Synchronous generator variable speed and constant excitation

In summary, a synchronous generator with a fixed excitation current is the same as a permanent magnet generator. It would be possible to use this kind of installation with a regenerative converter like in wind turbines, but there would be a feedback loop that compares terminal voltage with a set point, and manipulates excitation to hold that voltage constant.
  • #1
Vanguard
2
0
TL;DR Summary
will an electrically excited synchronous generator act as permanent magnet generator if provided with the similar excitation current at any speed?
The question is regarding an electrically excited synchronous generator.
Consider that this generator is not connected to the grid and thus not locked with the grid frequency.
This generator is spinning at variable speed and gets constant and similar excitation current
meaning that the excitation current does not change with the speed.
Will this in fact mean that this generator is acting as a permanent magnet generator?
 
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  • #2
Vanguard said:
Summary:: will an electrically excited synchronous generator act as permanent magnet generator if provided with the similar excitation current at any speed?

The question is regarding an electrically excited synchronous generator.
Consider that this generator is not connected to the grid and thus not locked with the grid frequency.
This generator is spinning at variable speed and gets constant and similar excitation current
meaning that the excitation current does not change with the speed.
Will this in fact mean that this generator is acting as a permanent magnet generator?
Welcome to PF.
The synchronous generator frequency is always proportional to the RPM.
The output voltage is proportional to the product of RPM and field strength.

If you replace the field with permanent magnets, then the voltage and the frequency will still be proportional to the RPM. So a fixed field current is the same as a permanent magnet field.
 
  • #3
thank you.
I'm wondering if this kind of application makes sense over a PMSG.
would it be possible to use this kind of installation with a regenerative converter like in wind turbines
that usually use an induction machine or a PMSG.
Also, how would you determine what is the optimal excitation current?
intuitively, I would use the current that produces the rated voltage at rated speed (e.g 11kV@1500RPM)
 
  • #4
Often, there is a feedback loop that compares terminal voltage with a set point, and manipulates excitation to hold that voltage constant.
 

FAQ: Synchronous generator variable speed and constant excitation

1. What is a synchronous generator?

A synchronous generator is a type of electrical generator that produces alternating current (AC) by converting mechanical energy into electrical energy. It consists of a rotor (rotating part) and a stator (stationary part) that work together to create a magnetic field and induce voltage in the stator windings.

2. What is variable speed operation in a synchronous generator?

Variable speed operation in a synchronous generator refers to the ability to adjust the speed of the rotor to match the required frequency of the generated AC output. This is achieved through the use of electronic control systems that can vary the speed of the prime mover (such as a turbine or engine) that drives the generator.

3. What is constant excitation in a synchronous generator?

Constant excitation in a synchronous generator means that the magnetic field produced by the generator's rotor remains at a constant level, regardless of changes in the generator's output or speed. This is achieved through the use of a voltage regulator that adjusts the amount of current supplied to the generator's field winding.

4. What are the advantages of using a synchronous generator with variable speed and constant excitation?

Using a synchronous generator with variable speed and constant excitation allows for more efficient and flexible operation. It can adapt to changes in load demand and maintain a stable output frequency, resulting in improved power quality. It also allows for better control of the generator's output and can reduce wear and tear on the generator and its components.

5. What are some common applications of synchronous generators with variable speed and constant excitation?

Synchronous generators with variable speed and constant excitation are commonly used in renewable energy systems, such as wind turbines and hydroelectric power plants. They are also used in diesel-electric generators, combined heat and power (CHP) systems, and in industries that require precise control of power output, such as steel mills and chemical plants.

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