* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Electrical Engineering and Control System Lab
Survey
Document related concepts
Josephson voltage standard wikipedia , lookup
Standing wave ratio wikipedia , lookup
Integrating ADC wikipedia , lookup
Schmitt trigger wikipedia , lookup
Operational amplifier wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Power MOSFET wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Surge protector wikipedia , lookup
Current source wikipedia , lookup
Voltage regulator wikipedia , lookup
Opto-isolator wikipedia , lookup
Current mirror wikipedia , lookup
Power electronics wikipedia , lookup
Transcript
JAYA ENGINEERING COLLEGE Department of Electrical and Electronics Engineering Lab Manual Sub: Electrical Engineering and Control system Lab (EE 1292) Class : IV Semester Computer Science & Engg. Prepared by: Mr.P.Musthafa, Lecturer/EEE Electrical Engineering and Control System Lab Name of the Experiments 1. Verification of Kirchoff’s laws 2. Study of RLC series and parallel circuits 3. Open circuit and load characteristics of self-excited DC generator 4. Load test on D.C. shunt motor 5. Speed control of D.C. shunt motor 6. Swinburne’s test 7. Load test on single phase transformer 8. Load test on three phase induction motor (Squirrel Cage) 9. Load test on single-phase induction motor 10. Transfer function of separately excited D.C. generator 11. Transfer function of armature controlled D.C. motor 12. Transfer function of field controlled D.C. motor 13. Transfer function of A.C. servo motor 14. Transfer function of Compensating network VERIFICATION OF KIRCHOFF’S LAWS Aim: To verify Kirchoff’s Current law and Voltage law. Apparatus required: S.No Name of the apparatus 1. Ammeter Type MC Range Quantity 0-30 mA 1 0-10 mA 2 2. RPS Variable 0-30 volt 1 3. Resistors Carbon 1kohms 3 4. Voltmeter MC (0-10)V 3 Theory: Kirchoff’s first law: The algebraic sum of currents flowing through any junction is zero at all instants of time. Kirchoff’s voltage law: The algebraic sum of voltages around a closed loop is equal to zero at all instants of time. Procedure: To Verify KCL 1.) 2.) 3.) 4.) Connections are given as per the circuit diagram. The input voltage is set at 8 Volt. The ammeter readings are noted and tabulated. The above steps are repeated for 10V, 12V and 15V. To Verify KVL 1.) 2.) 3.) 4.) Connections are given as per the circuit diagram. The input voltage is set at 8 Volt. Using Digital Multimeter/Voltmeter, voltage across each resistor is measured and tabulated. The above steps are repeated for 10V, 12V and 15V. Tabulation To verify KCL S.No. I mA Input Voltage I1 mA I2 mA I1 + I2 mA V Volt 1.) 2.) 3.) 4.) To verify KVL S.No. Input Voltage Voltage across Voltage across Voltage across R1 R2 R3 V1 + V2 + V 3 Volt Volt V1 Volt 1.) 2.) 3.) 4.) Circuit Diagram for Kirchoff’s Laws: Kirchoff’s Current Law Kirchoff’s Voltage Law V2 Volt V3 Volt Observations: It can be observed that the current I is equal to ( I 1 + I2 ) Also it can be observed that the applied voltage V is equal to (V1 + V2+ V3 ) Note: The differences in the above is due to tolerances in the resistors, meter resistances etc. Result: Thus the Kirchoff’s laws have been verified. STUDY OF RLC SERIES AND PARALLEL ELECTRICAL CIRCUITS Aim: To study about RLC series and Parallel circuits also series and parallel resonance in electrical circuits. Apparatus required: S.No 1. 2. 3. 4. 5. Name of the apparatus Ammeter DRB DCB DIB Function generator Type MI Range (0-50)mA Quantity 1 Theory: A circuit is said to be in resonance when applied voltage V and the resulting I are in phase. Thus the resonance , equilalent complesx impedenace of circuit cosists of only resistance R since V and I are in phase the power factor of a resonance circuit is unity . Series resonance : The RLC series circuit of figure das a complex impedance z = r+j (L-1/c) = R+jx . the circuit is in resonance when x=0 i.e L=1/c = 1/Lc = o Then since =2f resistance frequency is given by fo =1/2Lc Parallel resonance: The parallel circuit consisting of trancher with single pure elements R, L, C is an ideal circuit. However R, L, C is a circuit of interest in general subject of resonance. This ideal circuit can be compared to the series circuit examined above and it can be that a duality can be estimated. For calibration purpose in parallel resonance we equate the imaginary part of the admittance of the circuit to be zero to obtain the condition for resonance. For an ideal forllel circuit fo =1/2Lc Procedure: Series Resonance 1.Connections are given as per the circuit diagram-I. 2.The input waveform is chosen as sinusoidal waveform and its Voltage is set at 10 volt. 3. The frequency of the waveform is varied in suitable steps and in each step the values of ammeter (I) and voltage across DRB (V) are noted down. 4. As the frequency is increased, it will be observed that the current in the circuit and voltage across the DRB increase gradually and reach maximum values at a particular frequency, which is referred to as resonant frequency. Thereafter, the current in the circuit and also the voltage across the DRB decrease as the frequency is increased. Parallel Resonance 1. Connections are given as per the circuit diagram-II. 2. The input waveform is chosen as sinusoidal waveform and its Voltage is set at 10 volt. 3. The frequency of the waveform is varied in suitable steps and in each step the values of ammeter (I) and voltage across DRB (V) are noted down. 4. As the frequency is increased, it will be observed that the current in the circuit and voltage across the DRB decrease gradually and reach minimum values at a particular frequency which is referred to as resonant frequency. Thereafter, the current in the circuit and also the voltage across the DRB increase as the frequency is increased. Tabulation: Series Resonance: S.No. Frequency of the Input Voltage Hz. I mA Parallel Resonance: S.No. Frequency of the Input Voltage Hz. I mA Graphs: Graphs are drawn with Current or Voltage along Y-axis and Frequency along the X-axis. Circuit Diagram for Study of Series and Parallel Resonance: Result: Thus the resonance had been studied in series and parallel electrical circuits. SWINBURNE’S TEST Aim: Estimate the total constant loss of a DC shunt machine by conducting no load test and hence to predetermine it’s when running as a motor and as a generator Apparatus required: S.No. 1. Particulars Voltmeter 2. Ammeter Range 0-300V 0-20A 0-1A, 0-2A, 0-5A 3. Rheostat 400 ohms, 2A Type MC Qty 1 MC - each 1 2 Theory: Precautions: 1. The field Rheostat is kept at minimum position 2. The armature circuit resistance is kept at maximum position initially & by starting the machine the rheostat Rg is selected so that starting current 3. Fuse with current rating of 20% of full load current are selected. Procedure: 1. Connections are made as per the circuit diagram 2. The field rheostat is kept at minimum position and the armature resistance is kept at maximum position. 