On 3/21/2019 9:47 AM, J.B. Wood wrote:
On 3/21/19 9:33 AM, Adrian Caspersz wrote:

After a quick google, I found this paper.

Â*Â*Design and Construction of 1kVA Inverter
Â*Â*http://www.ijeert.org/pdf/v2-i3/29.pdf

and also

Â*Â*250W PWM inverter circuit SG3524
Â*Â*http://www.circuitstoday.com/pwm-inverter-circuit

Hello, and thanks for the above link and the others! Looks like those
designs depend on R-C time constants rather than crystals.Â* And
crystals, like resistors and capacitors can age with time.Â* Whether or
not those designs you referenced are employed in inverter generators is
TBD.Â* It's not so much an issue which time-base (oscillator frequency)
works better when new at room temp but how it behaves in the outdoor
operating environment of temperature, humidity, vibration,
rough-handling, etc, including component aging.Â* Mea culpa for posting
design questions to a repair ng.Â* Sincerely,

Youa culpa because you posted a vague question and expected a precise/exact
answer.
How much accuracy do you need?
Call up a few vendors and ask if they can meet that spec over all your
environmental conditions and time. Good luck with that.

If you need PRECISE frequency, you'll probably also be unimpressed with
the phase noise, or high frequency components of the digital approxmiation
to a sine wave.

The reason to have an inverter is reduced fuel consumption under light load.
I don't have any specific info, but expect that there are inverter
generators
that do not have accurate sine wave output.

Your problem is likely much more complex than you think.

People can't help solve your problem if you can't disclose it.
Feel free to continue to waste your (and other's) time.