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DOL Motor Starter can support 160KW, 1000KVA Pump?

  1. Jul 30, 2014 #1
    Hello! Everyone,

    I am Lincoln from Singapore. I am from mechanical background. Recently, I am handling a rain-water tank with sump pumps project.

    May I seek you guys who are in electrical expertise for some professional advice for the following:

    Is the DOL starter possible to support 160 KW, 1000 KVA sump pump?

    Beside DOL, any other starter is optional to support this pump's capacity?

    Hear you soon. Thanks. :shy:
  2. jcsd
  3. Jul 31, 2014 #2


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    160 KW ???
    Three phase or single phase?

    DOL = “Direct On Line” is not a starter, it is a simple switch or contactor.
    A 1kW, 3 phase motor can probably be started DOL as the pump impeller does not represent a significant initial load.
  4. Jul 31, 2014 #3
    It mainly depends on the grid it is connected to. The problem faced with starting is the voltage drop in the cables/grid becomes to large due to the large starting current. Thus a reduced terminal voltage will reduce the output torque of the motor, and it may not be enough to overcome the load torque.

    The DOL starting current may be in the range of 4-6 times the nominal current. Does the grid support this with respect to protective relays and such?

    Other starting methods are:
    variable frequency drive
    (there exists many more, but these are the most used)
  5. Jul 31, 2014 #4


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    We need confirmation from the OP of the power involved here.
    If it is really a 1 MW motor then it will need a star-delta starter.
    I suspect that there are scale factors here that are out by a factor of 1000.
  6. Aug 3, 2014 #5
    Hi! Baluncore,

    I checked the specification of the motor, its stated as following:

    Power Supply: 3 Phase x 400V x 50Hz
    Rated Power: 160 KW
    No of Poles: 6P
    Rated current: 288A
    Load: 50% 75% 100%
    Efficiency: 89.3% 90.7% 82.1%
    Power Factor: 78.4% 83.5% 87.0%

    Likewise, the pump specification as follows:

    Pump Eff: 81.0%
    Shaft Power: 138.1 KW
    Revolution: 980 rpm

    Having given the above data from the pump manufacturer, is it ok to use DOL to start this motor? If we use Soft-starter, how much the voltage drop by starting a pump?

    The project needs to start 4 pumps in operation.

  7. Aug 3, 2014 #6
    Hi! SirAskalot,

    I refer back to the pump manufacturer proposal, the recommended electrical connection is DOL and Star-delta starting. The electrical engineer proposed the motor starters shall be DOL type.

    "Where Star-delta or Autotransformer Starters are used with Closed Transition type and the maximum transient current surge changing from one stage to another must not exceed 3 x motor Full Load Current (FLC)."

    With both pump and motor technical specifications and the above proposal, do u guys think is it workable?

    Let's say if Star-delta is used, how much voltage drop to drive the initial torque? There are 4 pumps in operation. Can this starter design start a pump at a time or 2?

    Please impart me any input to rectify any potential problem. During the meeting, the contractor's engineer failed to draw a conclusion. They simply said they couldn't drive any of the 4 operating pumps.

    Thanks. :-)

    Last edited: Aug 3, 2014
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