Performance of dc motors experiment 2

10,600 views
10,112 views

Published on

Performance of dc motors experiment
The result getting is not 100% legit

Published in: Education
1 Comment
4 Likes
Statistics
Notes
  • See:
    http://winding.wix.com/design
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Views
Total views
10,600
On SlideShare
0
From Embeds
0
Number of Embeds
34
Actions
Shares
0
Downloads
204
Comments
1
Likes
4
Embeds 0
No embeds

No notes for slide

Performance of dc motors experiment 2

  1. 1. THEORYElectrodynamometer measures torque. Electrodynamometer is an electrical break, inwhich the breaking force can be varied electrically. It consists of a stator and a squirrel-cagerotor. The stator is free to turn; however, its motion is restricted by a spring. A DC current isapplied to the stator winding generating a magnetic field that passes through the stator andthe rotor. The strength of the stator magnetic field can be increased or decreased by thefront panel control. This strength determines the degree at which the revolving rotor cancause the stator to change position on its axis. As the rotor turns (being belt-coupled to thedriving motor), a voltage is induced in the rotor bars, and the resulting eddy currents reactwith the magnetic field causing the stator to turn. The electrodynamometer is calibrated inNewton-meters (Nm).Shunt motor. The field coil and the armature windings are connected in shunt or parallelacross the power source. The armature winding consists of relatively few turns of heavygauge wire. The voltage across two windings is the same but the armature drawsconsiderably more current than the field coil. Torque is caused by the interaction of thecurrent caring armature winding with the magnetic field produced by the field coil. If the DCline voltage is constant, the armature voltage and the field strength will be constant. Thespeed regulation is quite good; the speed is a function of armature current and is notprecisely constant. As the armature rotates within the magnetic field, an EMF is induced inits wining. This EMF is in the direction opposite to the source EMF and is called the counterEMF (CEMF), which varies with rotational speed. Finally, the current flow through thearmature winding is a result of the difference between source EMF and CEMF. When theload increases, the motor tends to slow down and less CEMF is induced, which in turnincreases the armature current providing more torque for the increased load.Motor speed is increased by inserting resistance into the field coil circuit, which weakens themagnetic field. Therefore, the speed can be increased from “basic” or full-load, full-fieldvalue to some maximum speed set by the electrical and mechanical limitations of the motor.The power difference between the motor input and the output is dissipated in form of heatand constitutes to the losses of the machine. These losses increase with load, since themotor heats up as it delivers mechanical power.
  2. 2. Series motor. The field coil and armature windings are connected in series to the powersource. The field coil is wound with a few turns of heavy gauge wire. In this motor, themagnetic field is produced by the current flowing through the armature winding; with theresult that the magnetic field is weak when the motor load is light (the armature windingdraws a minimum current). The magnetic field is strong when the load is heavy (thearmaturewinding draws a maximum current). The armature voltage is nearly equal to the PS linevoltage (just as in the shunt wound motor if we neglect the small drop in the series field).Consequently, the speed of the series wound motor is entirely determined by the loadcurrent. The speed is low at heavy loads, and very high at no load. In fact, many seriesmotors will, if operated at no load, run so fast that they destroy themselves. The highforces, associated with high speeds, cause the rotor to fly apart, often with disastrousresults to people and property nearby. The torque of any DC motor depends upon theproduct of the armature current and the magnetic field. For the series wound motor thisrelationship implies that the torque will be very large for high armature currents, such asoccur during start-up. The series wound motor is, therefore, well adapted to start largeheavy-inertia loads, and is particularly useful as a drive motor in electric buses, trains andheavy duty traction applications. Compared to the shunt motor, the series DC motor hashigh starting torque and poor speed regulation
