Open Source Electric Generator Calculations

Efficiency

Note: this is an explanation for novices, and terms are inaccurate for the purpose of conveying concepts, not for technical correctness.

To understand generator efficiency - for a PM motor, not a winding-based generator, it is important to understand the distinction between theoretical and practical efficiency. There is a subtle difference here, whose implications are significant for achieving industrial productivity on a small scale. The point is: what matters is the efficiency of using a force input (for conversion from mechanical to electical energy). It is important to understand what matters and what does not matter - from the viewpoint of achieving effective industrial productivity for a Regenerative civilization.

What matters is the efficiency of conversion from a mechanical input to an electrical output. Period. This is based on a given permanent magnet spinning in front of wires, in which voltages are created. This should not be confused with how much energy it is theoretically possible to extract if effective magnetic forces are optimized. This is because unoptimized magnetic forces, such as magnets not being sufficiently close to the wires - do not matter - because conversion happens only on the forces that are used. The EMF that 'could be used' does not not detract from efficiency - simply because it is not used - and does not drag down the generator. As long as frictional losses are negligible - the 'loss' of not having used the full EMF is inconsequential to the basic 'efficiency of converting mechanical to electric energy.'

To understand the above - it is important to note that when spinning a magnet rotor in front of stator wires - energy is created from a Conservative Force - if friction is ignored. So as long as friction is much less than the converted EMF - the efficiency of mechanical to electric conversion will be near perfect - limited only by the resistivity of the conductors, and mechanical friction of bearings.

Note that this argument does not apply to electric motors. This is because in an electric motor, energy is expanded (electricity) in making a motor spin. Thus, if that energy capture is not optimized, it is being dissipated as heat or stray electromagnetic radiation. Thus, it is important to optimize the usage of the electricity.

The concepts must be studied carefully in order to understand that near perfect energy conversion efficiency is possible from permanent magnet generators, while it is much more difficult to achieve near perfect energy efficiency of permanent magnet electric motors. Further, if an engineer warns of low energy efficiency conversion of permanent magnet motors - the first question one should ask from an applied perspective is whether they are talking of practical or theoretical efficiency - according to the subtleties mentioned above.