Hello again, everyone. I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs. My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input. The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation). So
the crystal has to remain reasonably stable in a variety of operating
environments. Sincerely,
--
J. B. Wood e-mail:

On Wednesday, 20 March 2019 16:38:13 UTC, J.B. Wood wrote:
Hello again, everyone. I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs. My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input. The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation). So
the crystal has to remain reasonably stable in a variety of operating
environments. Sincerely,

why would they waste money on a crystal?


NT

On 3/20/19 9:50 PM, wrote:
On Wednesday, 20 March 2019 16:38:13 UTC, J.B. Wood wrote:
Hello again, everyone. I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs. My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input. The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation). So
the crystal has to remain reasonably stable in a variety of operating
environments. Sincerely,

why would they waste money on a crystal?


NT


Hello, and what do you mean by "waste'? Microprocessors typically use a
crystal as a timebase. While I appreciate all the responses to my OP,
It appears no responders have intimate knowledge of the subject internal
circuitry. If I did, I wouldn't have posted. The 50 or 60 Hz output of
the inverter-generator has to be traceable/locked to some internal time
reference, not the rpm of the engine. A crystal seems a likely
candidate as I don't think these appliances have an internal cesium or
rubidium clock :-) Sincerely,

--
J. B. Wood e-mail:

On Thursday, 21 March 2019 10:26:42 UTC, J.B. Wood wrote:
On 3/20/19 9:50 PM, tabbypurr wrote:
On Wednesday, 20 March 2019 16:38:13 UTC, J.B. Wood wrote:
Hello again, everyone. I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs. My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input. The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation). So
the crystal has to remain reasonably stable in a variety of operating
environments. Sincerely,

why would they waste money on a crystal?


NT


Hello, and what do you mean by "waste'? Microprocessors typically use a
crystal as a timebase. While I appreciate all the responses to my OP,
It appears no responders have intimate knowledge of the subject internal
circuitry. If I did, I wouldn't have posted. The 50 or 60 Hz output of
the inverter-generator has to be traceable/locked to some internal time
reference, not the rpm of the engine. A crystal seems a likely
candidate as I don't think these appliances have an internal cesium or
rubidium clock :-) Sincerely,

Welcome to the filter.

On 20/03/2019 16:38, J.B. Wood wrote:
Hello again, everyone.Â* I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs.Â* My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input.Â* The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation).Â* So
the crystal has to remain reasonably stable in a variety of operating
environments.Â* Sincerely,

After a quick google, I found this paper.

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

and also

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


The mentioned IC SG3524 is primarily intended for DC-DC inverter
designs, and the oscillator is programmable by values of R & C.

TI SGx524 Regulating Pulse-Width Modulators
http://www.ti.com/lit/ds/symlink/sg2524.pdf

Although in the above two circuits, I see they set the oscillator lower
(50Hz) than TI's spec sheet (Sec 7.7 , Fig 2)


Have a look around for SG3524 schematics. It's popular!

3 High Power SG3525 Pure Sinewave Inverter Circuits
https://www.homemade-circuits.com/sg...erter-circuit/



--
Adrian C

On 3/21/19 9:33 AM, Adrian Caspersz wrote:

After a quick google, I found this paper.

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

and also

Â*250W PWM inverter circuit SG3524
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. And
crystals, like resistors and capacitors can age with time. Whether or
not those designs you referenced are employed in inverter generators is
TBD. 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. Mea culpa for posting
design questions to a repair ng. Sincerely,

--
J. B. Wood e-mail:

On Thu, 21 Mar 2019 06:26:39 -0400, "J.B. Wood"
wrote:

The 50 or 60 Hz output of
the inverter-generator has to be traceable/locked to some internal time
reference, not the rpm of the engine. A crystal seems a likely
candidate as I don't think these appliances have an internal cesium or
rubidium clock :-) Sincerely,

Ceramic (piezo) resonators are a more likely frequency determining
element.
https://en.wikipedia.org/wiki/Ceramic_resonator
I'll resist the temptation to tear apart my neighbors Genrac inverter
generator to see what it uses. Ceramic resonators have 3 big
advantages over quartz crystals:
1. They're cheaper.
2. They're cheaper.
3. They're cheaper.
However, for a non-critical frequency reference, such as the 50/60Hz
from an inverter, a simple RC time constant with some temperature
compensation would probably be good enough.

Conventional gasoline generators usually run at 3600 rpm, which sets
the output frequency. Inverter generators can adjust the rpm to match
the load and have the inverter section determine the output frequency.
That also allows the generator to brushless, quiet, more efficient,
and have a faster response to changes in load.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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.

