The Secret Lives Of Motorcycle and ATV 3-phase stator windings

Published: 21st June 2011
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Motorcycle and ATV stators have windings about them that turn the magnetic field changes into electricity we require for the vehicle. Accomplishing this while keeping the windings in a safe operating temperatures are an essential design problem that will need to be overcome.

How do we determine the amount of winding turns

First thing to watch out for is the number of turns on each pole, you also need to look at the size of copper wire utilized, and how the windings are hooked up together. Frequently you may raise the output voltage by raising the number of turns per pole. This also enhances the resistance of the winding which can be bad and cause overheating. With a wire size that's too big you will find the risk of a very high peak output causing the stator to overheat. Too small diameter wire may also cause overheating due to higher resistance, or it may simply mean that the output of the stator is too low for the application.

Configuration options in three phase windings

In a three phase configured stator winding there are two basic ways to connect the copper windings. Each wire has two ends, and three wires (windings) are used in a three phase setup. If you connect the ends of two different windings together and connect them to the stator output and do this three times, you have a stator winding configuration that kind of looks like triangle, or DELTA configuration.
You may also connect three ends on the three copper wires together, and feed each other copper wire end into an output wire. This configuration looks similar to a star, or a "Y" which is termed as Y-configuration.

There are advantages to both configurations. For high rpm and high power applications typically a Delta setup is used. The Y setup offers better low rpm power and as a consequence is more suitable in lower rpm applications.
Windings in DELTA connection typically work with a smaller copper wire size and use more turns per pole compared to Y-connected windings. For some applications a Y-connected stator can be substituted for a correctly configured DELTA-connected stator to help increase output.

The golden compromise

As with everything there is a golden compromise in each design that's based on the specific needs of the vehicle, average engine rpm, diameter of the stator and the magnet strength of this rotor.

Stator failure

Stator failure is attributable to the winding insulation to fail because of excessive heat. The copper wire itself is normally not the issue. As the insulation fails the outsides of the copper windings start touching, which lowers the resistance and raises the temperature even more.

Which coatings are used

As the windings must be stacked on top of each other they simply cannot electrically make contact on the outside. Therefore the insulation layers around the perimeter of copper wire are very important. Normally copper wire has multiple layers of clear insulation, as well as motorcycle stator applications this insulation ought to be oil resistant and in addition rated to resist increased temperature before it in time breaks down.
Standard copper winding wire is rated at 160-170 degrees Centigrade, high temperature rated wire is with a rating of around 180 degrees Centigrade and the highest rated wire uses insulation which is rated at around 200 degrees Centigrade.
By having an increase in insulation coating layers on the copper wires the diameter of the wire grows limiting the number of turns that can be put on a stator pole. This can mean insufficient output, or too high a current output and/or temperature.
The type and material of the insulation coating used determines the maximum winding operating temperature. Top quality winding wire that is rated at a high temperature therefore is more expensive than standard wire.

What about the wire leads between the connector and the winding?

The lead wires need to be of high quality stranded wire, which has an insulation that won't melt with rising temperature as these output lead wires get surprisingly hot during normal use. Additionally a superb connection between lead wires and copper winding wire is extremely important for long term reliability.

Which coatings can be used to protect the winding

To help improve longevity manufacturers typically apply an outside coating about the copper windings. This coating prevents motion inside wires that induce chafing and insulation failure.

Roger Fuara writes about health, recreation and other interesting topics. Get more information online about motorcycle stator deals as well as helpful tips and tricks for choosing and installing motorcycle parts at ElectroSport.com.

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