  3. 3. Cumulative compound motor combines the operating characteristics of the series andshunt motors. The high torque capability of the series wound DC motor is some whatcompromised by its tendency to overspeed at light loads. This disadvantage can beovercome by adding a shunt field, connected in such a way as to aid the series field. Themotor then becomes a cumulative compound machine. Again, in special applications whereDC motors are used in conjunction with flywheels, the constant speed characteristic of theshunt wound motor is not entirely satisfactory since it does not permit the flywheel to give upits kinetic energy by an appropriate drop in motor speed. This kind of application (which isfound in punch-press work), requires a motor with a "drooping" speed characteristic, that is,the motor speed should drop significantly with an increase in load. The cumulativecompound wound DC motor is well adapted for this type of work. The series field can also beconnected so that it produces a magnetic field opposing that of the shunt field. Thisproduces a differential compound motor, which has very limited application, principallybecause it tends to be unstable. As the load increases, the armature current increasesincreasing the strength of the series field. Since it acts in opposition to the shunt winding, thetotal flux is reduced, with the result that the speed increases. An increase in speed willgenerally further increase the load, which raises the speed and could cause the motor to runaway. The shunt field winding places a practical limit on maximum no-load speed and it maybe operated at no load. The shunt coil also provides for better speed regulation than a seriesmotor; while the series coil provides for greater starting torque than a shunt motor. After themotor is started, the series coil is shorted out for better speed regulation. Cumulativecompound motors are used where fairly constant speed under irregular loading is needed.
  4. 4. PART A : DC SHUNT MOTOR LOAD CHARACTERISTICSOBJECTIVE 1. To construct the direct current (dc) shunt motor circuit. 2. To determine the load characteristics of dc shunt motor. 3. To interpret the load characteristics of a dc shunt motor.LIST OF REQUIREMENTSEquipment(Experimental panel system unit 1000 W) 1. Variable dc power supply 2. Brake unit 3. Control unit servo brake 4. Display panel 5. Coupling collar 6. Shaft and cover 7. DC shunt motor 8. Connection mask (3125111) 9. Voltmeter (1 unit) 10. Ammeter (2 units)
  5. 5. PROCEDURE 1) The connection was performed according to the Figure 2.3. 2) The ammeter 1 connect to 10A, ammeter2 connect to 1A and voltmeter connect to 1000V. 3) Before this experiment started, the operating elements of the control unit servo brake was adjusted as in below table 2.1 :Table 2.1 Operating switch on position M const/T Switch “Torque range” position 10Nm Switch “Speed range” position 6000 4) The power supply was switched on.The Dc voltage was adjusted to 220V.A constant voltage of 220V was maintained throught the experiment.The direction of the motor was checked and turn in clockwise direction. 5) The “store/start” button was pressed twice. The torque load was adjusted from 0Nm to 2Nm. The data was recorded in the Table2.2. 6) Then the calculation had be made and the result also recorded in Table 2.2.
  6. 6. I) Total output power,P2=(Torque X Speed)/9.55 II) Power input,P1=Voltage X Total Current III) Efficiency =P2/P1 IV) Total Current=Current A + Current E 7) N,IA,P2 and Ƞ was graphically as a function in Figure 2.4PART B: DC SERIES MOTOR LOAD CHARACTERISTICSOBJECTIVES 1. To construct the DC series motor circuit. 2. To determine the load characteristics of a DC series motor. 3. To interpret the load characteristics of a DC series motorLIST OF REQUIREMENTSEquipment(Experimental panel system 1000W) 1. Voltage supply 2. Brake unit 3. Control unit servo brake 4. Display panel 5. Coupling collar 6. Shaft and cover 7. DC series motor 8. Connection mask(3125113)
