3-phase brushless

[VadimS]

Heat = energy. Whats is a measurement of energy.
Therefore if the total resistance changes the energy lost as heat will change. Adding more switching devices will lower the electrical resistance. Using devices with lower on resistance will have the same effect. But when you are talking about 7000w and high voltages dissipating 1 or 2% (70-140w) in the controller is insignificant.

Actually if you double the number of devices you will quarter the amount of heat in each one. Because the total resistance is halved and the number of devices is doubled.

Please think back to high-school physics class before posting.

I'm currently taking "Computer Engineering Technology", it's a 4 year course and this information is tout in the first semester.

 

[Qmavam]

Heat = energy. Whats is a measurement of energy.

Whats? The proper spelling is watts.

Therefore if the total resistance changes the energy lost as heat will change. Adding more switching devices will lower the electrical resistance. Using devices with lower on resistance will have the same effect. But when you are talking about 7000w and high voltages dissipating 1 or 2% (70-140w) in the controller is insignificant.

Only insignificant if you provide proper heatsinking. Try holding
a 100 watt light bulb.

Actually if you double the number of devices you will quarter the amount of heat in each one. Because the total resistance is halved and the number of devices is doubled.

Yes, because dissipation in the device is I^2R.
I just didn't do the math in my last post. You also
spread the heat over more area when you double
the number of devices.

Please think back to high-school physics class before posting.

Smart *** youngsters remark.

I'm currently taking "Computer Engineering Technology", it's a 4 year course and this information is tout in the first semester.

Wow!
tout? maybe you meant taught.
Mike

 

[VadimS]

Yes my spelling is horrible but that has nothing to do with that matter at hand.

By insignificant I was referring to overall efficiency and a modern computer cpu puts out over 50w (an older p4 about 80w).

Oh and yes I'm an @ss.

 

[truesprocket]

that small of a motor is equivlent to a 60 or 80cc ! I'm stunned 9+ HP stunned again , man these things are getting good.

I too am interested in using the big brushless motors from hobby city...

But the issue of a motor controller capable of the amp draw necessary would indeed be expensive...

One could probably use this?
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=10332

Link update on the motor:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5139
(9.38 hp peak btw, @ 8640 rpm)

 

[HelloYOU]

Instead of using PM based brushless DC motors, I would go with a 3-phase AC induction motor which have been brushless since 1888 when Tesla invented them and they dominate 90% of the market in industry. A complete package that includes the controller and motor with all other parts can be bought from: http://www.electricmotorsport.com/store/ems_ev_parts_motors_ac-induction.php

 

[j.m.]

Probably because those systems are extremely expensive...

I'd rather use two of the HK outrunners and two ESCs than the cheapest system on that website... Lighter, smaller, more power, 1/5 the price...

Jon

 

[HelloYOU]

Actually, in the industrial setting, 3-phase AC induction motors are cheaper than brushed DC motors, but in the EV world it is the opposite. It's anybody's guess as to why the polar opposites in pricing exists from the industrial world to the EV world. I am not sure of DC 3-phase brushless motors pricing against AC induction in the industrial setting.

 

[j.m.]

AC power is readily available in a wall outlet.

to use an AC system on a car you have to convert the DC from the batteries to AC.

 

[dpaxson]

that's 1 phase AC in a wall outlet. and a controller converts the dc to variable frequency 3 phase AC

 

[zabac70]

that's 1 phase AC in a wall outlet. and a controller converts the dc to variable frequency 3 phase AC

Controllers for DC motors converts DC from batteries to 3 phase DC. Inverters do that for the AC motors.
BTW , I'm a fan of PM BL motors , especially hub motors (efficiency) , and they aren't so expensive (used or salvaged ones especially) and could be found pretty much everywhere (e bikes/scooters).

 

[HelloYOU]

Controllers for DC motors converts DC from batteries to 3 phase DC. Inverters do that for the AC motors.
BTW , I'm a fan of PM BL motors , especially hub motors (efficiency) , and they aren't so expensive (used or salvaged ones especially) and could be found pretty much everywhere (e bikes/scooters).

Actually for brushed DC motors it is square waves with varying duty cycle according to how much speed is needed and is not 3-phase... I suppose you were talking about Brushless DC motors, but it was not specific in your post.

AC variable frequency drives do not use transformers, but instead have a waveform with variable sized square waves feed to the windings of the motor and the windings of the motor turn this wave into a sinusoidal current.

Have a look:

 

[zabac70]

@HelloYou
You are right. I've meant brushless DC and didn't wrote it. For AC matter, I have no remarks.
However , it would be great to see that somebody implement AC system on a go kart (well, somebody with lots of money and know how).

 

[wheels]

posting in this thread for future reference.

 

[fowler]

what??????

 

[wheels]

what??????

i was posting in this thread b/c i learned from it. and instead of not remembering where it was a week from now, i simply posted in here so i could later search thru my own posts(and easily find it). bad habit of mine... and now that i've searched and read a good bit more, i realize that it is discussed in a number of threads.