Draw a start/stop/retain relay control circuit for a 3 phase drill machine

[Didawdidaw]

Hey, I'm just wonder if I can get some feedback on this drawing that I've made? any feedback will be very appreciated thanks in advance.

 

[ElectroChem]

Very neat and tidy, all components in place from what I can see.

Can you explain in words how this reversing starter works? That's the next step I would get a student of mine to do to demonstrate their understanding.

 

[Didawdidaw]

Very neat and tidy, all components in place from what I can see.

Can you explain in words how this reversing starter works? That's the next step I would get a student of mine to do to demonstrate their understanding.

Thanks! I've just realized that i need to also add 2 emergency stops positions. I don't suppose you could help me out wit that as well? I'm thinking that I would have one next to the normal stop button, then I suppose I'd also have one on the other part of the circuit next to the resistor. The one next to the resistor is a bit of a guess if I'm honest but I'm pretty confident about the one next to the normal stop button. I've attached the new picture if you could be so kind to take a look?

To your question this would work by when the forward button is pressed it would power up M1. This would create a electromagnetic field what would pass current threw M1 on both parts of the drawing; this would include the 3 phase power going to the drill causing rotation. The button wouldn't need to be held down as once its pressed it would by-pass the forward button threw the M1 relay. when the stop button is pressed this will break the circuit causing the electromagnets to de-energize stopping the drill. This would then tell TD1 not to open for a set amount of time to stop the drill from causing damage. Once TD1's timer has run it course then the reverse button can be pressed; this will use M2 of the motor and since the wires are switched around (instead of T1 going to T1, T2 going to T2 and T3 going to T3) it will make T1 go to T1, T2 go to T3 and T3 go to T2 causing a backwards rotation.

 

[ElectroChem]

Thanks! I've just realized that i need to also add 2 emergency stops positions. I don't suppose you could help me out wit that as well? I'm thinking that I would have one next to the normal stop button, then I suppose I'd also have one on the other part of the circuit next to the resistor. The one next to the resistor is a bit of a guess if I'm honest but I'm pretty confident about the one next to the normal stop button. I've attached the new picture if you could be so kind to take a look?

Both e-stop buttons can be placed in series with the stop button, they all serve the purpose of cutting the control circuit and thus stopping the drill.
In more advanced machines these emergency stops would be connected to a dedicated Safety Relay or Safety Controller with special functions for safely stopping the machine, but for a simple drill press this is not needed.
The 'resistor' you have drawn is actually a transformer; its job is to take the 400V power voltage and reduce it to a safe control voltage, usually 24V. Simpler control systems like enclosed DOL starters will often just use 240/400V rated contactors and buttons to reduce cost.

To your question this would work by when the forward button is pressed it would power up M1. This would create a electromagnetic field what would pass current threw M1 on both parts of the drawing; this would include the 3 phase power going to the drill causing rotation. The button wouldn't need to be held down as once its pressed it would by-pass the forward button threw the M1 relay. when the stop button is pressed this will break the circuit causing the electromagnets to de-energize stopping the drill. This would then tell TD1 not to open for a set amount of time to stop the drill from causing damage. Once TD1's timer has run it course then the reverse button can be pressed; this will use M2 of the motor and since the wires are switched around (instead of T1 going to T1, T2 going to T2 and T3 going to T3) it will make T1 go to T1, T2 go to T3 and T3 go to T2 causing a backwards rotation.

Pretty good explanation. A few small corrections.

• The electromagnet doesn't directly pass the current, what happens is the magnetic field pulls a metal piece in the contactor down, causing metal contacts to touch and make the electrical circuit.
• TD1/2 open when energised, then don't close again for the set time after stopping.

As drawn, you would need a 'True Off-Delay' timer, this uses a spring or pneumatic bellows to delay the re-closing. An electronic off-delay timer could also be used, but would need a slightly different drawing. I leave it to your interest to look up the difference. But this is an electronic off-delay timer if you want to check its datasheet.
- Just noticed that you haven't drawn the thermal overload in the power circuit, this can be placed either before or after the two contactors, just make sure neither one bypasses it.

