Contactors and Relays - What's inside, how they work

[@bazboy24]

Thank you for this very clear and simile explanation of a contactor you are a great teacher

[@saravanashanmukham6108]

0 to 1. uncomplicated and powerful/impactful explanation of core concepts enabled me to appreciate relays and contractors. I learnt more than what I would have learnt if I had spent the same time in a physical electrical lab. World definitely needs teachers like you. It might help to scale this approach if you can teach other how to teach. Thanks a ton! Please add more videos.

[@benharris2217]

I knew how relays and contactors worked but I watched this out of interest. Love the analogy with the mockup wooden version. excellent description

[@samuelberry9152]

I understand how this stuff works for the most part but watching this very simplistic demonstration of the various components really helps!! Thank you for what you do here on youtube!

[@rossmurdoch7870]

Once again clear, concise and with the simple demo rig knocked up it will be logged as a visual memory. Many thanks John

[@markpirateuk]

very clear description, you would make an excellent teacher.

[@Prince-ep8pv]

markpirateuk *He is an excellent teacher 😁

[@trinityadam]

its like ElectroBoom... haha He should make a you tube channel called JWBoom haha

[@user-yh4kl3hx2o]

Electrician by trade then went and did an electrical services engineering degree but this man is by far better then any instructor I ever had

[@getsmike6596]

Making a complex system easy to understand is not an easy task and you did a fantastic job. Now I know.

[@yossakornchaiboonthawit4018]

Giving knowledge of magnetic fields is excellent. Thanks you, by Yossakornchai from Thailand.

[@JohnDop]

Thank you for the time taken to make this video!

[@deangreenhough3479]

Just subscribed. Mr John Ward, you sir are a star. What a massive help your work has been today. Thank you very much🙏

[@christopherwoodward3872]

Well up to the high standard we have come to expect, especially in terms of knowledge and clear communication. Particularly appreciated the dismantling of the old-style relay, as I am working with some of these at the moment.

[@ianharrison6597]

Thanks for the video. Very well explained. That wooden model of a switch is a gem for teaching.

[@kevingray707]

Excellent. Deeply appreciate your approach to showing how things work. Please please please more videos

[@Jimmy-xk1oe]

brilliant, simple yet very detailed...Informative and well worthwhile watching..keep up the sterling work and thankyou

[@JohnGotts]

Thanks for teaching me how relays work. I always wondered what the loud click was all about in my Astron 20 and 35 amp 12 V power supplies. I've known all along that they have relays and that relays click but I had no idea of the mode of operation.

[@benhurley280]

What a good teacher easy to understand 👍🏻

[@SultansKitchen1]

Brilliant demonstration,👏🏼.👍🏼

[@ShokaLion]

That's brilliant. Dead simple and a great explanation of all the component parts. Really excellent; more videos explaining electrical bits and pieces should follow your example.

[@eliotmansfield]

An Automatic Transfer Switch uses a pair of interlocked contactors - would make an interesting item to examine and explain.

[@stevecraft00]

I watched a fridgey at work dealing with a chattering contactor in an integral fridge. He replaced the contactor, but it was still doing it. It was quite something to watch the contactor doing this as it wasn't fastened to anything so was juddering about in free air and the internal arc from the compressor startup load was very visible (and causing shop lights to flicker). Anyway it turned out the fridge controller was putting out all sorts of random voltages between 250 and 290 volts. Where it was getting this voltage from I don't know, since it was a single phase fridge, and the controller was using a smaller relay to power up the contactor. Mad.

[@vink6163]

I guess when it was disconnecting the coil it was producing a voltage spike (since the coil is inductive), which might not normally be measurable but since it was rapidly switching the coil on and off the higher voltage spikes were probably present for long enough for the meter to pick them up.

[@BoydWaters]

Such a great demonstration. Many thanks!

[@byronjones3579]

john your videos are amazing thanks so much. please keep the videos coming.

