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What is the main advantage of having multiple generators operating in parallel?
What is the main advantage of having multiple generators operating in parallel?
What is the condition required for paralleling generators?
What is the condition required for paralleling generators?
What is the purpose of the governor mechanism on a prime mover?
What is the purpose of the governor mechanism on a prime mover?
What is the speed droop (SD) of a prime mover defined by?
What is the speed droop (SD) of a prime mover defined by?
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What is the characteristic of a synchronous generator with increasing power demand?
What is the characteristic of a synchronous generator with increasing power demand?
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Why is it possible to operate only a fraction of the generators in parallel?
Why is it possible to operate only a fraction of the generators in parallel?
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What is the consequence of the failure of one generator in a parallel system?
What is the consequence of the failure of one generator in a parallel system?
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What is the advantage of using multiple generators in parallel over a single large generator?
What is the advantage of using multiple generators in parallel over a single large generator?
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What is the typical speed droop of most generator prime movers?
What is the typical speed droop of most generator prime movers?
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What is the relationship between the shaft speed and the resulting electrical frequency?
What is the relationship between the shaft speed and the resulting electrical frequency?
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What determines the terminal voltage of a synchronous generator when a lagging load is added?
What determines the terminal voltage of a synchronous generator when a lagging load is added?
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What is the characteristic of an infinite bus power system?
What is the characteristic of an infinite bus power system?
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What controls the generator's operating frequency when operating alone?
What controls the generator's operating frequency when operating alone?
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What is the purpose of a governor mechanism in a generator?
What is the purpose of a governor mechanism in a generator?
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What is the relationship between the real power and the frequency of a generator?
What is the relationship between the real power and the frequency of a generator?
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What is the advantage of connecting a generator to an infinite bus system?
What is the advantage of connecting a generator to an infinite bus system?
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What is the formula for calculating electrical frequency in a synchronous generator?
What is the formula for calculating electrical frequency in a synchronous generator?
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Why are synchronous generators operated in parallel?
Why are synchronous generators operated in parallel?
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What is the characteristic of a cylindrical-rotor synchronous generator?
What is the characteristic of a cylindrical-rotor synchronous generator?
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What is the effect of increasing the mechanical speed of rotation of a synchronous generator?
What is the effect of increasing the mechanical speed of rotation of a synchronous generator?
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What is the typical rating of a hydrogenerator?
What is the typical rating of a hydrogenerator?
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What is the purpose of a governor mechanism in a synchronous generator?
What is the purpose of a governor mechanism in a synchronous generator?
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What is the characteristic of a salient-pole synchronous generator?
What is the characteristic of a salient-pole synchronous generator?
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What is the effect of increasing the number of poles in a synchronous generator?
What is the effect of increasing the number of poles in a synchronous generator?
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What is the advantage of using a direct-conductor cooling system in a synchronous generator?
What is the advantage of using a direct-conductor cooling system in a synchronous generator?
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What is the term for a system where multiple generators are connected to a common bus?
What is the term for a system where multiple generators are connected to a common bus?
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Study Notes
Advantages of Operating Generators in Parallel
- Several generators can supply a bigger load than one machine by itself.
- Having many generators increases the reliability of the power system, as the failure of one of them does not cause a total power loss to the load.
- Having many generators operating in parallel allows one or more of them to be removed for shutdown and preventive maintenance.
- Operating multiple smaller generators in parallel allows for more efficient operation, as only the required number of generators need to operate near full load.
Conditions Required for Paralleling
- The rms line voltages of the two generators must be equal.
- The two generators must have the same phase sequence.
- The phase angles of the two a phases must be equal.
- The frequency of the oncoming generator must be slightly higher than the frequency of the running system.
Frequency-Power and Voltage-Reactive Power Characteristics of a Synchronous Generator
- Prime movers tend to behave similarly, with speed decreasing as power drawn from them increases.
- Governor mechanisms are used to make the decrease in speed linear with an increase in power demand.
- The speed droop (SD) of a prime mover is defined by the equation SD = (n nl - n fl) / n nl.
Synchronous Generator Types
- Salient-pole synchronous generators have a non-uniform air-gap and are typically used for hydroelectric power generation.
- Cylindrical-rotor synchronous generators have a uniform air-gap and are typically used for turbogeneration.
Operation Principle
- The rotor of the generator is driven by a prime-mover.
- A dc current flowing in the rotor winding produces a rotating magnetic field within the machine.
- The rotating magnetic field induces a three-phase voltage in the stator winding of the generator.
Electrical Frequency
- The electrical frequency produced is locked or synchronized to the mechanical speed of rotation of a synchronous generator: fe = (120 * P) / nm.
Parallel Operation of AC Generators
- Synchronous generators are operated in parallel to provide a larger total power output and to improve system reliability.
- The relationship between frequency and power can be described quantitatively by the equation.
- The relationship between reactive power Q and terminal voltage VT can be derived similarly.
Operation of Generators in Parallel with Large Power Systems
- An infinite bus is a power system so large that its voltage and frequency do not vary regardless of how much real and reactive power is drawn from or supplied to it.
- The power frequency characteristic of such a system is shown in Figure.
- When a generator is connected to an infinite bus in parallel, the generator's prime mover and field controls determine the operating frequency and terminal voltage.
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Description
Discover the benefits of operating multiple generators in parallel, including increased reliability and efficiency. Learn how this setup can improve power supply and maintenance.
