Question { L&T, 146715 }

Why a starter is used for a motor?

Answer

starter are use to reduce the high starting current and provide protection against under voltage & overload condition
in dc motor 3-pt & 4-pt starter are use. the resestance are ude to limit high starting current & nvc are use to other protection.
in ac motor dol ,star-delta,& autotransformer are use.

Question { 11846 }

there are a transformer and a motor. both are connected to
3phase, 415 Volt, 50Hz power supply. Both are working with
induction principles. Then, why, motor is rotating and
transformer is not rotating.

Answer

In transformer both primary & secondary wdg are wound on same core material so there is no need to cutting the flux as it link with secondary. eg mutual induction.
But in motor both wdg are wound seprately so to produce induce e.m.f. there is need to cut the flux so the rotor rotate to cut the flux .eg dynamic induction.
Therefore motor rotate due to dynamic induction & trancformer not rotate due to mutual induction as both are induction principal.