If your homemade alternator is generating a square wave instead of a sinusoidal wave, there could be a few reasons for this behavior.
Design and Construction: The design and construction of the alternator can greatly influence the output waveform. The shape of the rotor, the placement of the magnets, and the configuration of the windings can all affect the waveform generated. If the rotor or stator has a non-uniform shape or the magnets are not properly aligned, it can result in a distorted output waveform.
Number of Poles: The number of poles in the alternator affects the shape of the waveform. A higher number of poles can result in a more sinusoidal waveform, while a lower number of poles can produce a square or trapezoidal waveform. If your homemade alternator has a small number of poles, it may be a contributing factor to the square wave output.
Commutation: In commercial alternators, the commutator or the rectifier diodes are responsible for converting the alternating current (AC) output into direct current (DC). If you're not using a commutator or rectifier diodes in your homemade setup, the output may remain in the form of a square wave.
Magnetic Saturation: Magnetic saturation can occur if the magnetic field strength exceeds the saturation point of the material. This can cause the flux lines to become nonlinear and result in distorted waveforms. If the magnets in your alternator are reaching or exceeding their saturation point, it could contribute to a square wave output.
To improve the waveform and generate a more sinusoidal output, you can consider adjusting the design, increasing the number of poles, ensuring proper alignment of magnets, and implementing commutation or rectification techniques to convert the AC output into a smoother waveform. It's worth noting that designing and constructing an alternator that generates a sinusoidal waveform can be complex, and it may require careful consideration of various factors such as magnetic field strength, rotor design, and winding configuration.