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

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Discussion Overview

The discussion revolves around the suitability of a Direct On Line (DOL) starter for a 160 KW, 1000 KVA sump pump, as well as alternative starting methods. Participants explore technical specifications, starting current implications, and the impact of grid conditions on motor performance.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Lincoln inquires whether a DOL starter can support a 160 KW, 1000 KVA sump pump and asks about alternative starters.
  • Some participants question the power rating, suggesting that a 1 MW motor would require a star-delta starter instead of DOL.
  • Concerns are raised about the starting current of DOL, which may be 4-6 times the nominal current, potentially causing voltage drops in the grid that could affect motor torque.
  • Alternative starting methods mentioned include autotransformer, star-delta, softstarter, and variable frequency drive, with some participants noting that these are commonly used.
  • Lincoln provides detailed specifications of the motor and pump, seeking confirmation on the feasibility of using DOL and asking about voltage drop implications when using a soft-starter.
  • Another participant references the pump manufacturer's recommendation for DOL and star-delta starters, questioning the practicality of these options given the project's requirements.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of using a DOL starter for the specified pump, with some suggesting it may not be suitable due to the high starting current and potential voltage drop issues. There is no consensus on the best starting method, and the discussion remains unresolved.

Contextual Notes

Participants highlight the importance of grid conditions and protective relays in determining the feasibility of using DOL starters. There are also indications that the initial load and starting current may significantly impact the choice of starter.

Lincoln
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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:
 
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Lincoln said:
160 KW, 1000 KVA sump pump?
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.
 
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:
autotransformer
start-delta
softstarter
variable frequency drive
(there exists many more, but these are the most used)
 
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.
 
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.

Baluncore said:
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.
 
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. :-)

SirAskalot said:
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:
autotransformer
start-delta
softstarter
variable frequency drive
(there exists many more, but these are the most used)
 
Last edited:

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