31/12/2019

Compare Direct ON Line Starter & Star Delta Starter


The comparison between Direct ON Line Starter and Star Delta Starter is given as below.
Sr.No
1
The control circuit consists of only one contactor.
The control circuit consists of three contactors. ( 1 ) Main connection ( 2 ) Star connection  ( 3 ) Delta connection. The rating of the star contactor should be 1 / √ 3 times that of main / delta contactor rating.
2
Each winding gets rated line voltage.
Each winding gets only 58% of the rated line voltage.
3
The starting current is 5 to 6 times as that of full load current
The starting current is 1/3rd that of in the Direct ON line starter.
4
The three winding is generally connected in the star.
The three winding is connected first in the star at the time of starting then delta at the time of running condition.
5
The starting torque is 1.5 to 3.0 times that of full load torque.
The starting torque is reduced 1/3th that of in the Direct ON line starter. The star delta starter is equivalent to auto transformer with 57.7% tapping.
6
The Direct ON Line Starter is used where high starting torque requires
The Star delta starter is not used where high starting torque is required.
7
Only one contactor operates for entire operation.
First main and star contactor operates, then main and delta contactor operates.
8
Only three wires are brought out from the motor terminals
There are six wires are brought out from the motor terminals
9
Application : up to 5 HP motor
Application : up to 10 HP motor
10
Compact size
Large space requires
11
Low cost
High cost

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