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§ 11 Theory of the method of winding an induction electric meter using the "transformer" method.



As we found from the previous paragraphs, the electric meter is an asynchronous electric motor with a squirrel-cage rotor. circuitry of the meter In this case, the role of the short-circuited rotor is played by the electric meter disk. And the windings form Wi (current winding of the electricity meter) and Wu ( winding voltage meter). Figure 1 shows a simplified electrical diagram of the electric meter. The remaining additions are aimed at increasing the accuracy of the counter and they are not indicated here. And if it's an electric motor, then it obeys two basic laws of electromechanics:
1. Any electric motor can work as an electricity generator and vice versa. (In this case, we do not need this law)
2. Any electric motor rotating in one direction can rotate into the other.
Hence the theoretical obstacles to making the counter spin back is not.
In order for the engine to start rotating in the opposite direction, it is necessary to change the direction of the current in one of the windings of the electric motor (of course for an AC motor it would be more correct to say that it is necessary to change the angle of the current phase shift, but we will not climb into theoretical subtleties, and under the current direction we mean the angle of phase shift). That is, if we manage to change the direction of the current in the current winding of the electricity meter, it will start to rotate backward.
Pic_2

Now let's look at Fig. 2. Suppose that we found an alternating current source Uobp, which gives the current in the opposite direction (antiphase), connected it to the points E1 and E2 (or terminals 1 and 2 of the electricity meter). The current through the winding Wi, will be equal to the sum of all currents through the winding (Kirchhoff's law), that is, Iwi = Iн-Iobr.
What follows from this formula? If In = Iob, the counter will stop, although the load Rn will consume power. If In <Iob the counter goes back, and the load Rn will still consume power.
The most interesting is that in order to stop the meter, the voltage Uob should be of the order of 2-3 V, since the resistance of the current winding of the counter Rwi is rather small, of the order of 0.2-0.3 Ohm. Accordingly, according to Ohm's law, Iob = Uob / Rwi and even 3 V create a current of the order of 10 A.
Now we need to find a device with an output voltage of 2-3 V, and it showed it in antiphase to the main current of the load. Fortunately, such a device is there and it is not difficult to find it - it is called an ordinary step-down transformer for 2-3 V and a power of about 100 W.
Transformer phasing
Let's look at Figure 3 - if the magnitude of the secondary voltage is clear, it is measured elementary by the tester, then everything is a bit more complicated with the phase. In order for the transformer to produce a current in antiphase, simply turn the secondary winding around. Now we have everything to make the counter spin back.
Pic_4
Now if you insert new elements into Figure 2 and bring it closer to reality, we get the diagram shown in Figure 4. This is already a real device, with which you can make the counter rotate both forward and backward (just turn the plug in the socket). But this version is full of significant flaws:
1. The lowering transformer is in the shield, and this is an obvious fuse.
2. It is necessary to pull two additional wires into the electrical panel, which is quite problematic, and also a fuse.

Let's try to solve the first problem, that is, to transfer the transformer to the apartment. In part, you can solve the second. Pay attention to Fig. 4, the point E2, L2 and the upper pin on the socket are connected, so that one wire from the wiring can be used to supply the primary winding of the transformer Tp1.

Pic_5
Now look at Fig. 5. This is a modified circuit in Fig. 4, but now some of the problems have already been solved - now the transformer is already in the apartment and it is easy to hide, one wire from the apartment to the shield has disappeared. But all the same it would be desirable, that from an apartment up to a board any snot did not last. That is, it remains only to find a free bypass wire from point E1 to terminal 1 of the electricity meter. Extra wires to the apartment are not wound up and it would seem that the problem is unsolvable. But for our happiness in the apartments we have a network with a deadly neutral. What does it mean ? In the power shield, the neutral wire is electrically connected to the ground. And at us in an apartment the earthing is present everywhere - these are the pipes of the central water supply.

Pic_6
That is, we had the same missing third wire, but it can not be used in this form, as shown in Fig. 6, because the current winding of the meter is connected to the phase wire, and the neutral wire is grounded. Means it is necessary to make so that the current winding of the electric meter has been included not in a phase chain, and zero. For this, it is necessary to change the incoming wires to the counter, i.e. going to terminals 1 and 3. (See figure 7)

Pic_7
And now this bypass wire can be used. Instead of the dashed bypass we use grounding. (see Figure 8) What we get - everything you need is in the apartment, it remains to perform only a few shamanic actions.

Pic_8
So what you need to do to the counter started to rotate back:

  1. It is necessary to find a step-down transformer 220/4 V with a power of at least 100 W.

  2. Need an outlet next to the water pipe.

  3. It is necessary to change the incoming wires on the meter, so that the phase conductor comes to the third terminal of the counter, and zero to the first one.

  4. Strip the heating pipe to the metal.

  5. Collect the diagram shown in Figure 8.

In the winding of electricity meters, the main sense of proportion. If it turns out that you have not consumed a kilowatt for half a year, wait for the inspections of the energy supervision with all the consequences. That is, it is still necessary to pay for electricity, preferably regularly and not less than 100 kW. And the rest can be slightly and subtracted. If you follow these simple rules and do not get impudent, then zalet is virtually eliminated.

PS See also on the site Sparkling.ru - Winding, braking, stopping electricity meters. The newest ways from the authors. Free consultations.