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More current in the field coils means a stronger magnetic field for the armature to rotate in. This causes the output voltage for a generator to increase.
For a motor, more magnetic field means that the supply voltage can be matched at a slower armature rotation speed, so the motor runs more slowly but can supply more torque.
What else can I help you with?
Why does external voltage U decrease more with shunt than with separate excitation?
In shunt excitation, the field winding is connected in parallel with the armature, which means that the field current is influenced by the armature current. As load increases, the armature current rises, leading to a higher voltage drop across the armature resistance, which reduces the terminal voltage more significantly than in separate excitation. In separate excitation, the field winding has a constant supply independent of the armature current, maintaining a more stable voltage output under varying loads. Therefore, shunt excitation results in a greater decrease in external voltage due to the combined effects of increased armature current and associated voltage drop.
What is the effect of a increasing the excitation current?
Increasing the excitation current in an electrical machine, such as a generator or motor, typically raises the magnetic field strength. This can lead to an increase in output voltage for generators or enhance the torque and performance in motors. However, excessive excitation can cause saturation of the magnetic core, leading to diminished returns and potential overheating. Proper management of excitation current is essential for optimal machine performance and longevity.
How to test Excitation Current of a transformer?
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
If the excitation of generator changes what happens to the terminal voltage?
By Decreasing the excitation voltage the terminal voltage will decrease and similarly by increasing the excitation voltages the terminal voltage will also increases.
Why voltage regulation of separately excited generator better than that of shunt excited generator?
Voltage regulation of a separately excited generator is generally better than that of a shunt excited generator because it allows for independent control of the excitation level. In a separately excited generator, the excitation current can be adjusted without being influenced by the load current, leading to more stable output voltage under varying load conditions. In contrast, a shunt excited generator's field winding is connected in parallel with the load, making voltage regulation more susceptible to changes in load, which can lead to voltage fluctuations. Thus, the separate excitation enhances performance in terms of maintaining a constant voltage.
Why does external voltage U decrease more with shunt than with separate excitation?
In shunt excitation, the field winding is connected in parallel with the armature, which means that the field current is influenced by the armature current. As load increases, the armature current rises, leading to a higher voltage drop across the armature resistance, which reduces the terminal voltage more significantly than in separate excitation. In separate excitation, the field winding has a constant supply independent of the armature current, maintaining a more stable voltage output under varying loads. Therefore, shunt excitation results in a greater decrease in external voltage due to the combined effects of increased armature current and associated voltage drop.
Why The Excitation current is non-sinusoidal when applied voltage is sinusoidal?
excitation voltage is sinusoidal because it is taken from the terminal of alternator but excitation current is non-sinusoidal because it always dc.
What is meant by regulation or an alternator?
Regulation of an alternator is varying or adjusting the d.c. current flow (excitation current) in the revolving field coil to control the output voltage. When an alternator is subject to varying load conditions, and therefore changing load resistance at the output, the output voltage will vary in response. When output voltage is reduced in response to increased load (reduced output resistance), the "voltage regulator" will respond by increasing the excitation current to increase the voltage output. If load is reduced, the generator will momentarily become over-excited and the ouput voltage will increase. The voltage regulator responds by decreasing excitation current, returning the generator output voltage to its nominal level.
What effect if excitation voltage raise on load?
The generator terminal voltage will increase.
Why does the no-load characteristic differ for increasing and decreasing excitation current?
The no-load characteristic of a generator differs for increasing and decreasing excitation current due to magnetic hysteresis, residual magnetism, and core saturation effects. When the excitation current increases, the magnetic domains in the iron core gradually align with the applied magnetic field, resulting in a higher generated electromotive force (EMF). However, as the excitation current decreases, these magnetic domains do not immediately return to their original unaligned state. This lag in realignment causes the generated voltage to remain higher during the decreasing phase of excitation than during the increasing phase at the same level of excitation current. This phenomenon is known as magnetic hysteresis. Even when the excitation current is zero, the magnetic core retains some level of magnetisation, known as residual magnetism. This residual magnetic field means that when the excitation current starts increasing again, it takes additional current to overcome this residual alignment before the generated voltage rises significantly. As a result, the voltage is initially lower when increasing the excitation current from zero. Conversely, during the decreasing phase, the residual magnetism keeps the voltage higher than it would be if the core were fully demagnetised, further contributing to the difference between the increasing and decreasing curves. As the excitation current increases, the magnetic core of the generator approaches saturation. Near saturation, any further increase in excitation current results in only a small increase in generated voltage because the core's magnetic domains are almost fully aligned. When the excitation current decreases from this saturated state, the magnetic domains gradually return to a less aligned state. This gradual realignment causes the generated voltage to decrease differently than it increased, contributing to the asymmetry between the increasing and decreasing excitation phases.
What is the formula for excitation voltage?
E=Vt + Ia jXS Where E excitation voltage Vt Terminal voltage Stator Current Ia Xs synchronous Reactance
What is knee point voltage of current transformer?
10 % increase in voltage gives you 50 % increase in excitation current is called knee point voltage. To measure this first demagnetise the CT and apply voltage gradually from secondary keeping primary winding open circuited. while doing this above phenomeneo will be obsesrved.
How do you calculate the excitation voltage and current of an alternator?
formals to calculate exciation voltage of alternator
What is the effect of a increasing the excitation current?
Increasing the excitation current in an electrical machine, such as a generator or motor, typically raises the magnetic field strength. This can lead to an increase in output voltage for generators or enhance the torque and performance in motors. However, excessive excitation can cause saturation of the magnetic core, leading to diminished returns and potential overheating. Proper management of excitation current is essential for optimal machine performance and longevity.
What components comprise the excitation current of a transformer?
A transformer's excitation current can be resolved into two components. The first is in phase with the primary voltage, and is responsible for the losses. The second lags the supply voltage by 90 degrees, and is responsible for magnetising the core.
How to test Excitation Current of a transformer?
To test the excitation current of a transformer, you can perform an open-circuit test, where the primary winding is connected to the rated voltage while the secondary winding is left open. Measure the current flowing through the primary winding using an ammeter; this current is the excitation current. It's essential to ensure the transformer is at the specified voltage and frequency during the test for accurate results. Additionally, record the voltage and power factor for further analysis if needed.
If the excitation of generator changes what happens to the terminal voltage?
By Decreasing the excitation voltage the terminal voltage will decrease and similarly by increasing the excitation voltages the terminal voltage will also increases.
