Unipolar Induction. What is characteristic of fundamental discoveries, for great achievements of the intellect, is the fact that they retain much power over the imagination of the thinker. I mean the unforgettable experiment of Faraday with the rotation of the disk between the two poles of a magnet, which brought such an excellent result, which has long been tested in everyday experiments; Yet there are some topological elements in this seed of existing dynamos and engines, which even today attract attention, and deserve the most careful study.
Consider, for example, the case of a disk made of iron or another metal rotating between two opposite poles of a magnet and polar surfaces completely covering both sides of the disk, and assume that the electrical current is removed and transmitted by the contacts evenly from all points of the disk edge. Take the engine case first. In all conventional motors, the rotation of the rotor depends on some displacement or change in the total magnetic attraction acting on the rotor, this is achieved technologically or with some mechanical device on the engine or the effect of electrical currents of proper polarity. We can explain the rotation of such an engine just as we can do for a water gear.Unipolar Induction
But in the above example of a disk surrounded by completely polar surfaces, there is no bias of the magnetic action, no change at all, as far as we know, and yet the rotation occurs. The usual arguments do not work here; we cannot even give a superficial explanation, as in conventional engines, and the principle of action will be clear to us only when we understand the very nature of the forces involved, and comprehend the mystery of invisible interaction.
Considered as a dynamo machine, the disk is a rather interesting object of study. In addition to its features of generating electric currents in one direction without using switching devices, such a machine differs from conventional dynamos, in which there is no interaction between the rotor and the stator field. The rotor current causes a magnetization perpendicular to the direction of the electric current, but since the electric current flows evenly from all points of the edge, as well as being precise, the external circuit can also fit perfectly symmetrical to the permanent magnet, no interaction can simply occur. This, however, is true only for weak magnets, because when magnets are more powerful, both magnetizations at right angles seem to interact with each other.
For the above reason, it is logical to conclude that for such a machine, for the same weight, the recoil should be much greater than for any other machine in which the current flowing in the rotor tends to demagnetize the field created by the stator. Forbes’s extraordinary conclusion about the unipolar dynamo and the experience with the device confirm this view.
So, the main principle on the basis of which such a machine can be made itself exciting is striking, but it can be natural, since there is a lack of interaction of the rotor, and accordingly, the current of disturbances free from disturbances and the absence of self-induction. (Dragons’ Lord: Hereinafter, under the term “self-excitation” Tesla means the effect of the appearance of electric current in the device, since there are no permanent magnets in the device of its “unipolar”, but there are electromagnets. Thus, “self-excitation” is not (!) An analogue of the appearance of SUPERINCINAL ENERGY – here it is not mentioned at all).
If the poles do not cover (do not cover) the disk completely on both sides, then, of course, if the disk is not properly divided, the mechanism will be very inefficient. Again, in this case there are moments worthy of attention. If the disk rotates and the field current is interrupted (the circuit supplying the electromagnet is broken), the flow through the rotor disk will continue to flow and the field of the magnets will lose power relatively slowly. The reason for this is immediately there, when we consider the direction of the currents in the disk.
Take a look at Figure 1, d represents a disk with sliding contacts B and B ‘on the axis and periphery. N and S are two poles of a magnet.
If the pole N is higher, as indicated in the figure, the disk is assumed to be in the plane of the paper and rotating in the direction of arrow D. The current established in the disk will flow from the center to the periphery, as indicated by arrow A. Since the magnetic effect is more or less limited the gap between the poles N and S, other parts of the disk can be considered inactive. The steady current will therefore not completely pass through the external circuit I ‘, but will close directly through the disk, and in general, if the arrangement is similar to that shown, of course, most of the produced flow will not manifest outwardly, since circuit F is actually short-circuited by the inactive parts of the disk.
The direction of the resulting currents in the disk can be taken to be, as indicated by dashed lines and arrows m and n; and the direction of flow of the excitation field, indicated by arrows a, b, c, d, analysis of the figure shows that one of these two branches of the eddy current, i.e. A-B’-mR, will tend to demagnetize the field, while the other branch that is, A-B’-nB will produce the opposite effect. Therefore, an A-B’-mB branch, that is, one that approaches a field, will repel lines, while an A-B’-nB branch, that is, a leaving field, will collect the lines of force on itself.
