DC Machine Syllabus Diploma in Electrical Engineering, Regulation 2010, Short Suggestion, Exam Dates, Exam Routine, Question Out, Book list with code

  • To develop knowledge and skill on cell and battery and the process of electroplating.
  • To provide understanding on DC generator.
  • To develop knowledge and skill on DC motor.
  • To provide knowledge on characteristics of DC generator.
  • To develop knowledge on electric traction.

 

SHORT DESCRIPTION

 

Cell and battery : Principle, construction, uses and maintenance; Electroplating; DC Generator : Principle, construction, winding, losses, efficiency, characteristics and parallel operation; DC Motor : Principle, construction, torque/speed curves, efficiency, speed control, starting and tests; Electric traction.

 

DETAIL DESCRIPTION

 

Theory :

 

CELL AND BATTERY

  • Understand the construction of different types of cell and battery.
    • Describe the construction of dry cell and its chemical reaction.
    • Describe the construction of alkaline batteries.
    • Describe the construction of lead acid battery and its chemical reaction.
  • Understand the features of battery charging.
    • Name the types of battery charging system.
    • Describe the charging procedure of battery by 220-230VAC source.
    • Describe the procedure of slow charging.
    • Describe the procedure of quick charging.
    • Describe the procedure of preparing electrolyte.
    • Describe the construction of dry charged battery.
    • Explain the charging procedure of sulfated battery.
    • Describe the process of charging more than one battery at a time.
  • Understand the efficiency and testing of batteries.
    • Describe the internal resistance and efficiency of a battery.
    • Explain ampere – hour (A – H) rating of battery.
    • Solve problems related with internal resistance affecting terminal voltage.
    • List at least three factors on which the capacity of a battery depends.
    • Describe the procedures of testing a storage battery by hydrometer, voltmeter and ammeter.
    • State the maintenance and routine inspection procedure of a battery.
  • Understand the process of electroplating.
    • State fundamental principles of electroplating.
    • State Faraday`s laws of electrolysis.
    • Describe briefly the process of extraction and refining of metals.
    • State a simple method of producing copper plating upon a carbon brush.
    • Describe electro-deposition process.
    • Identify power supply for electrolytic process adopted in electroplating.

DC GENERATOR

  • Understand the working principle of DC generator.
    • State generator principle.
    • Mention the conditions for generation of emf in a single coil generator.
    • Describe the constructional details of a DC generator.
    • Explain the functions of different parts/components of a DC generator.
    • Sketch the magnetic circuit of a DC generator.
    • Express the deduction of the emf equation of a DC generator.
    • List the various losses in a DC generator.
    • Explain power stages of a DC generator.
    • Express the condition for maximum efficiency.
    • Solve problems relating to DC generator.
  • Understand the principle of winding of DC generator.
    • Define the terms pole pitch, coil pitch, front pitch, back pitch, average pitch and commutation pitch.
    • Describe lap and wave winding.
    • Sketch the developed diagram of simplex and duplex (lap and wave) winding.
    • Name at least four major differences between the lap and wave windings.
  • Understand the armature reaction and commutation of DC generator.
    • Explain armature reaction.
    • Describe the effect of armature reaction.
    • State de-magnetizing and cross magnetizing.
    • Explain the action of commutation.
    • Identify the value of reactance voltage.
    • Express the deduction of Hobart’s formula for coefficient of self-induction.
    • Mnetion the methods of improving commutation.
    • Explain the necessity of interpoles and compensating winding.
    • State the need for equalizing bar and rings.
  • Understand the principle of excitation.
    • Explain the excitation of DC generator.
    • Explain the necessity of excitation.
    • Identify self excited and separately excited generator.
    • Describe the condition for excitation.
  • Understand the characteristics of DC generator.
    • Explain the process of building up voltage of shunt generator.
    • State the critical resistance and critical speed for shunt generator.
    • Plot the terminal voltage Vs load current characteristic curve of shunt generator.
    • State the reasons for decreasing terminal voltage with increasing load.
    • Solve related problems relating to shunt generator.
    • Plot the internal and external characteristic curve of DC shunt, series and compound generator.
  • Understand the concept of voltage regulation and efficiency of a DC generator.
    • Explain the formula for voltage regulation of a DC generator.
    • Discuss the importance of voltage regulation of DC generator.
    • Solve problems relating to voltage regulation of DC generator.
    • Express the formula for efficiency of a DC generator.
    • Solve problems relating to efficiency of a DC generator.
  • Understand the principle of parallel operation of DC generator.
    • State the need for parallel operation of DC generator (shunt, series and compound)
    • List the conditions for parallel operation of DC generator.
    • Discuss the condition of sharing loads in DC generators operating in parallel.
    • Draw the circuit diagram of two long shunt compound generators connected in parallel.
    • Calculate the load shared by individual machine at the time of parallel operation.

DC MOTOR

  • Understand the working principle of DC motor.
    • Explain the working principle of DC motor.
    • Explain generator action of motor.
    • Explain the significance of the back emf.
    • Express the deduction of voltage equation of motor.
    • Define the term torque (mentioning its unit), running torque and break down torque.
    • Express the deduction of equation for speed of DC motor (for series and shunt motors).
    • Plot the torque/speed curve of series, shunt and compound motors.
  • Understand losses and efficiency.
    • State the losses in DC motor.
    • Calculate the efficiency of DC motor from a given data.
    • Explain the power stages of DC motor.
  • Understand the starting methods and speed control of DC motor.
    • Describe the factors controlling the speed of DC motor.
    • Discuss the general methods of speed control of DC motor.
    • Explain speed control of shunt, series and compound motor.
    • Mention the merits and demerits of rehostat control method.
    • Describe electric braking of shunt and series motor.
    • Explain the necessity of a starter for DC motor.
    • Describe three point and four point starter used in DC motor.
    • Explain the heating and cooling of DC machine.
    • Explain brake test and no-load test of DC motor.

