im tpn Hw — LIBRARY Michigan State University MSU LIBRARIES ye RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date Stamped below. ~ Pragram of Connections. eT ars No. F. Experiment No. 4. Variations of I and § with varying Inductance and Capacity. References ;~ F. Exp. 5, 6. Object ;— to note the changes in current and phase angle on varying (1) inductance and (2) capacity, letting other comiitions remain constant, also to compare power factor results obtained by theory and from experimental data. Apparatus ;~ l= Ammeter. l- Voltmeter. le Wattmeter. Method;=- (1) To vary the inductance. Measure resistance of inductive coil. Connect apparatus as shown by diagram. Maintain constant frequency, voltage, resistance and capacity. The inductance may be varied by using an ad= justable coil or by putting iron in the circuit. Take readings of amperes in line, line voltage (El), voltage across condenser (Ec), voltage. across inductance (Ei) and wattmeter. (3) To vary the capacity. Connect as shown by Pig. 3 and vary the capacity by means of a dial arranged to give parallel connection of the condensers. Take readings ag in (1). Caution;~ Care must be taken to discharge the con- Ganser before a change of connections is made, as dangerous voltages may exist at a near resonance. Report;~ Notation: r equals resistance of inductive part of circuit L & coefficient of self inductance. Z ® impedance. 6 * tan -1 2*fL « FO r (1) Plot ourves showing variation phase angle and current with each change in inductance using latter vaules as absoissae. Also curves showing variation of pressures across the inductance. Compute power factor (cos ¢) and compare with same of watt meter. The capacity should be varied thru as Wide a range as possible. Readings of current should be taken for each value of capacity, the pressure, frequency, resist= ance and induction being constant. (3) Plot curves between current and phase angle with values of capacity as abscissae, also curve show ing variations of pressure across capacity with variations in Capacity. ae pal cS (S) ean ca eed ane >) a Load a Sy BS) a = a) —{=x)— fe) . Ny Ny \ See : , Fig 5. er LVv.i¥,. 0.4," (ROAD DA Uf i cae iis on a OmnOn Fig 4. DT tied ae hd IST Trae e er Experiment No. 6&. Measurement of Power, Varying the Number of Phases and Type of Connections. Referencesj;- Sheldon and Mason p 47 and 6& Bcott or T connection, 8 & M Pig. 150 and 151. Object;~ To study the different methods of connect~ ing transformers, and what values of voltage and current to measure in order to calculate the power. Apparatus ;~= 1 Wattmeter. e Anmeters. 2 VYoltmeters. Met hod;~ Connect as per diagram in each case. Take all readings for three loads for each connection, | (One load being inductive) Caution;- If the secondary potentiol is high current and potential transformers will be necessary for the instru- ments, and the load must be suitable for that voltage. It is better to use low ratio transformers or use the high voltage - * a ae side for the primary. Report;- Calculate the power input and output in each case and compare with that of the wattmeter. Calculate the power from both the line voltage and the coil voltage. Questions;~- What are the advantages of using A connections? Y connect ions? For what measurements does Pe SEI coos ¢, 3EI cos @, y _S EY coup, Va EI cos $? hy fa mA -——-f) a ei Be Lae eT Te OE Tata e No. 6. Rxperiment No. 6. A Study of Wave Form References 8 and F p 204 Object3- To determine the wave form of an A.C. generator by determining the instantaneous E.M.Fs. at intervals of 10 electrical degrees. Apparatus ;~ 1 D.C. Voltmeter 1 A.C. ° i Contact maker 1 Telephone receiver or galvanometer 1 nesistance coil 1 Double throw switch. 98 Ft. #50 Advance R. vire. Method;- rmMershon Connect according to diagram. Keep V, constant absolutely. Beginning with the sliding contact of the resistance near point A determine which position of the Double Throw switch puts the E MF of the battery in opposition to that of the machine. Adjust the resistance until a balance is obtained i.e. until the T.R. ia silent. Read the voltage Vo for positions of the contact 10 electrical degrees apart. The double throw switch must be reversed when the voltage passes through sero. Report;- Draw a diagram of the connections used. Describe the expt. Plot a curve with volts as ordinates and degrees as abscissa and draw the curve thru all the points. Z OW BP EieTy Leg dof sueyrauyor we ated me oO ats vedo GS eee | Expcriment No. 7, Efficiency Test of a Transformer. References;~ Swenson and FPrankenfield, p79. Object;—- Zo determine the efficiency of a transformer under various loads and to study its losses. Apparatus j= 1 Ammeter. 