Avoid short circuit of RPS output terminals. Give the limitations of Superposition theorem? This theorem permits in to transfer source from one position in the circuit to another and may be stated as under. OR In any linear bilateral network, if an e. However, currents in other branches will not change. Adjust the output voltage of the regulated power supply to an appropriate value Say 20V. Note down the current through 2. Reduce the output voltage of the RPS to 0V and switch-off the supply.
Disconnect the circuit and connect the circuit as per the fig 2. Connect the circuit as shown in the above figure. Apply the voltage 12V from RPS. Now vary the load resistance RL in steps and note down the corresponding Ammeter. Tabulate the readings and find the power for different load resistance values. Draw the graph between Power and Load Resistance. After plotting the graph, the Power will be Maximum, when the Load Resistance will be equal to source Resistance 12 Where Vth is the open circuit voltage across branch the two terminals and Rth is the resistance seen from the same two terminals by replacing all other sources with internal resistances.
Connect the circuit as per fig 1 2. Adjust the output voltage of the regulated power supply to an appropriate value Say 25V. Note down the response current, IL through the branch of interest i. AB ammeter reading. Reduce the output voltage of the regulated power supply to 0V and switch-off the supply.
Disconnect the circuit and connect as per the fig 2. Adjust the output voltage of the regulated power supply to 25V. Note down the voltage across the load terminals AB Voltmeter reading that gives Vth. Disconnect the circuit and connect as per the fig 3. Note down the current I supplied by the source ammeter reading. The ratio of V and I gives the Rth. Disconnect the circuit and connect as per the fig 4. Adjust the output voltage of the regulated power supply to 25V Note down the response current, IN through the branch AB ammeter reading.
What is Rth? Verify IL? NO Characteristic D. C Motor D. C machine. Varying the field current and noting cor responding values of induced e.
For a self-excited machine the theoretical shape of the magnetization Curve is as shown in the figure. The induced e. Hence the curve starts, a little above the origin on y-axis. The field resistance line Rsh is a straight-line passing through the origin. If field resistance is increased so much that the resistance line does not cut the OCC at all then obviously the machine will fail to exite.
If the resistance line just lies along the slope, then machine will just excite. The value of the resistance represented by the tangent to the curve is known as critical field resistance Rc for a given speed. First OCC is plotted from the the readings then tangent is drawn to its initial position. The slope of this curve gives the critical field resistance.
Connect the circuit as per the circuit diagram shown in fig. Keep the motor field rheostat Rsh at minimum position and generator field rheostat at maximum position. Check that the belt on the pulley is free so that there is no load on the pulley. Switch on the DPST swatch. Start the motor slowly by using starter. Adjust the current so that the motor runs at its rated speed.
Now vary the generator field rheostat to increase the field current and take the no load voltage and field current readings. Take the no load voltage values until field gets saturated. Finally set the field rheostats to initial positions then switch off the supply.
Draw the graph between generated voltage and field current. Find the critical field resistance from the tangent line. What is meant by critical field resistance? Residual magnetism is necessary for self excited generators or not. Why this test is conducted at constant speed? C machine and predetermine the efficiency at any desired load both as motor and as generator.
It is a simple indirect method in which losses are determined separately and from their knowledge, efficiency at any desired load can be predetermined. The only test needed is no-load test. This test cannot be performed on DC series motor.
The machine is run as a no load shunt motor at rated speed and with a rated terminal voltage. However, this test is applicable to those machines in which flux is practically constant.
Note down the readings of Ammeter and Voltmeter at no load condition. No Voltage Current 26 We should start the motor under no load 2.
Take the reading without parallax error. The connections must be tight. If voltmeter gives ding then interchange voltmeter terminal connecting of voltmeter. Why the magnetic losses calculated by this method are less than the actual value? Is it applied to D. C series machines? Comment on the efficiency determined by this method.
C shunt motor and to draw its performance curves. In this test the motor directly loaded by connecting brakes which are with pulley and motor is subjected to rated load and entire power is wasted. The belt tightening hand wheels h1 and h2 help in adjusting the load on the pulley so that the load on the motor can be varied. All the connections are as per the circuit diagram. Vary the field rheostat until the motor reaches its rated Speed and take voltmeter and ammeter readings.
Note down all the readings in the tabular form carefully. The field regulator must be kept at its minimum output position. The brake drum of the motor should filled with cold water. The motor should be started without load. Why a 3-point starter is used for starting a D. C shunt motor? If a 3-point starter is not available, how can a D. C motor be started? Explain the function of overload release coil in 3-point starter.
The performance of any transformer calculated by conducting tests. OC and SC tests are conducted on transformer to find the efficiency and regulation of the transformer at any desired power factor.
To find out the constant losses or iron losses of the transformer. To find out the no load equivalent parameters. To find out the variable losses or copper losses of the transformer. To find out the short circuit equivalent parameters.
By calculating the losses and equivalent parameters from the above tests the efficiency and regulation can be calculated at any desired power factor. Connections are made as per the circuit diagram 2. Initially variac should be kept in its minimum position 3. Close the DPST switch 4. By varying Auto transformer bring the voltage to rated voltage 5.
When the voltage in the voltmeter is equal to the rated voltage of HV winding note down all the readings of the meters. After taking all the readings bring the variac to its minimum position 7.
Now switch off the supply by opening the DPST switch. Connections are made as per the circuit diagram. Short the LV side and connect the meters on HV side.
