Special Elecrical Machines

EE 2403 SPECIAL ELECTRICAL MACHINES 2 MARKS UNIT-I - SYNCHRONOUS RELUCTANCE MOTOR 1. What is synchronous reluctance motor? A reluctance motor is a type of synchronous electric motor which induces non-permanent magnetic poles on the ferromagnetic rotor. Torque is generated through the phenomenon of magnetic reluctance. 2. Define the characteristics of synchronous reluctance motor. The synchronous reluctance motor is not self starting without the squirrel cage. During run up it behaves as an induction motor but as it approaches synchronous speed, the reluctance torque takes over and the motor locks into synchronous speed. 3. Write the applications of syrm. Used where regulated speed control is required in applications suc as metering pumps and industrial process equipment. 4. What are the classification of syrm Axially laminated,Radially laminated 5. What are the primary design consideration of syrm?  High o/p power capability,Ability of the rotor to withstand high speed,High reliability,Low cost ,High efficiency 6. Define power factor of syrm PF max=(Ld/Lq-1)/(Ld/Lq+1) Higher Ld/Lq ratos yield higher power factors,which corresponds to reduced I^2R losses and reduce volt ampere ratings of the inverter driving the machine.

7. What are the applications of the torque – speed characteristics of syrm?  Comparable power density but better efficiency than induction motor  Slightly lower power factor  Sensorless control is much easier due to motor saliency. 8. What are advantages of syrm over pm machine?  More reliable than PM machine  There need not be any excitation field as torque is zero,thus eleiminating electro magnetic spinning losses. 9. What are applications of syrm? Synthetic fiber manufacturing equipment Wrapping and folding machine Auxiliary time mechanism Synchronized conveyors Metering pumps 10. What is vernier motor? It is an unexcited reluctance type sync.motor.the peculiar feature of this motor is that a small displacement of the