3. Switch is closed and motor is started using starter. 4. The armature resistance is gradually decreased to bring the machine to rated voltage. 5. The field circuit resistance Rf is increased so the machine is brought to rated speed. 6. At rated voltage & speed the current drawn by the machine Io the field If & applied Vo are noted. 7. After taking the readings the resistance Rf & Rg are brought back to their initial values and the machine is switched off. 8. The total constant losses are determined. 9. The efficiency of the machine is calculated when running as a motor & as a generator. 10. The output Vs are drawn. Measure of armature Resistance 1. Connections are made as per the circuit diagram 2. The motor is prevented from rotation by means of the break drum. 3. The rheostat is kept at maximum position & supply is given by closing DPST switch 4. The readings of ammeter & voltmeter are noted & Ra is found. Formula Used 1. Determination of Constant Losses No load power I/P No load Copper loss = Vo Io = Ia2 Ra Determination of while running as motor Power Input = VL IL Armature Copper loss = Ia2 Ro Power Output = VL IL – Losses Total Losses = wc + Ia2 Ro = Output / Input X 100 Determination of while running as generator Power Output = VL IL Armature Current = Ia = IL + If Armature Copper loss = Ia2 Ro Power Input = VL IL + Losses Total Losses = wc + Ia2 Ro = Output / Input X 100 SWINBURNE’S TEST Name Plate Details Tabulation Determination of when running as Motor: IL Ia=IL-If VL I/P (A) (A) (V) (W) Copper losses (W) Total losses (W) O/P (W) (%) Determination of when running as generator IL VL Ia O/P (A) (V) (A) (W) Copper losses (W) Total losses (W) I/P (W) (%) To Measure RA S.No. Voltage (A) Current (A) Ra () Speed (rpm) No load Voltage Vo No load Current Io Field current If At No Load Model Calculations: Viva Questions Swinburne’s Test 1. What is the difference between brake test and swinburne’s test? 2. Advantages of Swinburne’s test. 3. Why the generator efficiency is always greater than motor efficiency? 4. What is the other name for swinburne’s test? Result Thus the total constant losses of a DC shunt machine by conducting no load test are estimated & its efficiency is predetermine while running as a generator and as a motor. SPEED CONTROL OF DC SHUNT MOTOR Aim To draw the speed control characteristics of DC shunt motor by (i) Armature control method (ii) Field control method. Apparatus Required S.No. Equipment Used Range Type Qty Theory Armature Control Method This is used when speed of motor below the no load speed is required. As the supply voltage is normally constant, inserting a variable resistance in series with the armature circuit varies the voltage across the armature. As the control resistance is increased the Pd across the armature id decreased. So the armature speed also decreases. In this method speed can be varied up to the rated speed. This method is very expensive because of power loss and not suitable for rapidly changing loads. Field Control Method The speed of a DC motor is inversely proportional to the flux per pole, when the armature voltage is kept constant. By increasing the flux, the speed can be decreased and vice versa. Changing the field current can change the flux per pole of a DC motor. The field current can be changed with the help of the shunt field current is relatively small, the shunt field rheostat has to carry only a small amount of current, therefore the power loss is less. By this method, speed below the rated speed cannot be obtained. By combining the field control and armature control methods it is possible to sped variations below or above normal speed. Precautions 1. 2. 3. 4. Check for the correct fuse ratings. Ensure there are no loose connections. Field rheostat should be kept in minimum position initially. Armature resistance rheostat is kept initially at maximum position. Procedure 1. 2. 3. 4. 5. 6. 7. The connections are made as per the circuit diagram. Field rheostat is initially kept in the minimum position and the armature rheostat is in the maximum position. Supply is given to the motor by closing the DPST switch. Motor is started using a three-point starter. Adjust the armature rheostat to get rated voltage. In actual case adjust to about 200v, beyond this speed will be more than 1500 rpm. The field rheostat is adjusted to make the motor run at the rated speed. Armature Control Method 1. By varying the field rheostat, set the value of field current to a particular value say If=0.45A. 2. Now, by varying the armature rheostat, for various values of armature voltages, find the values of speed and armature current repeat this procedure for various values of field current say 0.4A, 0.35A 3. Bring back the armature rheostat and field rheostat to initial position. Field Control Method 1. By varying the armature rheostat, set the value of armature voltage to a particular value say V=180V. 2. Now by varying the field rheostat set the value of armature voltage field currents from 0.5A to 0.3A and note down the values of speed. 3. Repeat this procedure for various values of armature voltages say 160V, 140V. Bring back the armature rheostat and field rheostat to the initial position. 4. Switch off the DPST switch. Speed Control of DC Motors Name Plate Details Tabular Column Armature Control Method Field Current (If) = A Field Current (If) = A Field Current (If) = A S.No. Armature Speed Armature Speed(N) Armature Speed(N) Voltage V (N) (Rpm) Voltage V (Rpm) Voltage V (Rpm) Field Control Method S.No. Armature Voltage V V Field Speed Current (N) (IA) AMPS (Rpm) Measurement of Ra Armature Voltage V V Field Speed(N) Current(IA) (Rpm) Amps Armature Voltage V V Field Speed(N) Current(IA) (Rpm) AMPS S.No Armature Voltage (Va ) (Volts) Armature Current (Ia) (Amps) Armature Resistance (Ra) (Ohms) Model Calculation Viva Questions 1. 