When DC Motor routes on the action of driving torque, the conductors move through the magnetic field and hence emf induce the direction of this emf oppose to applied voltage. This is called as back emf.

ব্যাখ্যাঃ Star delta starter is mainly used to reduce the flow of current at the starting of the three phase induction motor to avoid sparking, overheating, coil burning etc.

As increased load means that it requires more torque to turn at that speed. The motor is not producing that torque. So motor will slow or decrease a little bit.

ব্যাখ্যা: Stator-এর চারপাশে তৈরি হওয়া সেই Stator-কে ঘিরে একটা নির্দিষ্ট কৌণিক গতিতে ঘোরে। এই গতিকে Synchronous speed বলে।

Slip ring induction motor is a type of motor where its external circuit is connected using some rings. This rings attached with high resistance acts as an external circuit for the rotor. This external circuit helps in developing a high starting torque with low current

ব্যাখ্যা : At no-load a DC series motor rotates at dangerously high speed. A DC series motor should always be started on load. When the motor is connected across the supply mains without load, it draws small current from the supply mains.

ব্যাখ্যাঃ সিঙ্গেল ফেজ ইন্ডাকশন মোটর সেল্ফ স্টার্টি। প্রি-ফেজ ইন্ডাকশন মোটর নিজে নিজে স্টার্ট নিতে পারে।

N₁= 120f/P = 120x50/4 = 1500 грm

When the DC motor is connected across the supply without load then it will draw a small amount of current form supply. As low current will flow through the field winding as well as armature widing so main flux produced will be lesser. As, main flux is lower. speed will tend to increase. As speed increases back em also increases and thus current drawn from the supply will become more and more lower and thus main flux will also become more and more lower and thus speed will tend to increase more and more.

ব্যাখ্যাঃ ট্রান্সফর্মারের Open সার্কিট টেস্ট হতে আয়রন লস এবং শর্ট সার্কিট টেস্ট হতে কপার লস বের করা হয়।

The effect of a armature reaction is to- - Reduction of generated emf due to decrease in value of flux per pole. -The maximum value of gap flux density increases. -The armature reaction shifts brush axis from GNA

ব্যাখ্যা: A Synchronous motor usually has two slip rings to supply DC power to the rotating magnetic field.