Description : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is (1) 1000V (2) 100V (3) 600V (4) 10,000V
Answer :
The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V
asked
Apr 29, 2018
by
anonymous
Answer :
In a D.C. machine stray loss is the sum of iron loss and mechanical loss.
asked
Mar 21, 2018
by
anonymous
Answer :
To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.
asked
Mar 21, 2018
by
anonymous
asked
Mar 20, 2018
by
anonymous
Answer :
Iron losses in a D.C. machine are independent of variations in load.
asked
Mar 20, 2018
by
anonymous
Answer :
In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.
asked
Mar 20, 2018
by
anonymous
Answer :
Open circuited armature coil of a D.C. machine is identified by the scarring of the commutator segment to which open circuited coil is connected and indicated by a spark completely around the commutator.
asked
Mar 20, 2018
by
anonymous
Description : A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively
Answer :
A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively 19,17
asked
May 3, 2018
by
anonymous
Answer :
Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.
asked
Mar 20, 2018
by
anonymous
Description : In a dc machine, interpoles are used to (1) neutralize the effect of armature reaction in the interpolar region (2) generate more induced emf in the armature (3) avoid interference of the armature flux with the main -field flux (4) reduce the demagnetizing effect of armature reaction
Answer :
In a dc machine, interpoles are used to neutralize the effect of armature reaction in the interpolar region
asked
Apr 29, 2018
by
anonymous
Description : The magnetic neutral plane shifts in a dc machine (A) in the direction of motion of motor (B) in the direction of motion of generator (C) due to increase in the field flux (D) cause reduction of flash over between commutator segments
Answer :
The magnetic neutral plane shifts in a dc machine in the direction of motion of generator
asked
Apr 28, 2018
by
anonymous
Answer :
Copper losses,iron losses,variable losses , constant losees
Description : Explain concept of back emf in DC machine. State how it governs armature current.
Answer :
Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.
asked
Jul 27, 2019
by
anonymous
Description : What is the percentage of stray losses in DC machine?
Answer :
Percentage of stray losses in DC machine is about 1 % .
asked
Mar 8, 2018
by
anonymous
Answer :
Iron loss, copper loss and mechanical losses these are the losses in DC machine.
asked
Sep 27, 2017
by
anonymous
Description : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is
Answer :
A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87
asked
May 8, 2018
by
anonymous
Description : Aluminium is not used as winding wire for the armature of a dc machine because (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper
Answer :
Aluminium is not used as winding wire for the armature of a dc machine because (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper
asked
Apr 29, 2018
by
anonymous
Description : Why poles of dc machine are laminated?
Answer :
Poles of DC machines are laminated to reduce the eddy current losses in the poles.
asked
Apr 27, 2020
by
anonymous
Description : Brushes of DC machine are made up of ?
Answer :
Brushes of DC machine are made up of carbon.
asked
Mar 3, 2018
by
anonymous
Answer :
In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called armature.
asked
Mar 21, 2018
by
anonymous
Description : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents
Answer :
The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only
asked
Apr 29, 2018
by
anonymous
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.
asked
Mar 20, 2018
by
anonymous
Answer :
In D.C. generators the pole shoes are fastened to the pole core by counter sunk screws.
asked
Mar 20, 2018
by
anonymous
Description : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator
Answer :
In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator
asked
May 1, 2018
by
anonymous
Description : What is fuzzy logic in a washing machine?
asked
Mar 10, 2018
by
anonymous
Description : Define Feed and speed in shaping machine
Answer :
1) Feed: Feed (S) is the relative movement of the work or tool in a direction perpendicular to the axis of reciprocation of the ram per double stroke. It is expressed in mm per stroke. 2) Speed: ... speed is the speed at which the metal is removed by the cutting tool in a period of one minute.
asked
May 7, 2020
by
anonymous
Description : function of exposer in photocopier machine.
Answer :
A bright lamp illuminates the original document, and the whitws areas of the original document reflect the light onto the surface of the photoconductive drum. The areas of the drum that are exposed ... discharge to the ground. The areas of the drum not exposed to light remains negatively charged
asked
Sep 2, 2019
by
anonymous
Description : In 8085 microprocessor, how many T-states does OPCODE FETCH machine cycle normally require (i.e., when HOLD and WAIT signals are NOT forced)? A) 4 to 6 B) 3 to 8 C) 2 to 3 D) 8 to 12
Answer :
In 8085 microprocessor, how many T-states does OPCODE FETCH machine cycle normally require (i.e., when HOLD and WAIT signals are NOT forced)? A) 4 to 6 B) 3 to 8 C) 2 to 3 D) 8 to 12
asked
Jun 18, 2018
by
anonymous
Description : Explain the basic parts of a slotting machine with neat sketch.
