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Hi all,
After working on the Cap Dump circuit, the last stage of my generator upgrades involves trying to extract (recycle more exactly) some of the rotational kinetic energy from the generator rotor that is spinning between 2,500 - 3,000 rpm. I don't want to extract all of course or there would be no triggering of the Hall sensor with the consequent production of HV spikes central to the generator, but if I can tap off 15-20% of the estimated 27W of the rotor's energy that might be of use.
The obvious way to do this is to set up an EM induction process on the top surface of the rotor to induce an EMF in a set of coils by the rotation of a set of disc magnets beneath it. This is shown in the graphic where the proposed arrangement is laid out.
There are various ways to set up such EM induction. A simple way is to spin some disc magnets under a set of air coils but, with the relatively little circulation of magnetic flux, the voltage produced is calculated to be less than 1 volt and so of little use. A better method is the wrap the coils around ferrite cores and then mount them on a magnetically conducting plate (Iron). Similarly with the magnets on the rotor beneath. Four magnets and five coils are proposed so that each output is out of phase with its neighbour but also it is possible to have alternate poles facing upwards on the magnets with an even number.
The aim is to achieve at least 15V output which could then be directed to the large capacitor used in the Cap Dump circuit and so contribute to the battery's charging. However, there would likely be a lot of experimentation involved and in particular, the height of the stator above the rotor. Too close and the magnetic field will hold the stator ferrite cylinders tightly and make starting the rotor spinning difficult or impede it too much during normal operation. In addition, once it can be made to spin, the result of the induced EMF in the coils, with subsequent rectification (see schematic), will have a slowing effect on the rotor due to Lenz's Law.
Various questions arise that serve as good discussion points and to clarify if it really is worth the effort for maybe 5-10 extra watts of power.
1: Is there an optimum number of turns for the coils? Increasing the number of turns (N) creates more EMF but the resistance goes up as well so there might be an optimal balance point between these two factors.
2: Let's say for argument that an output of 15V DC was available; should that be applied to the Cap Dump circuit capacitor simultaneously alongside the HV spikes or supplied to its own dedicated capacitor, or indeed directly to the batteries or circuit after regulating to 12V?
So there are some interesting discussion points and I look forward to any thoughts.
Thanks,
Jules
After working on the Cap Dump circuit, the last stage of my generator upgrades involves trying to extract (recycle more exactly) some of the rotational kinetic energy from the generator rotor that is spinning between 2,500 - 3,000 rpm. I don't want to extract all of course or there would be no triggering of the Hall sensor with the consequent production of HV spikes central to the generator, but if I can tap off 15-20% of the estimated 27W of the rotor's energy that might be of use.
The obvious way to do this is to set up an EM induction process on the top surface of the rotor to induce an EMF in a set of coils by the rotation of a set of disc magnets beneath it. This is shown in the graphic where the proposed arrangement is laid out.
There are various ways to set up such EM induction. A simple way is to spin some disc magnets under a set of air coils but, with the relatively little circulation of magnetic flux, the voltage produced is calculated to be less than 1 volt and so of little use. A better method is the wrap the coils around ferrite cores and then mount them on a magnetically conducting plate (Iron). Similarly with the magnets on the rotor beneath. Four magnets and five coils are proposed so that each output is out of phase with its neighbour but also it is possible to have alternate poles facing upwards on the magnets with an even number.
The aim is to achieve at least 15V output which could then be directed to the large capacitor used in the Cap Dump circuit and so contribute to the battery's charging. However, there would likely be a lot of experimentation involved and in particular, the height of the stator above the rotor. Too close and the magnetic field will hold the stator ferrite cylinders tightly and make starting the rotor spinning difficult or impede it too much during normal operation. In addition, once it can be made to spin, the result of the induced EMF in the coils, with subsequent rectification (see schematic), will have a slowing effect on the rotor due to Lenz's Law.
Various questions arise that serve as good discussion points and to clarify if it really is worth the effort for maybe 5-10 extra watts of power.
1: Is there an optimum number of turns for the coils? Increasing the number of turns (N) creates more EMF but the resistance goes up as well so there might be an optimal balance point between these two factors.
2: Let's say for argument that an output of 15V DC was available; should that be applied to the Cap Dump circuit capacitor simultaneously alongside the HV spikes or supplied to its own dedicated capacitor, or indeed directly to the batteries or circuit after regulating to 12V?
So there are some interesting discussion points and I look forward to any thoughts.
Thanks,
Jules