2. 3. 4. What are factors considered for controlling the speed? What are the methods for speed control of motors? Why field control method is better than armature control method? Give Advantages and disadvantages ward-leonard system? Result Thus the speed control characteristics of DC shunt motor by (i) Armature control method (ii) Field control method are done. OCC and Load Characteristics of a DC Shunt Generator Aim: To draw the OCC and load characteristics of Self Excited DC Shunt Generator Apparatus Required: S.No. Apparatus Range Type Qty Theory Precautions a. Check for Correct Fuse Ratings. b. Avoid loose connections. c. The generator field rheostat is kept in maximum position and motor field rheostat is minimum position. d. Speed should be maintained constant through out the experiment. Procedure To Draw OCC 1. The connections are given as per the circuit diagram. 2. Supply is given to Motor by enclosing DPSTS 1. 3. Motor is started using Three point Starter. 4. The field Rheostat of Motor is varied to make the motor run at rated speed of the generator. 5. The Voltmeter and Ammeter readings are noted. 6. The field rheostat of generator is varied gradually and the readings of ammeter and volt meter are noted in steps. 7. Bring the generator field rheostat and motor field rheostat to the original position and open the DPSTS 1. To Draw Load Characteristics 1. The connections are given as per the circuit diagram. 2. Supply is given to Motor by enclosing DPSTS 1. 3. Motor is started using Three point Starter. 4. The field Rheostat of Motor is varied to make the motor run at rated speed of the generator. 5. By adjusting the field Rheostat of the generator, the generator Voltage is brought to the rated value. 6. Now the load side DPST2 is closed and load is applied gradually upto 1255 of rated load. 7. The speed is maintained constant at each load. 8. The Readings of Ammeter and Voltmeter are noted at each load. 9. Remove the load completely. 10. Open the load side DPST2. 11. Bring the field rheostat of generator and motor to its original position and open the DPST1. Tabulation To draw OCC S.No. Open Circuit Voltage Field Current (Volts) V0 (Amps) If To Draw Load Characteristics S.No. Load Current (Il) Amps. Terminal Voltage (V) Volts. Field Current (If) Amps Armature Current (Ia) Amps Induced Voltage Eg=V+IaRa To Find Ra S.No. Model Calculation Viva Questions Armature Voltage (Va) Volts Armature Current (Ia) Amps Armature Resistance (Ra) Ohms Result Thus the OCC and load characteristics of DC shunt generator when it is self & separately excited are determined. LOAD TEST ON SINGLE PHASE TRANSFORMER Aim: To determine the efficiency & regulation of a single transformer conducting load test. Apparatus Required: S.No. Apparatus 1. Voltmeter 2. Ammeter 3. Wattmeter 4. 5. Range (0-300)V (0-150)V (0-10)A 3000V,10A 150V,29A Variac Single phase (230/115)V transformer 2KVA Type MI MI UPF UPF Qty Each 1 Each 1 1 1 1 Precautions 1. The zero error in the meters is corrected. 2. The variac is kept at minimum voltage position initially & its output is made to zero after the completion of the experiment. 3. While energizing & dancercising there should not be any load on the transformer. Procedure 1. The circuit connections are given as per the circuit diagram 2. The variac is kept at minimum output voltage position. 3. Here the transformer is used in step down configuration. The supply is given to low voltage winding and the load is connected to high voltage winding. 4. The DPSTs2 is kept open and the transformer primary is energised by closing switch S1the output of variac is increased to rated voltage 115V. 5. The NL power input, primary voltage and the no load secondary voltage 0V2 are noted. 6. Then switch s2 is closed and the transformer is loaded in steps up to 120% of full load. In each step the power input w1, primary voltage V1, secondary winding voltages are noted. 7. The primary voltage V1 is maintained constant through out the experiment. 8. The load is reduced in steps & switch S2 is opened. The supply is switched off by making the output of variac to zero. 9. The efficiency & regulation are calculated. Formula used 1. 2. 3. 4. 5. 6. No load secondary voltage = 0V2 No load primary voltage = 0V1 Power input = W1watts Power output = W2 watts Efficiency = output / input X 100 Regulation = UP = 0V2 – V2 / V2 X 100 Down = 0V2 – V2 / 0V2 X 10 Model Calculation Viva Questions OCC and Load Characteristics of DC Shunt Generator 1. What do you mean by self-excitation? 2. List the conditions for voltage build up of a dc shunt generator? 3. Name the different losses taking place in a DC machine? 4. Define eddy current loss and hysteresis loss? 5. What is the function of brushes in dc generator? 6. Define critical speed and critical resistance? 7. State the principle of generator? 8. What are the types of DC Generators? 9. What are the parts of dc generator? Why carbon is used as a brush material in a dc machine? 10. Tell the function of commutator in DC generator? 11. Why the armature core is laminated in dc machine? Result The load test is conducted on the given single phase transformer and the following curves are drawn. 1. Output Vs Efficiency 2. IL Vs % Regulation LOAD TEST ON THREE PHASE SLIP RING INDUCTION MOTOR AIM To obtain the performance characteristics of a three-phase slip ring induction motor by conducting a load test. APPARATUS REQUIRED: S. No. 1 2 3 Name of the Equipment Ammeter Voltmeter Wattmeter Range Type 0 –10 A 0 – 600 V MI MI 2 Eleme nt 500 V, 10 A, UPF Quantity 1 1 1 4 Tachometer 0 – 3000 RPM 1 Digital / Analog THEORY In an induction motor, the torque is proportional to the product of flux per stator pole, the rotor current and power factor of the rotor. Torque, T I2 cos2 Where, I2 = rotor current at stand still 2= angle between rotor EMF and rotor current The starting torque of the three phase induction motor, Ts R2 / Z2 In the slip ring induction motor, external resistance can be added to the rotor circuit at starting. Hence the power factor of the rotor circuit is easily improved. Therefore the starting torque of such a motor is high. The external resistance, however, increases the rotor impedance and so reduces the rotor current. The torque developed in the rotor is dependent upon the rotor resistance. Inserting external resistance in series with each phase in a slip ring induction motor we can increase the value of