Before taking the single phase, V, 50 Hz supply the variac should be in minimum position. Now close the DPST switch so that the supply is given to the transformer. By varying the variac when the ammeter shows the rated current i. Bring the variac to minimum position after taking the readings and switch off the supply.
In this test direct brakes are applied on the pulley of the motor by using spring balances. When the braking power is increased by tightening the springs then the line current is increased. Connect the circuit as per the circuit diagram. Close the TPST switch. Apply the rated voltage to the stator windings of 3 Phase induction motor with the help of starter. Note down the readings of all meters on no-load. Load the induction motor in steps using the brake-drum arrangement.
At each step note down the readings of all meters up to full load of the motor. Gradually release the load and switch OFF the supply. Using thread, measure the circumference of the brake-drum when motor is at rest. Output Vs Efficiency 2. Output Vs Torque 3. Slip Vs Torque 39 Starting from the other end, identify the first band - write down the number associated with that color Now read the next color, so write down a its vale next to the first value.
Now read the third or 'multiplier exponent' band and write down that as the number of zeros. If the 'multiplier exponent' band is Gold move the decimal point one to the left. If the 'multiplier exponent' band is Silver move the decimal point two places to the left. If the resistor has one more band past the tolerance band it is a quality band. To get better failure rates, resistors are typically specified to have twice the needed wattage dissipation that the circuit produces.
Some resistors use this band for temco information. In general, a capacitor consists of two metal plates insulated from each other by a dielectric. One classification of capacitors comes from the physical state of their dielectrics, which may be gas or vacuum , liquid, solid, or a combination of these. Each of these classifications may be subdivided according to the specific dielectric used. Capacitors may be further classified by their ability to be used in alternating-current ac or direct-current dc circuits with various current levels.
Most plastic film types Figure1 have printed values and are normally in microfarads or if the symbol is n, Nanofarads. Working voltage is easily identified. The unit is picofarads and the third number is a multiplier. Capacitance, tolerance, working voltage and temperature coefficient may be found. Capacitance values are given as number without any identification as to units. Odd looking numbers such as is the previously explained system and means 47 nF.
Figure3: ceramic Disk capacitor 44 Figure 4: miscellaneous schemes. Also under some circumstances and current sourced from them needs to have low source impedance, for example when the capacitor is being used in a power supply circuit as a reservoir capacitor.
If the ESR is high, then it will not be able to deliver the required amount of current in the circuit, without a voltage drop resulting from the ESR which will be seen as a source resistance. It is found that their ESR rises with frequency and this generally limits their use to frequencies below about kHz.
This is not a problem for most applications, such as when they are used in power supplies. However under some circumstances they are not suitable. For example they should not be used around the input circuitry of an operational amplifier. Here even a small amount of leakage can cause problems because of the high input impedance levels of the op-amp. It is also worth noting that the levels of leakage are considerably higher in the reverse direction.
Capacitors have a maximum ripple current they can supply. Above this they can become too hot which will reduce their life. In extreme cases it can cause the capacitor to fail. This is not normally a problem in applications such as decoupling or power supply smoothing, etc.
However they should not be used in circuits where the exact value is of importance. The capacitors themselves are marked so that polarity can easily be seen.
In addition to this it is common for the can of the capacitor to be connected to the negative terminal. Figure 5: Electrolytic capacitor It is absolutely necessary to ensure that any electrolytic capacitors are connected within a circuit with the correct polarity. A reverse bias voltage will cause the centre oxide layer forming the dielectric to be destroyed as a result of electrochemical reduction.
If this occurs a short circuit will appear and excessive current can cause the capacitor to become very hot. Procedure: 1. Connect the main cord to v, 50Hz AC supply and switch on trainer kit. Connect V1 to the voltmeter and adjust voltage to read e. Do the connection as shown in fig. Note the value of V1, V2 and current I through R3. Repeat the steps 5 when only V2 connected as shown in fig. Now verify the superposition theorem. Repeat the experiment for different values of V1 and V2.
Record reading in observation table 1. Refer connection diagram fig. Current meter between H and I. Prepared By: Mr. Sable 4. Sable 5. Verify the superposition theorem. Record your readings in observation table Refer connection diagram fig-3 a , b and c. Sable 6. The small difference is due to meter error, observation error and due to neglecting the internal resistance.
Companybloom Wk Dec. Radia Preetii Oct. Aseel Mustafa Mar. Total views. You just clipped your first slide! An AVO Meter. Superposition theorem states that:. Suppose an electrical circuit having several branches and or loads and also several source some being current source and some being voltage source.
Then Superposition theorem suggests that:. If we find the branch responses Voltage drop and Current through it on a branch due to only of those source by ignoring effect of all other sources or replacing all other sources by their corresponding internal impedance , and repeat the process for every source on the circuit. Then the Combined responses Voltage drop and Current through it on a branch due to all the sources combined is the algebraic sum of responses on the branches due to each individual sources.
If a number of voltage or current source are acting simultanously in a linear network, the resultant current in any branch is the algebraic sum of the currents that would be produced in it, when each source acts alone replacing all other independent sources by their internal resistances.
Circuit Diagram:. In a given figure apply superposition theorem , let us first take the sources V1 alone at first replacing V2 by short circuit. Next, removing V1 by short circuit, let the circuit be energized by V2 only. As per superposition theorem,.
For procedures, see your Electrical Laboratory Manual on page Thevenins Theorem. Apparatus: See in First Experiment above. For single frequency AC systems, the theorem can also be applied to general impedances, not just resistors.
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