ELECTRIC TRACTION

  • Understand the system of electric traction.
    • State the meaning of electric traction.
    • Describe the system of electric traction.
    • List the characteristics of an ideal traction system.
    • Describe the feeding and distribution system for tram ways and trolley buses.
    • Explain the diesel electric drive, battery electric drive and electric drive of locomotives.
    • Explain the working principle of tram ways and trolley buses.
    • Explain the DC system used in traction.
    • Explain the reasons for using DC series motor for traction purpose.
  • Understand the concept of speed control of traction motors.
    • Explain different methods of speed control of DC traction motors.
    • Explain starting methods and speed control of 1-phase AC series motor.
    • Explain starting method of 3-phase induction motor used in traction.
    • Explain speed control system of 3-phase induction motor used in traction.
    • Explain different braking systems.
    • Explain the systems of supplying power in electric traction.

Practical :

  • Charge a lead acid battery.
    • Sketch the connection diagram for constant potential/Constant current method of charging.
    • Identify the equipment and materials required for charging a lead acid battery.
    • Record the readings by measuring the terminal voltage of the discharged battery and specific gravity of electrolytes.
    • Connect the positive and negative terminal of the battery to the positive and negative terminals of the charger respectively.
    • Set the charging voltage and switch on the charger.
    • Record the readings by measuring the specific gravity of electrolyte and the terminal voltage of the battery.
  • Measure the internal resistance of a battery.
    • Sketch necessary circuit diagram.
    • Connect a resistance (known value) with the battery.
    • Record the readings by measuring the voltage and current of the battery.
    • Calculate the internal resistance using the formula.

I =

 

 

 

  • Test of Battery
    • Discharge test

 

  • Dis-assemble and re-assemble the parts of a DC generator/ DC motor.
    • Select the necessary tools required for dis-assembling and re-assembling the parts of DC generator/ DC motor.
    • Identify at least ten main parts of the generator/motor.
    • Sketch at least ten main parts of the generator/motor.
    • Re-assemble the parts of the generator/motor.
    • Connect the generator/motor to the proper power source.
    • Start the generator/motor.
  • Develop a 4 poles, 24 slots, double layer lap winding (simplex & duplex) of a DC generator.
    • Select pole pitch, back pitch, front pitch and commutator pitch for the generator.
    • Sketch the developed winding diagram (simplex and duplex) showing the position of carbon brushes.
    • Select the coil turns, coil number and coil grouping for the winding.
    • Select the sizes and types of wires required for the winding.
    • Construct required number of coils.
    • Insert the coils into the slot using the proper insulation.
    • Connect the coils in proper way.
    • Test the winding step by step.
    • Note down the observations.
  • Develop a 4 poles, 16 slots, double layer wave winding (simplex & duplex) of a DC generator.
    • Identify pole pitch, back pitch, front pitch, commutator pitch.
    • Sketch the developed winding diagram (simplex & duplex) showing the position of carbon brushes.
    • Determine the number of turns required on the basis of coil grouping and layer of winding.
    • Determine the size and type of wires required for the winding.
    • Perform winding.
  • Determine generated emf of a DC shunt generator.
    • Sketch the required diagram of the shunt generator.
    • Set the experiment as per diagram.
    • Start the generating set and build up the voltage.
    • Measure the developed emf by starting the generator.
    • Record the required data.
    • Plot the If versus Vg curve from the data.

 

  • Plot the VL– IL characteristic curves of a shunt generator.
    • Sketch the required diagram for the experiment.
    • List the materials, meters and equipment required for the experiment.
    • Connect all the meters and equipment as per diagram.
    • Record the necessary readings from the meters.
    • Plot the VL– IL curve from the data.

 

  • Plot the VL – IL characteristic curve of a series generator.
    • Sketch the required diagram for the experiment.
    • List the required instruments & materials.
    • Connect all the meters and equipment as per diagram.
    • Record the necessary readings from the meters.
    • Plot the VL-IL curve from the data.
  • Plot the VL– IL characteristic curve of a compound generator.

9.1       Sketch the required diagram for the experiment.

9.2       List the required instruments & materials.

9.3       Connect all the meters and equipment as per diagram.

9.4       Record the necessary readings from the meters.

9.5       Plot the VL-IL curve from the data.

  • Run the two DC shunt generators in parallel.
    • Sketch the required diagram.
    • List tools and materials required for the experiment.
    • Connect the machines as per diagram.
    • Check connection and start incoming machine.
    • Observe the voltage of incoming machine and compare this with bus bar voltage.
    • Switch on the incoming machine with the bus bar when it is ready.
  • Run a small size DC shunt motor and control its speed.
    • Sketch the required diagram.
    • List tools and materials required.
    • Connect the machine as per diagram.
    • Start the machine.
    • Regulate speed of the motor.
  • Start a DC shunt motor by a three-point starter.
    • Sketch the required diagram for the experiment.
    • List tools, equipment and materials required.
    • Connect the machine as per diagram.
    • Start the motor with the help of three point starter.

 

 

 

  • Start a DC compound motor by a four point starter.
    • Sketch the required diagram for the experiment.
    • List the tools and materials required.
    • Connect the machine as per diagram.
    • Start the motor with the help of four point starter.

 

  • DC Machines

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