Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
The tank can be modelled from first principles with the provision of certain assumptions. For the sake of simplicity, it is possible to consider the top section of the tank with p
Cellulosic Electrodes In the AWS E 6010 and E 6011 series of electrodes, the protective covering is composed of cellulose (C6H10O5) and silicate binders. The cellulose decomposes
Calculate diameter of shaft in maximum direct stress: A shaft is designed for transmitting 100 kW power at 150 rotation per minute. Shaft is supported in bearings 3 m apart a
Y ield stress and ultimate stress Yield stress: Yield stress can be defined as lowest stress at which extension of test piece increases without increase in the load. It is
Find out the forces in cantilevers frame: Find out the forces in the members of the cantilevers frame by the method of sections. Solution Let the equilibrium of the fr
constructing and working of he- ne laser
pdf on
Find out Deflection under the load: A beam of span 4 m is subject to a point load of 20 kN at 1 m from the left support and a Udl of 10 kN/m over a length of 2 m from the righ
Determine the resultant of the system of forces: Four forces act on a body as illustrated in Figure. Determine the resultant of the system of forces. Figure Sol
Q. Show the Sources of Ignition? Sources of Ignition - Possible sources of ignition include the following: • Electrical: Sparks or arcs may occur when current carrying cont
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd