EC To expose the students to the basic operations of electrical machines and help them to develop experimental skills. To study the concepts, performance characteristics, time and frequency response of linear systems. To study the effects of controllers. Open circuit and load characteristics of separately excited and self excited D.

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Open circuit and load characteristics of separately excited D. Open circuit and load characteristics of self excited D. Load test on D. Swinburnes test on D. Shunt motor and Speed control of D. Load test on single phase transformer 6.

Open circuit and short circuit test on single phase transformer 7. Load test on three phase induction motor. No load and blocked rotor tests on three phase induction motor Determination of equivalent circuit parameters 9. Transfer Function of separately excited D. Transfer Function of armature and Field Controller D. Motor Study of D. Digital simulation of linear systems. Design of Lead and Lag compensator. You have to be very careful.

You must clearly know the supply system to your worktable in particular and the entire laboratory in general. You have to submit your records and have to show the day's experiment's circuit diagram and get it attested.

You have to occupy the respective worktable of the machine. Collect required meters etc as per indent slip. There should not be any loose connection. Thoroughly check the connections and choose correct rheostat positions before starting. Also keep all meters in horizontal position to read the readings conveniently. Call staff to check the connections.

First check for the direction of rotation in case of machines and deflection of meters. Note down the multiplication factor of any meter immediately. Arrest gently the vibrations and take the reading. Show model calculations for any one set of readings only. Draw the necessary graphs. Write the result. Show it to the staff for getting signature.

Write neatly; Draw circuit diagrams neatly and label correctly. Complete the record before you come for next lab class. After the experiment inform the technician so that supply to the worktable can be switched off. Write the answer for all the discussion questions in the observation note.

If not, marks for concerned observation will be proportionately reduced. They will have to repeat the lab course in subsequent semester after paying prescribed fee. Know where the various live points are situated in your table. The same must be done when there is a power breakdown when the experiment is being carried out. Open Circuit Characteristics O. C Separately Excited Shunt Generator. AIM: To determine the no load magnetization or open circuit characteristic of a separately excited dc shunt generator, compare it with self excited one, and hence to deduce the O.

To determine the critical field resistance and critical speed. To determine the external and internal load characteristics of the separately excited DC shunt generator by actually loading the machine. C In any D. C generator generated emf is directly proportional to the exciting field current i. C shows the relation between the no-load generated emf in the armature, 'Eo' and the field or exciting current 'If at a given fixed speed.

It should be noted that OCC for a higher speed would be above this curve and for a lower speed, below it. If there were no armature reaction and armature voltage drop, then this voltage would have remained constant as shown in model graph by the dotted horizontal line I. But when the generator is loaded, the voltage falls due to these two causes, thereby giving slightly drooping characteristics.

If we subtract from Eo, the value of voltage drop due to armature reaction for different loads, then we get the value of E, the emf actually induced in the armature under load conditions. If we subtract from E the armature drop laRa, we get terminal voltage V. The reverse procedure may also be adopted to obtain Internal characteristic ie adding laRa to V.

Comparison of self and separately excited generator gen characteristics: Since the field current depends on terminal voltage in self excited generator, its load characteristics would be more drooping than the other one. Name Plate Details: D. Test: 1. Connections are given as shown in the circuit diagram.

After the connections are checked, Keeping R1 minimum resistance position and R2 in maximum resistance position, the supply switch is closed. The motor is started with the help of a dc 3 point starter. The field rheostat R1 of the motor is adjusted to make it run at the rated speed. Then SPST switch is closed. By varying the field rheostat R2 in the field circuit of generator, different values of generated emf Eo and field current If are noted from voltmeter and ammeter and tabulated.

Load Test: 1. Keeping the generator side DPST open, the field rheostat in the generator side is adjusted for the rated voltage of the generator which is seen in the voltmeter. Now the DPST switch is closed and the resistive load is put up on the generator step by step.

The terminal voltage, armature and load current values are noted down for each step from the respective meters. Note that while taking each set of readings, the field current is maintained constant as that for rated voltage [because due to heating, shunt field resistance is increased] Measurement of Ra and Rsh : 1. Keep the resistances in maximum position and close the supply switch and take Minimum three readings. Load Test: Speed RPM; Sl. Draw Rc line, such that it is tangent to the initial portion of O.

C E0 N So, for different speeds, O. N1 N2. To find critical field resistance: From the origin a tangent is drawn to OCC at the linear portion. The slope of the tangent will give the critical field resistance. Calculate E0 at different speeds and draw O. External characteristic is drawn taking load current 'IL' along x axis and terminal voltage 'V' along yaxis.

Internal characteristic is drawn by adding laRa drop to external characteristic curve, 'la' along x axis and 'E' along y axis. What is the principle of operation of DC generator? Where the field winding is placed in DC generator? List out the factors involved in voltage build up of a DC shunt generator.

Explain briefly the function of a commutator in a DC machine. Can commutator action be performed by a solid state device. Define and explain critical field circuit resistance and critical speed of DC shunt generator.

What is armature reaction? What are the applications of DC shunt generator? Kothari Electrical Machines. Albert E. Murugash Kumar D. No : Date: 2. C Shunt Generator.

AIM: To determine the no load magnetization or open circuit characteristic of self excited dc shunt generator for various speed, and rpm.

To determine the external and internal load characteristics of the self excited DC shunt generator by actually loading the machine. By varying the field rheostat R2 in the generator side, different values of generated emf Eo and field current If are noted from voltmeter and ammeter and tabulated. Measurement of Rsh of Generator :. Model Calculation: O. No Name of the apparatus 1. Current carrying armature conductors cause additional magnetic field to be set up. Interaction of this magnetic field with the main magnetic field set up by the stator poles cause a force to be developed around the conductors.


EC2259 LAB Manual

This lab manual can be used as instructional book for students, staff and instructors to assist in performing and understanding the experiments. In the manual, experiments as per syllabus are described. Acknowledgement We would like to express our profound gratitude and deep regards to the support offered by the Chairman Shri. We also take this opportunity to express a deep sense of gratitude to our Principal Dr. Karthikeyan, M.




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