1 Voltmet eT. 1 Wattmeter. Method of lossesj;=- Determine the ratio of trans formation. Measure the resistance of both coils; that of the primary by the drop in potential method, and that of the secondary by an acme testing set. Connect as shown in the diagram. Keep the frequency constant by means of a tachtometer on the generator and vary the voltage by means of a rheoasatat in the generator field. For each voltage take simultaneous readings of watt~ meter, ammeter and voltmeter and also of the tachtometer (or frequency). Caution; Insulate, or beware of the secondary leads as they are of high potential. Report;- The wattmeter reading is the core loss of the transformer and the ammeter reading is the exciting current. The I°R loss is very small when the secondary is open circuited and may be neglected. Hence the wattmeter reading at normal voltage is very nearly the core loss for all loads at normal voltage. Use this core loss in the following formla and calculate the efficiency at 1/4, 1/2, 3/4, 1, 1¢ and 1} times rated load. Plot curves for ccre loss and exciting current with A.C. volts as abscissa. Plot a curve of efficiency with load as abscissa. Effioienay = e4 Core loss Wo = output at various fractions of rated load. aoe ee YY 7 4 = Current Supply Opp os/tion ee ymer Jest Vi) aa SF Conrections Experiment Lan <3 Rxperiment No. 8. Heat Test of Transformers. References;~ K. Vol. 2 par 492. G. EK. Inst. Bk. $8317 p. 30, Object;- To determine the temperature rise ina transformer under continuous full rated load conditions. Apparatus;- 1 A.C. Ammeter. 1 D.C. Voltmeter. Met hod;= "Opposition® or *Motor Generator® method. Measure the resistance of the high tension windings before and after the test, i.e. cold and hot. Test each transformer for polarity in this manner. Put a D.0. voltmeter across the low tension side and observe the direction of the kick of the voltmeter needle. If the transformers have the game polarity connect them as shown in the diagram. Apply an A.C. voltage to the low tension windings approximately equal to normal low tension voltage. By this method the voltage supplies all the 4ron and other losses, and as the two high tension coils are connected in opposition, no current will flow. Send full rated load A. ©. current through the high tension windings. This will supply the full load current and copper losses. The low tension coils receive just a little magnetizing current. Take temperature of room. Report;= Caloulate rise in temperature by equation; (238 + t) (@el) = degrees C where R. is initial resistance at room temperature, t degrees C, and Q is final resistance, Plot curve of heat test, using degrees 0 as ordinates and hours as abscissae. wote: By thie method a full load test mey be run on large transformers with no loss of energy except that due to inefficiency of the set. Lot |e a JMG. Set 7a Petermine Core Loss of Gesreratoy Diagram of Conzections Experiment No. 2. Experiment No. 9. petermination of Core Loss of an A. C. Generator. Referencesj;- K 2 p 129. Obdject;—- To determine the core loss of an A.C. generator with different voltages. Apparatus ;- l- Voltmeter, a~ Ammeters. le Potential Transformer. Methodj=- Connect apparatus as per diagram. (1). To measure core loss of motor plus friction loss of set, run the motoregenerator set at normal speed without field of alternator excited. fgead watta input to ammature of D.C. motor, Note;- To obtain accurate results, the capacity of the motor should nearly equal core loss of motor plus friction loss of set. (2). To measure core loss of set plus friction loss of set. Run set at normal speed. Keep speed constant by vary~ ing voltage on ammature of motor by means of a booster set connected in series with the D.C. supply. Keep excitation of motor constant to maintain its core loss constant. Q Excite field of alternator and vary voltage from , 25% below to 25% above normal. Take simultaneous readings / of input to mot®? and K.M.F. of alternator. This gives total / ogre and friction loss for each voltage. | } ; (3). Measure resistance of motor armature to get ite I?R loss. Report;- Compute the constant losses (Wc) of the motor generator set consisting of friction losses plus core loss of motor by the formula: Wo * I, Bq - I® Ra. I, and E, are readings from (1) and (3). | The core loss for each voltage of alternator /is obtained by formula, | Watts core loss = I, E, = We - 4 Ra I, and Eg are readings from (2) and (3) | Plot a curve of voltage and core loss uging voltage : as abscissae. YA SNES aw ies (a7 se oa EMM Fibpdes: Oa yarn ox Cormections / IT takes ent NW. (a. Experiment No. 10. Synchronization and Parallel Operation of A.C. Machines. Reforences;~ To synchronize two alternators and study their behaviour when operated in paraliel. Apparatus ;- None. Method;=- Alternators to run in parallel must be similar in wave form, voltage, frequency and phase relation. (1). There are two methods of synchronising A.6. generators: by using lamps , as shown by diagram (a) which indicates the time to connect the two machines together by their brightness and (b) by their darkness. mis exact time is when the algebraic sum of the voltages of the, two machines is zero, or when they are bucking each other as . shown by their curves of E.M.F. : \ : Bring one machine up to normal speed and voltage and adjust speed of second till lamps go out and brighten slowly. Test voltage of each machine to see that they are sinilar within a few volts. With synchronizing switches in pasition Close them at the centre of a long dark period (a) or a long light period (b). (3). A synchronous motor may be started by eyed running it up to speed (a) as an induction motor and; then CGlosing the field switch or (b) by some prime movey and then synchronizing. | ! (3). Rotary convertersare similarly started and operated, and in addition may be started from the D.C. end. Experiment No. ll. Efficiency Test of and A.C. Generator. References;=- K 2p 129. Object;- To determine the losses of an A.C. generator under all conditions of loading, and to use these losses in caloulating the efficienoy of the machine, Method;= To determine the losses. The machine is to be driven by a small motor to determine its friction, windage and iron losses. Friction and iron losses should be measured by driving the alternator at rated speed with field excited, by a motor of which the efficiency is known for all values of input. The motor should be direct coupled if possi- ble so that no allowance need be made for belt friction. The capacity of the motor should be not greater than that sufficient to run the alternator an open cirouit with field fully excited, for the motor on full to overload its effi- ciency is more nearly constant. Input to motor times its efficiency equals watts lost in friction, windage and drons. The 17R losses require a measurement of resistance of windings. The armature resistance loss = ni. R, where n= no. of phases. The field resistance loss = Ete where E is voltage of exciting current. | Report;~= Plot efficiency curves from half to one, and to one and one half full load. | Having determined the losses, the ef ficiency may be found from the following formula. Ea Wo (output 1 o+n a+ Be + Stray power losses. PT Ie 4 BIG add oe Fig ¢. Ne —{A) Le ee « oy eras ae rs Piagrats of Canaechons far lta TE aE Mo. /2. Experiment No. 1é. No Load Characteristics of an A.C. Generator. ptferences. Karapetoff l- p 3548. Obdject;= To determine the voltage drop and the synchronous impedance with full load current. Apraratus;= 1 Voltmeter. 1 Ammeter. \ 1 Potential transformer. 1 Current ® Method (a) First connect as in Fig. 1 and read voltage across one phase and amperes field current, varying the fidid current, (bd) Oonnect as in Fig. 8, i.e. short circuiting one phase through a ourrent transformer with an ammeter. Read armature amperes and field amperes up to lt times full load. (c) Do the same as in (b) but short oirauit both phases. 7 (d) Leave the field cirouit closed(being separately excited) and stop the machine. Observe the action of the armature current. | Note; yt is well to take readings increasing the field current and also decreasing it. The average will | Gliminate the effect of residual magnetisn. | , Reportj;= Plot results of (a) (b) and (co) with field amperes as absoissa. From curves (b) and (c) find the field current necessary when full load current flows thru the arma- ture. ey en ee ee @) te Measurement of Fower Piagvam of Connections iia Experiment (ya /J. Experiment No. 13. Test of an Induction Motor.. The Circle Diagram. Referencesf{- K 2 p 167-172. 8 & M Art. 84=5 Objeot3= To determine the preformance of an induction motor. Apparatus ;-~ l- Ammeter. l= Voltmeter, l- Wattmeter. wethod;- (1). Applying to a two phase motor. Measure resistance of stator windings per phase. Connect to a two phase circuit as in Fig. 1. Run motor idls and measure current ( exciter current per phase), vcltage, and watts input per phase. I, is found by lockingthe rotor and putting full load current into motor at reduced voltage, afterwards correcting to current at normal voltage. Having determined Io and I, the point K may be found. | . (2). Applying to three phase. Connect as in Pig. 2 and proceed as above. Report;= Plot curves shown on p 238 8 8 N. Question;- Explain why the point I, does not coincide with K. Experiment No. 14. Hunting of Synchronous Converters. References;- cC.P.8. Lectures p 120. Object;~ (a) To logate the machine at fault and determine the cause. (b) To remedy the defect. Note;~ Since tiie 125 V rotary hunts but may be oured by putting inductance in series with one phase adjust this inductsarce in series with one phase adjust this ine ductance so that machine will still hunt but not enough to throw it out of step. Method;= With the two rotaries running from alt. Count the beats (including intermissions) and the inter= | missions per min and get the two frequencies ( = beats <= intermissions) Do they correspond with any known speed in the oystent Compare ammeters with Station ammeter. 1.0. «JO rotaries hunt with each other, or with the generator? Vary the field excitation and note effect.. Kitner connect D.C. sides in parallel or ‘separate them and note effect. Run either one alone and see if it hunts. - yt the hunting is magnetio varying field may stop it, or putting on a flywheel or belt. f If they hunt against each other connect foul rings together and watch brushes for sparking. Try pole pieces or short cirouiting rings. Reportj= Write a discussion of the events which ccocured. laws oS 5 ia PEA Tes N r , aed, Ns iS iT ML Eee WLM Lad % ‘ : : fo : P ) e S ow $f | Co 7 OeWa sa ios eee Aas @ ae Tne eeeicee aM ah wey COLI Set 4 27 , baa | ao ¢:8 7 eed Experinent No. 15. The Influence of Fxoitation of a Synchronous Motor on the Power Factor. References Sheldon and Mason Art. 965. Objectj;~= To study the effect of varying the excitation of a synchronous motor. Apparatus j= 1 4.0. Aureter. 1 D.c. " 1 A.C. Voltmeter. 1 Current Transformer. Methodj;- Connect as per diafram and read the amperes per phase for different values of exciting current for 0, $ and full rated load. Keep the frequency and A.C. voltage constant and have all control in the Blectrical Laboratory. Reportj=- Plot a curve for each load, plotting amperes, armature current as ordinates and amperes field Current ag absoissa. Discuss the significance of the curves. B a @ wi ies Of frerency a of Fr Cea a Aetastea Beas ye ka Fxperim ent Vie a | Rxparimsnt Wo. 16, Efficiency Test of a Rotary Converter. References;=- F232 yp 368. Object;- To determine the efficiency of a rotary converter under various loads, and power factors but with the same frequency and A.C. voltage. Apoaratus3- 1 A.C. Ammeter. 1 A.G. Yoltmeter. 2 D.C. Aumeter, 1 D.C. Voltmeter. Method;~ (a) Connect as per diagram and read imput and output at from $ to 1$ times the full rated load, with fleld rheostat adjusted for unity power factor. (b>) Same at .80 power factor (lagging) . (c) Same at .80 * " (leading). Keep a constant A.C. Voltage and frequency throughout. Reportj=- Plot curves of efficiency with load as abscissa. 8 What effect does power factor have on efficiencyt Disouss the difference between corresponding | f A.C. and D.C. voltages. B.'s 5 | i aa ae EY Ls of Running Rotary Pa verter %o eler mine 175 aT Tare | F199 vom of ee ae Experiment No. 17 Experiment No. 1?. Capacity Test of a Rotary Converter. References;~ S. and M. p 291. Objects= To study the action of a given rotary converter when run as a single phase, two phase and three phase converter and D.C. generator respectively, asa regards the maximum output obtainable and the limiting condition (sparking or heating) in each case. Note;=