to get the motor so that it overheats at the same time as your controller (i.e same current limitations on both). If your controller can deliver 220A continuous, and your motor can handle 380A continuous and it is in delta, you would probably want to change it to wye, and re-gear 1.73x taller. This one is hard to explain, since upon intial calculations you might figure out this:

Imagine a 70V 220A controller, with a 380A continuous rated motor with a 40RPM/V kv in delta. That should spin up to 2800 RPM and deliver 220/380 of its rated continuous torque, I am lazy to calcualte a valid continuous torque, so lets call it 1000 sheep (Sheep is a new unit of torque), so in this configuration it should be delivering 579Sheep of torque. So the max theoretical power of the motor is 1.6 Mega Sheep RPM (power is rotational speed times torque) and the motor shouldn't get too hot since you can't deliver its rated current.

Now with the same 70V 220A controller, switch the motor to WYE, the continuous current rating drops by a factor or 1.73, 380A/1.73 = 220A (convienient eh?). Not so nifty is the kV alo decreases by 1.73 to 23RPM/V which means the 70V controller can get you to 1600 RPM. The good news is that your 220A now delivers the full 1000Sheep of torque. So you now have a motor that can still only deliver 1.6Mega Sheep RPM of power, but gets hot. That seems lame.

So then why aren't all motors designed to have a really high kV so that you can spin them extremely fast and deliver lots of power and not overheat. The answer to that is complicated. I just like to go by the common intuition which is that if everything fails at the same time, it was designed properly. If you have a motor and controller with the same current rating, you probably have the optimal system without going into all the crazy math to figure out why it is the best system.

-ryan
*note I am lazy and not really thinking everything through so there could very well be an error in my logic above.

 

[crap]

thanks for clearing that up.

but to answer the the "question" from crap.

if we are limiting battery current there will be no performance gained

correct?

what about if we limit the phase current?

Correct, if battery amps is the limiting factor a y/d switch will not improve performance. However, since the amp limit of controllers generally apply to both motor side and battery side (sometimes they can take some more amps on the motor side, but rarely 1.73 times as much), and the motor amps are always greater than or equal to battery amps, the motor amps (phase current) will set the limit. In this situation a y/d switch will improve performance.

If you have a controller that can feed the motor with full battery amps from start (meaning a hell of a lot of motor amps) and all the way to max rpm (where motor and battery amps are about the same), a y/d switch will not improve performance. But does such a controller exist? and at a reasonable price?

 

[Arlo1]

Hey biff what if the limit is motor saturation? Like on my x5 I am able to power with enough power that I can up both phase and battery currents and see no gains.
WYE DELTA switching wont help that either right?

 

[Biff]

Hey biff what if the limit is motor saturation? Like on my x5 I am able to power with enough power that I can up both phase and battery currents and see no gains.
WYE DELTA switching wont help that either right?

If you are able to saturate the iron, then you are getting all the torque that motor can possibly deliver. If you can do that in WYE or Delta, then you probably want to keep it in delta so that you can get the highest speed possible for your voltage. You might consider re-winding it with fewer turns so that you can get it even faster, as long as your controller can still deliver the higher current requred to deliver the original maximum torque. If you decrease your turns per tooth from 6 to 5, you would then need to provide 6/5 times the original current to get the same torque so doing that would increase the demands on your controller to get the same motor torque.

-ryan

 

[Arlo1]

Marko has good news for this motor BTW He said they were sucsessfull with a 36 fet controler. I am hoping they post the results soon!

 

[satanicoo]

90 pages, interesting as you guys made it a breeze an fun to read
I guess even myself will give it a go at building a controller for it, but with a simple digital encoder for rotor positioning, i don't think i have the knowledge to do hall sensors, or even a sensorless controller.

Do you think this motor, water cooled, can do 20KW continuous?

 

[Arlo1]

90 pages, interesting as you guys made it a breeze an fun to read
I guess even myself will give it a go at building a controller for it, but with a simple digital encoder for rotor positioning, i don't think i have the knowledge to do hall sensors, or even a sensorless controller.

Do you think this motor, water cooled, can do 20KW continuous?

It will be ~20 hp watercooled continious the new version might be less but still close!

 

[Accountant]

Marko has good news for this motor BTW He said they were sucsessfull with a 36 fet controler.


YES, in the test lab, under 3,2 KW constant load, without any cooling.

Upgraded and modified 36 infineon controller was doing fine.

After 30 minutes testing under constant load motor temp was under 90 C.

New controllers (prototypes with 36 and 40 mosfets ) from another company just started their trip today.

We will have them in 5-10 days, load will be increased, and that everything will be tested to the limits, and over.

Tests will be done in the test lab, and on the real life testing platform.


Colossus /Infineon combination will be compared with Etek/Kelly.

Batery pack is 72 V 20 Ah A123

Details are here :

http://www.greyb.org/dEgeneric.html

 

[markobetti]

Accountant, u write insufficient details and you ll get people confused.... *?*?*
Test was under 48v , second thing is that phases rewadings were off( hal sensors werent aligned )thats why second test is planned next week ( because at least one phase is doing the drag and working as a generator .. ) .One phase was 30 ,second 60 and third 90 amps at one moment...and still with this continuous power was 3,2 kw and this is good result considering all things said . The windings are perfect and kv is as stated . Hal created new board for Hal sensors so that on second test we are able to optimize and adjust phases in Slovenia . Nevertheless we didn't do the test with cooling , so that's also important .

 

[markobetti]

One more thing : power was measured professionally on output : SHAFT, not battery current .

 

[Nuts&Volts]

bump

Any updates??

 

[tostino]

I am also interested in an update. I prolly should get back to work on my 36 fet controllers though, so they are ready by the time this thing is available =p

 

[Arlo1]

I have been informed they are just tring to get a sinusoidal controler to test it with before releasing collossus. I agree the weight sucks but i have two of the prototypes and untill we have a good controller they are just paper weights!

 

[Arlo1]

I got it running and I plan to ride it by the weekend! Right now it is limited by my power supply!
[youtube]c0WZ2pkAbYs[/youtube]
[youtube]_kS6Sbc67V4[/youtube]

 

[Thud]

Lookin good Arlin,
I am anxious to see if you run into the throttle cut-out issues under load. (hope not) Keep the video running & good Luck!

 

[Arlo1]

Here is a picture of my ossicillope mesuring one phase.
SO this showes one revalution per 9.9 miliseconds! Thats 6060 rpm!

 

[Arlo1]

Some more videos Stock shunt this time and I found at very hi rpm it cuts out but if you let of and grab the throttle again it goes again!
BTW The most I could gear it down was 4:1 and the tire DIA is 19 inches...... So at 6060 Rpm.......... thats 85mph
[youtube]gQ90NPxyXeM[/youtube]
[youtube]WPojeKyi5fQ][/youtube]
[youtube]xkRJUerKoZo[/youtube]
[youtube]yfPVAcUfDj4[/youtube]

 

[markobetti]

what gearing did you put ?

 

[Arlo1]

what gearing did you put ?

As I said the reduction is 4:1 so thats 12 tooth front and 48 tooth rear.