The first alternators. Part 2

Generators for powering electric lighting

PN Yablochkov was the initiator of the introduction of an alternating current into the electric lighting system. In this regard, various designs of alternating current machines have been proposed, specifically designed to supply the energy for an installation for electric lighting in the Yablochkov system.

Around 1878, Yablochkov together with the Gramma plant developed several similar designs of generators for feeding 4, 6, 16 or 20 candles. Consider, for example, the design of a 16-candle generator. The ring fixed anchor had a sectioned winding, the sections of which formed four separate chains of four coils per chain.

On the shaft of the machine, eight poles were rotating, excited by a constant current. Thus, for each pole there were two coils, in which currents were induced, shifted in phase relative to each other by a quarter of the period. The coils are connected to each other through one so that the currents in one circuit coincide in phase. Four candles of Yablochkov fed from each chain. Consequently, the considered generator was nothing more than a two-phase synchronous machine with electrically non-connected phases.

However, the designers did not seek to create a multi-phase system of currents, and, solving the problem of "dividing the light," they were looking for the possibility to build a generator with several circuits and at the same time improve the use of the machine, which they achieved by making the armature of the two-phase armature.

Yablochkov proposed also some other designs of alternating current generators that had not played any, or at that time, a significant role in the history of electrical engineering. Such machines include a generator with reciprocating armature movement (1876) and inductor generators (1877 and 1881).

Problems in the development of alternators

The most serious obstacle to the development of alternators was the heating of steel cores. It was mentioned above that the heating of the cores of electromagnets was one of the main drawbacks of the Wilde generator. But no less impeded the development of generators and the heating of the armature core. An alternating current flowed in the windings of the anchors, and the question of reducing the magnitude of losses in steel anchors over time became of primary importance, while being difficult to resolve.

Indeed, the practice of making laminated cores began to be established only in the 80s, and before that and even in the early 1980s the cores of both core, ring and even drum anchors, mainly because of technological difficulties, were made massive.

Under these conditions, two main trends in the development of alternating current generators become clear:

1) to increase the power of the machine, increase the number of armature coils (the same trend as in DC machines in the 1940s and 1950s)

2) to diminish the losses in the cores (and, consequently, their heating) to reduce the volume of steel in the anchor.

The latter direction led to the fact that some generators were made with coils that did not have steel cores at all.

The first generator at Paddington Power Station

In 1885, a generator was installed at the Paddington thermal power station in England, which was made with a two-phase coil winding and was designed, like the Yablochkov-Gramm generator, to separate the various lamps. The machine had a power of 115 kW at a voltage of 105 V and weighed 18 tons. It was driven from a piston steam engine at a speed of 146 rpm and produced an alternating current with a frequency of 40 Hz. The causative agent was driven from a separate steam engine.

Thus, it can be stated that by the mid-1980s, AC generators that were suitable for practical purposes had already been developed and used.

The current period in the development of alternators began in the 90s of the last century, when they began to manufacture three-phase machines with laminated cores and a drum type of anchor windings.

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Source of information: LD Belkind, ON Veselovsky, I. Ya. Konfederatov, J. A. Schneiberg. History of power engineering . M., L .: Gosenergoizdat, 1960.