What types of commercial relays/contactors?

Thread Starter

Graham Engley

Joined Mar 17, 2016
6
Hello All,

I hope I can post this question in this section.

What types of commercial relays/contactors can be used for a 3 phase Motor start/stop safety system.

See image., would M parallel with START be high voltage or low?

What types of relays/contactors could be used for this purpose?

Thanks
 

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MaxHeadRoom

Joined Jul 18, 2013
20,686
My first go-to for contactors is the DIN rail mount Telemecanique, they have many snap on options if needed such as coil snubbers, bemf diodes, among auxiliary contact choices.
The common control voltage now is 24vdc, in this case this would be the coil voltage.
M is a auxiliary contact one the contactor itself.
Telemecanique wiring diagrams
Is this homework?
Max.
 
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englewood

Joined Jul 24, 2015
25
Thank you for your reply.

Would the holding contact be 240v?
I know that the motor is 3 phase but only one phase (L1) is connected to the holding contact .
 

MaxHeadRoom

Joined Jul 18, 2013
20,686
In your drawing the method used is not, and never was really recommended as it places high phase voltages on the control circuit, in the pic it would be what ever is across the 2 phases together with the contactor coil (M), 230v etc..
The holding or retaining contact is part of the control circuit which traditionally now is low voltage, typically 24vdc, previously 120vac was common.
The method was only really found in all-in-one contactor control units that were termed Motor Starters.
Max.
 

strantor

Joined Oct 3, 2010
5,231
Hello All,

I hope I can post this question in this section.

What types of commercial relays/contactors can be used for a 3 phase Motor start/stop safety system.

See image., would M parallel with START be high voltage or low?

What types of relays/contactors could be used for this purpose?

Thanks
I have seen this circuit in Chinese machines with 480V across the pushbuttons. This is not good. Better to use 24vdc as max suggests .
 

englewood

Joined Jul 24, 2015
25
I have tried to design a Start/Stop circuit with Design Spark can you comment on what I've done wrong or what's good?.

I'm not sure if I've got the right symbol for the Motor coil as I cant find the correct one within the software.

Really appreciate your help.
 

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MaxHeadRoom

Joined Jul 18, 2013
20,686
That is totally wrong, you have the start P.B. shorted out, among other things, you should find the correct one in the Telemecanique link, if you still cannot find it I can post one for you.
Max.
 

englewood

Joined Jul 24, 2015
25
That would be great Max, tomorrow is fine. :).

Really appreciated your reply's, just trying to get to grips with Electrical Drawings :).

I need the circuit to contain 2 E-stops as well as Start and Stop
 

englewood

Joined Jul 24, 2015
25
Thank you very much - Max.

I can see you have used a transformer for the start stop buttons circuit, is a transformer used in a "contactor" to supply the 24V coil?
 

MaxHeadRoom

Joined Jul 18, 2013
20,686
The normal method now for control circuitry is 24v, ac or dc, I prefer to use DC as it tends to be more reliable for the devices than ac, also if you have indicator lights or P.B.'s the new LED style can be used.
If going this route just a simple bridge on the transformer output is all that is needed.
The transformer is a separately supplied device to the contactor itself.
The previous norm was 120vac for control, but still usually required a transformer as the 3ph was usually 220v and up.
Max.
 

englewood

Joined Jul 24, 2015
25
thanks Max.

You sure know your stuff.

I was asked to Draw a Start/Stop circuit as an electrical Drawing and obviously got it wrong but you have but me in the right direction.

Which software did you use for the drawing or was it an previous one?
 
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MaxHeadRoom

Joined Jul 18, 2013
20,686
I have a couple, but my primary one for electrical schematics is Autocad, which I have used since the DOS days, I have quite a library built up over the years of electrical/mechanical/hydraulic blocks.
Max.
 
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