Calculate the motor efficiency, Mechanical Engineering

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.

Posted Date: 2/18/2013 2:50:43 AM | Location : United States







Related Discussions:- Calculate the motor efficiency, Assignment Help, Ask Question on Calculate the motor efficiency, Get Answer, Expert's Help, Calculate the motor efficiency Discussions

Write discussion on Calculate the motor efficiency
Your posts are moderated
Related Questions
What do you mean by synchromesh device ? explain the basic working of a synchromesh gear box.

Every loaded blade rod is consists of 400 pieces of blades which around 25cm tall. The blasting nozzle vertical height different is just about 10 cm. The nozzle will blast the blad

Cell Covers: Each cell is covered from the top of the cell covers and the terminals projected from the cell covers. The terminals are arranged alternatively in a line.

what is the formula for measuring the safe speed to drive for a cyclist

STATE - Thermodynamics: The State of system is its condition or configuration described in detail. State is the condition of the system which is identified by thermodynamic

Bucket conveyors are used to moves the granular powdered or liquid materials. The buckets may be mounted on a chain or a belt. The movement may be vertical or flat. The ver


law of belting

why compression molding process is impractable for thermoplastics?

Clutch cable routing :Ensure that the cable is routed as per standard routing, through the brackets provided.