Reducing starting current of motor

Discussion in 'The Projects Forum' started by arcteryx, Feb 13, 2012.

  1. arcteryx

    Thread Starter New Member

    Feb 14, 2011
    8
    0
    Is there any way to reduce the starting current of a motor since it will cause trip/blackout during start? The start configuration for the motor is direct-on-line (DOL).Need suggestion.Thanks!
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,221
    You can momentarily switch in a power resistor or inductor in series with the motor to limit the starting current and then switch it out (short across it) when the motor has finished its start.
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    If this is a typical 3-phase AC induction motor with stator windings configurable in Star or Delta then a useful technique is the star/start-delta/run method. This requires some control hardware - as will any soft starting method.
     
  4. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    what's tripping, your overcurrent or overload? Does the load require a softstart scheme? Are you hooked into inadequate supply?
     
  5. arcteryx

    Thread Starter New Member

    Feb 14, 2011
    8
    0
    I just got the datasheet from the supplier. The starting current of the motor is high. 390A. The start configuration of the motor is DOL. So, is there any way that I can reduce it? By the way, is there any effect to the motor if the starting current is high?
     
  6. arcteryx

    Thread Starter New Member

    Feb 14, 2011
    8
    0
    Overcurrent tripped.
     
  7. jimkeith

    Active Member

    Oct 26, 2011
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    99
    Check out this soft start control--they are available for even higher currents, but this seems to be the largest handled by Grainger--the line current passes through antiparallel SCRs that are phased on gradually to reduce starting surge--75A is the full load current--during starting, the current will be roughly 150A. To reduce conduction losses, some units have a contactor that bypasses the SCRs after starting.

    http://www.grainger.com/Grainger/SCHNEIDER-ELECTRIC-Soft-Start-6VMA0?Pid=search
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    I don't want to sound like a grumpy old guy but a 390amp motor is an expensive professional device and the way it is started, wired, safely fused and run should all have been handled by a properly trained professional.
     
  9. sonda

    New Member

    Oct 30, 2012
    10
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    can you please explain this bit more, if possible. thanks..
     
  10. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
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    If you don't understand that then you should not be messing with this motor and those currents.

    See RB's post. You could easily kill yourself or someone else. Even a whole group of people or cost you company millions of US dollars in a burned down building and / or lost business.

    Get someone that knows exactly what they are doing to install this motor for you. A motor of that size must cost a lot of money. It is not going to cost much more to have it installed properly.

    While we have some extremely talented and helpful people on this forum. a hobby forum is no place to seek advice of this type. No one is on location to see the exact situation.

    We have a saying "Penny wise and pound foolish".

    It means you are trying to save a small amount of money while risking a great deal of money.
     
  11. sonda

    New Member

    Oct 30, 2012
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    thanks for your advice mate. i m not trying to burn down a place or people... i just ask this because i thought its interesting to know. thanks anyway.
     
  12. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    show the motor + the power supply.
     
  13. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    Also, remember that reduced current=reduced torque. What kind of load is on the motor? Does it require full starting torque of the motor?
     
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