rotor resistance. Load Test on Slip Ring Induction Motor Name Plate Details The maximum value of the torque, however, is independent of the resistance. The speed regulation can be obtained by varying the rotor resistance. The condition for maximum starting torque is that the rotor resistance equals rotor reactance. The torque is given in terms of slip as follows: T sR2 / (R2 + s X2). If the resistance and inductance of a given rotor is kept constant, the magnitude of the torque depends solely upon the slip, for a constant applied voltage and frequency. For low values of slip, the reactance is negligible compared with the resistance and hence, the torque is almost proportional to the slip. For large values of slip, the reactance is large compared with the resistance and hence, the torque is now approximately, inversely proportional to the slip. The starting torque of a slip ring induction motor is more compared to squirrel cage induction motor. Also higher running torque can be obtained by introducing extra resistance in the rotor circuit. Therefore, wherever a high starting torque or running torque or both are required, slip ring induction motor can be used. PRECAUTIONS 1. While starting and stopping there should not be any load on the brake drum. 2. Pouring water, cools the brake drum. PROCEDURE 1. 2. 3. 4. 5. The connections are made as per the circuit diagram. TPSTS is closed and the supply is given. The no load readings of Ammeter, Voltmeter, Wattmeter and speed are noted. The brake drum is loaded by tightening the belt in steps of 1Amps. For each load, note the readings of Ammeter, Voltmeter, Wattmeter, Tachometer and spring balance are noted. 6. The load is gradually removed and the TPSTS is opened. FORMULAE USED 1. 2. 3. 4. 5. 6. 7. Torque, T = (S1 ~ S2) R x 9.81 Nm Input Power = W * mf Output Power = 2NT / 60 Watts Percentage Efficiency (%) = [Output Power / Input Power] x 100 Percentage Slip = % s = [( Ns – N ) / Ns] x 100 Power factor = W / 3 VL IL Where, S1 and S2 are spring balance readings c = Circumference of the brake drum t = thickness of the belt TABULATION Circumference of the brake drum Radius of the brake drum ( r ) Thickness of the belt ( t ) = ___ m. = ___ m. = ___ m. IL VL W N Spring Balance Amps Volts Watts rpm Readings S1 Kg Input Torque Output Power % %s Power (T) in Power factor Effici Slip Watt Nm in Watt ency S2 Kg Model Calculation Viva Questions 1. Write the difference between squirrel cage IM and Slip ring IM? 2. 3. 4. 5. 6. Why does the rotor rotate? Define slip and give the expression for the slip? What is the use of adding external resistance in rotor circuit? What is the condition for maximum torque? Tell the type of starter used for slip ring IM? Draw the slip- torque characteristics. RESULT: Thus the performance and load characteristics of a three phase slip ring induction motor are drawn. LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR AIM To obtain the performance characteristics of a three phase squirrel cage induction motor by conducting a load test. APPARATUS REQUIRED S. No. 1 2 3 4 Name of the Equipment Ammeter Voltmeter 2 – Element Wattmeter Tachometer Range 0 –10 A 0 – 600 V 600 V, 10 A 0 – 3000 RPM Type MI MI UPF Digital / Analog THEORY Quantit y 1 1 1 1 In an induction motor, the torque is proportional to the product of flux per stator pole, the rotor current and power factor of the rotor. Torque, T I2 cos 2 Where, I2 = rotor current at stand still 2= angle between rotor EMF and rotor current The starting torque of the three phase induction motor, Ts R2 / Z2 The resistance of a squirrel cage rotor is fixed and small as compared to its reactance. The reactance is very large at the start because at standstill, the frequency of the rotor currents equals the supply frequency. Hence, the starting current of the rotor, though very large in magnitude (It is roughly 1.5 times the full load current), lags E2 by a very large angle. Therefore the starting torque of a squirrel cage induction motor is very small. Load Test on Squirrel Cage Induction Motor Name Plate Details The condition for maximum starting torque is that the rotor resistance equals rotor reactance. The torque is given is terms of slip as follows: T sR2 / (R2 + s X2). If the resistance and inductance of a given rotor is kept constant, the magnitude of the torque depends solely upon the slip, for a constant applied voltage and frequency. For low values of slip, the reactance is negligible compared with the resistance and hence, the torque is almost proportional to the slip. For large values of slip, the reactance is large compared with the resistance and hence, the torque is now approximately, inversely proportional to the slip. The starting torque of a squirrel cage induction motor is very low. Therefore this motor can be used only for the works which need low starting torque such as centrifugal pumps, fans, blowers, line shafting, lathe works, etc. PRECAUTIONS 1. While starting and stopping there should not be any load on the brake drum. 2. The motor is started using a star – delta starter. 3. The starter handle is moved from ‘Off’ position to ‘Start’ position and after the motor picks up speed the handle is quickly moved to ‘Delta’ position. 4. The brake drum is cooled by pouring water. PROCEDURE 1. Connections are made as per the circuit diagram. 2. TPSTS is closed and the supply is given. 3. Starter handle is moved from ‘Off’ to ‘Star’ position and after the motor picks up speed, the handle is moved from ‘Star’ to ‘Delta’ position. 4. The no load reading of all the meters are taken. 5. Apply the load by tightening the belt in steps of 1A. For each load, note the readings of Ammeter, Voltmeter, Wattmeter, Tachometer and spring balance. 6. Apply load up to 120% of full load current. 7. Gradually remove the load by loosening the belt and open the TPSTS. FORMULAE USED 1. 2. 3. 4. 5. 6. 7. Torque, T = (S1 ~ S2) R x 9.81 Nm Input Power = W * mf Output Power = 2NT / 60 Watts Percentage Efficiency (%) = [Output Power / Input Power] x 100 Percentage Slip = % s = [( Ns – N ) / Ns] x 100 Power factor = W / 3 VL IL Where, S1 and S2 are spring balance readings c = Circumference of the brake drum t = thickness of the belt TABULATION Circumference of the brake drum = ________ m. Radius of the brake drum (r) = _________ m. Thickness of the belt (t) = ________ m. IL Amps V W N Volts Watts rpm Spring Balance Readings S1 Kg Input Power KW Torque Output % %s (T) in Power Efficie Slip Nm in Watt ncy S2 Kg Model Calculation Viva Questions 1. 