Calculate the motor efficiency, Mechanical Engineering

Assignment Help:

A 4- pole DC motor is known to have an armature resistance of 0.5 Ω, and is operated as a separately excited motor.

(a)  When the motor is connected to a 250V DC supply with no external mechanical load and with rated field current, it runs at a speed of 1488 rpm with an armature current of 4A. Calculate the no load rotational losses under these conditions.

(b)  The motor is now mechanically loaded until the armature current reaches 40A, under which conditions the DC supply voltage sags to 245V. Calculate the motor speed if the field current is unchanged.

(c)  Assuming that the motor rotational losses vary proportionally with speed, calculate the motor efficiency under the load condition of (b).

(d)  The motor field current is now accidentally set to half rated value. Calculate the DC supply voltage that is required to return to the same no load operating conditions of part (a)

(HINT: remember that the rotational power losses must stay the same if the speed is unchanged).

(e)  Discuss the two possible ways of achieving variable speed operation for a DC machine. Show the torque speed characteristics of a DC motor operating under both these types of speed control strategies, and discuss how they relate to the concepts of the "constant torque" and "constant power" regions of variable speed operation. Discuss the advantages and disadvantages of each speed control strategy.


Related Discussions:- Calculate the motor efficiency

Welding procedure specification (wps)-variables, Variables used in WPS ...

Variables used in WPS Depending on their influence on obtaining a desired weldment, the welding variables are then classified and listed. Some of them are listed as "Essential

Concept of plane stress, Concept of plane stress: Define the concept ...

Concept of plane stress: Define the concept of plane stress. Sol.:   In cubical element of strained material is acted on by stresses acting on only 2 pairs of parallel plane

Explain the working of michelsons interferometer, Explain the working of Mi...

Explain the working of Michelson's interferometer. How circular fringes he produced with it. (a) What are antireflection films and interference filters? (b) Find the reflecti

Temperature scales - thermodynamics, Temperatur e Scales: The tempera...

Temperatur e Scales: The temperature of a system can be determined by bringing a 2 nd body, a thermometer, into contact with the system and allowing thermal equilibrium to b

Determine contact reactions and force, Determine contact reactions and forc...

Determine contact reactions and force: Figure given below shows a sphere resting in smooth V shaped groove and subjected to a spring force. The spring is compressed to

Stress distribution in beams, Stress Distribution in Beams: 1. learn t...

Stress Distribution in Beams: 1. learn the section modulus of beams of several cross section. 2. found the normal force for partial beam section & its moment around the neu

Explain the function of screw conveyor with auger, Function of screw convey...

Function of screw conveyor with auger "To spread the road making raw material on the road during the operation"An auger/cut off assembly for a floating screed asphalt paver. Th

Final project , Hi ... I have a final project I need to finish it soon abou...

Hi ... I have a final project I need to finish it soon about 3 weeks from now ... to design any machine by the Solidworks program .... please feed me back if you can .. thank you

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd