# Explanation for Differing Stator Winding Orientations

As a layperson, I'm trying to understand the basic configuration for an induction motor or generator. I've looked at many diagrams and photos/cutaways of stator wiring and I've noticed two different orientations for the windings:

All the diagrams/photos I've seen show an individual winding in the shape of a rectangle with rounded corners.

1. Type One - The axis of the winding points toward the shaft of the rotor.
2. Type Two - The axis of the winding points 90deg away from the the shaft of the rotor.

The difference between these two orientations is making it difficult for me to conceptualize the "rotating electromagnetic field" that exists in motors/generators. I am looking for an explanation of the pusposes behind these two winding orientations.

[EDIT]

45deg orientation:

0deg orientation:

90deg orientation: I can't find one right now.

• I'm not sure I understand you. Could you add some links to some of the diagrams you mention? Commented Oct 23, 2012 at 14:21

I think you may have found a good example of something that I've been looking for which came up in my answer to this question. Namely, the difference between a sinusoidally wound motor and a trapezoidally wound motor.

The way in which a motor is wound controls the distribution of the magnetic flux density throughout the motor. Which in turn controls the shape of the Back-EMF, which in turn dictates how best to drive the motor (i.e. which commutation method you choose). The different control methods can be read about in the aforementioned answer.

The below diagrams are taken from the master's thesis of James Mevey. This first diagram shows two simplified motors. Each has only a single winding. The motor on the left has "sinusoidally shaped" magnets and the motor on the right has "trapezoidally shaped" magnets.

The resultant flux densities look like so:

Having magnets of the shape in the right hand motor and modifying the distribution of the windings would have a very similar effect.

I think that your "45° orientation" motor is sinusoidally wound. And if you were able to look at how the windings are connected and overlapped you should be able to see how the magnetic field would get stronger and weaker in a sinusoidal pattern.

And I think that your "0° orientation" motor is trapezoidally wound. Which you can almost see since the windings are distributed in just a few big blocks.

As for your "90° orientation" motor, I think you mean this:

Which is a whole different beast. That is a picture of Shane Colton's Less Epic Axial Flux (LEAF) motor.

The motors shown at the top of my answer and in the OP are radial flux motors. In this design, the rotor is on the inside (or occasionally on the outside) of the stator windings. In an axial flux motor, the rotor is in front of the stator windings.

The benefits of an axial flux motor are that it can be made thinner and lighter allowing it to fit better into certain geometries and change direction quicker.

Visualization of the rotating magnetic field can be difficult without good software.

But usually a good motor manufacturer will provide you with all the details on how best to drive their motor on the side of the box. Still, the references in the answer I linked above and in this answer provide a wealth of information (perhaps too much) on what exactly is going on inside a motor as it's driven.

• Thanks. I'll read more about what you've mentioned to see if I can get my head wrapped around it. The 90deg I'm thinking of is not the flattened one you show but my 45deg plus 45 more. Commented Oct 25, 2012 at 14:19
• And what's the disadvantages of pancake motors? Commented Aug 3, 2015 at 6:59

The first photo ("45deg") shows a "lap winding" while the second photo ("0deg") shows a distributed winding for sinusoidal wave. The purpose in using one over the other has a lot to do with ease of manufacture and application. Most windings process tries to make it easier to automate the insertion of the coils into the slots of the stator. Lap windings most often have to be inserted by hand.

• what are the advantages of both windings? Concentric winding are easy to manufacture, so why should someone choose a "lap winding"? What's it's benefits that justify the increased manufactury costs? Commented Aug 3, 2015 at 6:57
• Could you please elaborate a bit on pancake motors too? Advantages and disadvantages? Commented Aug 3, 2015 at 7:00

The way I know it, the windings are arranged as you see for practical purposes. In the first one, you can see the windings don't have that much copper, nor is the motor too large, compared to the second one. This means that the physical materials themselves are not a waste. The iron core is comprised, in both cases, of "I" shaped teeth, thus the magnetic field follows the iron, not the winding.

Pan cake motors are axial flux machines with the magnets embedded on the stator plate with let's say N at the bottom and S at the top for the first magnet; and vice-versa for the adjacent magnet. There will be ahuge no. of poles. The rotor may be a PCB consisiting of tracks emanating from the centre of the rotor disc towards the outer periphery -like the spokes in a bi-cycle wheel- the overhang portion can be minimised if there are a huge no. of stator poles. (You can look at the image by Googling PCB motor). It cannot be used for very high power applications- rotor and the shaft will not have enough strength. Inertia will be low; so, response is very quick.