[@michaelwalsh1023]

very useful for heating and priority domestic hot water

[@gtperez1050]

Extremely well put tutorial Great job. Thanks.

[@milesbancroft]

Another great video. I thought the model made it very clear.

[@rustyrob]

Hi JW, any chance of a video of a digital voltmeter and ammeter connections with shunt ,Regards.

[@edgarajala6910]

Thank John for this wonderful video

[@joeya5438]

you are the man J dubz

[@أستغفرالله-ج7ت2ش]

Mr. John, we need a video about USB switch socket. thanks.

[@ZEROSTATIC72]

It's the Ward, Wooden Relay. :) Thanks.

[@thornwarbler]

Another great description ............Thankyou

[@mosialive]

You deserved my subscription.

[@rokvald]

Hello John, thank you for the video. What kind of solution would be for noise issue ?

[@stefantrethan]

There are installation contactors that are quieter, although most of the noise reduction is geared towards the buzzing of the AC coil. Mechanical means of dampening the impact (rubber bumpers) and mechanical vibration isolation (rubber mounts) would be effective. I have resolved the clunking issue of solenoid valves (same principle) by unscrewing them from the metal enclosure they were mounted to and using some foam rubber to hold them in place instead. You can barely hear them now, but always be mindful of that the coil doesn't overheat if you attempt a similar fix. It's always the same strategy with any kind of noise. Eliminate the source and/or decouple it from the recipient.

[@JohnDoe-qx3zs]

+stefantrethan One additional way of cause: Just put it somewhere else, so you can't hear it.

[@edmundfisher4951]

On the last contactor you looked at, what's behind the flap on the font?

[@vink6163]

Only a guess but many of them have a plastic arm that moves in and out with the switching action, and you can buy additional modules that attach to this point and give you "auxiliary contacts" that switch in tandem with the main contacts. The modules are like relays/contactors but without the coil, as they use this arm to move the metal contacts back and forth instead, effectively piggybacking off the main contactor's coil. Typically the aux contacts are lower current than the main ones and used for things like remote monitoring of the coil state, indicator lights, etc.

[@johnpriceuk]

brilliant bit of teaching

[@martinuk1001]

Hello John, thanks for all your excellent videos. I have a question:- what is the usual way to provide the 24v power supply for a 24V AC contactor, i.e what piece of equipment is commonly used for this?

[@jwflame]

Usually a small transformer, either with a 240V primary (line -neutral) or sometimes a 400V primary (line - line).

[@otm646]

By 24 volt AC contactor I'm assuming you mean 24 volt coil on the contactor. Step down transformers are ubiquitous in industry. They are used to provide power to the control circuit (it's safer than using high voltage) so you will often have a transformer which takes 240v AC from the mains down to 24v (or often 12v) AC to run the contactor coil. Common transformers run about $100 and usually fit inside the electrical enclosure where the contactor is housed. HVAC equipment is almost universally run on 24 volt AC but it is also used widely in industry.

[@MrSJT]

Hi John, you mentioned it's a 24VAC coil if used with DC the current would be excessive, what if the coil was 24VDC and you use AC, what happens then? Current too low and may not work?

[@blumbotough1076]

John, what is the difference between an AC coil and a DC coil?

[@jwflame]

Resistance of the windings - for DC the current is only limited by the resistance, but for AC the inductance of the coil is the main current limiting factor.

[@otm646]

They are construction is nearly identical however they operate differently. They are both inducing a magnetic field. The DC coil is the simplest. It uses the resistance of the coil to limit current flow. An AC coil relies on the impedance of the coil along with a shaded pole to a maintain that magnetic field when the voltage drops to zero as the voltage alternates.

[@laernulienlaernulienlaernu8953]

A good example of how a relay works would be the call buttons on a lift - every button connects to the lift mechanism but if they were directly connected then when you pressed one button they would all light up. Although these days they are controlled by electronic circuit boards much like everything else

[@Madness832]

Looks like one could use that wooden assembly as a telegraph sounder.

