DEPARTMENT OF ELECTRICAL AND ELECTRONICS
AARUPADAI VEEDU INSTITUTE OF TECHNOLOGY,
Old Mahabalipuram Road, Paiyanoor-603104, Kanchipuram (dt),
VINAYAKA MISSIONS UNIVERSITY
; Name of the Laboratory : ELECTRICAL MACHINES-II
; Year/Semester : II/IV
; Branch : EEE
This Laboratory book in Electrical Machines – II has been revised in order to be up to date with
Curriculum changes, laboratory equipment upgrading and the latest circuit simulation.
Every effort has been made to correct all the known errors, but nobody is perfect,
if you find any additional errors or anything else you think is an error, Please contact the
HOD/EEE at email@example.com
The Authors thanked all the staff members from the department for their valuable
Suggestion and contribution
Department of EEE
TABLE OF CONTENTS
Safety Rules and operating Procedures I
Laboratory Safety information II
Guidelines for Laboratory Notebook III
Troubleshooting Hints IV Sl.No Experiment Name Page No 1. Regulation of 3-phase alternator by EMF and MMF 1
2. Regulation of 3-phase alternator by ZPF and ASA
3. Slip test on 3-phase alternator. 4. Load characteristics of 3-phase alternator by bus bar
5. V and inverted V curve of synchronous motors. 6. Load test on 3-phase induction motor. 7. No load and blocked rotor test on 3-phase induction
8. Study of Synchronous induction motor. 9. Study of induction motor starters. 10. Separation of losses in three-phase induction motor. 11. Load test on 1-phase induction motor. 12. Equivalent circuit and pre–determination of performance
characteristics of single-phase induction motor.
1. SAFETY is of paramount importance in the Electrical Laboratories.
2.Electricity NEVER EXECUSES careless persons. So, exercise enough care and attention in handling electrical equipment and follow safety practices in the laboratory. (Electricity is a good servant but a bad master).
3.Avoid direct contact with any voltage source and power line voltages. (Otherwise, any such contact may subject you to electrical shock)
4.Wear rubber-soled shoes. (To insulate you from earth so that even if you accidentally contact a live point, current will not flow through your body to earth and hence you will be protected from electrical
5.Wear laboratory-coat and avoid loose clothing. (Loose clothing may get caught on an equipment/instrument and this may lead to an accident particularly if the equipment happens to be a rotating machine)
6.Girl students should have their hair tucked under their coat or have it in a knot. 7.Do not wear any metallic rings, bangles, bracelets, wristwatches and neck chains. (When you move your hand/body, such conducting items may create a short circuit or may touch a live point and thereby subject you to electrical shock)
8.Be certain that your hands are dry and that you are not standing on wet floor. (Wet parts of the body reduce the contact resistance thereby increasing the severity of the shock)
9.Ensure that the power is OFF before you start connecting up the circuit.(Otherwise you will be touching the live parts in the circuit)
10.Get your circuit diagram approved by the staff member and connect up the circuit strictly as per the approved circuit diagram.
11.Check power chords for any sign of damage and be certain that the chords use safety plugs and do not
defeat the safety feature of these plugs by using ungrounded plugs.
12.When using connection leads, check for any insulation damage in the leads and avoid such defective leads.
13.Do not defeat any safety devices such as fuse or circuit breaker by shorting across it. Safety devices
protect YOU and your equipment.
14.Switch on the power to your circuit and equipment only after getting them checked up and approved by the staff member.
15.Take the measurement with one hand in your pocket. (To avoid shock in case you accidentally touch two points at different potentials with your two hands)
16.Do not make any change in the connection without the approval of the staff member. 17.In case you notice any abnormal condition in your circuit ( like insulation heating up, resistor heating up etc ), switch off the power to your circuit immediately and inform the staff member. 18.Keep hot soldering iron in the holder when not in use.
19.After completing the experiment show your readings to the staff member and switch off the power to your circuit after getting approval from the staff member.
20.While performing load-tests in the Electrical Machines Laboratory using the brake-drums:
i. Avoid the brake-drum from getting too hot by putting just enough water into the brake-
drum at intervals; use the plastic bottle with a nozzle (available in the laboratory ) to pour
the water.(When the drum gets too hot, it will burn out the braking belts)
ii. Do not stand in front of the brake-drum when the supply to the load-test circuit is switched
off. (Otherwise, the hot water in the brake-drum will splash out on you)
iii. After completing the load-test, suck out the water in the brake-drum using the plastic
bottle with nozzle and then dry off the drum with a spongewhich is available in the
laboratory.(The water, if allowed to remain in the brake-drum, will corrode it) 21.Determine the correct rating of the fuse/s to be connected in the circuit after understanding correctly the type of the experiment to be performed: no-load test or full-load test, the maximum current expected in the circuit and accordingly use that fuse-rating.(While an over-rated fuse will damage the equipment and other instruments like ammeters and watt-meters in case of over load, an under-rated fuse may not allow one even to start the experiment)
22. At the time of starting a motor, the ammeter connected in the armature circuit overshoots, as the starting current is around 5 times the full load rating of the motor. Moving coil ammeters being very delicate, may get damaged due to high starting current. A switch has been provided on such meters to disconnect the moving coil of the meter during starting. This switch should be closed after the motor attains full speed. Moving iron ammeters and current coils of wattmeters are not so delicate and hence these can stand short time overload due to high starting current. No such switch is therefore provided on these meters. Moving iron meters are cheaper and more rugged compared to moving coil meters. Moving iron meters can be used for both a.c. and d.c. measurement. Moving coil instruments are however more sensitive and more accurate as compared to their moving iron counterparts and these can be used for d.c. measurements only. Good features of moving coil instruments are not of much consequence for you as other sources of errors in the experiments are many times more than those caused by these meters. 23. Some students have been found to damage meters by mishandling in the following ways:
i. Keeping unnecessary material like books, lab records, unused meters etc. causing meters to
fall down the table.
ii. Putting pressure on the meter (specially glass) while making connections or while talking
or listening somebody.
STUDENTS ARE STRICTLY WARNED THAT FULL COST OF THE METER WILL BE
RECOVERED FROM THE INDIVIDUAL WHO HAS DAMAGED IT IN SUCH A
Copy these rules in your Lab Record. Observe these yourself and help your friends to observe..
I have read and understand these rules and procedures. I agree to abide by these rules and procedures at all times while using these facilities. I understand that failure to follow these rules and procedures will result in my immediate dismissal from the laboratory and additional disciplinary action may be taken.
Signature Date Lab
GUIDELINES FOR LABORATORY NOTEBOOK
The laboratory notebook is a record of all work pertaining to the experiment. This record should be sufficiently complete so that you or anyone else of similar technical background can duplicate the experiment and data by simply following your laboratory notebook. Record everything directly into the notebook during the experiment. Do not use scratch paper for recording data. Do not trust your memory to fill in the details at a later time.
Organization in your notebook is important. Descriptive headings should be used to separate and identify the various parts of the experiment. Record data in chronological order. A neat, organized and complete record of an experiment is just as important as the experimental work.
The experiment identification (number) should be at the top
of each page.Your name and date should be at the top of the first page of each day's experimental work.
A brief but complete statement of what you intend to find out
or verify in the experiment should be at the beginning of each experiment 3.Diagram:
A circuit diagram should be drawn and labeled so that the
actual experiment circuitry could be easily duplicated at any time in the future.
Be especially careful to record all circuit changes made during the experiment. 4.Equipment List:
List those items of equipment which have a direct effect on
the accuracy of the data. It may be necessary later to locate specific items of equipment for rechecks if discrepancies develop in the results.
In general, lengthy explanations of procedures are
unnecessary. Be brief. Short commentaries along side the corresponding data may be used. Keep in mind the fact that the experiment must be reproducible from the information given in your notebook.
Think carefully about what data is required and prepare
data tables. Record instrument readings directly. Do not use calculated results in place of direct data; however, calculated results may be recorded in the same table with the direct data. Data tables should be clearly identified and each data column labeled and headed by the proper units of measure.
Not always necessary but equations and sample calculations
are often given to illustrate the treatment of the experimental data in obtaining the
Graphs are used to present large amounts of data in a concise
visual form. Data to be presented in graphical form should be plotted in the laboratory so that any questionable data points can be checked while the experiment is still set up. The grid lines in the notebook can be used for most graphs. If special graph paper is required, affix the graph permanently into the notebook. Give all graphs a short descriptive title. Label and scale the axes. Use units of measure. Label each curve if more than one on a graph.
The results should be presented in a form which makes the
interpretation easy. Large amounts of numerical results are generally presented in graphical form. Tables are generally used for small amounts of results. Theoretical and experimental results should be on the same graph or arrange in the same table in a way for easy correlation of these results.
This is your interpretation of the results of the experiment as
an engineer. Be brief and specific. Give reasons for important discrepancies.
TROUBLE SHOOTING HINTS
1. Be Sure that the power is turned ON
2. Be sure the ground connections are common
3. Be sure the circuit you build is identical to your circuit diagram (Do a node by node check) 4. Be sure that the supply voltages are correct
5. Be sure that the equipment is set up correctly and you are measuring the correct parameters 6. If steps I through 5 are correct then you probably have used a component with the wrong
value or one that doesn’t work. It is also possible that the equipment does not work
(although this is not probable0 or the protoboard you are using may have some unwanted
paths between nodes. To find your problem you must trace through the voltages in your
circuit node by node and compare the signal you expect to have. Then if they are different
use your engineering judgment to decide what is causing the different or ask your lab