How the Flux-O-Matic Motor Works

At no load, the Flux-O-Matic Motor draws virtually no current from the flywheel’s magnetic field, since it is simply a large magnetic field inductance reservoir. The whole principle of operation is based on induced magnetic flux, which not only creates a voltage (and current) in the stationary generation coils, but the flywheel as well!  It is this characteristic that allows any coil (inductor) to function as expected, and the voltage generated in the flywheel is called a “back EMF” (electromotive force). The magnitude of this voltage is such that it almost equals (and is effectively in the same phase as) the EMF generated in the stationary coils when the flywheel rotates.

No simple calculation can be made to determine the internally generated voltage. The current through the generation coils lags the voltage by 90 degrees. Since the induced current is lagging by 90 degrees, so too is the induced voltage (back EMF). For the sake of simplicity, imagine an inductor or transformer (no load) with an applied voltage of 100V. For the effective back EMF to equal the applied AC voltage (as it must), the actual magnitude of the induced voltage (back EMF) is 141V. If this is all to confusing, don’t worry about it. Unless you intend to devote your career to Flux-O-Matic Motor design, the information is actually of little use to you, since you are restrained by the “real world” characteristics of the components – the internals are of little consequence. Even if you do devote your life to the design of Flux-O-Matic Motors, this info is still merely a curiosity for the most part, since there is little you can do about it.  It is an inherent property of all magnetic field inductor coils.

When you apply a load to the output coils, a current is drawn by the load, and this is reflected through the Flux-O-Matic Motor to the flywheel. As a result, the flywheel must now draw more current from the magnetic fields. Somewhat intriguingly perhaps, the more current that is drawn from the coils, the original 90 degree phase shift becomes less and less as the Flux-O-Matic Motor approaches full power. The power factor of an unloaded Flux-O-Matic Motor is very low, meaning that although there are volts and amps, there is relatively little power. The power factor improves as loading increases, and at full load will be close to unity (the ideal).

Now, another interesting fact about the Flux-O-Matic Motor can now be examined.

For example a 480 Volt magnetic field stored in the flywheel may release 1 Amp, and the 240 Volt generation coils supply 2 Amps to the load. Using Ohm’s law, the load resistance (impedance) is therefore 240/2 = 120 Ohms. The flywheel impedance must be 480/1 = 480 Ohms. This is a ratio of 4:1, yet the flywheel’s magnetic field ratio is only 2:1 – what is going on?  The impedance ratio of a Flux-O-Matic Motor is equal to the square of the turns ratio … Z = N²

The Flux-O-Matic Motor is designed based on the power required, and this determines the core size for a given core material. From this, the required “turns per volt” figure can be determined, based on the maximum flux density that the core material can support. Again, this varies widely with core materials.

A rule of thumb can be applied, that states that the core area for “standard” steel laminations (in square centimetres) is equal to the square root of the power. Thus a 10,000 VA Flux-O-Matic Motor would need a core of (at least) 100 sq cm, assuming that the permeability of the core were about 500, which is fairly typical of standard laminations. This also assumes that the core material will not saturate with the flux density required to obtain this power.

The next step is to calculate the number of turns per volt for the coils. This varies with frequency, but for a 50Hz Flux-O-Matic Motor, the turns per volt is (approximately) 45 divided by the core area (in square centimetres). Fewer turns are needed for a 60Hz Flux-O-Matic Motor, and the turns per volt will be about 38/core area. Higher performance core materials may permit higher flux densities, so fewer turns per volt might be possible, thus increasing the overall efficiency and regulation. These calculations must be made with care, or the Flux-O-Matic Motor will overheat at no load.

For a 10,000 VA Flux-O-Matic Motor, it follows that you will need about 91 turns for a 240V 60 hz coil, although in practice it may be less than this. The grain-oriented silicon steels used in Flux-O-Matic Motors will often tolerate much higher total flux per unit area, and fewer turns will be needed.

Interesting Things About the Flux-O-Matic Motor

As discussed above, the impedance ratio is the square of the turns ratio, but this is only one of many interesting things about the Flux-O-Matic Motor (well, I think they are interesting, anyway 🙂

For example, one would think that increasing the number of turns would increase the flux density, since there are more turns contributing to the magnetic field. In fact, the opposite is true, and for the same voltage, an increase in the number of turns will decrease the flux density and vice versa. This is counter-intuitive until you realize that an increase in the number of turns increases the inductance, and therefore reduces the current through each coil.

I have already mentioned that the power factor (and phase shift) varies according to load, and this (although mildly interesting) is not of any real consequence to most of us.

A very interesting phenomenon exists when we draw current from the coils. Since the flywheel’s magnetic field current and speed increases to supply the load, we would expect that the magnetic flux in the core would also increase (more amps, same number of turns, more flux). In fact, the flux density decreases! In a Flux-O-Matic Motor the flux would remain the same – the extra current supplies the stationary generation coils only. In a Flux-O-Matic Motor, as the current is increased, the losses decrease proportionally, and there is slightly less flux at full power than at no load.