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EN0567 - Assignment C003 Powerlab 3-phase Induction.docx
- 1. EN0567 - Assignment C003 Powerlab 3-phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-1 OBJECTIVES W hen you have completed this assignment you will be able to: -cage induction motor performance. -state operating characteristics of small induction motors. KNOWLEDGE LEVEL Before you start this assignment you should: AC circuits.
- 2. -500 Virtual Instrumentation System and the connections required to the 68- 441dynamometer. For details on the connections between the PC, the 68-441 Torque/Speed control panel and the 68-500 Multi-Channel Input/Output panel, see the Manual Multi-Channel Input / Output System – 68-500. See also this manual for details of the Virtual Instrumentation software 68-911. PRA determine and compare various steady-state operating characteristics of the motor under different loading conditions.
- 3. EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-2 FORMULAE voltage and current (rms values). The 3-phase power input is available directly from the virtual instrumentation system. where n is the speed in rev/min and T is the torque in Nm. Efficiency = 100 x % PowerInput PowerOutput (3) EQUIPMENT REQUIRED -105
- 4. age squirrel cage induction motor 64- 501 shunt DC machine 63-110 with a fitted 68-430 DC tacho- generator and 68-441 panel. -703 -200 Bin 91-240 -800 -911 software for Virtual Instrumentation. Notes Circuit diagrams for Virtual instrumentation are provided. Refer to the Multi-channel I/O Unit Manual 68-500 for the setting up of the virtual instrumentation voltmeters, ammeters etc, and the use of stored Set-Up files. DO refer to the Help information available in the 68-500 software.
- 5. EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-3 Circuit Diagrams and Wiring Figure 1: Virtual Instrumentation Wiring EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-4 Figure 2: Magnified Multi-channel I/O Unit 68-500 Patching Diagram from Figure 1 Figure 3: Star and Delta wiring
- 6. EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-5 Figure 4: Circuit Diagrams for Typical Loads with Instruments Connections EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-6 Preliminary Set-up Switch off all power at the circuit breaker on the Universal
- 7. Power Supply 60-105. Ensure that the dynamometer motor is connected to the Torque socket. Make up connections shown in Figs. 1 and 2, according to the circuit diagrams in Figs. 3 and 4, for the motor with (a) Y and configuration of the stator windings. Control Settings 60-105 Power Supply Make sure the Variable Supply control is on 0% and the Circuit Breaker switched off. Set the meter range to 500 V ac. 68-441 Set the Speed / Torque and the Torque control to their most anti- clockwise positions. Press the green Power button Press the black rectangular Machine Power button so that the adjacent red LED is lit.
- 8. 68-911 Software Switch on the PC, start the Virtual Instrumentation Software 68- 911 and set-up the virtual instruments required. SAFETY NOTE Do NOT leave the 68-441 powered up with the test motor NOT rotating and with a load demand. This will cause the dynamometer motor to overheat which may lead to permanent damage. EN0567 – Assignment C003 Powerlab 3-Phase Induction Motor Performance Dr M Jovanovic – EN0567 lab sheets Page-7 -connected motor Switch on the 60-105 circuit breaker. Slowly increase the variable supply control until the line-to-line voltage is about 415 V for Y-
- 9. -connection of the windings. All three voltmeters (and ammeters) should read approximately the same. Using the PC Virtual Instrumentation Software, take the following readings for values of the applied torque from the minimum to 1.6 Nm in increments of about 0.1 Nm and enter them into a table similar to the one below. Line Current (any one of the three) Input Power (user meter 1) Power Factor (user meter 3) Torque (dynamometer reading) Speed (dynamometer reading) Set the load torque to zero and then turn slowly the variable supply control back to 0% to stall the machines. Switch off the Universal Power Supply - 60105 at the circuit breaker. Reconfigure the stator windings and repeat the above procedure/measurements.
