How to make a protector against tension increases
One of the most frequent causes of the breakdowns in our computers there are the tension increases of the electrical network, hence we appear often acquiring some type of device to protect our teams.
In general, the increases take place when a neutral phase changes for an active phase into some repair of the lines and they shake our houses with neither more nor less than 380 volts. The sources of the computers bear almost all with enough safety up to the 250 V, but not much less 380 V as it happens in many cases.
In this article we tackle how to realize the economic, but effective one, protection for these cases; it is a question of mounting a few varistores in parallel with the cables that feed our computer.
A small theoretical explanation
The varistores are a few variable resistances for tension. Namely up to 250 V (in this case) they will not allow to spend any current to his turn, while when the 250 V are exceeded they will become drivers, leaving circular current between his terminals.
Therefore, if we put between the power cutoff points a few varistores, we will feed our computer normally, but if the tension rises of a dangerous form (to overcome the 250 V), they will become drivers and cortocircuitarán the phase with the neutral one or the phase with the landing, so that they will make to jump the protections of our housing cutting the current.
Namely we will create a species of "momentary electrical breakdown" that will make jump what normally is called like the "automatic one" or the "plomillos", but that technically they receive the name of distinguishing switch and of magnetotérmico, that nowadays is of forced use in all the housings.
Hands to the work, we are going to need 3 varistores from 250 V and from approximately 50 To. A space prolongador with several plugs, which will be where we will connect the computer and his peripheral ones. A little of macaroon termoretráctil. A small plastic box, and a junction card.
We can find all these components in any establishment of electronic components at a few very accessible prices.
The varistores come to go out for approximately 100 ptas unit, the box approximately 400, the macaroon termoretráctil approximately 200 ptas an one meter strip, and perhaps the most expensive thing the plugs space is, on approximately 1.000 ptas.
For this assembly we have made use of a simple space, but we advise one with switch.
The first steps and more theory
Preparation of the box: it does not have major difficulty, simply we will drill for two ends so that it could spend the feeding hose (7,5 mm aprox) and to realize the connections inside the box.
Later we will peel the hose extracting at sight three internal drivers (with a lot of care of not cutting the insulator of the interior cables), and we will peel the tops of the same ones leaving the cable of naked copper to realize the connections in the junction card.
We already have the cables connected in the card, each one with his color.
Three conductive cables that we appreciate in the photo are:
In the entry of our housings we have a small electrical panel with a distinguishing switch, and at least a magnetotérmico. The differential has a palanquita to activate it again and a test button, and the magnetotérmico simply has a lever fatter that is raised to tune in and bends when it jumps or we disconnect it.
Thus if a short circuit takes place (joining the brown and blue threads between them) there would be an excessive consumption, the magnetotérmico would warm up in excess and would jump. But so that the consumption is sobreelevado because of a device, in our case the computer, it means that the magneto will jump when our computer perhaps is already done a sorrow and the damage is already irreparable. That's why we are going to mount between the two a varistor, this way if the tension rises over the 250 V, he will become a driver, provoking a cut between the phase and the neutral one, jumping instantaneously our magnetotérmico.
Disadvantages? That some sporadic time that exceeds the tension limit, we will have a momentary blackout in the whole house, but we will save our team of a rapid way of a surge that might damage it more than a power outrage and a Scandisk on having started again.
Another form would be that the neutral (blue) or the phase (brown) were doing contact with the connector of (yellow - green) ground, in this case it would enter functioning the distinguishing switch or "lifebelt". Nowadays it is of forced assembly in any type of electrical installation of low tension.
How does it work? Since he is observer of the safety of the house, constantly it verifies that the current that goes out for the phase (brown), returns for the neutral (blue); this way, when there is a loss of current for any motive (a discharge or to ground for breakdown), it jumps a person automatically and it is not possible to activate until it does not stop the loss.
They are so sensitive that sometimes, in old facilities, they go so far as to jump over the rain, since the moisture produces current escapes. But the important thing is that if for any motive, some of us we were receiving an electrical discharge, the differential would jump saving us of course the life.
This way we are going to make use of this valuable home-made device to make it jump if it raises the tension.