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Report on Induction Machine Equivalent Circuit Parameter Identification andOperational Performance Laboratories 3 and 4A report submitted as part completion of course NHE2486Academic Year 2017-18NHE2486: Electrical Power & Drive SystemsStudent Name: Student registration number: Table of ContentsTable of Contents.......................................................................................................................21.1 Introduction..........................................................................................................................3

1.2 Discussion of Load Tests.....................................................................................................51.3 Test Results..........................................................................................................................71.4 Discussion of Results.........................................................................................................121.5 Conclusions........................................................................................................................141.6 References..........................................................................................................................151.7 Appendices.........................................................................................................................16A1. Scan of Laboratory 3 Notes and Risk Assessment...........................................................16A2. Scan of Laboratory 4 Notes and Risk Assessment...........................................................20

1.1 IntroductionThis lab session was carried out in two phases: laboratory 3 and 4. In laboratory 3, 2 experiments were conducted these are: three-phase induction machine characterization and load test, while in laboratory 4 a three-phase induction machine operation experiment was conducted. Laboratory experiment 3 aimed at determining two things; the electrical parameters of a 3-phase wound rotor induction machine per equivalent circuit phase and to test the torque of the induction machine versus the characteristics of the speed at full rated voltage and fixed frequency. Three experiments are conducted in laboratory 4 and among them two experiments that are to investigate further the performance capabilities of the induction machine and one experiment that illustrates the similarity between synchronous andinduction machines. The three experiments in laboratory 4 are:Controlling the torque-speed characteristics of an induction machine through externally connected resistance.Controlling the torque-speed characteristics of an induction machine through supply of voltage to the stator of the induction machine.Supply of DC current to the rotor windings in order to synchronize the machine.2. Induction Machine Per-phase, Approximate Equivalent CircuitInduction machine per-phase, approximate equivalent diagram[ CITATION Aus131 \l 1033 ]

Figure (1)Induction motors are usually asynchronous and the magnetic field of the stator rotate at the asynchronous speed of the motor. It is never possible for the motor to rotate at a synchronous speed otherwise; current will not be induced in the motor. The full speed of the rotor is usually between 2 and 6% of the synchronous speed and the deviation between the real asynchronous and synchronous speed is called the slip speed. The slip speed is the difference between the actual speed of the rotor and the synchronous speed of the motors and can be expressed either as a fraction or as a percentage[ CITATION Juh13 \l 1033 ]. Using the magnetic winding theory, the relationship between the number of poles, p, frequency in the stator, f and the synchronous speed can be established using the expression;f=nspThe equation fr= (ns-nr) p is used in finding the frequency within the rotor which is the difference between the frequency of the rotor and that of the stator. Combining the two equations above;fr =snsp=sf and the synchronous speed per second is given by ns=f/pIn the equivalent circuit diagram above, R1 - resistance of the stator winding while X1represents the reactance of the leakage of the stator i.e. the flux that is that has no linkage with the rotor and the air gap. Rc represents the core losses while Xm represents the magnetising reactance that is required to cross the air gap in the circuit[ CITATION The131 \l 1033 ].In an ideal transformer having N1 and N2 turns respectively represents the air gap. The slip affects the induced emf for the rotor side such that the slip reduces and less emf is induced as the speed of the rotor increases. R2 and X2 represent the resistance and reactance of the rotor

respectively in which X2 is a dependent variable on the frequency of the emf of the inductor[ CITATION Fou131 \l 1033 ].1.2 Discussion of Load TestsInduction Machine No-load TestProcedureThe test circuit was connected in such a way that the load impedance at thetransformer output set of variable resistancesThe tutor checked the circuitThe Variac was voltage was set at zeroThe circuit was connected to the mains supplyThe induction machine nameplate was read so as to note the rated line voltage and themachine rate voltage calculated[ CITATION Ste123 \l 1033 ].The Variac dial was turned up until the rated line was displayed on the FlukevoltmeterIn one phase of the machine supply is connected the Power Meter from whichreadings are taken when the machine when the machine operates at fully voltagesupply and when on no-loadThe power factor was calculated.The Variac was set to zero volts and the mains supply unplugged.Induction Machine Locked Rotor TestProcedureThe nameplate of the induction machine was read and the rated full load currentnoted.

The rotor-locking bar was fitted to test the ring.The circuit and the test-rig were checked by the tutor.The Variac output voltage was gradually increased to where a full load current isflowing in the stator windings of the induction machine[ CITATION Ngu15 \l 1033 ].Readings were taken from the Power Meter. The readings were taken swiftly andthe Variac voltage reduced back to zeroThe power factor was calculatedTorque versus Speed Test at Full Voltage and Fixed FrequencyProcedureIt was ensured that the rotor locking bar was removed and safely placed on thetest-rigThe Variac voltage was set to zeroThe circuit was checked by the tutorThe circuit was connected to the mains supply[ CITATION Fou131 \l 1033 ].The Variac was adjusted to the point where the rated line voltage was displayedon the Fluke voltmeter.The dynamometer control was varied such that a torque was registered on the dialof the test-rig. Readings were taken with the higher readings of the torque takenquickly.Winding DC Resistance TestProcedure The Variac was set to zero and the induction machine unplugged from the mainssupplyAll the circuitry was disconnected

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