On 3/21/19 1:49 PM, Mike wrote:

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.Â* Good luck with that.


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

Hello, and I see nothing "vague" about my OP. And I don't think I ever
implied I had a "problem" nor that I was attempting to construct the
subject appliance. I had a question about commercial design practice
and was seeking some info that I thought some folks on this ng might
know as a result of either repair experience and/or had seen circuit
schematics. Nothing else. Apparently some more polite folks on the ng
saw it this way and folks have helped despite my "lack of disclosure".
And if you thought it was a waste of your time why bother to respond at
all? Judging from your response I think you wasted your time. Sincerely,


--
J. B. Wood e-mail:

On 3/21/19 1:30 PM, J.B. Wood wrote:
And if you thought it was a waste of your time why bother
to respond at all?

Because, some people, all they have to contribute is to ****
in somebody's Wheaties.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

Put in a search (12 to 120 Volt true RMS inverter schematic) and got this, right on top.

https://web.wpi.edu/Pubs/E-project/A.../MQP_D_1_2.pdf

Complete with nice pictures and scope screen-shots.

Looks like the LM348 does the trick.

Peter Wieck
Melrose Park, PA

On Thursday, 21 March 2019 18:30:09 UTC, J.B. Wood wrote:
On 3/21/19 1:49 PM, Mike wrote:

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.Â* Good luck with that.


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

Hello, and I see nothing "vague" about my OP. And I don't think I ever
implied I had a "problem" nor that I was attempting to construct the
subject appliance. I had a question about commercial design practice
and was seeking some info that I thought some folks on this ng might
know as a result of either repair experience and/or had seen circuit
schematics. Nothing else.

I can disappoint you then. My answer comes from understanding the principles behind the designs, which comes from years designing electronic stuff. I've never taken such a gen apart nor do I need to to understand why no-one in their right mind is going to derive the 50 or 60Hz from a crystal. Nor are they likely to clock a rock bottom price processor with a crystal.

Everyone has their point of view, and that's all good, but when you have not a clue and repeatedly criticise those that do, and then criticise peoples' fair criticisms of you... at least the rest of us can figure out where that goes.

On Thursday, March 21, 2019 at 7:30:00 AM UTC-4, wrote:
On Thursday, 21 March 2019 10:26:42 UTC, J.B. Wood wrote:
On 3/20/19 9:50 PM, tabbypurr wrote:
On Wednesday, 20 March 2019 16:38:13 UTC, J.B. Wood wrote:
Hello again, everyone. I did some further online research and it
appears modern inverters use fast-switching insulated-gate bipolar
transistors (IGBTs) in sine-wave and modified sine-wave inverter
designs. My guess is that a microprocessor controls IGBT firing times
as well as engine speed (in an inverter generator) as AC output loads
increase and therefore demand more DC at inverter input. The
microprocesser itself would rely on a crystal as the reference time base
(frequency) source which would ultimately determine the inverter's
output frequency (e.g. 60 or 50 Hz +/- some acceptable deviation). So
the crystal has to remain reasonably stable in a variety of operating
environments. Sincerely,

why would they waste money on a crystal?


NT


Hello, and what do you mean by "waste'? Microprocessors typically use a
crystal as a timebase. While I appreciate all the responses to my OP,
It appears no responders have intimate knowledge of the subject internal
circuitry. If I did, I wouldn't have posted. The 50 or 60 Hz output of
the inverter-generator has to be traceable/locked to some internal time
reference, not the rpm of the engine. A crystal seems a likely
candidate as I don't think these appliances have an internal cesium or
rubidium clock :-) Sincerely,

Welcome to the filter.

The crystal filter? A crystal with several electrodes used to filter frequencies?

On Thursday, 21 March 2019 19:07:19 UTC, Fox's Mercantile wrote:
On 3/21/19 1:30 PM, J.B. Wood wrote:

And if you thought it was a waste of your time why bother
to respond at all?

Because, some people, all they have to contribute is to ****
in somebody's Wheaties.

do you never get fed up with people being stupid?

On 3/21/19 8:34 PM, wrote:
do you never get fed up with people being stupid?

Do you never get tired of always having to be right, even
when you're not?


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

On Friday, 22 March 2019 01:37:29 UTC, Fox's Mercantile wrote:
On 3/21/19 8:34 PM, tabbypurr wrote:

do you never get fed up with people being stupid?

Do you never get tired of always having to be right, even
when you're not?

that's not the situation here.