2. 3. 4. What are the types of ac motors? And Why Induction motor is named so? Which is the most commonly used induction motor and why? Tell the advantages and disadvantages of Induction motor. How hysterisis loss and eddy current loss is minimized? 5. Why the rotor slots are skewed in induction motor? 6. Write the principle of operation of induction motor? Result: Thus the performance and load characteristics of a three phase squirrel cage induction motor are drawn. TRANSFER FUNCTION OF AC SERVOMOTOR Aim To study the characteristics and transfer function of ac servomotor. Theory An ac servomotor is basically a 2Φ induction motor. The rotor of the servomotor is built with high resistance so that its A/R ratio is small so speed torque characteristics will be linear. The excitation voltage applied to stator windings should have a phase difference of 90ْ Working The stator windings are excited by voltage of equal RMS magnitude and phase difference. This results in exciting current and which causes rotating magnetic field of constant magnitude. Rotating magnetic field sweeps over the flux. Hence voltage induces current in stator conductors and current creates rotor flux. Working of ac servomotor in control system Constant voltage source excites the reference winding. The frequency is in range of 50-1000 Hz. W(s) / E(s) = Km/ S (Zm) s+1 Where Km is Motor gain constant Zm is Motor time constant Application: Control winding is excited by the modulated control signal and the voltage is of variable magnitude and polarity. For the production of rotating magnetic field the control phase voltage must be of same frequency as reference phase voltage. Hence the control signal is modulated by carrier signal whose frequency is same as that of reference voltage and then applied to the control voltage. For modulation purpose ac supply itself is used as carrier signal. Let ec is control signal Ecm is modulated control signal If ec is positive then ecm and ecar will be same in phase so ecm = /E+ec/wswct for ec co. Transfer function of AC Servomotor: W(s) / Ec(s) = K1 /Js + K2 + B = Km/1+STm Km = K1 / K2 + B = motor gain constant Tm = J/ K2 + B = time constant (or) motor time constant Let ω angular displacement of motor W = dө / dt = angular speed T = torque developed by the load. B = Frictional viscous coefficient of conductor J = moment of inertia of load. K1 = slope of speed torque characteristics Tm = torque developed by the motor. Tm = J d2ө/ dT2 + B dө/dt Tm = K1 – K2 dө / dt J d2ө/ dT2 + B dө/dt = K1 – K2 dө / dt J s2 ө(s) + Bө(s) = K1 E e (s) - K2 ө(s) ө(s)/ Ee(s) = K1/ JS2+Bs+K2 TF of ac servomotor = Km/1+S2m Km = K1/ K1+ B Zm = J / K2+ B Calculation Km = k1 / K2 + B = 16 / 0.026 + 0.01875 = 357.54 Zm = J / K2+ B = 0.052 / 0.026 + 0.01875 = 1.162 TF = 357.54 / 1+1.162 Result: Thus the characteristic of ac servomotor was studied and its transfer function To find K1 Torque T = 9.81 * r * S Nm. S = Load in Kg r = radius of shaft in m = 0.068m Load (Kg) Control Voltage Vc (V) To find K2 Torque T = 9.81 * r * S Nm. S = Load in Kg r = radius of shaft in m = 0.068m Speed (rpm) Load (Kg) Torque (Nm) Torque (Nm) Transfer function of separately excited DC Generator Aim: To determine the transfer function of separately excited dc generator. Apparatus Required: S.No. Name of the Apparatus 1 Rheostat 2 Voltmeter 3 Ammeter Type Range Qty Double tubular MC MI MC MI 400Ω / 2A 2 (0-300)V (0-300)V (0-2) A (0-1) A 1 1 1 1 Theory: Transfer function of a linear variant system is defined to be the ratio of Laplace transform of the other input variable under the assumption that all initial conditions are zero. A dc generator is commonly used in control system for power amplifications. The transfer function of a separately excited generator is given as Transfer function G(s) = Kg / Rf + SLf Kg ----- generator constant (V/A) Rf ------- resistance of field winding Lf ----- inductance of field winding Procedure Determination of Kg 1. 2. 3. 4. 5. 6. 7. Connections are given as per the circuit diagram. Close the DPST switch. The field rheostat of the motor is to be adjusted to bring the motor to the rated speed 1500 rpm. By varying the field rheostat of the generated voltage are noted down. Repeat the above step for various positions of the field rheostat of the generator. Plot the graph, between field rheostat i.e. field current and the generated voltage. The slope of the graph is a constant Kg. Determination of Lf 1. Connections are given as per the circuit diagram. 2. The DPST switch is closed. 3. Single phase variac is adjusted and the various values of field current and field voltage are noted down. 4. The field coil impedance is calculated by Zf = Vf / If Formula used To obtain the transfer function Zf ---- field impedance in Ω Rf ---- field resistance in Ω Xf ---- field reactance in Ω F ---- supply frequency in Hz Xf2 = Zf 2- Rf2 Field inductance = Xf / 2Πf To obtain the rettling time ts Rettling time = time required to reach 98% of steady state value (o.98iss) Calculation Derivation of transfer function Transfer function = L E (g)/ L E f = if Rf + Lf dit/dt = Ef(t) Taking Laplace transform, If (s) Rf + Lf (s) If (s) = Ef (s) Generator constant Kg = Eg / If ----- Eg = Kg If Eg (s) = Kg If (s) If (s) = Eg (s) / Kg Eg (s) / Ef (s) = Kg / Rf + sLf Kg = ∆ Eg / ∆ If Xf = √ Zf 2- Rf2 Xf = 2ΠfLf Lf = Xf / 2Πf Substituting value of Kg, Rf , Lf in transfer function we have transfer function of separately excited dc generator Eg (s) / Ef (s) = Kg / Rf + sLf TF = Eg (s) / Ef (s) = Kg / Rf + sLf From graph Kg = 307.69 Rf = 208.42 Ω Xf = √ Zf 2- Rf2 = √(4.01 * 10 3)2 – (208.42)2 Xf = 4004.58 Lf = Xf / 2Πf = 4004.58 / 2Π * 50 = 12.75 Eg (s) / Ef (s) = Kg / Rf + sLf = 307.69 / 208.42 + s 12.75 Result Thus the transfer function of separately excited dc generator was determined TF =307.69 / 208.42 + s 12.75 Circuit diagram Name Plate Details Voltage Current Speed DC Motor 220V 19A 1500rpm DC Generator 220V 13.6A 1500rpm Type Excitation Voltage Excitation Current Shunt 220V Shunt 220V 0.8A 0.8A Tabulation OCC S.No 1 2 3 4 5 6 7 8 9 10 11 Voltage (V) V (v) If (A) Field Current (A) To Find Rf To Find Zf RΩ V (v) If (A) Zf * 10 3 (Ω) Transfer function of Compensating Network (Lag , Lead, Lag – Lead) Aim To study the response of the following compensating network and to plot the magnitude and gain response for a given range of input frequencies 1. Lag Network 2. Lead Network 3. Lag – Lead Network Apparatus Required 1. 