menu search
person
thumb_up_alt 0 like thumb_down_alt 0 dislike
392 views

1 Answer

In D.C. machines the residual magnetism is of the order of 2 to 3 percent.

thumb_up_alt 0 like thumb_down_alt 0 dislike
← Prev Question Next Question →

Related questions

Description :

If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be?

Answer :

If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be zero.

thumb_up_alt 0 like thumb_down_alt 0 dislike
232 views 1 answer
Description :

Answer :

In D.C. machines fractional pitch winding is used to reduce the sparking.

thumb_up_alt 0 like thumb_down_alt 0 dislike
332 views 1 answer
Description :

In dc machines, the armature windings are placed on the rotor because of the necessity for  (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque

Answer :

3  Commutation

thumb_up_alt 0 like thumb_down_alt 0 dislike
218 views 2 answers
Description :

Answer :

Satisfactory commutation of D.C. machines requires brushes should be of proper grade and size, brushes should smoothly run in the holders, smooth, concentric commutator properly undercut.

thumb_up_alt 0 like thumb_down_alt 0 dislike
88 views 1 answer
Description :

Answer :

Brushes of D.C. machines are made of carbon.

thumb_up_alt 0 like thumb_down_alt 0 dislike
70 views 1 answer
Description :

Answer :

Hopkinson's test on D.C. machines is conducted at full-load.

thumb_up_alt 0 like thumb_down_alt 0 dislike
85 views 1 answer
Description :

Answer :

The purpose of retardation test on D.C. shunt machines is to find out stray losses.

thumb_up_alt 0 like thumb_down_alt 0 dislike
63 views 1 answer
Description :

The magnetic factor required to reduce the residual magnetization zero is called?

thumb_up_alt 0 like thumb_down_alt 0 dislike
67 views 0 answers
Description :

Explain the concept of anti-Ferro magnetism and state its significance.

Answer :

When the neighboring magnetic moments are aligned anti-parallel. This phenomenon is called anti ferromagnetism. This phenomenon occurs below a certain temperature known as Neel temp (TN) Eg.: Cobalt oxide, Nickel oxide, Chromium.

thumb_up_alt 0 like thumb_down_alt 0 dislike
70 views 1 answer
Description :

The process of removing the unwanted magnetism is called ______ A) Unmagnetization B) Degaussing C) Diamagnetization D) Depoling

Answer :

The process of removing the unwanted magnetism is called Degaussing

thumb_up_alt 0 like thumb_down_alt 0 dislike
268 views 1 answer
Description :

Draw the connection diagram of long shunt differential D.C. compound generator.

Answer :

Ans:

thumb_up_alt 0 like thumb_down_alt 0 dislike
10 views 1 answer
Description :

The inertia constants of two groups of machines which do not swing together are M1 and M2. The equivalent inertia constant of the system is

Answer :

The inertia constants of two groups of machines which do not swing together are M1 and M2. The equivalent inertia constant of the system is M1M2/M1+M2

thumb_up_alt 0 like thumb_down_alt 0 dislike
1.1k views 1 answer
Description :

Answer :

The speed control of universal motor used for sewing machines is by varying the resistance.

thumb_up_alt 0 like thumb_down_alt 0 dislike
86 views 1 answer
Description :

A transfer function has a second order denominator and constant gain in the numerator

Answer :

A transfer function has a second order denominator and constant gain in the numerator the system has two zeros at infinity

thumb_up_alt 0 like thumb_down_alt 0 dislike
116 views 1 answer
Description :

In order to regulate steady state error to zero, in a negative feedback control system, one employs

Answer :

In order to regulate steady state error to zero, in a negative feedback control system, one employs Integral control

thumb_up_alt 0 like thumb_down_alt 0 dislike
403 views 1 answer
Description :

A second order system shows 100% overshoot in its unit step response. It can be categorized as (A) underdamped system. (B) overdamped system. (C) Critically damped system. (D) undamped system.

