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enter image description hereSuppose we are dealing with an elementary AC generator having a single coil armature located between the curved north and south poles of a magnet(like the ones found in toy DC motors-only two poles). I wanted to know whether the output waveform would change if a magnet having a different shape is used.

Jonathan_the_seagull
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  • Add in a sketch so we know what you're thinking. Bear in mind that as the air gap increases - even slightly - the magnetic flux will fall off dramatically. – Transistor Jun 11 '21 at 19:18
  • @Transistor The magnets shown in the figure shown above helps generate a sinusoidal output. Will you tell me how the waveform will be affected when the shape of the poles changes? – Jonathan_the_seagull Jun 11 '21 at 20:00
  • I'm not a motor expert but the system in the diagram will be a poor generator because the armature has no iron core so the flux will be greatly reduced because of the very large air gap. – Transistor Jun 11 '21 at 20:36
  • The answer is yes. The shape of the magnets and iron core parts that direct the magnetic flux have an effect on the voltage waveform. Even toy motors have more attention paid to the shape than is shown in the diagram. The design of the flux path is quite a complex part of electric machine design. –  Jun 11 '21 at 23:29
  • Yes and it will also change with RPM. – Gil Jun 12 '21 at 03:15
  • @Charles Cowie Thanks a lot! Will you write it as an answer? If you can, please tell me whether the waveform shape can be predicted. – Jonathan_the_seagull Jun 12 '21 at 05:16

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In all electromagnetic devices and machines, the shape of the magnets and iron core parts that direct the magnetic flux have an effect on the magnetic flux. Compared to iron and other ferromagnetic materials it is much more difficult for magnetic flux to flow through air and other materials that are not ferromagnetic. Therefore the shape and dimensions of the iron flux path compared to the non-magnetic path is of critical importance.

In motors and generators, the voltage waveform shape is important and it is influenced by the shape of the magnetic materials and the shape of the non-magnetic part of the path. The change in path shape as the rotor turns is particularly important. Designing the shape of the flux path is quite a complex but important part of designing electric machines. Finite element analysis FEA modeling computer programs are used to predict, map and analyze magnetic flux density and path shapes. Prior to the availability of computers, tedious manual flux-mapping techniques were used.

To be at all useful, even the simplest toy motor requires that attention be given to the design of the flux path. It is fairly easy to make a motor that can overcome its own losses and demonstrate rotation by electric energy. To make any motor that can turn a load, the design of the flux path must be considered.