§ 11 Theory of the method of unwinding the induction meter by the method of "transformer".
As we found out from the previous paragraphs, the electric meter is an asynchronous electric motor with a squirrel cage rotor. In this case, the role of a squirrel-cage rotor is performed by an electric meter disk. And the windings form Wi (current winding of the electric meter) and Wu ( winding of the voltage of the electric meter). Figure 1 shows a simplified electric circuit of the meter. The remaining additions are aimed at increasing the accuracy of the meter and they are not listed here. And Since this is an electric motor, it obeys two basic laws of electromechanics:
1. Any electric motor can work as a generator of electricity and vice versa. (In this case, this law is not useful to us)
2. Any electric motor rotating in one direction can rotate in the other.
It means there are no theoretical obstacles to making the counter rotate backwards.
In order for the motor to begin to rotate in the other direction, it is necessary to change the direction of the current in one of the motor windings (of course for an AC motor, it would be better to say that the phase angle of the current needs to be changed, but we will not go into theoretical subtleties and under the current direction we will understand the phase shift angle). That is, if we manage to change the direction of the current in the current winding of the meter, it will begin to rotate backwards.
Now we look at Fig. 2. Suppose that we have found a source of alternating current Ubr, which delivers current in the opposite direction (antiphase), connected it to the points E1 and E2 (or terminals 1 and 2 of the electric meter).
The current through the winding Wi, will be equal to the sum of all currents through the winding (Kirchhoff law), that is, Iwi = In-Ibr.
What follows from this formula? If Iн = Ibr, the counter will stop, although the load Rн will consume power. If Iн <Ibr the counter will go back, and the load Rн will still consume power.
The most interesting thing is that in order to stop the counter, the voltage Ubr is about 2-3 V, since the resistance of the current winding of the counter Rwi is quite small, about 0.2 - 0.3 Ohm. Accordingly, according to Ohm's law Ibr = Uobr / Rwi and even 3 V, they create a current of the order of 10 A.
Now you need to find a device with an output voltage of 2-3 V, and gave it in antiphase to the main load current. Fortunately, such a device is there and it is not difficult to find it - it is called an ordinary step-down transformer of 2-3 V and with a power of about 100 watts.
Let's look at Figure 3 - if the magnitude of the secondary voltage is clear, it is simply measured by the tester, then the phase is a bit more complicated. In order for the transformer to deliver current in antiphase, it is sufficient to simply flip the secondary winding. Now we have everything to make the counter rotate backwards.
Now, if we substitute new elements into Figure 2 and bring it a little closer to reality, we get the scheme shown in Figure 4. This is a real device with which you can make the counter rotate both forward and backward (to do this, simply turn the plug in the outlet). But this option is full of significant drawbacks:
1. The step-down transformer is in the shield, and this is an obvious fuse.
2. It is necessary to pull in an additional two wires in an electrical board, which is quite problematic, and it also has a crush.
Let's try to solve the first problem, that is, to move the transformer to the apartment. Partially it is possible to solve the second one. Pay attention to fig. 4 point E2, L2 and the upper pin on the socket are connected, so one wire from the wiring can be used to power the primary winding of the transformer Tr1.
Now look at the pic. 5. This is a modified diagram of Fig. 4, but now some of the problems have already been solved - now the transformer is already in the apartment and is easy to hide, one wire from the apartment to the shield has disappeared. But I still want to see that there are no snot from the apartment to the shield. That is, it remains only to find a free bypass wire from point E1 to terminal 1 of the electric meter. Extra wires to the apartment are not instituted and the problem would seem insoluble. But for our happiness in the apartments we have a network with a deafened grounded neutral. What does it mean ? In the power board, the neutral wire is electrically connected to ground. And in our apartment, grounding is present everywhere - these are central water supply pipes.
That is, we have the same missing third wire, but in this form, as shown in Figure 6, it cannot be used because the current winding of the electric meter is included in the phase wire and the neutral wire is grounded. So you need to make sure that the current winding of the meter was not included in the phase circuit, but zero. To do this, change the incoming wires to the meter, that is, going to terminals 1 and 3. (See fig. 7)
And now this bypass wire can be used. Instead of a dashed bypass wire, we use grounding. (see fig. 8) What we get - all you need is in the apartment, it remains to perform only a few shamanic actions.
So what you need to do to start spinning counter:
You need to find a step-down transformer 220/4 V with a capacity of at least 100 watts.
Need a socket near the water pipe.
It is necessary to change the incoming wires on the counter, so that the phase wire comes to the third terminal of the meter, and the zero to the first.
Clean up the heating pipe to the metal.
Assemble the circuit shown in Figure 8.
In the unwinding of electricity meters, the main sense of proportion. If it turns out that in half a year you have not consumed a single kilowatt, wait for the inspection of power control with all the consequences. That is, you still need to pay for electricity, preferably regularly and not less than 100 kW. And the rest can be slightly and subtract. If you follow these simple rules and do not be impudent, then zalit practically excluded.
PS See also on the website Sparkling.ru - Winding, braking, stopping electricity meters. The latest ways from the authors. Free consultation.