The No Load Circuit And Short Circuit Characteristics Biology Essay

The No Load Circuit And Short Circuit Characteristics Biology EssayThe Ward-Leonard clay is a conventional speed control method. It consists of a 3 kind induction simple mould controlling a separately excited DC reservoir. The DC generator in turn supplies a variable DC voltage to a DC move. It is basically a DC variable speed drive 2. The Ward-Leonard system is shown below in enroll 1.Figure Ward-Leonard system frame-upThe principle behind the Ward-Leonard system is that the DC generator back tooth actually influence the motor to develop a torque and speed required by the load 3. Thus the speed of the generator is directly proportional to the armature voltage applied to the DC motor 2. The output voltage of the DC generator is controlled by adjusting the exciting voltage (field voltage), this then controls the speed of the DC motor 2.ApplicationsTravelling cranesLiftsMine hoists softened machinesTable Ward-Leonard system advantages and disadvantagesAdvantagesDisadvantagesV ery wide range of speedsHigh costProvides step less speed controlLow over-all efficiencyExperiment weapon2- coupled induction machine and dc motor (as shown below in Figure 2)4- digital multimeters (DMM)2- Variac (Excitation field)TachometerFigure Coupled induction machine and dc machineObjectives of the experimentCharacterise the DC machines and determine the equivalent circumferences.Derive the power flow comparabilitys between the DC machines in terms of the equivalent tours. lead the power flow between the DC machines by adjusting the field authoritatives. Then compare the measured results with the expected theoretical power flow.Experiment procedure and setupNo-load TestThis interrogation was used to determine the armature voltage.Before the experiment began the armature and field resistance were both measured.The Variac (exciter) was then committed to the field port on the DC machine.The Digital multimeter was connected to the armature port on the DC machine in order to measure the armature voltage.The DC machine was coupled to a three phase induction machine which was first turned on to run the DC machine. The setup is shown below in Figure 3. apply the knob on the Variac, growth the field voltage with an increment of 10V ( in addition increases) and for each case determine the armature voltage. This was done from 0V to the rated field voltage one hundred tenV.Now decrease the field voltage to delete the DC machine from cxV to 0V in addition with an increment of 10V. Note the residual magnetism.Figure No-Load test setupShort-Circuit TestThis test was used to determine the armature current.The kindred procedure for the No-Load test was followed but in this case the digital multimeter was connected in series in the armature port in order to measure the current.Using the knob on the Variac, increase the field voltage with an increment of 10V and for each case determine the armature current. This was done from 0V to the rated field voltage 110V .The DC machine was demagnetised from 110V to 0V also with an increment of 10V recording the armature current.Ward Leonard experimentThis setup was used to determine the power flow between the machines.The cardinal coupled machines were connected together as shown below in Figure 4. A coupled machine is shown in Figure 1. The coupled machines were connected together through the armature.The positive terminals of the armature were connected together and the negative terminals were connected together.A digital multimeter was connected in between the positive terminals of the armature in order to measure the current.Each DC machine was connected to Variac through the field port. Both the Variac machines were turned down to 0V.The two induction machines were switched on both at the same time from the 3 power supply.The Variac knobs were both turned at the same time with an increment of 10V from 0V. This is done up until the multimeter reads 0A.The 0A was obtained at a field voltage of 110V.At this stage the second machine was left changeless and the field voltage of the first machine was turned down at an increment of 10V, whilst recording the current and the speed of the machine without turn over the speed of 1502 rpm. A tachometer was used to measure the speed.After that the first machine was calibrated back to 110V, were the multimeter reads 0A.Now the first machine was left constant and the field voltage of the second machine was turned down at an increment of 10V, whilst recording the current and the speed of the machine without exceed the speed of 1502 rpm. A tachometer was used to measure the speed.After this then the practical is complete, the next step is to deduce an equation for the power as a function of ardour (field current) based on the machine characteristics. Then plot the graphs.Figure Power flow setupCUsersMashDesktopf.bmpSafetyDo not exceed the ratings of the machines and all the other equipment. refilling