List different starting methods of three phase synchronous motor. Explain any one of them.

List different starting methods of three phase synchronous motor. Explain any one of them.
by

1 Answer

Answer :

Different Starting Methods of Three Phase Synchronous Motor:

As synchronous motor is not self starting, different methods of starting are as follows:

1) By using an Induction (Pony) motor

2) By using a DC Machine / Source

3) By using Damper windings

1) By using an Induction (Pony) motor: A small induction motor (pony motor) is directly coupled with the synchronous motor. The number of poles of the induction motor should be less than the synchronous motor. First supply is given to the pony motor, when it rotates the rotor of the synchronous motor near to the synchronous speed, the main switch and DC switch of synchronous motor are closed. The rotor poles of synchronous motor are pulled into synchronism. After that, supply to the pony motor is disconnected and it can be de-coupled from the synchronous motor shaft.

2) By using a DC Machine / Source: A DC machine is coupled to the synchronous motor. The DC machine works like a DC motor initially and brings the synchronous motor near to synchronous speed. The main switch and DC switch of synchronous motor are closed. The rotor poles of synchronous motor are pulled into synchronism. Once it is achieved, the DC machine can be operated like a DC generator and DC power generated can be supplied to the rotor of the synchronous motor.

3) By using Damper Windings: In this method, the motor is first started as an induction motor and then starts running as a synchronous motor after achieving synchronous speed. For this, damper windings are used. Damper windings are additional windings consisting of copper bars placed in the slots in the pole faces. The ends of the copper bars are short-circuited. These windings behave as the rotor of an induction motor. When 3 phase power is supplied to the motor, the motor starts running as an induction motor at a speed below synchronous speed. After some time DC supply is given to the field winding. The rotor gets pulled into synchronism and starts running at constant speed as a synchronous motor. 
by

Related questions

State the various lighting calculations methods and Describe any one of them.

Description : State the various lighting calculations methods and Describe any one of them.

Last Answer : Lighting calculation methods: 1. Lumens or Light flux method 2. Point to point or Inverse Square law method 3. Watts per Square meter method i) Lumens or Light ... is taken according to the illumination desired on an average value considering overall efficiency of the lighting system.

List different types of stepper motor. State one application of stepper motor.

Description : List different types of stepper motor. State one application of stepper motor.

Last Answer : Types of stepper motor : (i)Variable - reluctance motor (ii) Permanent- magnet motors (iii) Hybrid motors. Applications of stepper motor : In robotics, In CNC machines, In computers, printers, ... In Watches, In biomedical applications such as X-ray machines, CT scan, In Process control systems. 

List different torques in synchronous motor.

Description : List different torques in synchronous motor. 

Last Answer : Different Torques in Synchronous Motor: 1) Starting torque 2) Running torque 3) Pull-in torque 4) Pull-out torque

In case one phase of a three-phase synchronous motor is short-circuited the motor will?

Last Answer : In case one phase of a three-phase synchronous motor is short-circuited the motor will not start.

How is a three phase cage induction motor self starting?

Description : How is a three phase cage induction motor self starting?

Last Answer : Any type of induction motor is self starting. Because the reason for torqe production require two flux displaced by some angle theta.If theta is constant with time then torqe will be constant;if ... torqe also pulsating. In induction motor this angle theta is not pulsating.so it is self starting 

Three phase synchronous motor will have how many sliprings?

Description : Three phase synchronous motor will have how many sliprings?

Last Answer : Three phase synchronous motor will have two sliprings.

Draw and explain V and inverted V curves for synchronous motor.

Description : Draw and explain V and inverted V curves for synchronous motor.

Last Answer : V curves' and inverted V curves' for Synchronous Motor:  V curve:  V curve is a plot of the stator current versus field current for different constant loads. The graph is plotted ... Vcurves of synchronous motor. The highest point on each of these curves indicates unity power factor.

List applications of stepper motor.

Description : List applications of stepper motor.

Last Answer : Applications of Stepper Motor: 1) Computer controlled systems 2) Numerical control of machine tools 3) Tape drives 4) Floppy disc drives 5) Computer printers 6) X-Y plotters 7) ... ) Extruders 21) Engravers 22) Analytical and Medical instruments 23) Embroidery Machines 24) Packaging Machines

Explain the activities carried out during weekly maintenance of 3 ph. Induction motor.

Description : Explain the activities carried out during weekly maintenance of 3 ph. Induction motor. 

Last Answer : Activities Carried out During Weekly Maintenance of 3 ph. Induction Motor:  1) Check belt tension. In cases where this is excessive it should immediately be reduces and in the case of sleeve ... and cooled by oil mist systems its important to check the oil mist flow paths/pressure components.

A synchronous motor can be made self starting by providing?

Description : A synchronous motor can be made self starting by providing?

Last Answer : A synchronous motor can be made self-starting by providing damper bar.

Explain three phase half wave controller or three phase unidirectional controller.

