Dodgy trade pictures for your amusement! - 1 Million Views!

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Mark Wright said:
Thanks, makes sense makes me think of electronics and Relays etc.
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Just another word for a relay.... although contractors are combined relays.... to switch so many poles through one switch.
Also can use a 12v momentary push button to switch and hold in a 400v 3 phase load (like a motor) or as described above, a simple light switch turning on a much higher load than the switch itself could handle
 
littlespark said:
Just another word for a relay.... although contractors are combined relays.... to switch so many poles through one switch.
Also can use a 12v momentary push button to switch and hold in a 400v 3 phase load (like a motor) or as described above, a simple light switch turning on a much higher load than the switch itself could handle
Click to expand...
I didn't want to go totally off-topic just been trying to get a better understanding of DOL and there always wired in such a way that there latched providing undervoltage protection totally forgot really there just like relays and do what relays do, also never seen them used for anything but DOLs.
Doh..
 
In a way a relay and a contactor are the same - both use an electromagnet to operate the switch contacts. The difference is more of size and application.

As a general rule "contactors" are high current, say 20A and above, and usually single-throw (i.e. on/off only, but can be 2, 3, 4, etc poles that are simultaneously switched).

Relays come in all sorts of shapes & sizes and are generally low-medium current, so some have gold contacts for "dry" switching of signals in the microvolt / milliamp range, but most have some sort of silver alloy contacts for up to the low tens of amps range. Often relays are available in double-throw (i.e. change-over contact) configurations with commonly 1 or 2, sometimes 3, rarely 4, simultaneous sets of contacts.

Also some relays are magnetically latched so have typically two coils and you momentarily energise one to set it "on" and the other for "off" (but with changeover contacts that is really positions 1 & 2, etc).
 
As a general rule relays are used in control circuits and contactors are used to switch loads.
Generally contactors provide simple switching with limited or no function beyond a simple make/break when the coil is energized, but they can have current ratings in the hundreds of amps.

Relays can provide all manner of functions for control, protection, sensing, latching, timing etc etc, and generally are rated for lower currents (usually in t

However there is no actual definition or hard and fast rule to what the difference is.
Relays can and do exist with current ratings in the hundreds of amps, and some contactors can incorporate timing or latching functions etc etc.
 
davesparks raises anther aspect: often the term "relay" is used more generally in electrical engineering (rather than electronics) as a control block element, not just as an electromagnetic switch.

So timers, phase loss protection, etc, are all often described as relays because they switch on something else happening.
 
i have implanted relays in my head. 4 of them.

1. clicks in when it's time to get up.
2 . clicks in when it's time for bed.
3. tells me when it's time for beer.
4. tells me it's not yet time to die.

i love electronics.
 
littlespark said:
Let’s hope no4 doesn’t get a loose connection
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no chance. there are too many people i still got to annoy. anyway, as i see it, i got to survive till 87 to recover all the taxes i've paid for 60 years, through the state pension.
 
telectrix said:
i have implanted relays in my head. 4 of them.

1. clicks in when it's time to get up.
2 . clicks in when it's time for bed.
3. tells me when it's time for beer.
4. tells me it's not yet time to die.

i love electronics.
Click to expand...
Bet it’s a messy day if 1 & 3 get connected arse about face ?
 
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davesparks said:
Contactors are used where you don't want, or can't have, the full load running through a switch, or when multiple circuits need to be switched by a single device.
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As in this case where four (?) separate high current loads are being switched by the one photocell. There's two contactors here because the ones used are only 3 pole - there are some with 4 poles, but often the 4th pole is relatively low current and used just for the hold-in circuit.
BTW - you can get a variety of add-ons for many contactors. Auxiliary contacts that clip on the side, delay relays (used to be pneumatic, I suspect some are electronic these days) that clip on the front and can be used for sequencing (e.g. start one motor, after a delay, start the second), interlocks that mechanically prevent two pulling in at the same time (e.g. for reversing or star-delta circuits). There's a lot of things you can do beyond simply switching on and off.
 
Went to price up for remedials today, 3L1 RCBO failed to trip when tested.

Easy enough I'll just replace it, then I saw this on site, no mention of damage to 3L2 and signs of water damage down the right hand side of the board. Luckily just external lighting so no major risk to life...

I think the water tank in the room above had sprung a leak at some point.

IMG_0944.jpg
 
Some of the others had bits of cut off MIG wire sticking out all over the place!
I can't laugh too much though, my first attempts at TIG welding were not good, at all. I did practice on scrap metal that went in the bin though, not on site!
 
freddo said:
Another non electrical seen when installing some heaters:
The 'weld' has completely failed and the bracket is no longer attached to the steel lintel.
View attachment 60416
Click to expand...

Even I can weld better than that!
[automerge]1598472448[/automerge]
freddo said:
Some of the others had bits of cut off MIG wire sticking out all over the place!
I can't laugh too much though, my first attempts at TIG welding were not good, at all. I did practice on scrap metal that went in the bin though, not on site!
Click to expand...

Same here, I'm still in the early stages of learning TIG and so far I have managed convert a lot of good metal into scrap.
 
freddo said:
I've also just started with TIG, It's probably one of the most difficult skills I've ever tried to acquire, very steep learning curve.
Click to expand...

My biggest issue at the moment is, I think, the incredibly low cost 'Chinese Export' machine the boss bought and I have been playing with.

On the plus side it has a plasma cutter which is great fun, definately the fastest way to convert big useful bits of metal into little bits of scrap whilst also setting fire to the workshop!
 
Do you mean TIG or MIG ? They are different and MIG is more common.
Remind me of an old Range Rover I bought for parts. It had an LPG conversion with a tank in the back. Whoever fitted it did neat little lengths of weld all around the tank cradle, really neat welding. But ... only one weld was to steel as most of the floor is aluminium ! The weight of the tank kept it in place so all the welds looked OK at first glance.
 
davesparks said:
I mean Tig personally, that's what I am slowly learning at the moment. I've git a reasonable handle on stick welding and now I've moved on.

Is MIG more common?
Click to expand...

I reckon so, especially in the automotive world.
 
Yes Mig is most common just like arc or mma. Once you have it set though you just point and shoot, it has an auto feed spool of wire in the machine that is the filler. I've never tried tig so far I keep meaning to get some gas and leads for my thermal arc 185 and have a go. I've heard it's an art form! Good luck you guys who are trying to master the art!!
 
I know loads of people with MIG machines - which is really the same as stick welding but with autofeed and a gas shield*. I only know one person with a TIG machine.

I have to say I fancy a go at TIG - I've seen it done a couple of times. For one thing, separates the arc from the filler feed which is a problem I seem to have with MIG. My welding is often not much better that the example a few posts back - and I usually end up adding too much material by the time I've put enough heat into a job :oops:

* You can use cored wire for gas-less work. Then it's very much like stick welding with a solid flux that creates the gas shield and/or a liquid barrier when subjected to the heat of the weld. For some reason the polarity needs changing between normal (gas shield) MIG and gasless (cored wire) welding. Some MIG machines, including mine, have the connections arranged so you can swap the earth and snake connections round.
 
that is awful, the only thing straight and level is the sink.
 
yeah, but what's the problem.you can see it working, and it is, of course, on a cure all RCD. we hope. anyway, anyone who needs to use hot water to wash hands is a wimp. also. thatpointing is diabollockal. looks like it's been tthown in from next door.
 
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