Electrical Power Applications - Statistics Project Example

AC/DC Three phase power application, DC/AC Motors, DC/AC Generators Executive summary The three-phase alternator constitutes a three single-phase windings spaced resulting in a 1200 displacement o the induced voltage in any of the one phase. The connection of the three phase connection is always called a wye connection because the windings looks like letter Y when without the neutral. Even though the AC and DC may serve in the same functions of conversion of electrical energy, the powering and construction occurs differently. Both perform in the conversion of electrical energy into mechanical energy. The existing difference between the two is the power source whereby AC motors get pwer from an alternating current. However, the DC gets its power from a direct current. Some of the sources of direct current include batteries, DC power supplies and AC-to-DC power converter (Brumbach p. 192). Further, the DC wound field motors constitutes a brush and a commutator. These two helps in complementing on the maintenance of motors while also limiting on the speed. Further, the commutator and the brush also help in reducing the life span of the DC motors. On the side of AC, the induction motor does not associate the use of the brushes nor the commutator. The absence of the brushed contributes to the long life expectancies of AC motors. Another main difference exists in the speed control associated with the two. The control of the speed of a DC motor arises from the existing armature winding associated to current. However, the control of the AC motor arises from the action of the fluctuating frequencies. The adjustable frequency drive control helps in varying the frequency of AC motor. The electromagnetic induction occurs when there is electric current, which passes through a fluctuating magnetic field. In an AC generator, there is periodical reversal of direction in the electrical current while a DC involves the flow off current in a specific direction. The difference existing between the AC and DC generators leads to the differences arising in the relationship between output voltage and output power (Brumbach p. 192). The design difference occurs in the way the current flow design occurs in both. In AC generator, the coil carrying the current flow is always in a fixed state while the magnet is in motion. The poles of the magnet are what cause the alternating current sine it force the current to achieve a flow in opposite direction. Aims and objectives To investigate the relationships between the output voltage, output power and power factor of a three-phase alternator and the output line current when supplying a balanced three-phase inductive load To investigate the relationship between the output voltage of a DC series generator and its output current, when driven at constant speed To investigate the relationship between the open circuit voltage and the field current for a DC shunt generator with the field separately excited and driven at constant speed To investigate the relationship between the efficiency of a shunt excited DC generator and its output current, when driven at constant speed. To investigate the relationship between the output voltage and the output power of a three-phase alternator supplying a balanced three-phase resistive load To investigate the relationship between the output voltage and the output power of a three-phase alternator supplying a balanced three-phase resistive load To investigate the relationships between the output voltage, output power and power factor of a three-phase alternator and the output line current when supplying a balanced three-phase inductive load A). DC generator: 1.Test rig_1: The DC series generator The object of this experiment is to investigate the relationship between the output voltage of a DC series generator and its output current, when driven at constant speed Straight portion of the curve: This occurs due to the increase in the output current from its small value which results to an increase in the flex and the subsequent output voltage as long as the object is at a constant speed. The shape of the lower portion of the graph, which is straight, is due to the air gap which exists as the result of the magnetic parts which have not undergone saturation. Test rig 2 Open-Circuit Characteristics of a D.C. Shunt Generator The object of this experiment is to investigate the relationship between the open circuit Voltage and the field current for a DC shunt generator with the field separately excited and Driven at constant speed Upper curve bending: There is a greater need for the field current to trigger a given increase in voltage as compared to the straight portion of the curve. This occurs because of the increasing flux density which results in the poles being saturated. This will require more field current as compared to the lower portion of the curve. This is what leads to the bending of the curve. The curving of the bend is due to the magnetic parts starting to undergo saturation, 3. Test rig_3: Self-excited D.C. Shunt Generator The object of this experiment is to investigate the relationship between the output voltage of a DC shunt generator and output current, when driven at constant speed. The curve for the output voltage against the output current does not start from the origin because of magnetic inertia arising from the residual magnetism occurring at the poles. There is release of emf even when the field current is constant. The flux and the generated emf is directly proportional to the output current meaning that an increase in the output voltage results to increase in the exciting current. This occurs due to the low flux densities and the presence of the air gap, which is constant. The curving bend results from the increasing flux densities thereby making the existing iron path reluctance to be small and straight. This diminishes the direct relation between the output voltage and field current thereby leading to the start of pole saturation. 