The No Load Circuit And Short Circuit Characteristics Biology Essay

The No Load Circuit And Short Circuit Characteristics biota EssayThe Ward-Leonard organisation is a conventional run control method. It consists of a 3 phase consequence political motorcar controlling a separately excited DC beginning. The DC generator in drama supplies a covariant DC electric potential to a DC motor. It is basically a DC variable speed drive 2. The Ward-Leonard system is shown below in propose 1.Figure Ward-Leonard system setupThe rationale behind the Ward-Leonard system is that the DC generator target actually influence the motor to develop a torque and speed required by the load 3. Thus the speed of the generator is directly relative to the armature electric potential applied to the DC motor 2. The output voltage of the DC generator is controlled by adjusting the raise voltage ( orbit voltage), this then controls the speed of the DC motor 2.ApplicationsTravelling cranesLiftsMine hoistsBoring utensils get across Ward-Leonard system advantages and disadvantagesAdvantagesDisadvantagesVery wide range of speedsHigh costProvides step less speed control natural depression over-all efficiencyExperimentApparatus2- coupled induction machine and dc motor (as shown below in Figure 2)4- digital mul eraters (DMM)2- Variac (Excitation battleground)TachometerFigure Coupled induction machine and dc machineObjectives of the look intoCharacterise the DC machines and watch over the equivalent dress circles.Derive the exponent flow equivalences amongst the DC machines in terms of the equivalent circuits.Control the power flow between the DC machines by adjusting the field accrediteds. thence compare the heedful results with the expected theoretical power flow.Experiment procedure and setupNo-load TestThis riddle was used to intend the armature voltage.Before the experiment began the armature and field resistance were both measured.The Variac (exciter) was then connected 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 origin turned on to run the DC machine. The setup is shown below in Figure 3. using the knob on the Variac, increase the field voltage with an increment of 10V ( also increases) and for each case get hold the armature voltage. This was done from 0V to the rated field voltage 110V.Now decrease the field voltage to demagnetise the DC machine from 110V to 0V also with an increment of 10V. Note the residual magnetism.Figure No-Load prove setupShort-Circuit TestThis runnel was used to determine the armature current.The same 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 do ne 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 two 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 by means of with(predicate) the armature.The corroborative 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 th e multimeter reads 0A.The 0A was obtained at a field voltage of 110V.At this stage the second machine was left eonian 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 sink 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 abutting step is to deduce an equation for the power as a function of excitation (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 t he other equipment.Switch off the equipment later completing the practical.ResultsCharacterisation of DC machine plank 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)001.691027.8103520.861.120.5683088.930.19740116.838.211950.1141.150.114860.6165.160.117070181.969.518580196.280.42009020990.5211 snow.2218100.9220110.3227110.3227Figure No load test results plotThe following table shows the calculated 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)00.00001.60.0028100.0175100.017520.80.036320.50.0358300.052430.10.0525400.069838.20.066750.10.087450.10.087460.60.105860.10.1049700.122269.50.1213800.139680.40.1403900.157190.50.1579100.20.1749100.90.1761110.3 0.1925110.30.1925Figure DC generator no-load characteristicsCommentsThe 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 colour, thus any increase in the field current does not result in an increase in the armature voltage.Consequently the demagnetizing plot is higher up the magnetizing plot, this is due to the residual magnetism and hence the curve begins just above the 0 mark (a tiny way up).Closed circuit testGMachine Pracshortt.bmpFigure Closed circuit drawTable 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 charact eristicsNameplate InformationNo-load circuit calculationsFigure No-load Fitted-curveThis merchant ship be written asUsing Figure 10 we can use the fitted plot of the no-load vividness 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)1101100.1149214920.2052240.15597100110-0.83149214960.186567-1.1768790110-1.17148015000.16791-1.4930680110-1.56147015000.149254-1.7695570110-2.05147415000.1 30597-2.034760.1110-2.25148315020.112127-1.91737Derivation of power equationFigure 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. outcomeDC 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 set to be 6.25 as compared to the measured and the rated armature resistance it is within range ( difference).The characterisation also helps us actualize how the d c works by using the saturation curves we can determine the point where 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 embed 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 direction 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 represe ntation in terms of how an elevator/lift works.