Quote: As a matter of fact these inverter style gensets are giving the RV A/C industry headackes, Migrains, in point of fact.
To this I say that the inverter gensets are getting a lot of undeserved blame from the RV industry. I've seen it pointed out how a conventional generator is superior for handling load surges because it has more rotating mass and is spinning faster. But I never see any acknowledgement that the inverter generators have an entirely different mechanism for handling load surges that is in many situations vastly superior to the surge handling of a like-sized conventional generator.
The inverter generators can (and do), when operating at less than full load, run their engines at a speed faster than required for the current power demand. This is something a conventional generator cannot do because of frequency control requirements, meaning that the inverter generator has excess kinetic energy available to it instantly. The excess speed figures aren't in the specs, and I have to use Honda numbers because that's all I have. One of the Honda throttle control patents uses 70% as the supplied power vs. maximum power in its design, meaning that the generator can instantly absorb a 43% increase from the current load with absolutely no surge-related voltage drop and no frequency variation. No like-sized conventional generator can do this. There will be an instant voltage drop due to the resistance in the generator windings which the voltage regulator will take at least a few ac cycles to react to, then when it does react and restore the voltage the engine speed will go down causing a frequency variation.
When the load increase exceeds 43% the inverter generator will join the conventional generator in having a power disruption. At the beginning of the disruption the conventional generator's greater rotational mass, also spinning faster, may well keep the voltage drop from being as great as with the inverter generator. Frequency control will suffer. Further into the disruption that increased rotational mass will work against the conventional generator restoring full voltage and the correct frequency. I'd expect the inverter generator to have a greater voltage dip, but to recover from it faster.
Real numbers with a Dometic 13,500 btuh air conditioner and an eu2000i are that on a/c startup the voltage dips to 90 for a second, it's back over 120 within 2 seconds, and there is no frequency hiccup whatsoever. I think it's reasonable to expect a Yamaha 2400 to perform better than this. Until somebody has some real side-by-side comparison numbers for like-sized conventional and inverter gensets, I think these criticisms are based on imaginary data.
2009 Fleetwood Icon 24A
Honda Fit dinghy with US Gear brake system
LinkPro battery monitor - EU2000i generator
Quote: As a matter of fact these inverter style gensets are giving the RV A/C industry headackes, Migrains, in point of fact.
To this I say that the inverter gensets are getting a lot of undeserved blame from the RV industry. I've seen it pointed out how a conventional generator is superior for handling load surges because it has more rotating mass and is spinning faster. But I never see any acknowledgement that the inverter generators have an entirely different mechanism for handling load surges that is in many situations vastly superior to the surge handling of a like-sized conventional generator.
The inverter generators can (and do), when operating at less than full load, run their engines at a speed faster than required for the current power demand. This is something a conventional generator cannot do because of frequency control requirements, meaning that the inverter generator has excess kinetic energy available to it instantly. The excess speed figures aren't in the specs, and I have to use Honda numbers because that's all I have. One of the Honda throttle control patents uses 70% as the supplied power vs. maximum power in its design, meaning that the generator can instantly absorb a 43% increase from the current load with absolutely no surge-related voltage drop and no frequency variation. No like-sized conventional generator can do this. There will be an instant voltage drop due to the resistance in the generator windings which the voltage regulator will take at least a few ac cycles to react to, then when it does react and restore the voltage the engine speed will go down causing a frequency variation.
When the load increase exceeds 43% the inverter generator will join the conventional generator in having a power disruption. At the beginning of the disruption the conventional generator's greater rotational mass, also spinning faster, may well keep the voltage drop from being as great as with the inverter generator. Frequency control will suffer. Further into the disruption that increased rotational mass will work against the conventional generator restoring full voltage and the correct frequency. I'd expect the inverter generator to have a greater voltage dip, but to recover from it faster.
Real numbers with a Dometic 13,500 btuh air conditioner and an eu2000i are that on a/c startup the voltage dips to 90 for a second, it's back over 120 within 2 seconds, and there is no frequency hiccup whatsoever. I think it's reasonable to expect a Yamaha 2400 to perform better than this. Until somebody has some real side-by-side comparison numbers for like-sized conventional and inverter gensets, I think these criticisms are based on imaginary data.
"..imaginary data."
NOT...!
Facts...
The major sales and marketing, market, appeal of these new inverter style gensets is QUIET, the manufacturers are "pushing", justifiably so IMMHO, this issue as a major sales tool.
The ONLY advantage, UNIQUE advantage, the inverter style gensets have over the non-inverter gensets is that there can run, operate, at an engine RPM cognizant with the load demand of the moment, whereas the competition MUST run at a constant, fixed, MAXIMUM speed.
And yes, I agree, I have heard that of more recent times most of the manufacturers of the inverter style gensets have begun, in recognition of the problem, to run the genset RPM significantly above the speed demanded by the current load.
But then that begins to eat into their markeing "advantage", the faster it runs the LOUDER it gets.
