okay so the most important thing here is the coil so we all know that when a coil is energized when
current starts going through the actual through the wire and a magnetic field is being produced
now with lots of coils wrapped around the same a small amount of current going through there
every extra turn of the coil the magnetic field is increased so when current goes through this coil
a large magnetic field is produced here and what happens is this coil this line here this contact
this is line that joins all the contacts together what will happen is when this is energized this
will shoot over and join all the contacts together in order for to do in order to do that obviously
we need to energize the coil so the coil on any type of starter circuit like this is known as
the control circuit and the idea of this is that only a small amount of current is going to be used
within this coil to actually start a much heavier load so they started a direct online starter
in this case could be one could be working a as another half horsepower motor or sort of like a 3
or 400 watt motor anything up to about 4 kilowatts you can use online starters for depending what
the motors being used for you can go bigger but general rule is up to about 4 or 5 about 3 4 or
5 kilowatts is the most that you really want to be running with a direct online starter and as
you can see this is single-phase okay so how do we energize the coil or obviously we this um this
start button is the thing that we're going to have to press so if we press the start button I'm not
going to draw on the diagram because it might I don't want to mess it up for you if we press
this button in fact no I will press it because it needs to so if we press this button it will
as that button is pressed it will link across numbers 17 and 18 and as we know number 17 is
wide to number 13 which is wired to number 1 in this case which is the permanent live supply as
soon as the start button is pressed both 17 which is live and 18 now also becomes alive also number
14 becomes live also the stop button becomes live and 95 and 96 become live has does A1 so as soon
as this is pressed current flow will go through the stop button through 95 96 back out through to
A1 through the coil and back through the neutral so suddenly you have a circuit you have a circuit
go and through the coil all the way back through the neutral all the way through here all and
everything is is and so so the A1 the actual core A1 and A2 and the coil is fully energized now what
would happen then is the magnetic field within here becomes magnet so so the field here becomes
magnetised and will pull over this what we would call it an armature it pulls it a class and then
it directly contacts it links these contacts here and so now electricity can go all the way through
the contacts all the way through to the motor back through here back through there and it all
becomes energized and the motor will work so you press the button the coil becomes energised this
shunts across joins all the contacts together the motor begins to run now that's all okay well
you've got your finger pressed on the start button but while you're working you don't want to stand
there with your finger on the start button this button they stop the start button is a normally
open button so in its normal state the contacts are not joined together only when we press them
together our both contacts joined as soon as you take your finger off the button spring pressure
what open the open the Start button so let's look what actually happens when you press this so we
press this button 17 is live 18 also now becomes live in parallel with this button with the stuff
that with the start button are the retaining contacts so now as soon as this is pressed
both the 13 and 14 feed become live as soon as you open there as soon as you take your finger
off and this opens this no longer becomes live but 13 and 14 are live and if you remember 14 is
connected to number 18 so now as soon as you take your button off this the retaining contacts are
keeping all of the contacts retained and so where as before I was saying as soon as you press this
button the electricity flow will come through here and through to the coil as soon as you take your
fingers off this it no longer comes across 17 to 18 but instead it comes down through 13 to 14 all
the way to 18 so 18 still remains energized even though Start button has been depressed I'll just
go over that again so we press this button and 18 becomes live and the circuit and the coil becomes
live and energized and the the armature shunts across and the contacts come into play 17 18 the
start button is in parallel with the retaining contacts 13 and 14 so as soon as you take your
finger off this 13 and 14 remain energised through the contact and so then the current flow now is
going through here and still following the same route keeping the coil energized so that's really
quite nice and simple as we've said as well this is normally closed stop button is in series with
the circuit so nothing much happens here nothing changes as soon as you press you become as soon
as you depress this button electricity is still flowing the electron flow is still going through
here because it's coming through this way now and then it just goes through 95 and 96 to anyone and
anything that everything's okay so what happens now if we press the stop button so a normally
closed contact now becomes open and so as you can see as soon as this becomes opened and I'll just
put my finger across there to represent the wires now aren't joined together suddenly no electricity
no electrons can flow through this wire and up to 95 or 96 so what happens is A1 now loses its
live feed and so common flow isn't going through the coil anymore so the coil becomes de-energized
under spring pressure the with the contacts this the the armature shunts back across and opens
the contacts and stops the motor so we'll just say that again so you the normally closed stop
button is in series normally you open it it takes that out of the circuit it breaks the circuit up
and that circuit breaks the coil the electricity going through the coil with the magnetic field
is broken so under spring pressure the armature returns back opening all of the contacts and the
start and the motor stops so I think that's all I need to sort of say for the control diagram
explaining the single-phase direct online starter it's quite it's quite a simple circuit let's just
I'll ask a couple of questions as to why we use a direct online starter okay so if you imagine
you in a workshop and there's a motor running around there's a lathe let's say for example
there's a lathe turning and that lathe that lathe is is turning and suddenly there's a power cut so
whoever's the electricity goes off the motor stops and everything becomes and everything
stops working ten minutes later the electricity comes back on if this was just a norm if the
motor was just working through a normal switch potentially the motor would start running and
the lathe would start running again so with when you use it the reason we use an online starter is
their motors can't just restart by themselves you have to physically press them again because let's
think about it as soon as there's a as soon as you lose electricity electricity supply to the
building through a power cut this coil will become de-energized therefore under spin pressure the
retaining contacts open again and so everything stops and nothing nothing will work when the power
comes back on this start button is a normally open button so physically needs to be pressed
in again to energise the coil again so that's why we'd use a direct online starter on a on a motor
coil that's the main reason it's also to do with there's only small amounts of electricity going
through the coil that can energize this too to bring the contacts in so a small circuit can
operate a large circuit so you could have 10 amps flowing through here and only sort of like a few
milliamps going through here so a small circuit can control a much larger circuit that's useful
to know when you are having and that's going to be in the next video when we are wiring in remote
stop starts so if you've got other circuits going around the building then you don't have to have
very large cables you can have very small cables through the control circuit because those small
cables are only going to be carrying milliamps rather than the full load current so the full
load current is only going through here it's not going through the control circuit a couple
of things to note these can also be wired up in three-phase to run either a electric motor
well to run an electric motor or they can be used for three-phase where you wouldn't need
a neutral going down to the motor but the coils I come with a 240 volt coil they all they come
with a 400 volt coil and so that's important to remember you don't need to know that for this
video but it is important to remember when you are actually wiring these up you need if it's a
single-phase you do need to make sure that your got 240 volt coil even if it's three-phase you
can still use a 240 volt coil it would just mean that you need to take a neutral to the circuit
as well that's enough now I think to explain the direct online starter and simply how to wire it up
you