Electrical Dost

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Answer

Why Delta Star Transformers are used for Lighting Loads?

Answer: For lighting loads, a neutral conductor is a must and hence the secondary must be star winding and this lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta/star transformer is used for lighting loads.

What are the advantages of star-delta starter with induction motor?

Answer :(1). The main advantage of using the star delta starter is the reduction of current during the starting of the motor. Starting current is reduced to 3-4 times Of current of Direct online starting. (2). Hence the starting current is reduced, the voltage drops during the starting of motor in systems are reduced

Why is the starting current high in a DC motor?

Answer: In DC motors, Voltage equation is V=Eb-IaRa (V = Terminal voltage, Eb = Back emf in Motor, Ia = Armature current, Ra = Armature resistance).At starting, Eb is zero. Therefore, V=IaRa, Ia = V/Ra, where Ra is very less like 0.01ohm. i.e, Ia will become enormously increased.