Automatic Phase Switch vs. Contactors for 16A+ Load Management?

Question

Hello An automatic phase switch costs from £200 and handles up to 16 A. Above 16 A you need to give contactors + phase switch. This would cost me 300 zł. I thought that maybe instead of playing around with an automatic phase switch, wouldn't it be cheaper to buy contactors ( at a cost of 20 zł )...

bumble · Answer

What exactly do you mean? Now phase loss does not happen. what is it supposed to be for? What is the point of this device?

lucjanobes · Answer

Maybe at your place they don't switch off the electricity at the power station. At our place they cyclically switch off as soon as the wind blows. It's mostly the same phase that goes off, which leaves me without light in the rooms. That's why I want to have automatic switching so that I don't have to short-circuit the wires like I used to do.

bumble · Answer

Then switch permanently to that phase which they do not switch off.

Added after 4 [minutes]:

https://www.fif.com.pl/pl/automatyczne-przelaczniki-faz/136-przelacznik-faz-pf-431.html
And there is nothing more to look for. It switches phases when the voltage drops below 195V, which is uninterruptible, and you can't do that with contactors, so if something goes wrong you can short-circuit the phases and you'll be on your way.

Janusz_kk · Answer

. Maybe a colleague could read the author's post with understanding? because that seems to have been lacking. To the author on contactors it is possible, but it is necessary to use contacts so that there is no It is possible to use contactors on contactors, but it is necessary to use contacts so that it is not possible to switch two or more phases at the same time. For this purpose you can use auxiliary contacts.

bumble · Answer

Is it possible? Maybe a colleague can upload a schematic of what? Like a small one? what is to control these contactors? How to manage switching without a power failure? Maybe a short description?

CYRUS2 · Answer

On a nut this is not done. It is not that simple - it is not zero-one. You have to define the cut-off voltage and the return voltage.

mawerix123 · Answer

. It is possible and you can look up the schematic yourself, this F&F does not switch without a blackout, it has three relays in it, so how do you imagine anyway, no one insists that there should be a blackout, even it is unhealthy for phase-to-phase switching. . for 20 zł hmm

Janusz_kk · Answer

. Where do they sell contactors so cheaply that have more than 16A from a relay? ww.tme.eu/en/details/ika25-22_230v/contactors-modules-glow/iskra/30-046-014/ this one costs 63zł. And here is my suggestion: .

lucjanobes · Answer

On a Chinese well-known portal .

bumble · Answer

This I would accept maybe 1.6A as it says 16A. If it's a phase for long term power supply to a house for example I wouldn't risk it. Single contactors ok but it will take up more space and risk more damage.

lucjanobes · Answer

What company are good contactors from?

bumble · Answer

Check out the electrical wholesalers. Maybe schneider.

czesiu · Answer

. My advice, however, is to use an automatic phase switch. In most cases, after a phase loss in the distribution network, a voltage close to half of the supply voltage is maintained on the sick phase (I will not now explain why, I suggest the author to check with a voltmeter at the next fault). Also, in most cases, the contactor, when the voltage drops to half of Un, will not switch off (there is such a parameter for contactors: dropout voltage). The idea with contactors alone will not work.

lucjanobes · Answer

Once when there was an outage for 3 days (three phases died) I had a voltage of 14 V to 70 V on one of these phases. Some equipment on 230 volts worked normally. Such a radio was playing, a laptop was charging and a fridge was working although its output was poor. As you can see, it is possible to squeeze quite a lot out of such a low voltage when the electronics have a large spread. The funniest thing was that first on the phase there was 180 V in two hours 150 V. The next day it was already 120 V. It went down like that for these three days to a final 14 V, on which the internet modem worked correctly. On the other two phases it was just a few volts from the beginning of the fault. Everyone in the neighbourhood laughed at this, because there was apparently no electricity, but the propaganda radio could be listened to normally.

elezibi · Answer

Oh I wouldn't be so sure about this arrangement When applying power before contactor L1 cuts off N to the coils of the other contactors, what will contactors L2 and L3 do ? Once it has cut the N to the coils of the L2 and L3 contactors, won't they have any desire to work interphase?

bumble · Answer

Always from a simple matter, colleagues are able to complicate everything to the maximum. There is a problem? There is a special solution. What else is there to look for? There are ready-made systems for this, not home-made constructions that pose a danger to people, animals and property. Apparently, what do we wear on our hands? A watch? What for? To tell the time. How about something else instead of a watch. And these examples can be multiplied at will. There is an automatic switch that operates without interruption, so we use it.
We have an L1 phase. Phase L1 disappears and we have 150V instead. However, the contactor does not switch phase L2 because L1 did not let go. Not together that on day three there was 120V and the fridge was still running.

Ryszard49 · Answer

elezibi , I don't suppose you suspect that colleague Janusz_kk was so unreasonable as to propose an untested solution? This can be checked by assembling the layout. bumble , we are already like that, we do everything to complicate our lives.

retrofood · Answer

.All contactors and relays have a voltage drive which has a certain hysteresis loop. That is, a different (higher) voltage is needed to attract the jumper and a different (lower) voltage is needed for it to drop out. This is why it is difficult and not cheap to make an automatic phase switch, because when one phase is de-energised, the voltage distribution changes! There is no longer a triangle! And with structurally simple systems, the voltage coil of the contactor from the phase that has decayed does not want to let go at all!That's why I advise against such games, the subject has been worked out for a long time, you only have to search in the literature.

bumble · Answer

You don't even need to look in the literature because there are ready-made devices. And that's what they are there for. In addition, they ensure uninterruptible switching and the voltage will not drop below 195V during a phase failure. In addition, the author writes that after a phase failure he has 180V and the devices work for several days. Somehow I cannot believe this. I remember a little from the past quite a long time ago and there was voltage on one phase loss but much lower. Usually it was repaired in a few hours. Well I didn't know there could still be such a situation because usually when a phase failure is detected on the MV the whole power supply is disconnected.

retrofood · Answer

. This can vary greatly. Depending both on how it is on the MV side, the LV side and even how the consumers at the end user were configured at the time of the fault. And where, at what point these voltages are measured. And with what.

Automatic Phase Switch vs. Contactors for 16A+ Load Management?

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