Answer :
Base or Bed The base is rigidly built to take up all the cutting forces and the entire load of the machine. The top of the bed is accurately finished to provide guideways on which ... return mechanism. 2. Variable speed reversible motor drive mechanism. 3. Hydraulic drive mechanism.
Description : Write down the basic parts of a lathe machine with their proper functions.
Answer :
Important Parts of Lathe and their Functions 1. Bed It is the main body of the machine. All main components are bolted on it. It is usually made by cast iron due to its high compressive strength and ... carriage on bed. 12. Spindle: It is the main part of lathe which holds and rotates the chuck.
Description : The 'Equal area criterion' for the determination of transient stability of a synchronous machine connected to an infinite bus (1) ignores line as well as synchronous machine resistance and shunt capacitances. (2) assumes accelerating power acting on the rotor as constant. (3) ignores the effect of voltage ... inherent damping present in the machine. (4) takes into consideration the possibility of machine losing synchronism after it has survived during the first swing.
Answer :
1
asked
Apr 30, 2018
by
anonymous
Description : During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)
Answer :
During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s) only at C
asked
Apr 29, 2018
by
anonymous
Answer :
Synchronsizing power of a synchronous machine is inversely proportional to the synchronous reactance.
asked
Mar 20, 2018
by
anonymous
Answer :
A synchronous machine with low value of short-circuit ratio has lower stability limit.
asked
Mar 20, 2018
by
anonymous
Description : Write down the steps involved for internal thread cutting on lathe machine.
Answer :
Steps involved for internal thread cutting on lathe machine 1) Hole is first bored to the root diameter of the thread. 2) Tool is fixed on the tool post or on the boring bar adjusted the angle of ... the start. 10) Keep going until the calculated depth of cut has been reached on the top slide.
Description : Types of slotting machine
Answer :
1. Puncher slotter 2. Precision slotter 3. Production slotter Working Principle of Slotting machine:- The slotting machine is a reciprocating machine tool in which, The vertical slide holding the cutting ... longitudinal and cross feeds, a rotary feed motion is also provided in the work table.
asked
May 7, 2020
by
anonymous
Description : Electrical specifications with values for washing machine.
Answer :
1. Type: Top loading / Front loading type 2. Capacity range: 6kg to 15kg 3. Motor Used: Induction motor 4. Input voltage: 100V- 240V 5. Power: in 1200W / Output power 100–400W{can go upto 1000W) 6. Efficiency: Max efficiency 31% 7. Wattage: 2.100-2.400 W 8. Current: 13A 9. Frequency: 50hz
asked
Sep 2, 2019
by
anonymous
Description : Draw block diagram for CNC drilling machine and explain its working.
Answer :
Block diagram consist of the following points: Machine tool with DC servo motor as feedback element. The transducer is added as adaptive control application. The auxiliary controller ... line. The interrupt pulses are generated by TBG and supplied to computer through inter
asked
Aug 10, 2019
by
anonymous
Description : UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor (Coil pitch and distributed winding) 1.7 Distribution factor 1.8 EMF equation of alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization
Answer :
1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.
asked
Aug 25, 2018
by
Notes
Description : Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop
Answer :
Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap
asked
Apr 28, 2018
by
anonymous
Answer :
The wattage of motor for driving domestic sewing machine will be around 100 to 150 W.
asked
Mar 20, 2018
by
anonymous
Answer :
To limit the operating temperature an electrical machine should have proper current rating.
asked
Mar 20, 2018
by
anonymous
Description : If we change the excitation of synchronous machine will it affect on power factor?
Answer :
Yes, If we change the excitation of synchronous machine it will affect on power factor. If the synchronous motor is overexcited then it will have leading power factor and if the motor is underexcited then it will have lagging power factor.
asked
Mar 18, 2018
by
anonymous
Description : If we change the excitation of synchronous machine will it affect on motor speed?
Answer :
No, If we change the excitation of synchronous machine it will not affect on motor speed.
asked
Mar 18, 2018
by
anonymous
Description : V - curve of synchronous machine shows the relation between?
Answer :
V - curve of synchronous machine shows the relation between AC armature current and DC field current.
asked
Mar 18, 2018
by
anonymous
Description : Why synchronous machine is called doubly excited machine?
Answer :
Armature windings of synchronous machines either deliver 3 phase AC or absorb 3 phase AC source, whereas field windings are energized from DC source. Thus due to presence of AC on armature and DC on field windings, synchronous machines are often referred as doubly excited machines.
asked
Mar 18, 2018
by
anonymous
Description : Which machine is the exciter of synchronous machine?
Answer :
DC shunt machine is the exciter of synchronous machine.
asked
Mar 18, 2018
by
anonymous
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.
asked
Mar 21, 2018
by
anonymous
Answer :
In a level compounded D.C. generator, full load terminal voltage is equal to no-load terminal voltage.
asked
Mar 21, 2018
by
anonymous