State working principle of alternator. State the meaning self and separate excitation. 

1 Answer

Answer :

Working principle of alternator: When a conductor is moved in magnetic field or a magnetic field moved with respect to conductor, according to Faraday’s law of electromagnetic induction, the conductor cuts the magnetic field and an electromotive force is induced in the conductor. 


Self-excitation: When the A.C. current from alternator itself is rectified and used for its excitation, then the excitation is said to be self-excitation.


Separate excitation: When D.C. excitation required for field winding of alternator is provided by using a separate source like battery or shaft-mounted exciter, then the excitation is said to be separate excitation.

Related questions

Description : State the working principle of gears and give its applications.

Last Answer : Working Principle:  Gears are mechanical elements which transmit motion by means of successively engaging teeth.  Gears are used to transmit motion from one shaft to another or between ... Agricultural equipment.  Industrial construction.  Mining equipment.  Automotive equipment.

Description : State working principle of PMMC instrument.

Last Answer : Working Principle of PMMC Instrument: When current carrying conductor is placed in a constant magnetic field, it experiences a force proportional to the current and produces proportional deflection torque. 

Description : State the working principle of transformer.

Last Answer : Working principle of transformer : Transformer works on the principle of mutual electromagnetic induction. When AC voltage is applied to the primary winding it causes ac current to flow through primary ... the secondary winding. The current flows in the secondary circuit if load is connected.

Description : Explain the working principle of induction motor. 

Last Answer : Working principle of induction motor: * When the motor is excited with three-phase supply, three-phase stator winding carries three-phase currents & produces a rotating magnetic field of constant magnitude and ... , which tend to move the rotor in the same direction as the rotating magnetic field. 

Description : Explain with neat sketch the working principle of MIG.

Last Answer : In metal-arc inert gas welding the Weld area is shielded by an effectively inert atmosphere of argon, helium, carbon dioxide, or various other gas mixtures . The consumable bare Wire is fed automatically ... of the molten-weld puddle. Multiple-weld layers can be deposited at the joint. 

Description : Describe the working principle of Thyristor operated dimmer with the help of circuit diagram.

Last Answer : Thyristor operated dimmer: A popular thyristor operated dimmer circuit employ TRIAC-DIAC phase control for low AC power control. During each half-cycle, the capacitor charges through (R1+VR1). When the ... time constant {C (R1+VR1)}. Thus by reducing VR1 the lamp brightness can be increased.

Description : Describe the working principle of photoelectric pickup type tacho-generator.

Last Answer : Working: Working principle: The light passes through the holes available on the rotating disc with a specific interval, depends on the angular speed of disc having equidistant holes. The frequency of this light pulses ... by N=f/HS  N=speed  f=frequency  Hs=holes on the disc

Description : Explain construction and working principle of single phase transformer.

Last Answer : A single phase transformers is an electrical device that accepts single-phase AC power and outputs single-phase AC. PRINCIPLE... The single-phase transformer works on the principle of ... and secondary windings. Thin steel laminations shall be employed to prevent power losses from the core.

Description : Draw symbol of LED and explain it’s working principle.

Last Answer : Construction of LED: The basic structure of LED is shown in fig.(a). The active region exists between the p and n regions. The light emerges from the active side in all the directions when electron hole-pairs ... fig.(c). In this way an LED emits light. This is the principle of operation of LED.

Description : Explain the construction of alternator with neat diagram.

Last Answer : Diagram: Construction of three phase alternator: Construction wise, an alternator generally consists of field poles placed on the rotating fixture of the machine i.e. rotor as shown in the ... of rotor used in construction of alternator, 1. Salient pole type. 2. Cylindrical rotor type. 

Description : Is the speed of alternator is directly proportional to frequency?

Last Answer : Yes, speed of alternator is directly proportional to frequency.

Description : At which power factor alternator is said to be overexcited?

Last Answer : At leading power factor alternator is said to be overexcited.

Description : The power factor of an alternator depends on?

Last Answer : The power factor of an alternator depends on load.

