Which characteristics of three point starter makes it unpopular ?

What protection does the four point starter offer ?

The use of three point starter presents a problem .The speed of the motor is controlled by means of the field rheostat .To increase the speed of the motor it is necessary to set the field resistance to a higher value .The current through the shunt field is reduced and so is the current through the coil of holding magnet . The reduced current through the coil reduces the strength of the magnet. Thus it makes motor susceptible to line voltage variations .In the weakened condition a slight reduction in line voltage would further weaken the holding magnet , releasing the arm of the starter and thus disconnecting the motor from the connection line. As a result unscheduled stoppages of the motor makes the three point starter quite unpopular.

The four point starter eliminates the disadvantage of three point starter .In addition to the same three point starter the other side of the line ,L2,is the fourth point brought to the starter .The coil of the hlding magnet is connected across the line when the arm is moved from the off position .The four point starter provides the motor with no voltage protection .Should the power fail the motor must be disconnected from the line .If not ,full line voltage will be applied to armature without the benefit of the starting resistors when the power is restored .The holding magnet being connected across the line ,when the voltage drops bellow a specific value, thus it protects the motor when power is restored.

Why it is impossible for the counter emf to equal the applied voltage in a motor?

What are the detrimental effects of armature reaction on the performance of a dc machine?

Mechanism of Solar Collector for Flat Plate

Why a self excited shunt generator will not build up voltage?

How can the voltage, current and power ratings of a generator be adjusted?

Protecting Coating Shop

Why Poppet Valve is Universal used in Automobile sector?

What is shaping operation? What are the classifications?

Spacecraft and Space Shuttle, Why it is not Shit plan for world People?

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How to Calculate Heat Rate of Generator Engine?

Types of Power Plant (Technology) Natural Gas Based power plant technology Diesel power plant technology Heat Rate of Engine= Fuel Flow or Fuel burned * Fuel Heating Value / Power Output 1 Liter Diesel = 0.85 Kg Example: Heat Rate of Diesel Generator at 100% Load Engine Model- 2506A-E15TAG2 Engine Capacity=400 eKW Fuel Consumption=84 L = 71.4 Kg Electrical Energy Output = 400 KW Heating Value of Diesel = 42.5 MJ/Kg Heat Rate of Engine= Fuel Flow or Fuel burned * Fuel Heating Value / Power Output Heat Rate of Engine = 71.4 Kg * 42.5 MJ/Kg /400KW Heat Rate of Engine =7.58 MJ/KWH Heat Rate of Gas Generator at 100% Load Engine Model- VHP5904LTD Engine Capacity= 900 eKW Fuel Consumption= 271 Nm 3 Electrical Energy Output= 900 KW Fuel Consumption= 0.28 Nm3/KWH Heating Value of Natural Gas= 35.22 MJ/ Nm 3 Heat Rate of Engine= Fuel Flow or Fuel burned * Fuel Heating Value / Power Output

Packing, Seals and Gaskets

Packing, seal and gasket resists the flow of fluid from machinery face, head, joint and machinery gap or clearance. Packing materials: Fiber, asbestos, cotton, synthetic materials, plastic, Teflon, graphite etc. Packing structure: Twisted, Braided and Consolidated. Gasket: A gasket is a mechanical seal that fills the space between two mating surfaces, generally to prevent leakage from or into the joined objects while under compression. Gaskets allow " less-than-perfect " mating surfaces on machine parts where they can fill irregularities. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, fiberglass, or a plastic polymer (such as polychlorotrifluoroethylene) Figure : Gaskets Name of the gasket uses

Why a dc generator fails to build up voltage?

How can the problem be remedied : No residual magnetism, reversed field connection and high resistance of field circuit are responsible for the failure of build up process of a dc generator. The factors are explained below: No residual magnetism: For the starting build up process requires some residual magnetism in the magnetic circuit then no voltage will be generated that can produce current flow through field circuit. Reversed field connection: The voltage induced inside the coil of field circuit due to residual magnetism that can permit the flow of current. For the following direction of this flux will be created and the direction of this flux will be same direction as the residual flux. If the field connections are reversed the lines of flux produced by current flow will oppose the residual flux, as a result generate voltage will decrease rather than increase. So voltage build up process failed. Field circuit resistance too high: A field

what is the difference between long shunt and short shunt dc generator?

