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In case of D.C. machines, mechanical losses are primary function of speed.

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Answer :

Iron losses in a D.C. machine are independent of variations in load.

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

Answer :

Friction losses windage losses 

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Answer :

In a D.C. generator, the iron losses mainly take place in armature rotor.

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Answer :

The total losses in a well designed D.C. generator of 10 kW will be nearly 500 W.

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Description :

In a d.c. motor, the mechanical output power actually comes from?

Answer :

In a d.c. motor, the mechanical output power actually comes from electrical input power.

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Description :

The mechanical power developed by the armature of a d.c. motor is equal to?

Answer :

The mechanical power developed by the armature of a d.c. motor is equal to armature current multiplied by back e.m.f.

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Answer :

As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for sound equipment.

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Description :

In Torque-Voltage analogy, the Moment of Inertia of a mechanical rotational system is analogous to (A) Capacitance C. (B) Inductance L. (C) Resistance R. (D) Inductive reactance XL

Answer :

In Torque-Voltage analogy, the Moment of Inertia of a mechanical rotational system is analogous to Inductance L.

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340 views 1 answer
Description :

The friction losses in Real Transformers are :  (A) 0% (B) 5% (C) 25% (D) 50%

Answer :

A

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Description :

In DC motor iron losses are occurred in?

Answer :

In DC motor iron losses are occurred in the armature.

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Description :

Reduction in core losses and increase in permeability are obtained with transformer employing?

Answer :

Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

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597 views 1 answer
Description :

In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

Answer :

In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.

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Description :

What are the losses in a transmission line?

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What are the types of power losses in inductor?

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Copper losses, Eddy current loss, and hysteresis loss are the types of power losses in inductor.

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Description :

Answer :

Iron loss, copper loss and mechanical losses these are the losses in DC machine.

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Description :

Briefly explain how an electrical generator converts mechanical energy into electrical energy.

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Working principle of DC generator: * Working principle of DC generator is the principle of dynamically induced emf or electromagnetic induction. * According to this principle, when flux is cut by a conductor, an ... , the flux is cut by the armature winding and an emf is dynamically induced in it. 

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Description :

Explain the suitability of aluminium as an electrical conductor with respect to its mechanical and electrical properties. 

Answer :

Following are requirements of conductor:- i) High conductivity :  Material should have high conductivity, So that * cross section of conductor (size) reduces, * Copper losses reduces, * So Efficiency ... . Boiling point is 1820°C 9. Specific gravity is 2.7 10. High resistance to corrosion. 

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100 views 1 answer
Description :

Define natural, mechanical, forced and induced draught systems.

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Natural draught system: - When the fuel is burnt (combustion) in the furnace due to natural circulation of air, the draught is called natural draught. Mechanical draught system: -  In a mechanical ... combustion. OR If fan/blower is placed after the furnace then it is called as induced draught

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Description :

Explain the mechanical properties of insulating materials.

Answer :

i) Mechanical strength: Mechanical strength depends on temperature and humidity. a) Temperature: High temperature badly affects the mechanical strength of insulating material. While selecting material ... material should have property of easy moulding and machined into required shape and size.

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Description :

Which of the following converts linear displacement from a mechanical reference into a proportional electrical signal containing phase and amplitude information? A) CRO B) LVDT C) RVDT D) None of these

Answer :

Which of the following converts linear displacement from a mechanical reference into a proportional electrical signal containing phase and amplitude information? A) CRO B) LVDT C) RVDT D) None of these

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Answer :

The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

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Description :

The synchronous motor which works on leading power factor and does not drive any mechanical load is called?

Answer :

The synchronous motor which works on leading power factor and does not drive any mechanical load is called synchronous condenser.

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83 views 1 answer
Description :

State the losses in secondary distribution system. 

Answer :

The losses in secondary distribution system: a) Technical losses: 1. Due to poor voltage 2. Due to unbalance load 3. Due poor quality of transformer & its components 4. Due to poor quality ... of induction type of energy meter. 3. Lack of administration. 4. Energy theft 5. Unmetered supply

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Description :

Explain following techniques related to energy conservation in transmission and distribution system. (i) By balancing phase currents (ii) Variable technical losses (I2R losses).