off the equipment after completi ng the practical.ResultsCharacterisation of DC machineTable Armature and field resistanceResistanceBeforeAfter7.3 9.8 573 542 No-load characteristicsGMachine Pracopennn.bmpFigure No-load circuitTable No-load test resultsMagnetizingDemagnetizingField volts (V)Armature volts (V)Field volts (V)Armature volts (V)001.691027.8103520.861.120.5683088.930.19740116.838.211950.1141.150.114860.6165.160.117070181.969.518580196.280.42009020990.5211100.2218100.9220110.3227110.3227Figure No load test results plotThe pastime table shows the addressd field current using the measured field resistance of 573 .Table Amperes in the field coilsMagnetizingDemagnetizingField volts (V)Field Amperes (A)Field volts (V)Field Amperes (A)00.00001.60.0028100.0175100.017520.80.036320.50.0358300.052430.10.0525400.069838.20.066750.10.087450.10.087460.60.105860.10.1049700.122269.50.1213800.139680.40.1403900.157190.50.1579100.20.1749100.90.1761110.30.1925110.30.1925Figure DC generator no-load characteristicsCom mentsThe graph shows the relationship between the no-load armature voltage and the field current at a constant speed of 1496 rpm. The magnetization curve is a straight line up to a field current of 0.1A, after this point the graph approaches a condition known as saturation, thus any increase in the field current does not result in an increase in the armature voltage. consequently the demagnetizing plot is above the magnetizing plot, this is due to the residual magnetism and hence the curve begins just above the 0 mark (a little way up).Closed circuit testGMachine Pracshortt.bmpFigure Closed circuit diagramTable Closed circuit resultsMagnetizingDemagnetizingField volts (V)Armature current (A)Field volts (V)Armature current (A)1.72.541.60.2110.83.6310.71.120.54.5218.81.8130.84.7229.52.64405.5439.93.3750.96.450.23.9360.75.5960.84.44706.0170.75.05806.180.85.5906.52905.91006.921006.541117.41117.4Figure Short-circuit characteristicsNameplate InformationNo-load circuit calculationsFigur e No-load Fitted-curveThis can be written asUsing Figure 10 we can use the fitted plot of the no-load saturation curve above to determine the constant. The measured speed is used.FromThus we can calculateBut in practice we can approximate the value of the torque constantShort-circuit calculationsFigure Short circuit fitted plotThis can be written asAs calculated aboveThus by substitutionThus now we can determine the armature resistanceCoupled machines (Ward-Leonard system))110.11100.1149214910.2052240.15597110.11000.15149214920.1865670.212687110.1900.49149014940.167910.62529911079.90.86148614990.1490670.974303110.1701.22149014980.1305971.210896110601.59148014990.111941.352687110.1502.03148415010.0932841.439179110.140.32.45148415030.0751871.399974Power flow)1101100.1149214920.2052240.15597100110-0.83149214960.186567-1.1768790110-1.17148015000.16791-1.4930680110-1.56147015000.149254-1.7695570110-2.05147415000.130597-2.034760.1110-2.25148315020.112127-1.91737Derivation of power equat ionFigure Ward-Leonard system setupFigure Ward-Leonard system equivalent circuitNow from Figure above we expect thatWhere(For the generator)(For the motor)(For the generator)(For the motor)Equate equation (1) and (2)Rewrite the equationNow we observe thatLetThis equation remains the same, it just depends which machine is a generator and which machine is a motor. As mentioned above to determine which machine acts as a generator or motor, we look at the following sign conversion.ConclusionDC machine CharacterisationThe DC machine characterisation of the generator was successfully done, both the no-load test and the short circuit test were done and all the parameters were calculated. The parameter calculated include the armature resistance which was found to be 6.25 as compared to the measured and the rated armature resistance it is within range ( difference).The characterisation also helps us understand how the dc works by using the saturation curves we can determine the point wher e the machine starts saturation and determine the critical resistance. We can also determine information about the machine which would normally be given in the nameplate.Ward-Leonard system and the power flowThe power flow equation was successfully derived and found as the equation belowThe equation was derived from the Ward-Leonard system that was setup in the practical. The practical showed that the power can be controlled between two DC machines using this setup. In the practical the power flowed from the generator to the motor, this was seen through the current having a negative current flowing in one cathexis and a positive current flowing to the other direction. The practical was successful and it clearly corresponds to the theory.What I leanedThe practical was useful in terms of helping us understand the concept of residual magnetism which is the same as in the theory.The practical was also a good representation in terms of how an cosmetic surgery/lift works.