Description : In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

Last Answer : In an alternator, at lagging power factor the generated voltage per phase as compared to that at unity power factor must be more than terminal voltage.

Description : The magnitude of various voltage drops that occur in an alternator depends on?

Last Answer : The magnitude of various voltage drops that occur in an alternator depends on load current.

Description : In alternator where the voltage drop occurs?

Last Answer : In alternator voltage drop occurs in armature resistance, leakage reactance, and armature reactance.

Description : While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then (A) It would over-run the other alternator (B) Its rotor ... (C) Its portion of share in load will increase (D) Its power factor would be decreased.

Last Answer : While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then Its portion of share in load will increase

Description : What is an alternator?

Last Answer : Ans. Alternator is a machine which converts mechanical energy into electrical energy

Description : Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.

Last Answer : Armature Reaction: The effect of armature flux on main flux is called as armature reaction.  Armature Reaction at Various Power Factors: When armature is loaded, the armature flux modifies ... lagging p.f. For capacitive loads the effect of flux is partly distorting and partly strengthening.

Description : Draw equivalent circuit of alternator.

Last Answer : Equivalent circuit of alternator

Description : Alternator

Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

Description : What is the frequency of an alternator which has 2 poles and makes 3600 revolutions per minute? A) 3600 HZ B) 60 Hz C) 120 Hz D) None of these

Last Answer : What is the frequency of an alternator which has 2 poles and makes 3600 revolutions per minute? A) 3600 HZ B) 60 Hz C) 120 Hz D) None of these

Description : The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is (A) 2/3 (B) 5/6 (C) 7/8 (D) 6/7

Last Answer : The fractional-pitch used for eliminating 7th harmonic from the emf wave of an alternator is 6/7

Last Answer : An alternator coupled to a hydraulic turbine runs at slow speed, as compared to others.

Description : What causes diodes to fail in alternator?

Last Answer : alternator

Description : State working principle of earth tester.

Last Answer : Earth tester:-The resistance of the earth is measured with the help of earth tester. It consists of a hand cranked type generator, the magnet poles, crossed coils and flexible spirals. It consists ... deflection of the pointer will indicate directly resistance in ohm of the earth under test.

Description : State the principle of operation of d.c. motor.

Last Answer : When a current carrying conductor is placed in a magnetic field, the conductor experiences the force. The magnitude of force is given by F = BIL newton  where F – Force   B – maximum flux density   I – Current   L – Length of conductor

Description : State principle of operation of piezo-electric transducer. State its application.

Last Answer : The piezoelectric element used for converting mechanical movement into electric signals. The mechanical deformation generates charges and this charge appears as a voltage across the electrodes.  ... destructive test (NDT) equipments 6. Piezoelectric materials are used in ultrasonic transducers. 

Description : If the excitation of an alternator operating in parallel with other alternators decreased, its: (1) Power factor becomes more leading (2) Output Kw will change (3) Power factor becomes more lagging (4) Power factor becomes unity

Last Answer : If the excitation of an alternator operating in parallel with other alternators decreased, its: Power factor becomes more leading

Description : A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a terminal voltage of 2000 V on open circuit. The magnitude of the internal voltage drop within the machine at a load current of 200 A is  (A) 1 V (B) 10 V (C) 100 V (D) 1000 V

Last Answer : 800

Description : Why have both principle and principal when they can both be used interchangeably?

Last Answer : Can they be used interchangeably? Correct me if I'm wrong, but I thought they had distinct meanings. Prinicpal being the leader of a school, or the original money down on a payment, or a sort-of ... a scientific law (and both probably having more meanings that I didn't think of). Am I mistaken?

Description :  operating principle of PUT.

Last Answer : Constructional diagram & Operating principle of PUT:  The PUT is a PNPN device similar to SCR, but its operation is similar to the UJT. The PUT behave like a UJT whose trigger voltage VP can be set ... low resistance and VAK ≈ 1V). The PUT is also referred to as a complementary SCR (CSCR). 

Description : Describe principle of operation of Doppler type ultrasonic flow meter with diagram. 