Description : Explain three phase half wave controller or three phase unidirectional controller.

Last Answer : Three phase half wave controller or unidirectional controller:

Explain three phase full wave controller.

Description : Explain three phase full wave controller.

Last Answer : Three phase full wave controller: Three phase full wave controller is also called as the three-phase bidirectional controller. Let the load is star connected so at each phase there are antiparallel connected SCRs. ... conduct at the same time and the third phase will be open.

List the different types of tariff.

Description : List the different types of tariff.

Last Answer : Various types of Tariff:-  1) Flat-demand Tariff  2) Simple-demand Tariff or Uniform Tariff  3) Flat-rate Tariff  4) Step-rate Tariff  5) Block-rate Tariff  6) Two-part Tariff  7) Maximum demand Tariff ... c) KW and KVAR Tariff 10) TOD (Time of Day) Tariff 11) TOU ( Time of Usage) Tariff

State the purpose of lighting control. List the different types of dimmer.

Description : State the purpose of lighting control. List the different types of dimmer.

Last Answer : Purpose of Lighting Control:- 1. To turn ON or OFF the lamps 2. For dimming: The dimming control permits the adjustment of lighting over a range. 3. For changing the lighting levels ... operated dimmer 6) Triac operated Dimmer 7) PWM (Pulse width modulation) Controlled technique.

Explain any four properties of Moulding sand.

Description : Explain any four properties of Moulding sand. 

Last Answer : 1. Porosity: Molten metal always contain a certain amount of dissolved gases, which are evolved when the metal freezes the molten metal coming in contact with the moist sand , generates steam or ... to the casting. Refractoriness is measured by the sinter point of the sand rather than its melting

Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a?

Last Answer : Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a magnetic relay.

In a capacitor start motor, the phase displacement between starting and running winding can be nearly?

Last Answer : In a capacitor start motor, the phase displacement between starting and running winding can be nearly 90°.

An unexcited single phase synchronous motor is ?

Description : An unexcited single phase synchronous motor is ?

Last Answer : An unexcited single-phase synchronous motor is reluctance motor.

Why is a capacitor used in a single phase motor and not in three phase motor ?

Description : Why is a capacitor used in a single phase motor and not in three phase motor ?

Last Answer : In 1-phase induction motor capacitor work is generate the auxiliary winding current than excite the main winding to rotor starts rotate. After rotor start rotating about 75% of their speed than auxiliary ... emf to start the motor.so,in 3-phase induction motor is self start induction motor.

State any four advantages of three phase induction motor.

Description : State any four advantages of three phase induction motor. 

Last Answer : Advantages of three phase induction motor https://youtu.be/27OIOCKN05U

The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is

Description : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 

Last Answer : The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 4 percent

What is mean by plugging in three phase induction motor?

Description : What is mean by plugging in three phase induction motor?

Last Answer : Plugging in three-phase induction motor means interchanging of any two phases of a stator for quick stopping.

how can we reverse the direction of rotation of three phase induction motor?

Description : how can we reverse the direction of rotation of three phase induction motor ?

Last Answer : The direction of rotation of three phase induction motor can be reversed by plugging i.e by changing any two out of three phases of the supply to the stator of the Induction motor terminal.

Draw & explain operation of phase detector.

Description : Draw & explain operation of phase detector.

Last Answer : In phase detector, the op-Amp basically acts as a zero crossing detector. If a sine wave is applied at the i/p, we get square wave at the op-Amp o/p (at point ... to two channel of the CRO. The time duration between the pulses corresponding to voltages represent the phase between them. 

Explain the concept of lagging and leading phase angle by waveform.

Description : Explain the concept of lagging and leading phase angle by waveform.

Last Answer : i) Leading phase angle :  When two ac quantities of same frequency do not attain their respective zero or peak values simultaneously, then the quantities are said to be out-of-phase quantities. The ... Similarly, in the second diagram, the voltage is said to be lagging the current by  Φ.

List the main parts of D.C. motor

Description : List the main parts of D.C. motor

Last Answer : Main parts of D.C. motor and their functions:  Part Functions Yoke i) Provides mechanical support for poles. ii) Acts as protecting cover for machine. iii) Carries magnetic flux. ... a fixed physical position relative to the stator.  Shaft Used to transfer mechanical power 

List the different level measurement methods.

Description : List the different level measurement methods. 

Last Answer : Liquid Level Measurement Direct method 1. Hook type 2. Sight glass gype 3. Float type 4. Dip stick Indirect method 1. Hydraustatic pressure type 2. Electrical type a) Capacitance level indicator b) Radiation level detector c) Ultrasonic level gauge 3. Radar type

List the different methods to produce damping torque.

Description : List the different methods to produce damping torque.

Last Answer : Methods of providing damping torque in indicating type instruments: 1) Air friction damping. 2) Fluid friction damping. 3) Eddy current damping.

How are nuclear reactors controlled? Explain two different methods in brief.

Description : How are nuclear reactors controlled? Explain two different methods in brief.

