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Carbon Brushs On Wound Im


tebit

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Hi

 

Back again with another question for the great minds on this forum. I have been studying a logic diagram for a rotor resistance starter and am confused about the operation of carbon brushes. The logic i have been given says

 

if START and NOT FINAL ROTOR CONTACT and BRUSHES DOWN then set RAISE BRUSHES

 

 

if START run a 70sec timer, use the output of this to set LOWER BRUSHES

 

START - the command to start the motor

FRC - the final conactor i.e the SC contact

 

now i am confused particularly with the first line of logic, i dont understand why the brushes would want to be raised during the motor starting period, i assumed that the starting resistances are wired directly onto the brushes, so if the brushes are raised the resistances will be open circuit.

 

ofcourse i might have raise and lower brushes confused i.e. raising the brushes may actually bring them into contact with the rotors slip rings.

 

could anyone please clarify that i have either misunderstood the logic, or explain the actual physical process here?

 

Thankyou in advance.

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  • 4 weeks later...

Not sure of your exact requirement however the basic operation should be as follows:

 

1. Confirm brushes down.

2. If so apply start.

3. Motor accelerates to speed.

4. Shorting contactor closes.

5. Brushes raised.

 

Followed by:

 

6. Apply stop.

7. When stop completed brushes down (ready for next start)

 

Hope that helps.

 

Regards,

GGOSS

 

 

 

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