1. Sep 12, 2015

### cnh1995

What is the exact procedure for finding regulation of a synchronous generator by direct loading? We have it in our syllabus..For full load,I know the initial steps till the rated voltage is obtained at rated speed on no load. But when the load is switched on, my book says:
1.Terminal voltage reduces, so it is brought back to rated value by changing excitation.
2. Speed reduces, so it is brought back to rated value by speeding up the prime mover.
3. Then the load is thrown off and further procedure is done.
But in some books, step 2 is omitted. What is the right way?

2. Sep 12, 2015

### Staff: Mentor

It sounds like you are connecting the synchronous generator to a local load, not to the power grid.

When serving a local load, voltage, speed and frequency may not be very important. If so, then either or both of steps 1 and 2 might be skipped.

The "natural" environment for a synchronous generator is connected to the grid, not to a local load. There is no reason to select a synchronous generator rather than an induction generator to serve a purely local load. I object to the educational practice of teaching synchronous generators labs with local loads.

3. Sep 12, 2015

### cnh1995

Yes, its connected to local load in our lab. But why voltage, frequency and speed are not important for local loads?
Also, due to the local load, alternator slows down. But what will happen if it were connected to the grid instead? It won't slow down, right?

4. Sep 12, 2015

### Staff: Mentor

Importance is determined by the load. A resistive load is insensitive to frequency. Also, most real life loads are designed for nominal voltage +- 10%. Inside that range, they don't care about voltage.

If you connect a synchronous generator to the grid, it's frequency becomes grid frequency exactly. That is why we use the word synchronous. It must be "syncronized" with the grid. The real power flow may be plus or minus, making the machine a generator or motor, depending on the mechanical power on the shaft.

If you raise/lower the voltage while connected to the grid, the reactive VAR flow increases/decreases changing the power factor. That may be good or bad, depending on what the grid needs.