Question { Dalkia, 158026 }

What is the d/f between DOL & star delta starter & automatic
star delta starter?

Answer

When the motor is connected in Delta and started by DOL method, the voltage applied across a coil is the voltage between two phases i.e, 415V approx. Therefore the current inrush is high. In order to minimize the starting current, voltage across the coils should be brought low, which can be done if we connect the coils in star. During star connection the voltage across a coil is 240V (approx) which is 1/(sq root of 3)times that in delta which results in a simultaneous lowering of current also. This eases the stress on relays and conductors.When the motor attains 90% of its rated speed the coils are connected in Delta. therefore generating higher power.

Question { Badve, 96027 }

what should be distance between two electrical earthing pit
as per i.e.e

Answer

It can be kept as far away from each other as possible but minimum distance may vary depending upon the length of the earth electrode used. Usually it must be at least the double of the earth electrode's length.