Because of this, there is a constant tendency to reduce the current flow in the track B’-mB, while on the other hand such opposition will not exist in the track B’-nB, and the branch or track effect will more or less prevail over the first. The combined effect of both branches of the currents could be represented by a single stream of the same direction as the field excitation. In other words, the eddy currents circulating in the disk will additionally amplify the magnet. This result is quite contrary to what could have been assumed first, since we naturally expected that the resulting rotor currents would counteract the current induced by the magnets, since this usually happens when the primary and secondary conductors have an inductive interaction.
But it should be remembered that this is a consequence of a specific mutual arrangement, namely, the presence of two paths provided to the induced and opposing current, each of them chooses the path that offers the least amount of counteraction. From this we see that the eddy current flowing into the disk partially excites the magnet field, and for this reason when the induced current interrupting the currents in the disk continues to flow and the field magnet will lose its strength relatively slowly and may even retain some force as long as the rotation of the disk going on.
The result will, of course, largely depend on the resistance and geometrical measurements of the eddy current path and on the speed of rotation; – and it is these elements that determine the deceleration of this current and its position in relation to the field. For a certain speed, there is a maximum exciting action; while at higher speeds, it would gradually decrease, tending to zero and finally completely reversed, that is, the effect of the eddy current would have to weaken the field.
The reaction can be better demonstrated experimentally by positioning the N and S poles, as well as N ‘and S’, on a freely moving axis, concentric with the axis of the disk. If the latter rotated as before in the direction of the arrow D, the field would act in the same direction with a moment, which, up to a certain value, will grow with the speed of rotation, then decrease, and, passing through zero, finally becomes negative; that is, the magnet would begin to rotate in the opposite direction to the disk.
In experiments with alternative electric motors, in which the field is changed by currents of different phases, an interesting result was observed. For very low field speeds, the engine showed a moment of 900 pounds, or more, measured on a pulley 12 inches in diameter. When the speed of rotation of the poles was increased, the moment decreased and finally decreased to zero, and became negative, and then the anchor began to rotate in the opposite direction to the field.
Returning to the basic idea, assume that conditions such that the eddy currents produced by rotating the disk reinforce the field, and assume that the latter gradually increases, while the disk remains rotating incrementally (Dragons’ Lord: however, the necessary thought slips here) . The current once began, and may be sufficient to support itself and even increase in strength, and then we have the case of Sir William Thomson’s “current battery”.
But from the above considerations, it would seem that for the success of the experiment the resistance of a solid disk would be significant, since if there was a radial partition, the eddy currents could not be formed and their harmful effects would cease. If such a star-shaped radially composite disk were used, it would be necessary to connect the spokes along the edge with a conductor or in any other way in order to form a symmetrical system of closed circuits.
The action of the eddy currents can be used to excite the machine of any design. For example, in Fig.2 and 3, devices are shown in which a machine with a rotor-disk could be excited by eddy currents.
Here, a multitude of magnets, NS, NS, are placed star-shaped radially on each side of the metal disk D and, in continuation of its periphery, a set of isolated coils, C and C. Magnets form two separate areas, internal and external. There is a hard disk rotating on an axis and a coil in a region remote from it. Let us assume that the magnets are a bit excited at startup; they could enhance the effect of the eddy currents in the hard disk to provide a stronger area for the peripheral coils. Although there is no doubt that under such conditions a machine could be excited by this or similar means, there is enough experimental evidence to guarantee that such a mode of excitation will be wasteful.
But a self-excited unipolar generator or motor of the construction shown in Fig. 1 can be excited efficiently, simply by separating the disk or cylinder in which currents are induced, and removing the excitation coils that are commonly used. Such a scheme is shown in Fig.4.
The disk or cylinder D is supposed to rotate between the two poles N and S of the magnet, which completely cover the disk on both sides, the contours of the disk and the poles represented by circles d and d ‘, respectively, the upper pole, is not shown for clarity. The cores of the magnet are supposed to have holes in the center, the disk drive shaft C pierces them. If the unmarked pole is lower and the disk rotates, the current of the screw form will, as before, flow from the center to the periphery, and can be removed by the corresponding sliding contacts, B and B ‘, on the shaft and the periphery, respectively. In this device, the current flowing through the disk and the external circuit will have no noticeable effect on the exciting magnet.
But let me now assume that the disk is divided into sectors, in a spiral, as indicated by solid or dotted lines in Fig.4. The potential difference between a point on a shaft and a point on the periphery will remain unchanged, in sign as well as in quantity. The only difference will be that the resistance of the disk will be increased and there will be a greater potential drop from a point on the shaft to a point on the periphery when the same current flows through the external circuit.