Answer :

A second order system shows 100% overshoot in its unit step response. It can be categorized as undamped system.

thumb_up_alt 0 like thumb_down_alt 0 dislike
65 views 1 answer
Description :

Cells are connected in series in order to?

Answer :

Cells are connected in series in order to increase voltage available.

thumb_up_alt 0 like thumb_down_alt 0 dislike
91 views 1 answer
Description :

Define transformation ratio in terms of current and voltage.

Answer :

(i) Transformation Ratio (K) is defined as the ratio of the primary current to the secondary current.  (ii) Transformation Ratio (K) is defined as the ratio of the secondary voltage to the primary voltage.

thumb_up_alt 0 like thumb_down_alt 0 dislike
12 views 1 answer
Description :

State any two applications of single phase autotransformer.

Answer :

Applications of single phase auto transformers: 1) Give small boost to distribution cable to correct the voltage drop. 2) As auto transformer starter for induction motors. 3) As furnace supply ... . 5) In control equipment for single phase locomotives. 6) As dimmer in lighting circuits.

thumb_up_alt 0 like thumb_down_alt 0 dislike
12 views 1 answer
Description :

State any two conditions for parallel operation of 3-phase transformer.

Answer :

Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.

thumb_up_alt 0 like thumb_down_alt 0 dislike
18 views 1 answer
Description :

Compare core type transformer and shell type transformer on the following parameters. (i) Types of winding used, (ii) Application

Answer :

Ans:

thumb_up_alt 0 like thumb_down_alt 0 dislike
11 views 1 answer
Description :

Define: (i) Commercial efficiency of a transformer and  (ii) All day efficiency of a transformer.

Answer :

(i) Commercial Efficiency : It is the ratio of output power in watt to the input power in watt. (ii) All day efficiency of a transformer: It is the ratio of output energy in kWh to the input energy in kWh in the 24 hours of the day

thumb_up_alt 0 like thumb_down_alt 0 dislike
19 views 1 answer
Description :

A 50 KVA transformer has iron loss 2 kW on full load. Calculate its iron loss at 75% of full load.

Answer :

Iron loss is dependent on voltage and independent of load. Hence iron loss at 75% of Load = Iron loss at full load = 2 kW

thumb_up_alt 0 like thumb_down_alt 0 dislike
29 views 1 answer
Description :

State any four properties of Ideal transformer.

Answer :

Properties of Ideal transformer: 1) No losses (iron and copper losses), hence no temperature rise. 2) No magnetic leakage i.e (Coefficient of coupling between primary and secondary windings is unity) 3) Zero winding ... drop i.e. E1 = V1, E2 = V2 5) Efficiency 100 %. 6) Regulation 0 %.

thumb_up_alt 0 like thumb_down_alt 0 dislike
12 views 1 answer
Description :

Answer :

For a D.C. machines laboratory following type of D.C. supply will be suitable induction motor D.C. generator set.

thumb_up_alt 0 like thumb_down_alt 0 dislike
103 views 1 answer
Description :

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?

Answer :

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.

thumb_up_alt 0 like thumb_down_alt 0 dislike
141 views 1 answer
Description :

Laminated cores, in electrical machines, are used to reduce?

Answer :

Laminated cores, in electrical machines, are used to reduce eddy current loss.

thumb_up_alt 0 like thumb_down_alt 0 dislike
63 views 1 answer
Description :

Silicon steel is used in electrical machines because it has?

Answer :

Silicon steel is used in electrical machines because it has low hysteresis loss.

thumb_up_alt 0 like thumb_down_alt 0 dislike
155 views 1 answer
Description :

Losses which occur in rotating electric machines and do not occur in transformers are?

Answer :

Friction losses windage losses 

thumb_up_alt 0 like thumb_down_alt 0 dislike
126 views 2 answers
Description :

Write measures to be taken to maintain the insulation resistance of electrical machines to healthy levels.

thumb_up_alt 0 like thumb_down_alt 0 dislike
54 views 0 answers
Description :

What type of motor is used for drilling machines?

