portable power generator architecture

 hi,
what is the method that is used in small scale diesal/petrol power
generators. are they using a DC generator and convert to AC using
invertors? or are they directly generate AC. in that case how do they
keep the frequency constant? any ideas on this? and /or any pointing
to resources on these subjects is appreciated.

thank you

 

     Inverter generators are still a premium technology and probably (at a wild
guess) represent less than 5% of the market.  Low price sells!

 >or are they directly generate AC
.
     Most generators today directly generate AC,

 >in that case how do they keep the frequency constant?

     Usually done with a very basic mechanical engine governor.


Vaughn

 Frequency on an ac generator depends upon the rpm of the engine.  Depending
upon the winding, the normal engine rpm is 1800 or 3600 rpm.  Better
generators run at 1800 rpm, while the inexpensive ones run at 3600 rpm.

A simple governor will tend to keep the frequency nearly constant.  For most
purposes, it does not matter if the frequency wanders a bit.  57 or 63 Hz
will run a tv set just as nicely as 60.  For clocks that have a synchronous
motor, all that is important is that the average is correct.  In the old
days, we used to see if the generator was running at the correct rpm by
using a clock with a second hand.

Even the power company is not perfect at 60 Hz.  They wander a big.
However, they count Hz, and at the end of the day, they will have the right
number - which keeps your clock happy.

If you buy a digital clock, you can let the generator wander.

Inverter technology is good when it comes to saving fuel at low loads.
Since the generator puts out dc, the rpm does not matter.  So, at low power
output, the rpm remains low.  The typical ac generator must run at full rpm
all the time just to keep the frequency constant.

Colin