Stranded motor windings. What is the purpose?

[jared1313]

I have several BLDC motors used for the so called "Hoverboard" devices that children seem to love these days. I have taken a few of these apart and noticed that some of them use stranded magnet wire on the rotor teeth. For example, my particular motor uses a five strand 24 gauge wire arrangement where each of the five strands are wired in parallel on each tooth. Certainly this is not litz wire and the motor operates at a relatively low switching frequency. I understand that it may have permitted them to fill each tooth with a larger number of turns while maintaining the same resistance.

I would like to know why the designer may have chosen to use a stranded wire on the windings and what effect this might have on the torque and power curves.

Thanks.

 

[waross]

1. Poor mans Litz wire? If they are using pulse-width-modulation, the square wave switching may be inducing high frequency components.
2. More wires in the space?
3. More bendable in a small space?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Gr8blu]

AWG 24 (24 gauge wire) has an outside bare conductor diameter of 0.022 inch, which is a bit more than 0.5 mm. It only has one strand; it is not a "stranded" conductor like some larger sizes (AWG 2, for example). So what you're seeing is one or more turns - the exact number depends on how the connection is made for a given coil (anywhere from 1 strand-per-turn up to 5 strands-per-turn). And yes - it is possible to have a different number of strands in each turn, as long as they space out evenly over the slot pattern. Most likely reason for using small-diameter wire is the minimum bend radius allowed; small wire makes for shorter end turns - which is important when real estate is at a premium.

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