2. 3. 4. Resistor (1.2 , 1 , 38 ,15KΩ) each 1 Capacitor (0.1 , 0.047 , 0.055 µF) each 1 CRO Function generator Theory The widely employed compensators are lag , lead , lag-lead compensators. These are two situations in which compensation is required. The first case the system is absolutely unstable and the compensation is done to stabilize current as well as to achieve a specified performance. The second case the system is stable but the compensation is required to obtain the desired performance system which all type or higher are absolutely unstable for such types lead compensation is suitable. A lead compensate speeds up the transient response and increase the margin of stability of a system. It also helps to increase the system error constant through to a limited extent. A lag compensator compensates improve the steady state behaviour of a system with i.e. while nearly preserving its transient response. When both the transition and steady state response improvement is required a lag lead compensator is required. Thus basically a lag lead compensator is connected in series. Procedure 1. Connections are made as per the circuit diagram. 2. Constant voltage is applied. 3. The output voltage of the circuit is observed for various frequencies of input. 4. The same procedure is repeated for all types of compensator. Result Thus the transfer function of compensating networks are studied. Lead Network S.No 1 2 3 4 5 6 7 8 Input Voltage E(volts) Frequency (Hz) Output Voltage E0 (V) Gain G (dB) 10V S.No 1 2 3 4 5 6 Frequency (Hz) Phase Angle Lag Network E (V) 10v Frequency (Hz) Output voltage Eo (v) Gain G (dB) Frequency (Hz) Phase Angle Transfer function of field controlled DC motor Aim To determine the transfer function of field controlled dc shunt motor. Apparatus Required S.No 1 2 3 4 5 6 7 8 9 Name of the Equipment Ammeter Ammeter Voltmeter Voltmeter Voltmeter Rheostat Auto Transformer Tachometer Stop Clock Type Range Quantity MC MI MC MI MC Tubular Single Phase 0-2.5/5A 0-15A 0-30v 0-300v 0-300v 400Ω/2A 2 1 1 1 1 1 Analog (0-5000)RPM 1 Theory The speed of a dc motor is directly proportional to armature voltage and inversely proportional to flux. In field controlled dc motor the armature voltage is kept constant and the speed is varied by varying the flux of the machine since flux is directly proportional to field current, the flux is varied by varying filed current. The speed control system is an electromechanical control system. The electrical system consists of armature and filed circuit but for analysis purpose, only field circuit is considered, because a constant voltage excites the armature. The mechanical system consists of the rotating part of the motor and the load connected to the shaft of the motor. The field controlled dc motor has an open loop transfer function. Determination of J and B Precautions 1. The motor field rheostat should be kept in minimum position 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. The DPTP switch is connected to 1-1’. 3. The motor is started by using three point starter. 4. The field rheostat of the motor is adjusted to speed above the rated speed (N+N) where N is the rated speed (i.e 1500rpm) and N is 200rpm (assumes) 5. DPDT is changed from 1-1’ position and the time taken for the speed to fall (N-N) i.e 1300rpm is noted as t1. 6. The motor field rheostat is brought to the minimum resistance position. The motor is switched off and again started. 7. The electrical load is switched on in order to compensate the armature drop. 8. DPDT is connected to position 1-1’ once again and adjust the field rheostat of the motor to get a speed slightly above (N+N) i.e 1800rpm. 9. DPDT is moved from position 1-1’ to 2-2’ and when the speed falls to (N+N) i.e 1700rpm, note down the voltmeter ammeter readings as VI and II and the stop clock is started. 10. The time taken when the speed falls to (N-N) i.e 1300rpm is noted as t2 and note down the values of voltmeter and ammeter reading as V2 & I2. 11. The field rheostat of the motor is brought to minimum resistance position. 12. DPST switch is opened. Determination of Zf Precautions 1. Single phase variac is kept in minimum position 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram 2. DPST switch is closed. 3. Single phase variac is adjusted and various values of the field current and field voltage are noted. 4. The field impedance is calculated using ohms law i.e Rf = Vf / If Determination of Kf Precautions 1. There should not be any load while starting and stopping. 2. Field rheostat should be in minimum position. 3. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. The motor is started by using three point starter and brought to rated speed by varying the field rheostat. The motor has to be loaded in steps till the rated value and each load, the values of armature current, voltage, field current and the spring balance readings are noted down. Determination of Rf Precautions 1. The rheostat should be kept in maximum position. 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. The rheostat is adjusted and various values of the field current and field voltage are noted. 4. The armature resistance is calculated using ohms law i.e Rf = Vf / If Determination of Ra Precautions 1. Armature rheostat should be kept in maximum position. 2. loose connections should be avoided. Procedure 1 Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. The rheostat is adjusted and various values of the armature current and armature voltage are noted. 4. The armature resistance is calculated using ohms law i.e Ra = Va/ Ia Formula Torque = 9.81 * (S1~S2) * R Where R = r+ t/2 Where r is the radius of the break drum and t is the thickness of the belt i.e C = 2Πr Lf = √Zf2- Rf2/ 2Πf (H) Pc = 0.5 * (V1I1 + V2I2 + I12Ra + I22Ra) (W) J = pc * t1 * t2 / 2Π2 (N12 – N22) (t1 - t2) (kg m2 / rad) Pstray - 2Π2 (N12 – N22) * J / t1 (W) P1 = Pstray / Π2 (N12 + N22) (NM /rad / Sec) Transfer Function G(s) = km / S(1+Tfs) Where km = kt / B(Rt) and J / B (kg m / N – S) (Rad / A Sec –Ω) Where Tf = Lf / Rf, Tm = J /B And time constant Tf = Lf / Rf Tabulation To obtain Armature resistance Ra S.No Armature Current (A) Armature Voltage (V) Armature resistance Ra – V/I Ω Field Voltage (V) Field Impedances Zf – V/I Ω To obtain Field Impedance Zf S.No Field Current (A) Determination of Kt S.No Voltage applied Field Current(A) Armature Current (A) Spring balance S1 (kg) S2 (kg) Torque, T (N – m) To obtain Field resistance Rf S.No Field Current (A) Field Voltage (V) Field resistance Rf – V/I Ω Determination of J and B Position of DPDT from 1-1’ to 0-0’ S.No Range of speed (rpm) Time taken for the speed to fall from (N+N) to (N - N). t1 seconds 1700 - 1300 Position o0f DPDT from 1-1’ to 2-2’ S.No Range of speed (rpm) 1. 