Franklin Electric Application/Installation Data
No. 1/2013
Franklin Electric submersible motors are offered in either DOL or Star-Delta version. Today’s
Franklin AID will show the differences between the two and characteristics of the Star-Delta
connection.
Depending on the geographical location in which the submersible motor is to be installed, the
local energy provider gives technical connection guidelines that have to be kept for the operation
of electrical drives. One of these guidelines implements reduced start-up current for submersible
motors for certain drive capacities which differ from region to region. The Star-Delta drive of subPHUVLEOHPRWRUVLVDFRVWHI¿FLHQWSRVVLELOLW\WRDGKHUHWRWKHVHJXLGHOLQHV
Risks and details of the Star – Delta start will be highlighted in our next FE-AID edition.
Picture 1: DOL (Direct Online) Motor
Picture 2:
Star-Delta Motor
Europa GmbH
D-54516 Wittlich / Germany
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Direct-on-line (DOL) starting motors only require adequate motor protection, whereas star-delta
starting implies a more complex circuitry composed of several relays and contactors.
The following two images demonstrate the different possibilities for electrical connection:
Picture 3: DOL
Picture 4: Star-Delta
Europa GmbH
D-54516 Wittlich / Germany
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The following images show the electrical circuitry of the three motor windings and their phase
voltages:
Picture 5: STAR connection of the motor windings
Picture 6: DELTA connection of the motor windings
Europa GmbH
D-54516 Wittlich / Germany
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As shown in Pic. 5 and 6, the difference in connections is not just limited to the different circuitries,
but also in the resulting voltages of the windings..Whereas in the DOL connection the windings are
supplied by the voltage they are designed for permanently, the STAR connection is operated at a
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by all means for a continuous operation of a STAR-DELTA motor:
The motor-current (Amps) of a STAR-DELTA motor during start (IԚ) is reduced roughly by factor
0,58; a motor with a nominal starting current of 400A will consume only 232 A in STAR – connection.
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(PԚ), the available mechanical performance on the shaft to drive the pump, is also reduced to 1/3
of the nominal performance. To avoid an overloading of t he motor, it is necessary to observe the
power demand of the pump during startup in comparison with the start current of the motor.
The available shaft torque (MԚ) also reduces while start to 1/3 of the nominal torque. This also raises
the necessity, to compare the demanded starting torque of the pump to the available torque of the
motor, and – to do the right selection.
For deeper questions/explanations please consult your Field Service Engineer or the technical staff
of FEE.
Europa GmbH
D-54516 Wittlich / Germany
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Seminars in FRANKLIN TECH TRAINING CENTER 2013
Please visit our website:http://www.franklin-electric.de and sign up.
Upon request we also offer in 2013 seminars tailored to your requirements.
Europa GmbH
D-54516 Wittlich / Germany
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