Why is S_{RATED}=I_{RATED}V_{RATED} Insufficient for Synchronous Generators?

In summary, when determining the voltage regulation of a synchronous generator, it is not sufficient to use the formula S_{RATED}=I_{RATED}V_{RATED} as we do for transformers. This is because the generator is a 3-phase machine, and the apparent power is calculated using √3 Voltageline ⋅ Currentline. It is important to divide S by three in order to get the correct result.
  • #1
sandy.bridge
798
1
Hey all,

If we are given a synchronous generator with the following nameplate values 10MVA, 13.8kV, 2 pole, 60 Hz

why is it not sufficient to go
[tex]S_{RATED}=I_{RATED}V_{RATED}[/tex]

as we did for transformers?

My reason for asking is because I am trying to determine the voltage regulation of a particular generator. However, if I determine the full load current using the above formula, I get an absurd result.
 
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  • #2
Is the generator a 3 phase machine? If so, the apparent power = √3 Voltageline ⋅ Currentline.
13.8kv is a line voltage.
 
  • #3
How silly of me. Honestly, this entire time my issue was that I did not divide S by three. Thanks!
 

FAQ: Why is S_{RATED}=I_{RATED}V_{RATED} Insufficient for Synchronous Generators?

What is a synchronous generator rating?

A synchronous generator rating is a measure of the maximum output power that a generator can produce under specific conditions. It is typically expressed in kilovolt-amperes (kVA) or kilowatts (kW) and is determined by the design and construction of the generator.

What factors affect the synchronous generator rating?

The synchronous generator rating is affected by various factors such as the size and type of the generator, speed and frequency, temperature, altitude, and type of cooling system. Other factors that can affect the rating include the type and quality of the materials used, the efficiency of the generator, and the load it is designed to handle.

What is the difference between prime and standby ratings for synchronous generators?

The prime rating of a synchronous generator refers to its continuous power output capability, while the standby rating refers to its maximum power output in emergency situations. The prime rating is typically used for continuous operation, while the standby rating is only used when the primary power source fails.

How do you calculate the synchronous generator rating?

The synchronous generator rating is calculated by multiplying the generator's voltage and current ratings. For example, if a generator has a voltage rating of 480 volts and a current rating of 100 amps, its rating would be 48,000 VA or 48 kVA. However, the actual rating may vary depending on other factors such as power factor and temperature.

What is the importance of the synchronous generator rating?

The synchronous generator rating is crucial because it determines the maximum power that the generator can supply. This information is essential for selecting the appropriate generator for a specific application and ensuring that it can handle the expected load without being overloaded. It is also necessary for proper maintenance and operation of the generator to avoid damage or failure.

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