Calculate the resistance of the armature

Assignment Help Electrical Engineering

Reference no: EM132489038

Question 1. To which type of winding do the following descriptions pertain:
(i) ‘the end of one coil is connected to the start of another coil occupying a similar position under the next pair of poles'
(ii) ‘two ends of each coil are connected to adjacent segments on the commutator and the finish of the coil in one slot is connected to the start of the coil in the next slot'.
(iii) A 4 pole lap wound armature has 16 coils each with a resistance of 0.1 ohms. Calculate the resistance of the armature.

Question 2. (i) Explain briefly why the terminal voltage of a d.c. machine is not equal to the generated or back emf except at no load when V = E. Hence state the relationship between V, E, the armature current and resistance that applies at normal loads for a generator.
(ii) A 250 V shunt motor has an armature resistance of 0.4 ? and runs at a speed of 750 rev min-1 when taking a full load current of 25 A. Estimate the speed of the motor at no load when the armature current is 3 A, assuming that the flux per pole remains constant. If the field resistance is 110 ?, calculate the value of the resistance required in the field circuit to increase the speed to 1000 rev min-1 if the load torque remains constant.

Question 3. (a) State the factors governing the speed of a d.c. motor.
(b) If the field current of a shunt wound d.c. motor is halved, what effect will this have on the speed?

Question 4. (i) Define commutation.
(ii) State two causes of poor commutation.
5. Define the following terms:
(a) shunt excitation
(b) over compounded
(c) retrogressive connected armature
(d) pole pitch.

Question 6. (i) A 20 kW, 500 V d.c. shunt wound motor draws a current of 45 A when running at full load with a speed of 600 rev min-1. On no load, the current drawn from the supply is 5 A. If the armature resistance is 0.3 ? and the shunt field resistance is 220 ?, calculate the armature current, speed and efficiency of the motor when the torque falls to half of its full load value, assuming that the flux per pole does not change. (Hint: don't forget that not all armature current is supplying torque. One must decide at some points what is the armature current producing torque and at others, to determine generator emfs, the total armature current).
(ii) State what you would expect to happen to the speed if a resistance is inserted into the field circuit.
(iii) If a resistance of 50 ? is inserted in series with the shunt field, calculate the armature current required to maintain half full-load torque. Calculate also the speed of the motor when supplying this torque.

Reference no: EM132489038

Questions Cloud

Advise emily of her contractual rights : Emily wants to buy a second-hand truck for use in the business, and visits a number of vehicle dealers before deciding to purchase an as-new 2013 Isuzu FVR

Occupational health and safety administration : If you called the Occupational Health and Safety Administration (OSHA) about your workplace safety during this coronavirus crisis, how would OSHA most likely

Define how your position will affect the community : Construct and post an argument that supports your assigned position. Focus your argument on how your position will affect the community and the implications.

Design the physical security requirements : Design the physical security requirements for a privately owned single story distribution center (warehouse for various retail goods). This question requires.

Calculate the resistance of the armature : Calculate the armature current required to maintain half full-load torque. Calculate also the speed of the motor when supplying this torque

Compute sheffields diluted earnings per share : Compute Sheffield's 2020 diluted earnings per share. The preferred stock pays an annual dividend of $5 per share. Sheffield's tax rate is 50%.

Prepare journal entries to record event related to copyright : Prepare journal entries to record the events related to the copyright and sales of the book during 2016 and 2017, assuming that sales were as projected.

How a persons perspectives directly influenced : When considering the Heinz dilemma, explain how a person's perspectives and decisions are directly influenced by their moral development. Be sure to define.

What amount should trigg report on the income statement : What amount should Trigg report on it's income statement for 2015? Trigg Corporation purchased treasury stock in 2014 at a price of $22 per share

User Account

All Pages