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.
Explain the Methods of solid modeling The various methods for representing the solids are : (i) Half-space method (ii) Boundary representation method (b-rep) (iii)
what is system of force?
Q. Corrosion resistance of tantalum? Tantalum is readily attacked by strong alkalis, even at room temperature, and therefore, is not suitable for use in processes where the pH
Camshaft : The camshaft controls the opening and closing of the two valves. The associated parts are push rods, rocker arms and valve springs. The camshaft is driven by a camchai
The steam that leaves the super-heater is expanded from 130bar at 535°C to 25.2bar at 310°C in a high pressure turbine. The steam from the exit of the HP turbine is reheated to 535
Determine reactions on compound beams: Determine reactions at the support A , B , C , and D for arrangement of compound beams shown in the figure given below.
Short Circuiting Transfer The short circuiting transfer occurs when the welding current and the arc voltage is low. Metal is transferred from the electrode to the work only wh
Assets Markets and the LM Curve The assets markets are the markets in which money, bonds, stocks, houses and other forms of wealth are traded. There are a large variety of asse
Assume the production function for a rm is given by the equation Q = L √K. Graph the isoquants corresponding to Q = 10, Q = 20, and Q = 50. Do these isoquants exhibit diminishing
What is elements with increasing dimensions?
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