 

[Didawdidaw]

Both e-stop buttons can be placed in series with the stop button, they all serve the purpose of cutting the control circuit and thus stopping the drill.
In more advanced machines these emergency stops would be connected to a dedicated Safety Relay or Safety Controller with special functions for safely stopping the machine, but for a simple drill press this is not needed.
The 'resistor' you have drawn is actually a transformer; its job is to take the 400V power voltage and reduce it to a safe control voltage, usually 24V. Simpler control systems like enclosed DOL starters will often just use 240/400V rated contactors and buttons to reduce cost.

• The electromagnet doesn't directly pass the current, what happens is the magnetic field pulls a metal piece in the contactor down, causing metal contacts to touch and make the electrical circuit.
• TD1/2 open when energised, then don't close again for the set time after stopping.

As drawn, you would need a 'True Off-Delay' timer, this uses a spring or pneumatic bellows to delay the re-closing. An electronic off-delay timer could also be used, but would need a slightly different drawing. I leave it to your interest to look up the difference. But this is an electronic off-delay timer if you want to check its datasheet.
- Just noticed that you haven't drawn the thermal overload in the power circuit, this can be placed either before or after the two contactors, just make sure neither one bypasses it.

Thank you for all of you feedback you have been relay helpful! I think that I've finally got the hang of it all now. I did think the emergency stop buttons went there but the way it was worded tripped me up and I though that they needed to be in different places. This is what the drawing looks like now.

I've also updated the explanation quite a bit since if your interested, this is what it's like now (I've used a image of a relay to help explain):
When the forward button is pressed on this circuit it would power up M1. This would create an electromagnetic field in the relay that will attract the armature to the yoke; this will then force the armature to pivot. This will then move the movable contact to the normally open fixed contact. When the movable contact is touching the normally open contact it will allow the electricity to pass. The movable contact is connected to all 3 ports on the 3 phase power allowing the 3 phase power to go to the drill; causing rotation. The forward button wouldn't need to be held down as once its pressed it would by-pass the forward button threw the M1 relay. When the stop button is pressed or one of the emergency stop buttons this will break the flow of electricity; causing the electromagnet to de-energize stopping the drill. When power to TD1 is present it will open up the connection to TD1 it will make it so that the reverse switch can’t be activated. Once the stop button has been pressed this will cut power to TD1 and a timer will count down. When the timer is up it will close this connection making it possible for you to activate the reverse mechanism; this stops the drill from causing damage to its self. The wires are switched around on this part of the motor (instead of T1 going to T1, T2 going to T2 and T3 going to T3) it will make T1 go to T1, T2 go to T3 and T3 go to T2 causing a backwards rotation. The power for the stop start mechanism will be got directly from the 3 phase power. The power from this source will be over powered for its purpose so this will need to be reduced by a transformer before it can enter the stop start part of the circuit; this is done for safety purposes and to reduce the cost.

 

[Crossbryte]

please this attachment cannot be opened could you reattached pls

 

[DPG]

please this attachment cannot be opened could you reattached pls

He's not been on here since October so I wouldn't hold out much hope.

 

[Darkwood]

Is this course work etc?

Electrochem touched on this in his replies - I would have a issue what they are asking of you here from a regulatory point of view, fitting 2 'E-Stops' (technically they are functional stops here not E-Stops regardless of them looking like E-stops) would require additional regulations to be applied under the machine control regulations BS 60204-1 meaning the control circuit would need to be fed by means of an isolating transformer if low voltage or be SELV.

I am concerned that you are been taught standard circuit theory here but not been corrected on real world application of such.

 

[Lister1987]

Is this course work etc?

Electrochem touched on this in his replies - I would have a issue what they are asking of you here from a regulatory point of view, fitting 2 'E-Stops' (technically they are functional stops here not E-Stops regardless of them looking like E-stops) would require additional regulations to be applied under the machine control regulations BS 60204-1 meaning the control circuit would need to be fed by means of an isolating transformer if low voltage or be SELV.

I am concerned that you are been taught standard circuit theory here but not been corrected on real world application of such.

Touching on this, we recently covered motors (DOL/AC/DC/Combined) with zero mention of e-stops (machinery directive and UK overarching regulations). My hope is it wasn't covered just for ease (i.e understanding the theory only, not the application (beyond start/stop, i.e no e-stop and other considerations), thought it odd so went off anddod my own research; it's an interesting topic.

 

[Deleted account]

“Relay helpful”

was that deliberate or meant to be a funny.

either way it made me smile.