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

What are rectangular combined footings, What are rectangular combined footi...

What are rectangular combined footings? Rectangular Combined Footings: In the design of rectangular combined footings it is assumed that the footing is rigid. Soil pressure

Explain about hydrostatic test, Q. Explain about Hydrostatic Test? All ...

Q. Explain about Hydrostatic Test? All paragraph must be met when the hydrostatic test is employed. UG-99(b), including footnote 32, shall be considered to be the standard hyd

Thermal stress, Derivation of formula of thermal stress

Derivation of formula of thermal stress

Heat transfer, an elctric current is passed through a wire 1mm in diameter ...

an elctric current is passed through a wire 1mm in diameter and 10mm long. the wire is submerged in liquid water at atmospheric pressure and current is increased until the water bo

Arm programming, In order to get your first experience of ARM programming, ...

In order to get your first experience of ARM programming, this way you are familiar with the problem itself, its design, its flow of execution and you can use your own C code as ps

Show bolt material, Q. Show Bolt Material? Bolt material must be select...

Q. Show Bolt Material? Bolt material must be selected with adequate yield strength at the operating temperature to provide the required strength to properly seat the gasket. It

Assignment , assignment on the topics of preservation of safety & accident

assignment on the topics of preservation of safety & accident

Explain sand and moulding sands, Q. Explain Sand and moulding sands? Sa...

Q. Explain Sand and moulding sands? Sand according to the amount of clayey matter they contain, the moulding sands are classified as: • Silica sand: Up to 20% clay. •

Thermodynamics, what is dryness fraction of dry air

what is dryness fraction of dry air

Physics, calculate wavelength fpr monocromatic light using newtons ring exp...

calculate wavelength fpr monocromatic light using newtons ring experiment notes

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