Answer :

universal motor also used in Handheld power tools, blowers, blenders, vacuum cleaners, polishers and kitchen appliances.universal motor is defined as a motor which may be operated either on direct or single phase AC supply at approximately the same speed and output

thumb_up_alt 0 like thumb_down_alt 0 dislike
86 views 1 answer
Description :

For protection of rotating machines against lightning surges _______ is used.  (1) lightning arrester (2) capacitor (3) combination of lightning arrester and capacitor (4) lightning conductor and arrester

Answer :

For protection of rotating machines against lightning surges combination of lightning arrester and capacitor is used. 

thumb_up_alt 0 like thumb_down_alt 0 dislike
4.3k views 1 answer
Description :

Answer :

Exciters of synchronous machines are d.c. shunt machines.

thumb_up_alt 0 like thumb_down_alt 0 dislike
65 views 1 answer
thumb_up_alt 0 like thumb_down_alt 0 dislike
162 views 0 answers
Description :

Identify the increasing order of voltage regulation of the following dc generators a same load :  (A) differential compound, shunt and under compound  (B) shunt, differential compound and under compound  (C) under compound, shunt and differential compound  (D) shunt, under compound and differential compound

Answer :

Identify the increasing order of voltage regulation of the following dc generators a same load : under compound, shunt and differential compound 

thumb_up_alt 0 like thumb_down_alt 0 dislike
97 views 1 answer
Description :

Can you guys explain the advantages of frequency converter against the star delta or soft starter?

Answer :

¬Soft starters  A soft starter is, as you would expect, a device which ensures a soft starting of a motor. A softstarter has different characteristics to the other starting ... at rated current from zero to full speed. Frequency converters are becoming cheaper all the time.

thumb_up_alt 0 like thumb_down_alt 0 dislike
364 views 1 answer
Description :

Answer :

If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be crossmagnetisation as well as demagnetising.

thumb_up_alt 0 like thumb_down_alt 0 dislike
106 views 1 answer
Description :

Answer :

In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.

thumb_up_alt 0 like thumb_down_alt 0 dislike
172 views 1 answer
Description :

Answer :

In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.

thumb_up_alt 0 like thumb_down_alt 0 dislike
76 views 1 answer
Description :

Answer :

Sparking, is discouraged in a D.C. motor because commutator gets damaged.

thumb_up_alt 0 like thumb_down_alt 0 dislike
121 views 1 answer
thumb_up_alt 0 like thumb_down_alt 0 dislike
86 views 0 answers
Description :

Answer :

Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.

thumb_up_alt 0 like thumb_down_alt 0 dislike
145 views 1 answer
Description :

Answer :

In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.

thumb_up_alt 0 like thumb_down_alt 0 dislike
85 views 1 answer
Description :

Answer :

In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.

thumb_up_alt 0 like thumb_down_alt 0 dislike
213 views 1 answer
Description :

Answer :

In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.

thumb_up_alt 0 like thumb_down_alt 0 dislike
122 views 1 answer
Description :

Answer :

In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

thumb_up_alt 0 like thumb_down_alt 0 dislike
231 views 1 answer
Description :

Answer :

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.

thumb_up_alt 0 like thumb_down_alt 0 dislike
168 views 1 answer
Description :

Answer :

In a D.C. shunt motor, speed is independent of armature current.

thumb_up_alt 0 like thumb_down_alt 0 dislike
68 views 1 answer
Description :

Answer :

When two D.C. series motors are connected in parallel, the resultant speed is normal speed.

thumb_up_alt 0 like thumb_down_alt 0 dislike
334 views 1 answer
Description :

Answer :

In D.C. shunt motors as load is reduced the speed will remain almost constant.

thumb_up_alt 0 like thumb_down_alt 0 dislike
63 views 1 answer
editAsk a Question
...