EDIT: I don't understand your generator's "economy, load dependent mode"...never seen that feature, please elaborate.
[...]
Here's what I measure on a nice cool 70 deg night:
volts 121
Amps 11.5
KVA 1.4
KW 1.3 [wow, quite close to our ACs]
PF .94
Inrush 63 amps
[...]
Now let's contemplate what these numbers tell us. If RUNNING the AC
was the only concern, a 1500 watt generator would be more than
enough. However, that's not the issue. In order to RUN the AC, I
have to START it. The issue is whether the generator can supply the
inrush KVAs required to start the compressor. From the above, 121
volts * 63 amps = 7623 volt-amps or 7.6 KVA. (This is worst case
since in reality, the line - even shore power - will sag a bit under
inrush conditions resulting in fewer KVA being required but worst
case is best in these analyses.)
[...]
Apparently it would take an 8 KVA generator to start my AC. That
can't be true since it runs just fine on my Onan 3kw AJ generator.
How? Each generator has a surge rating that is much higher than its
continuous rating. For conventional generators, the instantaneous
surge rating is determined by how much iron and copper there is in
the stator, how strong the field is and how much flywheel effect
there is on the rotating parts. Heavier = better!! After the first
few cycles of inrush, the motor starting capability depends in large
measure on how fast the governor reacts. For inverter generators
such as the Honda EU series, the main limiting factor is how much
current the inverter can supply before going into current-limit mode
and secondarily on how fast the engine can spool up to feed the
inverter. A TYPICAL inrush capacity is 3 times the continuous
rating.
Taking that number, my 3 KVA onan should be able to supply 3 * 3 = 9
KVA surge. Since it easily starts my AC, the evidence is that it
indeed can supply that much current. One can observe the governor
slam the throttle wide open almost instantly when the AC kicks on,
followed by tapering back to about half throttle to run.
This analysis has been pretty straightforward to this point. The
complication arises in that not all generators can supply 3X
starting current. Lightweight and/or cheap generators usually
can't. Iron and copper and rotating mass are minimized to reduce
cost and weight and it kills the inrush capability. For example, I
have a 4 KVA yamaha generator that will not start my 2 HP portable
air compressor even though the inrush is less than 3X the
generator's nominal rating. Just can't supply the umph to make it
happen!
[...]
I feel your predicament. I've read that among large cities, Lahore is one of the world's hottest.
And I've also read that Pakistan is running short of electricity and blackouts are common.
) Use a good generator, like the analysis you've included. Even with a 100% efficient stabilizer, the starting energy has to come from the generator. Large flywheel inertia and low generator impedance are the key. There is no way around this.
2) Use the stabilizer for your EXCLUSIVELY for your TV or other electronics. The stabilizer, will have its own losses, and worst, when the input voltage drops, it attempts to compensate and the input current increases, further exacerbating generator losses due to its impedance.
3) If there is anything you can do, is to correct the power factor to be as close to unity as possible. Things are tights as they are, and you don't want the additional losses created by VARs.
Actually, I heard one UPS manufacturer here say that the capacitors in a VFD could take care of the starting concern. I might possibly start a thread about frequency converters, and whether they can (easily?) be expanded into a UPS, maybe charge pump for charging the battery, and having the ability to connect to solar.
The thing on my mind is the PF of frequency converters. We still have to make an initial search to see what's actually available. I guess that, if we happen to find a versed FC manufacture willing to do a custom design, I might start the thread I mentioned above and also ask concerning improving the PF.
[...]Well, that is, if you have not bought your AC already.
Regarding starting a compressor, while the inrush current seen at startup may be high, it's very brief. Most digital ammeters can't pick it up fast enough.
As far as I understand, you are still chasing after using voltage stabilizers with your ACs (either conventional motor or inverter based).
I expect that the point said about conventional AC compressors also applies for inverter based: a voltage stabilizer doesn't help to run them from a generator.
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