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.
Q. Painting of structural components of skid? Sandblasting and priming shall be carried out prior to assembly, and shall include all bolt holes, flange faces, etc. Flange gaske
Load on beam: A beam AB as shown in the figure given below is hinged at A and supported at B by a vertical cord that passes over two frictionless pulleys C and
Analyse the beam: Analyse the beam illustrated in Figure and draw the SFD, BND & thrust diagram. Situated the point of contraflexure, if any. Figure Solution
The Winged-Edge Representation Perhaps the oldest data structure for a b-rep is Baumgart's winged-edge data structure. It is quite different from that of a wire-frame model, be
Q. Explain the Cushion Materials which used in moulding sand? These materials when added to the moulding sand burn and from gases when the molten metal is poured into the mould
what is the normalizing of steel
Gears interchange between Y2K and non Y2K model: Check for mixing of Y2K and non Y2K gears by seeing the identification marks provided on the gears.
constant volume1
Pole core and pole shoe The pole cores are made of steel laminations that are insulated from each other and riveted together. Every pole core has a pole shoe having a curved su
Find out ratio of strain-energy: A circular rod of diameter d and length l is fixed at one end and a torque T applied at the other. Now, if any close coiled helical spring is
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: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd