Control circuit
http://samplecode.rockwellautomation...d001_-en-p.pdf
Page 6
The concept is straighforward. If you do not understand it after the comment,
then have an electrican wire it up.
This is the CONTROL circuit of the contactor.
The Aux Contact are connected to the same closing mechanism as the
3 main phase lugs (the power to your blower). When the relay closes,
it closes the 3 main lugs AND the aux contact.
Why is this necesssary: The START button is only a momentary contact. When you push the START button, it closes the circuit. When you release the start button, it opens the circuit. SO what is happening is when you push the START button, the relay is closed and so is the AUX CONTACT which is in parellel with the start button. When you release the start button, the power now goes through the AUX contact instead of the Start button... and it will run forever....
Now, when you hit the STOP button (which is wired in SERIES with the whole circuit, the power is removed, the relay releases and the AUX contact is now open. When you release the STOP button, the circuit is perminently broken because the Aux contacts are open and the START switch is open.
Any other "emergency" buttons are wired in series with the STOP button (or shall we say that an emergency switch is just another STOP button in series)
Harold used the term SAFETY for this type of circuit, This circuit does have SAFETY in mind because if you have some sort of power outage, the power is removed and the relay is release just like hitting the stop button, the relay circuit is openned, the AUX contact is open as is the start switch. When the power comes back on, the machine will stay shut down.
If you had just used a switch for the machine, when the power came back on, so would the machine which would be unexepected for the poor operator.
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Any industrial electrician has wired hundreds of these circuits so if this is still confusing, hire an electrician for your safety!
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