[@AllenGoldsmith]

john please help i'm confusing myself, i have a 3 phase heater i need controlling by a timer. if i have a timer on a din rail next to it where do i pick up a 230v supply for the coil can i take it off one of the phases that goes into the contractor? sorry for the questions i haven't wired a contactor before.

[@jwflame]

You can use one of the incoming phases and neutral, which will be 230V. If there is no neutral, you will need a contactor with a 400V coil, and the coil supply is taken from any two of the phases.

[@AllenGoldsmith]

if the heater is 3 phase and earth can i bring 3 phase and neutral to the supply of the contractor so i can use the neutral, then run 3 phase and earth only to the heater?

[@jwflame]

Yes, that's an entirely normal thing to do.

[@robertsmith8452]

JW, many thanks for all your instructional videos. It's great to see these mysterious items de-constructed and I appreciate the time you put into your explanations of them. Robert

[@javierferrer4634]

Nice video , its interesting thank you!

[@LightSoySauce]

nice simple explanation thank you

[@feriklile1065]

Very good explanation

[@seanosomething]

John, My system is 12vdc To wire in (contactor)... i use the signal wires to the coil....(A1+A2) but for the power wires do i run my positive and negative from my transformer/power source to say, L1 and L2 then my Load wires From T1 and T2????? Thanks in advance..

[@otm646]

Yes that is correct. There is a standard IEC naming protocol for connections on contactors. L1,L2,L3 are for the supply power coming in from the 3 phase mains. T1,T2,T3 are for power going out to the device. A1 and A2 are for the coil. If it's only a single phase contactor you'll only have L1,L2 and T1,T2 along with the same A1 and A2 for the coil.

[@wesleyquarshi3]

If I wanted last man out switch at front of a cash desk controling 4 different circuits do I feed the switch first Double pole then to A1 And A2 on contactor

[@otm646]

All you need to do is de-energize the coil, so you simply need a switch which makes or breaks the connection depending on if you want the lights on or off.

[@saurabhtiwari2247]

thanks for this very informative video

[@paulmorrey733]

Great video Thanks John

[@maxsmith2320]

very nice tutorial

[@bigdick6666666]

Another excellent Video!

[@henrybartlett1986]

Very useful. Many thanks.

[@globalwhosanes2]

Thanks, good explanation..

[@hmnthr4008]

Great explanation.

[@KhaledBu23]

When a dc voltage is applied to the coil, how is that not a short circuit?

[@Mark1024MAK]

Although copper is a good conductor, it still has a resistance. Relay coils and contractor coils are wound with hundreds to thousands of turns of wire. So the combined resistance of all that wire adds up. It is this resistance that limits the flow of DC.

[@otm646]

Following the link, the table lists coil resistance for both AC and DC coils ranging from rather small to quite large capacity contractors. Based on that you can calculate watts consumed by the coil showing it's not a dead short. sprecherschuh.com/library/techdocs/posts/2014/01/ca7-coil-resistance.html

[@gartmorn]

In industry relays are often used as interlocks in control circuits. Cabinets full of relays are not uncommon! I spent many hours scratching my head fault finding in just such switchgear! Probably worth a video in its own right?

[@AbdennacerAyeb]

Thank you very much...

[@fieldsofomagh]

Great video.

[@HH-wh1kh]

this is awesome !

[@xaris.spyros5310]

great video

[@mavezy]

Good stuff!

[@Energy-et6pw]

Appreciated

[@Broken-Silencer]

Cheers!

[@hughsgarbagetrucks]

i made 1 using microwave parts

[@cooper512]

Genius

[@stevecoburn3085]

Awsum

[@fathemasultana1027]

Everybody should raise voice against Assange now. Moreover, I want to talk with the boys before Christmas.

[@anoopsingh7420]

That's what you call 'a topic well explained', contrary to the other crap videos available on this topic