Answer :

(i) Balancing Phase currents: Proper (healthy balanced) three phase loads always draw equal currents in all lines but single phase loads in the 3 phase 4 wire system or loads connected between two ... . 11) Minimize I2R losses. 12) Balance the load currents. 13) Regulate the system voltages.

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Description :

In a synchronous motor which losses varies with load?

Answer :

In a synchronous motor, copper losses varies with load.

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Description :

What is the percentage of stray losses in DC machine?

Answer :

Percentage of stray losses in DC machine is about 1 % .

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Description :

In synchronous motor, does the winding losses vary with load?

Answer :

No, in the synchronous motor the winding losses do not vary with load.

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Description :

Explain the on state losses in power BJT.

Answer :

On state losses in power BJT: Transistor have four types of losses one is turn on state losses second is turn off state losses third is turn on switching losses and fourth is turn ... ON = VCE sat x IC With increasing collector current collector to emitter saturation voltage increases.

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Description :

Explain the “mitigation of power theft” and “faulty meter replacement” for energy conservation techniques to reduce commercial losses. 

Answer :

Energy conservation techniques to reduce commercial losses:  1. Mitigation of Power Theft: Power theft being the most important issue which all of the service providing utilities ... agricultural sector. Prepaid meters may prove effective measures against unauthorized abstraction of energy. 

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Description :

Which of the following can reduce the Eddy current losses? A) By making the core of a stack of plates electrically insulated from each other B) By making the core of solid block C) By increasing the applied voltage  D) None of these

Answer :

Which of the following can reduce the Eddy current losses? A) By making the core of a stack of plates electrically insulated from each other B) By making the core of solid block C) By increasing the applied voltage  D) None of these

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Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is?

Answer :

Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is approximately equal to 1.

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Explain the electrical losses of magnetic materials used for the cores of inductors and transformer.

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Answer :

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

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Answer :

In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when number of poles is 2.

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A 3-phase, 50 Hz, 500 V induction motor develops 20 hp at slip of 5%. Mechanical losses are 1 hp, and stator loss is 1 kW. The efficiency will be   (a) 95.3% (b) 90.5% (c) 91.3% (d) 85.3% 

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163 views 0 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.

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Answer :

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

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Answer :

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

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Answer :

In a D.C. generator in case the resistance of the field winding is increased, then output voltage will decrease.

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Description :

Answer :

In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.

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Description :

Answer :

In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be 8.

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Answer :

Equilizer rings are required in case armature is lap wound.

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Description :

Hysteresis losses in electrical machines is equal to a. B1.2max f b. B1.6max f c. B1.2min f d. B1.2max fmin 

Answer :

Hysteresis losses in electrical machines is equal to a. B1.2max f b. B1.6max f c. B1.2min f d. B1.2max fmin 

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Description :

The primary function of the school as an agent of society is Options: A) To develop in children an adequate level of vocational competence B) To prepare the child for life C) To provide children with an understanding of their environment D) To provide youth with a uniform set of experiences as the basis for effective communication

Answer :

B) To prepare the child for life 

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Description :

Answer :

In case of a flat compounded generator voltage remains constant irrespective of the load.

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Answer :

In the case of lap winding resultant pitch is difference of front and back pitches.

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A poll of students appearing for masters in engineering indicating that 60% of the students believed that mechanical engineering is a profession unsuitable for women. A research study on women with master or higher degrees in mechanical engineering found that 90% of such women were successful in their professions. Which ... for women with masters or higher degrees in mechanical engineering. (D) The number of women pursing higher degrees in mechanical engineering is small.

Answer :

Correct option is (C). A poll says that women with masters or higher degrees in mechanical engineers are successful in their professions. This statement leads to the option (C) which is the best inference

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22 views 1 answer
Description :

Two d.c. series motors connected in series are driving a mechanical load. If the motors are connected in parallel to drive the same load, the speed becomes  (a) slightly less than double (b) slightly less than half (c) slightly more than double (d) slightly more than half 

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Description :

The most accurate statement about teaching machines is that Options: A) b. f. skinner Began The Movement For Their Use. B) They Were Designed As A Economy Measure To Replace Teachers. C) They Are Not As Efficient As Teachers In Reinforcing Responses D) They Can Be Used For All earning Programmes

Answer :

A) b. f. skinner Began The Movement For Their Use. 

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