  7. 7. 9. Voltmeter(1unit) 10. Ammeter(1unit)PROCEDURES 1) Firstly, connect all the wire according to the diagram that shown in Figure 2.7 Note the maximum range: ammeter1:10A, and voltmeter:1000V 2) After that, adjust the operating elements of the control unit servo brake was adjusted as in table 2.3 and then,the control unit was switched on
  8. 8. Operating Switch on Position M const/T constSwitch “Torque range” position 10 NmSwitch “Speed range” position 6000Table 2.3 3) The power supply was switched on.The Dc voltage was adjusted to 110V.A constant voltage of 110V was maintained throught the experiment.The direction of the motor was checked and turn in clockwise direction. 4) The “store/start” button was pressed twice. The torque load was adjusted from 0Nm to 1Nm. The data was recorded in the Table 2.4. 5) Then the calculation had be made and the result also recorded in table 2.4 i) Total output power,P2=(Torque X Speed)/9.55 ii) Power input,P1=Voltage X Current iii) Efficiency =P2/P1 6) N,IA,P2 and Ƞ was graphically as a function in Figure 2.8PART C: DC COMPOUND MOTOR LOAD CHARACTERISTICSOBJECTIVES 1. To construct the DC series motor circuit. 2. To determine the load characteristics of a DC compound motor. 3. To interpret the load characteristics of a DC compound motorLIST OF REQUIREMENTSEquipment(Experimental panel system 1000W) 1. Voltage supply 2. Brake unit 3. Control unit servo brake
  9. 9. 4. Display panel5. Coupling collar6. Shaft and cover7. DC series motor8. Connection mask(3125113)9. Voltmeter(1unit)10. Ammeter(1unit)
  10. 10. PROCEDURES 1) The connection was performed according to the Figure 2.11. 2) The ammeter 1 connect to 10A, ammeter2 connect to 1A and voltmeter connect to 1000V. 3) Before this experiment started, the operating elements of the control unit servo brake was adjusted as in below table 2.5 :Table 2.5 Operating switch on position M const/T Switch “Torque range” position 10Nm Switch “Speed range” position 6000 4) The power supply was switched on.The Dc voltage was adjusted to 220V.A constant voltage of 220V was maintained throught the experiment.The direction of the motor was checked and turn in clockwise direction. 5) The “store/start” button was pressed twice. The torque load was adjusted from 0Nm to 2Nm. The data was recorded in the Table2.2. 6) Then the calculation had be made and the result also recorded in Table 2.6. V) Total output power,P2=(Torque X Speed)/9.55 VI) Power input,P1=Voltage X Total Current VII) Efficiency =P2/P1
  11. 11. VIII) Total Current=Current A + Current E 7) N,IA,P2 and Ƞ was graphically as a function in Figure 2.12.RESULTPart ATable 2.2Measured ValueTorque ζ(Nm) 0.0 0.5 1.0 1.5 2.0Current IA(A) 0.8 1.2 1.8 2.4 3.0Current IE(A) 0.44 0.44 0.44 0.44 0.44Speed N(rpm) 2907 2867 2815 2765 2698Calculated ValuePower P! (W) 272.8 360.8 492.8 624.8 756.8Power P2 (W) 0.0 150.1 294.8 434.3 553.7Efficiency η(%) 0.0 0.41 0.60 0.70 0.73Total currentIcct(A) 1.24 1.64 2.24 2.84 3.44Part BMeasured ValueTorque Nm 0.0 0.2 0.4 0.6 0.8 1.0Current, IA (A) 2.4 2.7 3.0 3.4 3.7 3.9Speed, N (rpm) 4100 3670 3050 2660 2290 2110Calculated ValuePower,P1 (W) 264 297 330 374 407 429Power,P2 (W) 0.0 76.86 63.87 55.71 47.96 44.19Efficiency (%) 0.0 0.26 0.20 0.15 0.12 0.10Part CMeasured ValueTorque ζ(Nm) 0.0 0.5 1.0 1.5 2.0Current IA(A) 0.7 1.2 1.7 2.3 2.8Current IE(A) 0.43 0.43 0.43 0.43 0.42Speed N(rpm) 2810 2750 2660 2570 2478Calculated ValuePower P! (W) 268.6 358.6 468.6 600.6 710.6Power P2 (W) 0.0 144.0 278.5 403.7 519.0
  12. 12. Efficiency η(%) 0.0 0.40 0.59 0.67 0.73
  13. 13. REFERENCESMatthew N.O sadiku, Charles K. Alexander(2009), Fundamental Of Electric Circuit 4(ed), Singapore:Mc Graw Hill.Rusnani Ariffin, Mohd Aminuddin Murad(2009), Laboratory Manual : Electrical Engineering Laboratory 1 EEE230, Shah Alam: University Publication Centre (UPENA) Universiti Teknologi Mara. http://www.engineersedge.com/motors/dc http://www.micromotcontrols.com/htmls/Motor%20characteristics.html http://electriciantraining.tpub.com/14177/css/14177_59.htm
  14. 14. FACULTY OF ELETRICAL ENGINEERING UNIVERSITY TEKNOLOGI MARAELECTRICAL ENGINEERING LABORATORY 1 (EEE230) EXPERIMENT 2 PERFORMANCE OF DC MOTORS
  15. 15. TABLE OF CONTENT CONTENT PAGEABSTRACT TheoryOBJECTIVESLIST OF REQUIREMENTSEXPERIMENT PROCEDUREEXPERIMENT RESULTDISCUSSIONCONCLUSIONREFERENCEAPPENDICES

×