4.Test rig_4 Efficiency of a Self-Excited D.C. Shunt Generator The object of this experiment is to investigate the relationship between the efficiency of a shunt excited DC generator and its output current, when driven at constant speed. At constant speed, as the output current increases so does the efficiency of the self-exicited D.C shunt generator increases upto a certain point. However, the efficiency remains constant at the point where their beginning of increase in flux density which in turn leads to the start of pole saturation. Further, increase in the output current leads to increase in flux density thereby resulting to high flux densities. The high flux densities coincided with the saturation of the pole leading to the decrease in the efficiency of the self-excited shunt generator. B). AC generator 1. Test Rig_1: Alternator connected in Delta with a resistive load The object of this experiment is to investigate the relationship between the output voltage and the output power of a three-phase alternator supplying a balanced three-phase resistive load. Electrical Power Applications The increase in the output voltage results to the increase in the output power. The voltage waveforms produced on the phase are phase displaced at 1200 from each other. The increase in current, results to the increase in flux and the consequent emf. The curve shown by the power curve results from the exciting current, which helps in neutralizing the effects of armature reaction that are always weakening 2.Test Rig_2: Efficiency of Three-Phase Alternator The object of this experiment is to investigate the relationship between the efficiency of a Three-phase alternator and the output line current when supplying a balanced resistive load. The object of this experiment is to investigate the relationship between the efficiency of a shunt excited DC generator and its output current, when driven at constant speed. At constant speed, as the output current increases so does the efficiency of the self-exicited D.C shunt generator increases upto a certain point. However, the efficiency remains constant at the point where their beginning of increase in flux density which in turn leads to the start of pole saturation. Further, increase in the output current leads to increase in flux density thereby resulting to high flux densities. The high flux densities coincided with the saturation of the pole leading to the decrease in the efficiency of the self excited shunt generator. 3.Test Rig_3: Alternator connected in Delta with an Inductive load The object of this experiment is to investigate the relationships between the output voltage, output power and power factor of a three-phase alternator and the output line current when supplying a balanced three-phase inductive load. The curve for the output voltage against the output current does not start from the origin because of magnetic inertia arising from the residual magnetism occurring at the poles. There is release of emf even when the field current is constant. The flux and the generated emf is directly proportional to the output current meaning that an increase in the output voltage results to increase in the exciting current. This occurs due to the low flux densities and the presence of the air gap, which is constant. The curving bend results from the increasing flux densities thereby making the existing iron path reluctance to be small and straight. This diminishes the direct relation between the output voltage and field current thereby leading to the start of pole saturation. 4.Test Rig_4: Alternator connected in Delta with a capacitive load The object of this experiment is to investigate the relationships between the output voltage, output power and power factor of a three-phase alternator and the output current when supplying a balanced three-phase capacitive load. The loading of the generator leads to the fall of the output voltage due to the increasing flux density. The increase in the load of the generator is what causes the increasing flux density as a result of the armature reaction for the loads used in the process. The object of this experiment is to investigate the relationship between the efficiency of a shunt excited DC generator and its output current, when driven at constant speed. At constant speed, as the output current increases so does the efficiency of the self-exicited D.C shunt generator increases upto a certain point. However, the efficiency remains constant at the point where their beginning of increase in flux density which in turn leads to the start of pole saturation. Further, increase in the output current leads to increase in flux density thereby resulting to high flux densities. The high flux densities coincided with the saturation of the pole leading to the decrease in the efficiency of the self-excited shunt generator. C). D.C. Motor Experiments: Test rig_1: Load characteristics of a D.C. Series Motor The object of this experiment is to investigate the relationships between the speed, power output and efficiency of a DC series motor and the torque produced by the motor. At constant speed, as the output current increases so does the efficiency of the self-exicited D.C shunt generator increases upto a certain point. However, the efficiency remains constant at the point where their beginning of increase in flux density which in turn leads to the start of pole saturation. Further, increase in the output current leads to increase in flux density thereby resulting to high flux densities. The high flux densities coincided with the saturation of the pole leading to the decrease in the efficiency of the self-excited shunt generator. Test rig_2:StartingTorque of a D.C. Series Motor The object of this experiment is to investigate the relationship between the starting (Locked Rotor) torque of a DC series motor and the armature current supplied to the motor. The loading of the generator leads to the fall of the output voltage due to the increasing flux density. The increase in the load of the generator is what causes the increasing flux density because of the armature reaction for the loads used in the process. Test rig_3: 0: Load characteristics of a D.C. Shunt Motor The object of this experiment is to investigate the relationships between the speed, output power and efficiency of a DC shunt motor and the torque produced by the motor. The joint formation of a shunt field, and a series of field, results to desired external characteristics with considerable voltage decrease. The voltage decrease happens in the machine involved in production of the shunt of field, and the compensation (of the voltage drop) occurs in the series machine, which witness an increase in the voltage. Further, the increase in the number of turns also plays a role in compensating the drop in the armature IR. The increase in the number of turns also helps in offsetting the reaction effect thereby resulting to a generator, which has a shape of a flat compound. The generator usually possesses a constant voltage. Conclusion The difference existing between the AC and DC generators leads to the differences arising in the relationship between output voltage and output power. The design difference occurs in the way the current flow design occurs in both. In AC generator, the coil carrying the current flow is always in a fixed state while the magnet is in motion. The poles of the magnet are what causes the alternating current sine it force the current to achieve a flow in opposite direction. The loading of the generator leads to the fall of the output voltage due to the increasing flux density. The increase in the load of the generator is what causes the increasing flux density as a result of the armature reaction for the loads used in the process. Work cited Brumbach, Michael E. Industrial Electricity. Clifton Park, N.Y: Delmar, 2011. Print. Keljik, Jeff. Electricity 4: Ac/dc Motors, Controls, and Maintenance. Clifton Park, NY: Delmar Cengage Learning, 2009. Print. Read More