Quote: The ONLY advantage, UNIQUE advantage, the inverter style gensets have over the non-inverter gensets is that there can run, operate, at an engine RPM cognizant with the load demand of the moment, whereas the competition MUST run at a constant, fixed, MAXIMUM speed.
Other inverter genset advantages:
1. Frequency is always correct.
2. Superior waveform.
3. Handles poor power factor loads much better.
4. Will drop offline is voltage drops below specs.
I'd like to see some actual measurements to back up the claims of conventional generator superiority. There's a real chance that the inverter generators handle load surges better in an apples-to-apples comparison.
Running the engine faster for seamless response to load increases has been part of the Honda throttle control design from its early days. It's nothing new or recent.
1. Frequency is always correct. There is correct, and then there is MORE correct. Yes, a non-inverter genset's line frequency will vary somewhat as a result of sudden load changes. But can you name me just one load device wherein that will make any difference at all?
IMMHO if the line frequency of the inverter type gensets varied in the same range as the non-inverter type no one, NO ONE, would take notice.
NOT an advantage, certainly not a marketable one.
2. Superior waveform. By who's measure? What does the waveform look like if I have a high wattage battery charger in use? Load current, lots of it, flowing only at PEAK voltage
PUSH on this one, six of one a half a dozen of the other.
3. Handles poor power factor load much better.
Huh...??!!
Where did you fish this one up from? Are you saying that if I slap a highly capacitive load on one vs the other the result will differ? How? Why?
It is my understanding that the inverter circuits are designed with voltage feedback to provide a near perfect 60hz sine waveform, with NO feedback as to current level or current phase shift?
But suppose my highly capacitive load were to shift the current flow phase in comparison to the voltage, what, how, would the genset react in ways differing from a regular genset, or even power from teh commercial grid.
TBD, To be determined.
4. Will drop offline if voltage drops below specs.
My inexpensive 4000 watt electric start Generac does that, and it recovers automatically if the overload is removed. Or are you saying that the inverter type gensets will detect an internal flaw that results in the too low voltage and automatically shut down? The Generac doesn't detect any internal failures just shuts down the output if the voltage is too low.
Same result, a PUSH, again.
Again, the inverter type gensets have ONLY two unique advantages in the marketplace. First, and primarily, low operating noise due to using the inverter, and improved FE as a result of only needing to operate the engine at a high enough level to support the current load.
Start "edging" up the RPM to accomodate surge loads and marketplace the advantage disappear, vanishes.
As an engineer I also appreciate the other design aspects you mention of the inverter type gensets but I would NEVER try to sell them as advantages in the marketplace.
* This post was
edited 08/07/07 10:45pm by wwest *
"....the inverter generators have an entirely different mechanism for handling load surges that is in many situations vastly superior to the surge handling of a like-sized conventional generator."
"..different.." "..vastly superior.."
We shall see...
" The inverter generators can (and do), when operating at less than full load, run their engines at a speed faster than required for the current power demand."
Sorry, but isn't this EXACTLY the way regular gensets operate?
With loads below maximum, regular gensets always "run their engines at a speed faster than required for the current power demand..".
"This is something a conventional generator cannot do because of frequency control requirements, meaning that the inverter generator has excess kinetic energy available to it instantly."
I suppose you're implying that a regular genset running at full load speed, ALWAYS running at full load speed, doesn't have EXCESS kinetic energy to more quickly pick up a surge load.
How can that be..?
Are you by chance overlooking the fact that the engine in the regular genset is specifically designed to produce MAXIMUM HP at the RPM that results in a 60hz line frequency?
I make the assumption that we're talking about both types having equal HP and equal maximum power generation capability.
It seems the problem here is a quick inductive load (AC comp. motor) or a slow response source (Gen rather than shore power)
Now improving the gen. response seems somewhat complicated and therefore costly.
The resistive temporary load prior to compressor starts seems easily doable.
Use a heat strip which most RV'ers use in cooler weather. Use a switching circuit to apply the heat strip for 1,2,or 3 seconds prior to compressor start.
One or two seconds of heat strip would be un-noticed by the user.
Quote: As a matter of fact these inverter style gensets are giving the RV A/C industry headackes, Migrains, in point of fact.
I have never read anything on A/C failures due to inverter gensets here or anywhere on the net, has anybody else? Links? Not saying it ain't true, but lets see some proof.
Wayne Dohnal wrote: Actual test results powering PD9160 power converter with portable generators:
Powerking 2800 watt generator, maximum converter output 35 amps.
Honda 2800 watt generator, maximum converter output 45 amps.
Coleman 2800 watt generator, maximum converter output 50 amps.
Honda 2000 watt inverter generator, maximum converter output 64.5 amps.
The RV power converter is the only load on the generator. I assume this information speaks for itself.
I didn't say that the power converter and/or battery charger wouldn't work, just that without PFC, Power factor Correction, the genset waveform will pickup a LOT of odd harmonics, start looking more like a square wave. PFC generally only exists on PWM, Pulse Width Modulation, power converters.
And the waveform distortion isn't a function of maximum converter capacity as much as it is current load. At 64.5 amps of current draw, assuming no PFC, that genset,s output waveform will be "flat-topped".
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