Last Answer : Nuclear reactor is controlled using control rods: Control rods are made up of very high neutron absorbing material like boron, cadmium. By adjusting height of control rods on reactor core ... of nuclear reaction will increase. Whereas by pushing control rod towards the core it will reduce.

State the different methods of Power Generation adopted in India.

Description : State the different methods of Power Generation adopted in India. 

Last Answer : 1. Hydro energy or hydro Electric power plant  2. Nuclear energy or nuclear Power Plant  3. Fossil fuels: i) Thermal energy (by combustion of coal) or Thermal Power Plant ii) Natural gas ... from any organic waste materials. It contains mixture of methane(50-65 % in volume) and carbon dioxide

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

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.

Explain construction and working of AC servomotor.

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. 

List any two methods of reactive power measurement in 3 phase circuit.

Description : List any two methods of reactive power measurement in 3 phase circuit.

Last Answer : Methods of reactive power measurement in 3 phase circuit: (i) Two single phase wattmeter method (ii) One single phase wattmeter method

List any four casting defects.

Description : List any four casting defects.

Last Answer : The various types of casting defects are as follows: 1. Gas Porosity: Blowholes, open holes, pinholes. 2. Shrinkage defects: shrinkage cavity. 3. Mold material defects: Cut and washes, ... Pouring metal defects: Cold shut, misrun, slag inclusion. Metallurgical defects: Hot tears, hot spot.

List any four materials used for pattern making

Description : List any four materials used for pattern making

Last Answer : The various types of materials used are as follows: 1. Wood 2. Metal. 3. Plastic. 4. Plaster. 5. Wax.

List any four accessories used on lathe.

Description : List any four accessories used on lathe.

Last Answer : The various accessories used in lathe are as follows. 1) Lathe centers 2) Carriers or driving dog 3) catch plates 4) Chucks 5) Face plates 6) Angle plates 7) Mandrels 8) Rests

State suitable single phase motor for following applications: (i) Table fan (ii) Mixers and Grinders

Description : State suitable single phase motor for following applications: (i) Table fan (ii) Mixers and Grinders

Last Answer : Application Suitable Single Phase Motor Table Fan 1) Capacitor split phase motor 2) Capacitor start capacitor run motor Mixers and Grinders 1) Universal motor 2) A.C. Series motor

List the different errors in wattmeter & explain compensation for it.

Description : List the different errors in wattmeter & explain compensation for it.

Last Answer : Errors in Wattmeter Compensation method Error due to connection method To overcome this error, wattmeters are provided with additional compensating winding which is connected in series with ... due to friction The weight of moving system be reduced to minimum possible.

State the insulating materials used in motor. Write temperature class and withstand temperature ranges for them.

Description : State the insulating materials used in motor. Write temperature class and withstand temperature ranges for them. 

Last Answer : The insulating materials used in motor are as belows: 1. Cotton, 2. Silk, or paper, 3. Press board, 4. Resins 5. PVC 6. Cellulose-Fiber, 7. Enameled coating, etc  ... Over 180° Mica, porcelain, ceramics, glass quartz, asbestos, treated glass fiber or treated asbestos. etc.

The starting winding of a single-phase motor is placed in?

Last Answer : The starting winding of a single-phase motor is placed in stator.

If starting winding of a single-phase induction motor is left in the circuit, it will?

Last Answer : If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.

The rotor developed by a single-phase motor at starting is?

Last Answer : The rotor developed by a single-phase motor at starting is zero.

which single phase induction motor has highest starting torque?

Last Answer : Capacitor start motor has high torque in starting

A three-phase synchronous motor connected to ac mains is running at full load and unity power factor.

Description : A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

Last Answer : Leading

State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Description : State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Last Answer : Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows:  1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine 

Describe with neat sketch working of hysteresis motor.

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.

Explain Three Phase Bidirectional Delta Connected Controller.

Description : Explain Three Phase Bidirectional Delta Connected Controller.

Last Answer : Three Phase Bidirectional Delta Connected Controller:

Explain three phase bridge inverter.

Description : Explain three phase bridge inverter.

Last Answer : Three phase bridge inverter: Three phase bridge inverter converts DC voltage input to three-phase variable frequency variable voltage output. DC voltage source can be a DC source or output of the rectifier. ... in proper sequence. The switch may be thyristor or IGBT etc.

Describe the following energy conservation methods of electrical motor. i) By motor survey ii) By matching loads with motor rating

Description : Describe the following energy conservation methods of electrical motor. i) By motor survey ii) By matching loads with motor rating

Last Answer : Energy conservation methods of electrical motor:  1) By Motor Survey: Large industries have a massive population of LT motors. Load survey of LT motors can be taken-up methodically to ... -speed motors, eddy-current couplings, fluid couplings, and solid-state electronic variable speed drives.

What are the speed control methods of dc motor?

Description : What are the speed control methods of dc motor?

Last Answer : Field control of DC motor Armature control of DC motor