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
    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


    Mar 14, 2008
    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
    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
    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
    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
    Overcurrent tripped.
  7. jimkeith

    Active Member

    Oct 26, 2011
    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.
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    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
    can you please explain this bit more, if possible. thanks..
  10. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    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
    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
    show the motor + the power supply.
  13. BillB3857

    Senior Member

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