2 pole vs. 4 pole vs. 6 pole..What does it all mean?

[Mike Luszcz]

I am new to the FE scene, and would like to know what the amount of poles in a brushless motor means. Is one better than the other? I know the Feigeo 580L I was looking at for a big boat was a 2 pole..is that bad? Everyone raves about the motor for the price, but does that cause problems?

 

[Mark Bullard]

I am new to the FE scene, and would like to know what the amount of poles in a brushless motor means. Is one better than the other? I know the Feigeo 580L I was looking at for a big boat was a 2 pole..is that bad? Everyone raves about the motor for the price, but does that cause problems?

The lower pole number has less torque at a lower rpm but has a higher top rpm at full speed. It is reversed for the higher pole numbers. In standard motors that these are designed from, 2 pole @ 3600, 4 pole @ 1800, 6 pole @ 1200, 8 pole @ 900 rpm's. Now all of these motors are based at 60Hz.

 

[Mike Luszcz]

That is exactly what I was looking for! Thanks, Mike

 

[jayt]

While the above is true, it is not absolute when dealing with FE motors because things are never equal. For example, with the similar-size and Kv Neu 1515/1Y 4-pole and Feigao 8XL 2-pole motors, both have virtually equal top rpm at the same voltage - but the Neu is more efficient and has more power at virtually all loads and rpm. A Hacker 8XL versus a Feigao 8XL - both 2-pole motors - the Hacker has higher power and rpm under load due to its better materials and higher efficiency. You really have to go by experience as much as by some general rule of thumb. Fortunately this isn't difficult as you can get good (and unfortunately bad) experience/advice on sites like this one.

.

 

[Mark Bullard]

While the above is true, it is not absolute when dealing with FE motors because things are never equal. For example, with the similar-size and Kv Neu 1515/1Y 4-pole and Feigao 8XL 2-pole motors, both have virtually equal top rpm at the same voltage - but the Neu is more efficient and has more power at virtually all loads and rpm. A Hacker 8XL versus a Feigao 8XL - both 2-pole motors - the Hacker has higher power and rpm under load due to its better materials and higher efficiency. You really have to go by experience as much as by some general rule of thumb. Fortunately this isn't difficult as you can get good (and unfortunately bad) experience/advice on sites like this one.


.

I was going to let this go but when someone does not understand electric motors they do not need to tell someone that does that they are giving bad information. The information I provided is textbook. It stands true with all three phase electric motors including your FE motors. The advice I gave is good solid information of 40 years of experience.

 

[Mike Luszcz]

I appreciate both of your views. I did buy the Feigao 8xl yesterday with the understanding I was buying a $69.00 motor vs. a Neu $250.00 motor, so I can accept a 5mph speed loss, and maybe a couple minutes less run time. For me, budget is key! Its going in a Titan 29 with 120a Turnigy speed control, so I think it will be plenty fast. I don't race, so having the absolute edge is not a need..a want maybe! I do appreciate your views tho. I do foresee in the future, as I learn to drive boats faster and faster that I will want a full out SAW style boat, and the knowledge on good motors will be great then! Thanks, Mike

 

[Mark Bullard]

I appreciate both of your views. I did buy the Feigao 8xl yesterday with the understanding I was buying a $69.00 motor vs. a Neu $250.00 motor, so I can accept a 5mph speed loss, and maybe a couple minutes less run time. For me, budget is key! Its going in a Titan 29 with 120a Turnigy speed control, so I think it will be plenty fast. I don't race, so having the absolute edge is not a need..a want maybe! I do appreciate your views tho. I do foresee in the future, as I learn to drive boats faster and faster that I will want a full out SAW style boat, and the knowledge on good motors will be great then! Thanks, Mike

No problem Mike. I myself do not run electric boats. I do not have the want to race and play with the same motors I work with every day. We rewind and repair motors the size of the ones you run in the boats up to motors 20,000 hp. The thing to remember is the more poles a motor has the more torque a motor has thru it's speed range.

 

[Kris Flynn]

settle boys

 

[MitjaJ]

Do not confuse DC brushles (block comutated) motors with AC motors.

The number of motor poles says nothing (or little) about the amout the torque the motor will develop. Usually high pole count

motors are used for low rpm applications (no need for transmissions) , but cannot be used at high speeds because the switching

losses.

Motors with the same KV develop about the same torque at equal currents. (Kt = Ke = 1/Kv - torque constant = back EMF constant = 1/ motor KV). If two motors have about the same KV, the same internal resistance (!!!) they should be considered equal.

There may be some difference (because the loses in the iron, magnets, rotor core, and bearing friction) but without looking to an actual dyno there is hard to tell the difference between a Hacker, Neu, or Feigao motor.

Two motors with the same KV and internal resistance may develep the same torque let's say at 50 Amps but at 100 amp one

may develop much less torque than the other. This is due the internal design variations (very important !) and quality of the used materials.

 

[Mark Bullard]

Do not confuse DC brushles (block comutated) motors with AC motors.
The number of motor poles says nothing (or little) about the amout the torque the motor will develop. Usually high pole count

motors are used for low rpm applications (no need for transmissions) , but cannot be used at high speeds because the switching

losses.

