what does 'poles' mean?

[ReadyToCrash]

hi,
here you go two motors from scorpion:
http://www.scorpionsystem.com/catalo...III_4025_1100/
http://www.scorpionsystem.com/catalo...K_4025_1100_6/
one is 10 poles. the other one is 8.
apart from that (and the "no-load current"), they don't seem to have any difference.
could someone explain how important is it to have more or less poles in an electric motor?
thanks

[Stolla]

poles are magnets typically a 10 pole motor, all things being equal will have more power than 8 pole but that doesn't mean 14 poles will have even more power, somehow for our application and size motors 10 poles seems to be the sweet spot. On the mk 3 scorpions the magnets are also stronger which makes for more torque so this is the stronger motor.
Go have a read on powerditto.de you will find everything you need to know about motors

[phoenixheli]

Pole count is roughly a translation of the kv of the motor. If you look at scorpion hk22 series motors you will see a -6 -8 -10 -12 after the model numbers, the lower the appended number the higher kv and the higher the number the lower the kv. Other makers will list the Y count and effectively is the same thing, though not technically. A lower Y has a higher kv and a higher Y has a lower kv.

Why can't they just list the model number with the kv appended instead? Cause technical people like it technical. Some makers will list the kv right on the top of the page, but a lot don't. Futaba does the same thing with the rx connections. If you don't know what ch 1, 2, 3 is and you don't have a manual, you are fudged. Funny my "inferior" spektrum has ail, ele and pitch listed right on the rx.

[ReadyToCrash]

Originally Posted by phoenixheli

Pole count is roughly a translation of the kv of the motor. If you look at scorpion hk22 series motors you will see a -6 -8 -10 -12 after the model numbers, the lower the appended number the higher kv and the higher the number the lower the kv. Other makers will list the Y count and effectively is the same thing, though not technically. A lower Y has a higher kv and a higher Y has a lower kv.

Why can't they just list the model number with the kv appended instead? Cause technical people like it technical. Some makers will list the kv right on the top of the page, but a lot don't. Futaba does the same thing with the rx connections. If you don't know what ch 1, 2, 3 is and you don't have a manual, you are fudged. Funny my "inferior" spektrum has ail, ele and pitch listed right on the rx.

so,

1) if the kv tells the amount of torque the motor has;
2) the smaller the kv the bigger the torque;
3) the bigger the # of poles the better if i want a big torque?

thanks

[Stolla]

Originally Posted by phoenixheli

Pole count is roughly a translation of the kv of the motor. If you look at scorpion hk22 series motors you will see a -6 -8 -10 -12 after the model numbers, the lower the appended number the higher kv and the higher the number the lower the kv. Other makers will list the Y count and effectively is the same thing, though not technically. A lower Y has a higher kv and a higher Y has a lower kv.

Why can't they just list the model number with the kv appended instead? Cause technical people like it technical. Some makers will list the kv right on the top of the page, but a lot don't. Futaba does the same thing with the rx connections. If you don't know what ch 1, 2, 3 is and you don't have a manual, you are fudged. Funny my "inferior" spektrum has ail, ele and pitch listed right on the rx.

Nope you're wrong pole count is the total magnet count, sometimes magnets are placed in pairs and counted as one, pole count has absolutely nothing to do with kv!, although it will influence kv when changing magnet count all things being equal, ie. Scorpion 4035 mk 3 series, same pole count, different kv.

[Stolla]

Originally Posted by ReadyToCrash

so,

1) if the kv tells the amount of torque the motor has;
2) the smaller the kv the bigger the torque;
3) the bigger the # of poles the better if i want a big torque?

thanks

Note kv is not torque it's the speed of the motor, also not slower kv higher torque.
Sometimes more poles, i.e. magnets the stronger the motor but too many variables.
The old 4035 scorpion had 8 pole new ones 10 pole but also stronger magnets so is more powerful. But you can't compare different manufacturers by comparing poles and pole count.

all things being equal, i.e. on the same motor let's say pyro 700-45 and pyro 700-52 the 45 is 450 kv will have less max power than 520 but they have same pole count and strength magnets, i.e. 10 pole, if you want torque you go for bigger motors with single wire winding and strong magnets, i.e. scorpion le versions.

[ahahn]

Actually Kv is inversely related to the torque constant, Kt.

However to get actual torque, you need to multiply Kt by the current (in amps).

The trick of course is:
1) Having a high enough voltage to get that current to flow. This depends on the coil resistance and the back emf (=Kv*rpm)
2) That the iron in the stator teeth doesn't saturate. If it does, Kv and Kt mean little.