Motor control, Contactors

Discussion in 'General Electronics Chat' started by BiGe, Aug 3, 2010.

  1. BiGe

    Thread Starter New Member

    Aug 1, 2010
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    Hi I am a qualified electrician, but have not done motors and contactors since my apprenticship. Can anyone help me refresh how to wire them up. I have found this site and thought i should refresh my knowledge, and thought i should start with this. Anyone that can help would be greatly appreciated
     
  2. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    I'm still working on my 4th year hours, but the only work I've done is on motors/controls.

    I adhere to the CEC, which is a very close to the NEC. With this in mind, one can look at the topic from a theory, practical, and or legislative viewpoint.
     
  3. BillB3857

    Senior Member

    Feb 28, 2009
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    Exactly what kind of information are you looking for? Single direction Start/Stop, Forward/Reverse Start/Stop, Start/Stop with remote stations, etc, etc........ A lot of variations to cover.

    edit. Overly simplified, start button is bypassed by aux contact of starter. Stop button is in series with power feed to ladder rung.
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Connecting a motor to a contactor is pretty straight forward:

    Power to the coil goes to A1 and A2,
    Power for the Motor goes to L1,L2 and L3 if 3 phase
    Motor connects to T1,T2, and T3 if 3 phase...

    [​IMG]


    B. Morse
     
  5. rvh002@gmail.com

    Active Member

    May 15, 2009
    118
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    The above only holds for small motors, When you are talking about starters for motors in the range of 5kW or more, various starters may be used depending on the available current supply. In a starter for a 3phase motor, normal star-delta units draw approx. 3.5 times the running current (displayed on the label) A direct on line unit like mentioned above draws 7 times the running current during start up. The motor control circuit breakers like the one pictured has been designed to accomodate this in small motors.
    As per the previous questions, what are you looking for?
     
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    The question was HOW TO CONNECT IT, not what it can handle, the picture included is there to depict the connections, this was not by any means a recommendation to be used with his motor, regardless of the size of the motor, .... do not confuse this with a CIRCUIT BREAKER, motor contactors are not Circuit breakers, although some have built overcurrent and thermal protection, it is still not a circuit breaker.

    B. Morse
     
  7. kingdano

    Member

    Apr 14, 2010
    377
    19
    Good safety disclaimer, well done.
     
  8. BillB3857

    Senior Member

    Feb 28, 2009
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    While we all wait for the OP to re-appear, my interpretation of the original question was, "How do I hook up the contactors to make motors run?" That extends beyond simply connecting power to the contactors LINE terminals and the motor leads to the LOAD terminals. There are concerns for overload detection, proper interlocking when using reversing systems, etc.
     
  9. rvh002@gmail.com

    Active Member

    May 15, 2009
    118
    2
    Yes well bite my head off, on small motors the circuit breaker and the contactor is combined in one unit. Refer to Telemecanique and Merlin Gerin for starters
     
  10. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    I work with Telemecanique, Square D, and various other companies motion control products everyday, I have never heard of contactors referred to as circuit breakers....

    See pic below, this shows 2 contactors, with electromechanical interlock in between and thermal overload/over current protection module connected to the bottom of the right contactor...

    3 Phase contactor setup.jpg


    B. Morse
     
  11. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    Where, oh where, is the OP??? Ask a question then disappear????
     
  12. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Too bad cause it's an interesting topic
     
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