2. 1300 – 1700 1700 – 1300 Note: Km = motor gain constant = KLf / Rf . B Tf = Field time constant = Lf / Rf Tm = Mechanical time constant = J / B Time taken for the speed to fall from (N+N) to (N - N). t1 seconds t2 = Voltmeter reading (volts) Ammeter reading (amps) V1 = V2 = I1 I2 Result: Thus the transfer function of a field controlled dc shunt motor is found to be Q(s) / Vf (s) = km / S (1 + ST f) (1 + STm) Transfer function of armature controlled DC Shunt motor Aim To determine the transfer function of field controlled dc shunt motor. Apparatus Required S.No 1 2 3 4 5 6 7 8 9 Theory Name of the Equipment Ammeter Ammeter Voltmeter Voltmeter Voltmeter Rheostat Auto Transformer Tachometer Stop Clock Type Range Quantity MC MI MC MI MC Tubular Single Phase 0-2.5/5A 0-15A 0-30v 0-300v 0-300v 400Ω/2A 2 1 1 1 1 1 Analog (0-5000)RPM 1 Transfer function of a linear time invariant system is defined to be the ratio of the laplace transform of the output variable to the laplace transform of input variable under the assumption that all initial conditions are zero. A dc generator is commonly used in control systems for power amplification. The transfer function of a armature controlled motor is given by comparison of armature controlled and filed controlled dc motors. The time constant of the armature controlled dc motor is generally small compared to the field controlled dc motor and hence the time response of the former is usually faster. In armature controlled operation field requires a constant voltage source where as the field control operation requires constant current source. Determination of J and B Precautions 1.The motor field rheostat should be kept in minimum position 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. The DPTP switch is connected to 1-1’. 3. The motor is started by using three point starter. 4. The field rheostat of the motor is adjusted to speed above the rated speed (N+N) where N is the rated speed (i.e 1500rpm) and N is 200rpm (assumes) 5. DPDT is changed from 1-1’ position and the time taken for the speed to fall (N-N) i.e 1300rpm is noted as t1. 6. The motor field rheostat is brought to the minimum resistance position. The motor is switched off and again started. 7. The electrical load is switched on in order to compensate the armature drop. 8. DPDT is connected to position 1-1’ once again and adjust the field rheostat of the motor to get a speed slightly above (N+N) i.e 1800rpm. 9. DPDT is moved from position 1-1’ to 2-2’ and when the speed falls to (N+N) i.e 1700rpm, note down the voltmeter ammeter readings as VI and II and the stop clock is started. 10. The time taken when the speed falls to (N-N) i.e 1300rpm is noted as t2 and note down the values of voltmeter and ammeter reading as V2 & I2. 11. The field rheostat of the motor is brought to minimum resistance position. 12. DPST switch is opened. Determination of Za Precautions 1. Single phase variac is kept in minimum position 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram 2. DPST switch is closed. 3. Single phase variac is adjusted and various values of the Armature current and armature voltage are noted. 4. The armature coil impedance is calculated using ohms law i.e Za = Va / Ia Determination of Ra Precautions 1. Armature rheostat should be kept in maximum position. 2. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. The rheostat is adjusted and various values of the armature current and armature voltage are noted. 4. The armature resistance is calculated using ohms law i.e Ra = va / Ia The motor has to be loaded in steps till the rated value and each load, the values of armature current, voltage, field current and the spring balance readings are noted down. Determination of Kb Precautions 1. Armature rheostat should be kept in maximum position. 2. Field rheostat should be kept in minimum position. 3. Loose connections should be avoided. Procedure 1. Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. Motor is started by using 3 point starter. 4. By adjusting the field rheostat, the motor is brought to rated speed. 5. By adjusting the armature rheostat, various values 0f the armature current and armature voltage, field current and speed are noted. 6. The field current is kept constant through out the experiment. 7. Back emf is calculated using Eb = V-IaRa 8. Graph is drawn between Eb and N and slope of the graph gives Kb. Determination of KT Precautions 1. There should be any load while starting and stopping 2. Field rheostat should be kept in minimum position. 3. loose connections should be avoided. Procedure 1 Connections are made as per the circuit diagram. 2. DPST switch is closed. 3. The motor is started by using three point starter and brought to rated speed by adjusting the field rheostat. 4. The motor has to be loaded in steps till the rated value and for each load, the values of armature current voltage and the spring balance reading are noted down. Formula Torque = 9.81 * (S1~S2) * R Where R = r+ t/2 Where r is the radius of the break drum and t is the thickness of the belt i.e C = 2Πr Lfa= √Za2- Ra2/ 2Πf (H) Pe = 0.5 * (V1I1 + V2I2 + I12Ra + I22Ra) (W) J = pe * t1 * t2 / 2Π2 (N12 – N22) (t1 - t2) (kg m2 / rad) Pstray - 2Π2 (N12 – N22) * J / t1 (W) P1 = Pstray / Π2 (N12 + N22) (NM /rad / Sec) Transfer Function G(s) = ө (s) / Va (s) = Kt / Ra B / S {(1+STa) (1+STm) + Kbkt / Rab} Where Ta = La / Ra, Tm = J /B (kg – m/ N-S) And Kt and Kb can be calculated from the graphs. Tabulation To obtain Armature resistance Ra S.No Armature Current (A) Armature Voltage (V) Armature resistance Ra – V/I Ω To obtain Field Impedance Za S.No Armature Current (A) Armature Voltage (V) Armature Impedance Za = V/I Ω Determination of Kt S.No Voltage applied Field Current(A) Armature Current (A) Spring balance S1 (kg) S2 (kg) Torque, T (N – m) S.No Range of speed (rpm) Time taken for the speed to fall from (N+N) to (N - N). t1 seconds Determination of Kb S.No Range of speed (rpm) 1. 