Last Answer : Diagram: Working:  The flow meter consists of a crystal transducer mounted outside the pipe in which flow is to be measured. This transducer is a piezoelectric crystal which ... , so the frequency of the reflected wave is shifted to particle velocity, according to Doppler principle.

Description : Draw construction of Megger and write operating principle of it.

Last Answer : Megger:  Working: Two coils the current coil and pressure coil are mounted at an angle on the same spindle and form the part of the moving system. These coils are connected to a small hand driven ... . When the instrument is not working the pointer may rest at any position on the dial.

Description : Explain the operating principle of LASER and list applications of LASER diode.

Last Answer : A basic construction of Laser diode is as shown . A PN junction is formed by two layers of doped gallium arsenide. There is highly reflective surface at one end of PN junction and ... 6. laser scanning and light beam illumination. 7. Military applications 8. Medical surgery 9.Diamond cutting

Description : The transformer works on the principle of: (A) Mutual induction (B) Mutual capacitance (C) All of the above (D) None of the above

Last Answer : The transformer works on the principle of:  Mutual induction

Description : Principle of Thermocouple is based on :  (A) Thomson effect (C) Seebeck effect (B) Peltier effect (D) Kelvin effect

Last Answer :  The  principle is  based on Seebeck   effect.

Description : D' Alembert's principle is used for?

Last Answer : D' Alembert's principle is used for reducing the problem of kinetics to equivalent statics problem.

Description : According to principle of moments?

Last Answer : According  to  principle  of  moments  clockwise  moments  equals   anticlockwise  moments.

Last Answer : A hysteresis motor works on the principle of hysteresis loss.

Description : What is the principle of DC generator?

Last Answer : principle

Description : What is the principle of DC motor?

Last Answer : principle

Description : Explain the working of pump storage plant and also state its advantages. 

Last Answer : Working of Pumped storage hydroelectric power plant :-  It consists of head water pond (reservoir) and tail water pond by constructing a dam at tail race path.  Tail water pond and ... install as well as spinning reserve capacity of TPP as it provides additional power during peak load period.

Description : How to Lose Weight Without Working Out

Last Answer : How to Lose Weight Without Working Out Weight loss is a major concern among many people. Whether a person is obese or just wants to shed a few extra pounds, keeping fit and trim is an important ... still lose excess pounds with just a few activities that don't involve a lot of sweating and toning.

Description : Describe working of online UPS. List any two applications of UPS.

Last Answer : Online UPS: The block diagram of the on line UPS systems is as shown, where the load is connected to the invertor through the UPS static switch. The UPS static switch is ... 4) Healthcare: hospitals, clinics and retirement homes 5) Telecommunications 6) Special projects (events)

Description : Explain working of static AC circuit breaker. 

Last Answer : Static AC Circuit breaker: The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

Description : Explain construction and working of AC servomotor.

Last Answer : Construction of AC Servo Motor: AC servo motor is mainly composed of a stator and a rotor. Laminated stator core is usually made of silicon steel. Two phase windings are placed in the stator slots at 90 degree ... on rotor. Due to the force or torque acting on the rotor, it is set in motion. 

Description : Describe with neat sketch working of hysteresis motor.

Last Answer : Working: When stator is energized with single phase ac supply, rotating magnetic field is produced because of starting (auxiliary) and main windings, which remain in circuit permanently. The ... the principle of magnetic locking this motor either rotates at synchronous speed or not at all.

Description : Explain the working of Neon sign tube with diagram.

Last Answer : Neon sign tube: The construction & circuit diagram for neon tube is as shown in fig. Basically neon tube is used for advertisement or decoration purpose. The maximum length of tube is ... the HT transformer must be earthed separately. * Caution notice of danger board is required.

Description : Explain the working of HPMV Lamp with neat diagram.

Last Answer : High-pressure Mercury-Vapour Lamp (HPMVL):  Working:  * Whenever 1-ph, 230V, AC Supply is provided to the discharge tube of MVL, initially the current flows from Phase to the choke to ... : The function of power factor improvement capacitor is to improve the power factor from 0.5 to 0.95.