How do they differ from normal generator? Draw their V-I characteristics and explain them? In short shunt connection the shunt field is connected directly across the armature terminals and the armature connection equals the sum of the shunt field current plus the load current . In this instance the load current flow s through the series field winding so that the load current and series field current are one and same. In long shunt connection the voltage across the shunt field is the same as the terminal voltage of the generator and current in the armature will be the current in the series field. The armature current equals the shunt field current plus the load current. A shunt generator has the field circuit connected directly across the armature. As more devices connected in parallel the load on the generator increases that the generator current increases which results decrease in terminal voltage of the generator.

Therbligs and Basic 17 motion name of therblig

Therbligs : A graphical representation of the co-ordinated activities of an operators body members. These activities ar described in terms of basic or fundamental motions known as therbligs. At the time Frank Gilbreth was doing his work in the field of motion study, he also concluded that any manual activity could be described in terms of 17 fundamental motions. This comparable to our being able to describe every word in the English language in terms of some of the 26 letters of the alphabet. Each of these fundamental motions is called a Therblig. Basic 17 motion name of Therblig : Name of Therblig Letter abbreviation Search Select Grasp Transport empty Transport loaded Hold Release Load Position Pre-position Inspect Assemble Disassemble Use Unavoidable Delay Avoidable Delay Plan Rest Sh ST G

Various Methods of Drawing Flow Nets

1. Hydraulic models: a. Streamlines can be traced by injecting a dye in a seepage model or Heleshaw apparatus. b. They by drawing equipotential lines the flow net is completed. 2. Analytical Method: a. It is only applied to problems with simple and ideal boundaries conditions. b. The equation corresponding curve ǿ and Ѱ are first obtained and the same are plotted to give the flow net pattern for the flow of fluid between the given boundary shape. 3. Electrical Analogy Method: This method based on the fact that the flow of fluids and flow of electricity through a conductor are analogus. These two systems are similar in the respect that electric potential is analogus to the velocity potential. The electric current is analogus to the velocity of flow and the homogeneous conductor is analogus to the homogeneous fluid. This method only for a practical method of drawing a flow net for a particular set of boundaries.

Which type of Battery connection Series or Parallel Connection is used for Diesel Generator?

Diesel Generator Battery Connection Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To remove the possibility of arching, remove the negative battery cable is first and attach the negative battery last. When using jumper cables to start the engine make sure to connect the cables in parallel Positive to positive and negative to negative. When using external electrical source to start the engine, turn the disconnect switch to the OFF position. Remove the key before attaching the jumper cables. To avoid damage to engine parts do not connect jumper starting or battery charging cable to any fuel system or electronic component. Battery Parallel Connection: The accompanying illustration shows a typical parallel battery connection. This arrangement doubles the cranking amperage. Battery Series Connection: This illustration shows a typical

what is PIV drive? Why is PIV drive more effective than any other system of drive?

PIV Drive: A stepless drive where the transmission of torque takes place infinitly variable without slip is called PIV drive. There are some advantages of PIV drive: there is no slip in the transmission of power. Maximum transmission of power. Speed can be changed at running condition Any range of slip can be obtain It give constant cutting speed for the above reason PIV drive is more effective than any other system of drive

What are the main components of Automobile?

There have five basic parts for Automobile and they are given bellow: 1. Engine: Engine which is known to all as a power plant. Engine is the source of power which makes the car wheels rotate and the car move where it supply power to lubricating, fuel, electric and cooling systems. 2. Frame: Frame support the engine, body and wheels. 3. Power train: Power train transmit the power engine to the car wheels where its contain clutch, transmission, propeller shaft, axles and differential. 4. Car Body 5. Car body accessories: A car body accessory contains the heater, lights, radio, windshield wiper and convertible top raiser.

“Equalizer connection is needed in lap winding armature but not in wave winding “ why ?

The equivalent circuit of a four point – pole dynamo with a simplex winding. The voltage induced in each path is assumed to both to be same and should be if the reluctance of each magnetic path is the same, so that the lines of flux cut by each inductor of each path are the same. However wear of the bearings or deflection of the armature shaft may cause the armature to be closer to some poles and farther from others, thus changing the length of the air gap, and therefore the reluctance of the magnetic circuits of the poles is not identical. This factors cause the voltage in the materials making up the magnetic circuit. These factors cause the voltage in each parallel path differ, and the unequal voltages in turn cause flow of a circulating current through the windings and brushes , undue heating of the armature and waste the power. To reduce the circulating current, points on the winding which should be at the same potentials are brought to the same potentials by connecting

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