2. 1800 – 1700 1700 – 1300 Time taken for the speed to fall from (N+N) to (N - N). seconds Voltmeter reading (volts) Ammeter reading (amps) V1 = V2 = I1 I2 Determination of J and B Position of DPDT from 1-1’ to 0-0’ Position of DPDT from 1-1’ to 2-2’ S.No Voltage applied Field Current(A) Armature Current (A) Back emf Eb= V Eb=V-IaRa Speed(rpm) Result: Thus the transfer function of a field controlled dc shunt motor is found . LOAD TEST ON SINGLE PHASE INDUCTION MOTOR Ex. No Date Aim To determine the load characteristics of single phase capacitor start-capacitor run induction motor. Apparatus Required S.No Name of the Equipment Type Range Quantity 1. 2. 3 Voltmeter Ammeter Wattmeter MI MI I Element 4. Tachometer Analog / Digital 0-300V 0-10A 0-300V, 10A, UPF 0-3000RPM 1 1 1 1 Precautions 1. Check for correct fuse ratings. 2. Loose connections should be avoided. 3. There should not be any load on the brake drum initially. Procedure Connections are made as per the circuit diagram. Supply is given to the motor by closing the DPST switch and motor is started using auto transformer. The no load readings of ammeter, voltmeter, wattmeter and tachometer are noted. The motor is loaded gradually and the readings of ammeter, voltmeter, wattmeter, spring – balance, tachometer are noted and tabulated till the load current is 90% of its rated value. Then load on the motor is released and motor is switched off. Formulae used 1.R = r+ (t/2) (m) 2. Torque (T) = 9.81 * (S1~S2) * R (Nm) 3. Output power = 2пNT / 60 (Watt) 4. Slip = (Ns – N ) / Ns * 100 5. Efficiency = (output power / Input power ) * 100 (%) Tabulation 1. Circumference of the brake drum = m 2. Radius of the brake drum (r) 3. Thickness of the belt (t) S.No Line Voltage (V) in volt Line Current (I) in Amps Input power in watt = = m m Spring Balance Readings in kgf S1 S2 S1~ S2 Torque Speed (T) in in Nm RPM Slip Output Efficiency (%) power (%) in watt Graphs 1. Lin e Cur rent (A mp) Vs Out put pow er (wat t) 2. Tor que (N m) Vs Out put power (watt) 3. Efficiency (%) Vs Output power (watt) 4. Speed (rpm) Vs Output power (watt) 5. Torque (Nm) Vs Slip Result Thus the load test on single phase induction motor is conducted and the load characteristics were drawn. LOAD TEST ON DC SERIES MOTOR Ex. No Date AIM To conduct load test on DC series motor and to draw the performance and load characteristics of it. APPARATUS REQUIRED S.No. Equipment Used Range Type Qty THEORY PRECAUTIONS Ensure that some load is applied to the brake drum initially (S1=S2=5kg). Check the correct fuse ratings. Ensure that there are no loose connections. Under no circumstances, the motor should be unloaded fully during operation. PROCEDURE The connections are given as per the circuit diagram. Ensure that some load is applied to the brake drum initially (S1=S2=5Kg). Supply is given to the motor by closing the DPST Switch. Motor is started using the two point starter. The readings of ammeter, voltmeter, tachometer and spring balance are noted. The load is then gradually increased in steps and the readings are noted up to 125%of rated load. In actual case, take readings up to 8.5 A. Decrease the load on the brake drum (until S1=S2=5Kg). The motor is switched off using the DPST switch. Name Plate Details FORMULA USED Radius R=R+T\2 in Metres. Torque T=(S1 S2 )*R*9.81 NM Input Power P = Vi Ii Watts Output Power P = 2NT Watts Percentage Efficiency = (Output Power/ Input Power)*100 Model Calculation Viva Questions 1. 2. 3. 4. 5. 6. 7. State the principle of motor? Define back emf and why it is called so? Give the expression. What is the function of commutator in motor? Why the series motors are used in locomotives? Why series motors should not be started at no load? Tell the special features of DC series motor What are the applications of series motor? Result Thus the performance and load characteristics of a DC series motor are drawn. LOAD TEST ON DC SHUNT MOTOR Exp No: Date : AIM To draw the various characteristics curves by conducting load test on a DC shunt motor. APPARATUS REQUIRED S.No. Equipment Used Range Theory Precaution Ensure that there is no load on the brake drum initially. Type Qty Check for correct fuse rating. Ensure that there are no loose connections. Field rheostat should be kept in minimum position initially. Procedure The connections are made as per the circuit diagram. Ensure that no load is applied to the brake drum and the field rheostat is kept in minimum position initially. Supply is given to the motor by closing the DPST switch motor is started using a 3point starter. The field rheostat is adjusted to make the motor run at the rated speed. At no load, the readings of ammeter, voltmeter, tachometer and spring balance readings are noted. The load is then increased in steps and the readings are noted up to 125% of rated load. Remove the load on the brake drum. Bring the field rheostat to original position Open the DPST switch. An ammeter can be put into the field circuit to note the value of field current. FORMULA USED Radius R=R+T\2 in Metres. Torque T= (S1 S2)*R*9.81 NM Input Power P = Vi Ii Watts Output Power P = 2NT /60 Watts Percentage Efficiency = Output Power/ Input Power Model Calculation Viva Questions 1.What are the applications of shunt motor? 2.What is the other name for shunt motor? Why it is called so? 3.What is the necessity of starter? Tell the types of starters used for DC motor 4.Tell the protective devices used in three point starter. 5.What is the advantage of 4-point starter over 3 -point starter? 6.Give the voltage equation of motor? Tabulation: (DC Shunt Motor) Circumference of the brake drum: Radius of the brake drum (r) Thickness of the belt S.No Line Voltage (Volts) Line Current (Amps) : : Speed (Rpm) Spring Balance Readings S1-S2 S1 S2 Kg (KG) (KG) Torque (N-M) Output Power (Watts) Input Power (Watts) Efficiency % Result Thus the performance and load characteristics of a DC shunt motor are drawn. LOAD TEST ON DC SHUNT MOTOR TABULAR COLUMN: (DC Series Motor) Circumference of the brake drum: Radius of the brake drum (r) Thickness of the belt : : Tabulation Circumference of the brake drum: Radius of the brake drum (r) Efficiency % Input Power (Watts) S1-S2 Kg Output Power (Watts) Spring Balance Readings S2 S1 (KG (KG) ) Torque (N-M) Speed (rpm) Armature Current (Amps) S.No Line Voltage (Volts) Line Current (Amps) IL : Field Current (Amps) Thickness of the belt :