- 10. EN0567 – Assignment C003 Powerlab Table of Results Dr M Jovanovic – EN0567 lab sheets Page-8 Line Current (A) 3 Phase wattmeter (kW) Power factor Torque (Nm) Speed - motor (rev/min) Slip
- 12. EN0567 Assignment 1 Faculty of Engineering and Environment BENG (HONS) ELECTRICAL AND ELECTRONIC ENGINEERING Module title: Power, Machines and Renewable Energy Module code: EN0567 Assignment 2: 3-phase Induction Machine Performance Value: 10% of Module
- 13. Assignment Tutor: Dr Milutin Jovanovic Student Name: ID: Bench: Submission date: EN0567 Assignment 2 Requirements Students need to attend one laboratory session, as per the group timetable, where they will be given all the necessary instructions how to do measurements relevant for the assignment.
- 14. explicit responses to the questions below, and hand it in to the FEE Office in Ellison Building, room B201 by Thursday, 29 April 2016. Please use this Word file as a template and add the required number of answer sheets as appropriate. Make sure you populate the sections on the cover page above (e.g. name, ID, your bench number when you did your lab session, as well as the submission date). assignment will incur fail or zero mark. In the event that you submit the assignment late but with a genuine reason, you must complete a late submission form available from the FEE office referenced above, and then have it authorised/signed by the module tutor.
- 15. Content Induction machines are the main work force in industry today and about 75% of the installations are based on them one way or another, either in motoring or generating mode. Although it is possible to achieve variable speed operation using power electronics, many general-purpose drives or fixed speed wind turbines require a fixed voltage and frequency supply for the machine. In these systems, 3-phase induction machines are indispensable due to their unique self-starting ability and possibility of direct on-line operation unlike any other 3-phase AC machine. This inherent property represents a significant advantage over its counterparts, and it is mainly for this reason that they are difficult to beat on the market in a wide range of applications. The proper understanding of the machine fundamental operating characteristics and testing methods used in practice is therefore of extreme importance, especially if the
- 16. students wish to continue their further professional career in power companies, electric machines and drives industry or renewable energy sector (e.g. wind turbine manufacturers). The main objective of this assignment is to allow the students to gain the necessary practical experience and basic knowledge in this area. The experimental test rig, procedures and equipment used for testing of a small-scale cage induction motor have been described in the accompanying lab sheets hard copies of which you should have already received in the lab sessions. EN0567 Assignment 3 Tasks 1. From your test results, determine the machine synchronous speed and the number of poles.
- 17. [6 %] 2. The example cage induction machine was started using a variable voltage supply at 50 Hz. a. What is the main reason for adopting such a starting procedure as opposed to dead-on-line start, and especially with larger machines? [3 %] b. State alternative electro-mechanical and power electronics starters (at least one configuration for each) which can be used for the same purpose. What are the main advantages of the latter over the former? [4 %] c. Identify the common problem of fixed frequency operation of the motor with respect to the starting torque and current? [3 %]
- 18. 3. If the same 415 V, Y-connected machine was Δ-connected (as you did in your experiments), what maximum voltage could be applied to its terminals to prevent the current over-loading? Compare (in relative sense) the line current and torque values for the two winding connections of the motor for a given speed? [7 %] 4. Tabulate your measurements (similarly to the table on page 8 of the lab sheets) showing the following performance parameters: line current, 3- phase electrical power, power factor, load torque (the measurements may necessarily differ from the values in the above table), speed, calculated slip in motoring mode, and speed and electro-magnetic power predictions for the machine operated as a generator at the same absolute slip and shaft torque values as in motoring mode. [30 %]
- 19. 5. Using Excel spreadsheets or similar software available in the computer rooms or elsewhere, present graphically the following operating characteristics of the motor in terms of torque: speed, current, power factor, input power and slip (two plots/figure for each, one for Y and one for Δ connection for comparison). [30 %] EN0567 Assignment 4 6. Using the approximate equivalent circuit, show that the machine electro-magnetic torque is proportional to slip in the low slip region, and verify this linear relationship by the corresponding experimental plot(s) above. [7 %] 7. In your experiments, 3-phase power has been measured using two single phase
- 20. watt-meters connected as illustrated in Fig. 4 of the lab sheets (this is known as the ‘two-wattmeter method’ in the literature). Using phasor diagrams, an expression for instantaneous power, or applying any other approach you consider appropriate, explain how is this possible and why? [10 %]