Motors with the same KV develop about the same torque at equal currents. (Kt = Ke = 1/Kv - torque constant = back EMF constant = 1/ motor KV). If two motors have about the same KV, the same internal resistance (!!!) they should be considered equal.

There may be some difference (because the loses in the iron, magnets, rotor core, and bearing friction) but without looking to an actual dyno there is hard to tell the difference between a Hacker, Neu, or Feigao motor.

Two motors with the same KV and internal resistance may develep the same torque let's say at 50 Amps but at 100 amp one

may develop much less torque than the other. This is due the internal design variations (very important !) and quality of the used materials.

We are talking about three phase AC motors. And right about your math to come up with KV but if you really check the HP you would find it different. The formula is HP = Torque(lb.ft) x RPM / 5250

 

[MitjaJ]

The motors we use in our hobby are different than AC motors. AC motors are induction motors (have no magnets) and operate quite

differently and have different rpm/torque characteristics.

Our motors are brushless permanent magnet DC motors, they are BLOCK COMMUTATET (full current is applied on two motor phases at a time, PWM is used to control power) - no sinusisoidial exication is used like in synchronous motors.

 

[Mark Bullard]

The motors we use in our hobby are different than AC motors. AC motors are induction motors (have no magnets) and operate quitedifferently and have different rpm/torque characteristics.

Our motors are brushless permanent magnet DC motors, they are BLOCK COMMUTATET (full current is applied on two motor phases at a time, PWM is used to control power) - no sinusisoidial exication is used like in synchronous motors.

I understand that also. We rewind and repair those also. We call them "Brushless DC". There are many types of these motors. Most common are servos motors. The controllers you use are what we call dumb controllers. They are very dirty drives and have no way of knowing where the rotor position or timing position is except by the EMF that the motor generates. The controller trys to force the rotor to the next pole position and you hope that the rotor gets there. Of course if everything is in good working order it does get there. It is also why you don't have a good ramp in your speed control. In all of the brushless DC motor we repair they have feedback devices that the controller reads and can tell where the rotor position is to the phase position. This gives the best torque and speed control at all speeds.

But the main thing is all of these motors have the same kind of winding in them. They are three phase AC stators that follow all the rules of motors in their number of poles and the synchronous base speed of those poles for that speed at 60Hz. We can thank Nicoli Tesla for this great design and invention. One other thing to notice is the he had a thing for the number 3.

 

[Peter Zicha]

Mark If you are that good why don't you wind up a jem in your shop throw it in a boat and see if you can keep up........ :lol:

Incidentally 746 watts is also = to 1 HP

Mitjaj and Jay T excellent description and explanations , I have to agree with Jay on the fact that you may receive useful and unfortunately useless advice given on sites like this

 

[Mark Bullard]

Mark If you are that good why don't you wind up a jem in your shop throw it in a boat and see if you can keep up........ :lol:
Incidentally 746 watts is also = to 1 HP

Mitjaj and Jay T excellent description and explanations , I have to agree with Jay on the fact that you may receive useful and unfortunately useless advice given on sites like this

I have no desire to run a electric boat. I work with electric motors everyday but I do not have a problem trying to help you all to understand your motors.

 

[dwilfong]

You can also thank Tesia for that thing you hold in tour hand to run the boat.

The first use of radio was a R/C boat built by Tesia.

He is the father of all R/C and his choice was a boat!!!!

Sorry about the rant, but Tesia is my idol.

I'm waiting to hear about a gold or silver winding motor that some on with very deep pockets will build and piss every one off!

David Wilfong

 

[Mark Bullard]

You can also thank Tesia for that thing you hold in tour hand to run the boat.The first use of radio was a R/C boat built by Tesia.

He is the father of all R/C and his choice was a boat!!!!

Sorry about the rant, but Tesia is my idol.

I'm waiting to hear about a gold or silver winding motor that some on with very deep pockets will build and piss every one off!

David Wilfong

Good point on the first radio control. And it still works very much now as he made it work back then just like all of his other inventions. Electric motors today still work just like the one he built just improved.

I heard that the coils they used in the electro magnets at the Y 25 plant in Oak Rige TN for processing radioactive material were wound with about 2 tons of silver because of the shortage of copper in the late forties. Somewhere I read that there were 25 of them and they are just now able to scrape the material. I have never heard of any silver or gold magnetic wire but does not mean that there is not any out there.

 

[Don Ferrette]

FYI it's Tesla, Nikola Tesla. Not Tesia. And yes he was brilliant, way ahead of his time. B)

 

[dwilfong]

Gold has the lowest amount of resistance and silver is not far behind. It makes for a very efficient motor.

It may not mater in a large motor with high HP output but in a small motor it will make a difference.

Don thanks for the spell check, you think I could at least spell my idols name right. :blink:

 

[Ub Hauled]

.........edit

 

[Grimracer]

Tesla ROCKS!

O wait.. thats the band...

Nevermind!

Grim