Changing the characteristics of generators without rewinding the windings. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Electric motors

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Craftsmen are looking for generators that can operate at low speeds. Electric generators of modern cars operate only at high speeds. How to remake the most massive varieties of generators? How to adapt them for micro power plants? This article is about the easiest ways.

To date, the real cost of manufacturing individual wind farms is lower than the manufacture of micro-hydro, -TPP and -CHP of the same capacity. It is assumed that the most popular will be light, gearless, low-power wind power generators with recuperation of the generated current into the household power grid. It is best to create such micro wind farms on the basis of automobile alternating current generators. Today, such generators are the most common, as they have the highest power density and greater reliability.

Unlike previously produced DC generators, the new ones generate electricity by rotating in any direction, both in the right and in the left. Only phase rotation depends on the direction of rotation of the generator rotor.

I tried to reduce the operating speed of electric generators without rewinding the windings, only by changing their connection. Since the experiment was successful, I want to share its results with readers.

In the generators of the same type proposed for repair and alteration, there were three different windings: a triangle (∆), a double star (ΥΥ) and a star (Υ). The latter, after repair, worked quite satisfactorily. It was the oldest generator designed to work with low-speed engines. According to the type of this generator, the windings of two other, newer ones were redone.

Academician was right three times. E.Kh. Lenz, who established as early as 1834 the principle of reversibility of electric machines. The method of converting electric motors from a triangle to a star [1] is fully suitable for electric generators. For those who wish to maintain a high-speed mode of operation and be able to quickly switch modes, I advise switching according to the scheme shown in Fig. 1, which allows you to switch from a single or double star to a single or double triangle and back on the go. True, such switching is more suitable for wind farms, where there is good access to the generator, for example, for a balcony.

Switching the generator windings from a double star to a single star turned out to be more difficult, but gave an amazing result: the generator produced electricity at very low speeds. For better coordination of the low-resistance excitation winding located on the rotor, it was necessary to abandon the direct connection and install a self-made shunt from a thin iron wire twisted into a spiral into the gap of the jumper connecting the "Ш" and "+" terminals. The average temperature coefficient of resistance of iron is 0,0065 degrees^-1.

In favor of the use of iron as a two-terminal current stabilizer, its low cost (almost zero) and small dimensions compared to light bulbs speak. To make the spiral hang freely in the air, you can pass an asbestos fiber cord through it.

For those who want to make the characteristics of generators more acceptable for use in micropower, I will tell you more about switching windings from a double star (YΥ) to a single star (Y). To do this, it is necessary to disassemble the generator by removing the brush holder of the excitation system and unscrewing the 4 fixing screws. The stator must be separated together with the back cover from the rotor and the front cover. In this case, it is not necessary to remove the rotor from the front cover. Then unscrew 3 nuts securing the stator winding leads. The stator has the form of a ring made of iron plates. In our case, the stator had 36 slots (sometimes 18). The double star winding consists of thinner wire than the single star winding. Working leads consist of two wires soldered together. They need to be soldered.

It is also necessary to unsolder the zero point of one of the stars and connect the winding leads with three jumpers (Fig. 2).

The jumpers must be long enough so as not to interfere with the rotation of the rotor, and of the same cross section as the winding wire. It is better to take a rigid single-core wire for this.

To increase the voltage of electricity removed from the generator, it is necessary to make a transformer. I use a ready-made one by connecting the windings as shown in Fig. 3. 

For generators converted to 24 V, it is necessary to connect 2 transformers TS-180 (TS-180-2) in series as shown in Fig. 4.

All high-voltage windings form a secondary. They are connected in series (Fig. 3) in such a way that any voltage can be obtained.

To excite a generator that has lost the residual magnetization of the rotor, it is enough to connect a transformer to the network for 1 s. Loss of excitation occurs mainly when the load is completely disconnected.

Taking this opportunity, I want to propose to our deputies to introduce a law obliging the RES to pay money to the owners of mini-power plants for the energy supplied to the power grid. If such a law is adopted, then our craftsmen will master the production of small power plants based on hydraulic engines and steam engines. Mass character in this matter will help pull us out of the energy and economic crisis.

References:

1. Y. Bearded. Experience in connecting industrial electric motors to a household network // Electrician. - 2001. - N12. C.10.

Author: Y. Bearded

See other articles Section Electric motors.

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