The first designs of DC motors. Part 1
The electric machine has traveled a long and complex path from physical toys and laboratory instruments to complete industrial designs. However, at first the development of electric generators and electric motors proceeded in completely different ways, which fully corresponded to the state of the science of electricity and magnetism of that period: the principle of the reversibility of an electric machine was discovered in the 1930s , but its use on a large scale begins only in the 1970s XIX century .
Since in the period before 1870 all the first consumers of electric energy were fed exclusively by a constant current and this kind of current was the most studied, then the first electric machines were DC machines.
In the development of a DC electric motor, three main steps can be outlined, which will be discussed in detail below. It should be noted that this division into stages is conditional, since the designs and principles of the action of electric motors, characteristic of one stage, in individual cases appeared again many years later; On the other hand, later and more progressive designs in their embryonic form can often be found in the initial period of the development of the electric motor.
The first stage of the development of electric motors of direct current
The initial period of development of the electric motor (1821 - 1834) is characterized by the creation of physical instruments demonstrating the continuous conversion of electrical energy into mechanical. The first such device was a Faraday installation for demonstrating the mutual rotation of magnets and conductors with a current.
Investigating the interaction of conductors with current and magnets, Faraday in 1821 established that an electric current passing through a conductor can cause this conductor to rotate around a magnet or cause the magnet to rotate around the conductor. Consequently, Faraday's experience was a graphic illustration of the principle possibility of constructing an electric motor .
The possibility of converting electrical energy into mechanical energy has been shown in many other experiments. Thus, in P. Barlow's book "Investigation of magnetic attraction", published in 1824, described a device known as the "Wheel Barlow" and is one of the historical monuments of the prehistory of the development of the electric motor.
Barlow's wheel by the principle of action is a unipolar electric machine operating in the propulsion mode: as a result of the interaction of the magnetic field of permanent magnets and the current passing through both copper gears sitting on the same axis, the wheels begin to rotate rapidly. It is easy to determine (using, for example, the rule of the left hand) that both wheels will rotate in the same direction.
Barlow found that changing the contacts or changing the position of the poles of the magnets immediately causes a change in the direction of rotation of the wheels. The wheel of Barlow had no practical significance and remains until now a laboratory demonstration device.
Electric motor Henry
Typical for the first stage of the development of the electric motor, an example reflecting a different direction in the creation of constructive forms is the device of the American physicist J. Henry . Henry in 1831 published an article "On the rocking motion produced by magnetic attraction and repulsion," in which he described the electric motor built by him.
This device, like the wheel of Barlow, did not go beyond laboratory demonstrations, and the inventor himself did not attach any serious importance to it.
Historically, Henry's electric motor is interesting because in this device an attempt was made to use the attraction of unlike magnetic impulses for the first time and to repel the same magnetic poles in order to obtain a continuous motion (in this case - a rocking one). The change in the polarity of the electromagnet due to a change in the direction of the current flowing through its winding led the electromagnet to a uniform swing motion.
In the model constructed by Henry himself, the electromagnet made 75 oscillations per minute. The power of engines of this type was very small: one of these engines, built in 1831, had a capacity of 0.044 W (according to modern estimates).
As in the first stage, and later, many engine designs were proposed with the rocking motion of the anchor. However, attempts to construct an electric motor with rotational movement of the armature turned out to be more progressive.
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