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What is the excitation system in a generator used for?
The excitation system is used to control the excitation of the rotating field in the armature. By increasing the armature current, it in turn increases the magnetic flux in the armature coil. This has the effect of increasing the voltage output of the generator. By lowering the armature current this in turn lowers the generator output voltage. The generator's voltage regulator automatically adjusts the output voltage continuously as the applied load on the generator changes.
What voltage is generally used for field excitation?
For a small generator like the 125 Watt Alternator/Generator in your car, 12 Volts at a couple Amps. For a large 1,200,000,000 Power Plant Generator typical excitation is 600V at 8000A.
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 the formula for excitation voltage?
E=Vt + Ia jXS Where E excitation voltage Vt Terminal voltage Stator Current Ia Xs synchronous Reactance
How do you explain excitation?
by increasing the terminal voltage
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.
What effect if excitation voltage raise on load?
The generator terminal voltage will increase.
What is the excitation system in a generator used for?
The excitation system is used to control the excitation of the rotating field in the armature. By increasing the armature current, it in turn increases the magnetic flux in the armature coil. This has the effect of increasing the voltage output of the generator. By lowering the armature current this in turn lowers the generator output voltage. The generator's voltage regulator automatically adjusts the output voltage continuously as the applied load on the generator changes.
What happens at the rated value of the voltage of the generator?
The rated voltage of a generator decreases due to many causes such as armature reaction, overloading of the generator and AVR failure/ weak excitation voltage.
How variable speed generator works and its specification?
First you have to understand how a generator works. Basically the excitation voltage is what varies according to generator output. Usually on a power source that has a inconsistant rpm, the excitation voltage will vary similar to a govenor in order to hold the generator output constant.
What voltage is generally used for field excitation?
For a small generator like the 125 Watt Alternator/Generator in your car, 12 Volts at a couple Amps. For a large 1,200,000,000 Power Plant Generator typical excitation is 600V at 8000A.
What is the excitation of the generator?
The rotor must have a magnetic field in order to generator voltage in stator winding. The exciter circuit generates this DC filed in the rotor.
Where does the voltage that is necessary for field excitation on the rotor originates from?
The excitation current is provided by a small self-excited pilot generator, attached to the same shaft as the alternator's rotor.
What is excitation and why is it needed for start up in an AC generator?
An alternator is just another name for a synchronous generator. Excitation is needed to create a magnetic field in the rotor. When to rotor is spun with excitation the magnetic field will cut through the stator field and produce an AC voltage in the stator field. In terms of an alternator with built in rectifier the stators AC voltage in the rectified to DC. The strength of excitation will determine the alternators output voltage. The AVR Automatic Voltage Regulator built into almost every alternator controls field current to maintain a constant output voltage.
What is meant by the term excertation current when refering to generator?
Excitation current in a generator refers to the current supplied to the rotor windings to create a magnetic field necessary for generating electricity. This current is crucial for controlling the voltage output and overall performance of the generator. By adjusting the excitation current, operators can regulate the generator's voltage and ensure stable operation under varying load conditions.
What is meant by static excitation?
Static excitation refers to a method of supplying direct current (DC) to the rotor windings of a synchronous machine, such as a generator, to establish a magnetic field. This excitation is "static" because it typically involves the use of a stationary power source, like a rectifier, to convert AC voltage from the generator into DC. The static excitation system allows for precise control of the machine's output voltage and reactive power, enhancing stability and performance. It contrasts with dynamic excitation systems, which use rotating equipment to provide excitation.
Why terminal voltage of the self-excited shunt generator lower than that of the separately excited shunt generato?
Some generators are self excited; this means their terminal voltage is fed back to the excitation system to supply power to the rotor of the generator (which makes it into an electromagnet); the more power that is fed back, the stronger the electromagnet becomes, which makes it harder to turn the generator, which causes the generator to push out more power (simplified, really quick version). If there is a fault electrically near the terminal of a self excited generator, the terminal voltage will sage to near zero; this means the voltage supplied to the excitation system will drop by the same percentage (say the terminal voltage is 30% of what it should be, then the maximum supplied voltage to the excitation system drops to 30% of what it normally is, since P = V*I). Since the input power is less, the output of the generator will decrease (current will decrease). The terminal voltage is determined by the impedance between the generator and the fault such that V = I*Z; As I decreases, V will also continue to fall, causing the terminal voltage to sag even more. A non-self excited generator gets its' excitation power from the grid, specifically from a location that is electrically separated from its' terminal voltage. If the terminal voltage sagged to 30% (same fault location as above example), the excitation system voltage may be impacted slightly (say 2%) so the excitation system power is near maximum (98% for this example). Since the excitation system is much farther removed from the terminal voltage, it is not dependent upon it, thus the terminal voltage will not continue to sag as with a self excited system.
