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Onan Paralleled with an Inverter Based Machine?

Zephyr7

Registered
If the inverter is outputting a frequency based on an oscillator it would be a constant frequency and should act like an isochronous non inverter set (steady frequency with no droop). It seems to me the only way to couple them would be to parallel them with the inverter set at full load, then add throttle on the non inverter set to share that load. Possibly add more load until both sets are st or near full output. Problem now is when you shed ANY load from the “grid” the mechanically governed set will try to raise the grid frequency above the oscillator frequency (basically a reverse current situation”. I have no idea how the inverter could deal with that other than having a frequency droop option as it cannot control the mechanical governor which is now attempting to raise frequency :shrug:
It's actually pretty simple on the control side. The "smart" generator's brain only really needs to know two things: how much power is going to the load from the generator it controls, and what is the phase/frequency of the inverter with respect to the line?

All the generator's brain is really doing is the following:
1 - Match the frequency of the line
2 - Measure the output kw of the smart generator
3 - Advance or retard the phase of the output sinewave until the kw measured in step (2) is whatever is desired.

Phase control of an inverter is REALLY simple. Numerically controlled oscillators have some similarities, so this link might provide more info as to how it can work: https://en.wikipedia.org/wiki/Numerically_controlled_oscillator

Most of those inverters are going to be PWM based, so a microprocessor is already under complete control of the waveform. Phase can be controlled by simply changing the timing of the PWM modulator a little bit (wider pulses sooner means a leading phase angle, for example). Its really easy to implement. Since the phase of the generator with respect to the line is what controls how much power the generator puts into the line, all you need to do is adjust the output phase until you see the load you want on the generator. There's not a whole lot more to it.

Bill
 

Zephyr7

Registered
Ok, now I'm really intrigued! How exactly does THAT motor operate? It looks REALLY neat!! :D
That does look cool!

I'm going to guess that as those brushes are moved, which appears to be a form of speed adjustment, the timing (or phase) between the stator and rotor varies. I'm guessing though. I've never seen such a fancy commutator before!

Bill
 

Zephyr7

Registered
no a Honda inverter generator will not pair with "standard" generator, i just tested, this out quick, :D
https://youtu.be/a5S3RaQftbs
Did you have them paralleled directly (really wired together), or just through the light bulbs? I’m thinking if only through the lightbulbs, the high-ish impedance might have been a problem.

Might also just be a problem for it trying to track a drifty governor like I’d mentioned earlier too.

Bill
 

turtmaster

Subscriber
Last Subscription Date
10/03/2019
Just through the light bulbs, I might later try to parallel through 1500 watt 240 volt halogen light bulb, don't want to try doing it directly, the cck was at about 62 Hertz, I don't think the high impedance, is a problem, before starting the Honda when just cck was running, the light bulbs will light up.
 

Zephyr7

Registered
Light bulbs are very nonlinear in their resistance. When they heat up, the resistance of the filament is MUCH higher. That might also be a problem.

If you want to do the paralleling experiment safely, parallel the two generators through a fuse. Use a 600V fuse, which will be one of the kinds used in electrical panels, NOT one of the small glass body fuses. I’d try maybe a 5 or 10 amp fuse. The fuse should pop fast enough to protect things, but it won’t have any weird resistance issues the way the light bulbs do.

Bill
 

Vanman

Subscriber
Last Subscription Date
07/10/2019
Yeah, those bulbs are WAY too much resistance. Looked like the Honda kept sensing the voltage from the Onan, but as soon as it would try to take current, the voltage would fall off, being dropped across the bulbs.

The heater stands a chance of working. A larger one is more likely to work. But the fast blow fuse is the best test, as long as it is big enough to pass the current the Honda might try to take from the Onan, which will, at least in part, depend on the load on the system...
 

turtmaster

Subscriber
Last Subscription Date
10/03/2019
The way the Hondas parallel with another Honda inverter series generator, is that you electrically parallel the two generators, start one generator, then start the other generator, in the second generator then "matches the phase" of the other generator. How I paralleled these 2 generators, was by wiring the neutrals together, and then wiring the two light bulbs in series between the two hot conductors, with no other load on the system. It was just basically a test to see if the Honda could "match" to a different frequency, there were no loads across the parallel, the control Transformer, to supply the voltage to the oscilloscope, was wired across the two hot conductors, just like light bulbs, basically all the wiring was basically a "poor man's synchroscope" set up, with no actual "parallel feature/switch-gear",

I would be willing to repeat the test sometime with the 1500 watt 240 volt light bulb, but I I'm not willing to repeat the test with an actual parallel with a fuse, if I needed a 600 v fuse, like that one mentioned, I do have access to them, I just a not ready willing to take a chance of possibly, of frying a $600-$800 inverter board, on a generator with only 105 hours on it.
 

willie1959

Registered
I have done this for 10 years like this . Onan Bge 4.5kw

Start ac unit draw 13 amps loaded .

Start Onan set hertz at 60.2

Let inverter lock on .

Readjust hertz if necessary. Inverter seems to like low hertz 59-60 .

Next problem is total harmonic distortion . Most inverters require below 3%. So this is a good test to see how clean the power you are producing is.

Mechanical governor is too slow . Current project is to put fuel injection on Onan, it can be done. GM injector hall sensor on PTO shaft and control board .

or
electronic governed carburetor

Note: max amps from Onan set at 10 amp by inverter control. Suggestion you need a current limiter to do this restricting current flow though to main circuit.

yes I have too much spare time until the NFL starts

going to the lake today

Fishing opens next Saturday yabba dabba doo
 

armandh

Sponsor
Last Subscription Date
09/02/2010
Ok, now I'm really intrigued! How exactly does THAT motor operate? It looks REALLY neat!! :D
these are [pre VFD] Very old school, variable speed 3 phase AC motors.
VERY EFFICIENT near constant torque and the KWH went up with the speed and load
popular with one of the two machine manufacturers to the industry I was in.
I even saw a few in the 3hp range made by GE [1960s]

https://www.electrical4u.com/schrage-motor-operation-principle-and-characteristics-of-schrage-motor/
[not shown in their drawing is the segment connection to the tertiary rotor winding]

as I recall the rotor primary 3 phase was often 12 lead and could be re bolted on the back of the slip-rings
380/760 Y or 220/440 delta [wound for other custom voltages as needed]

Dreisilker in Chicago could rewind them, $$$ and one learned not to neglect contact maintenance

BUT ON SECOND THOUGHT...
a large inverter run from paralleled DC supplies might be easier to control.
 
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Zephyr7

Registered
I would be willing to repeat the test sometime with the 1500 watt 240 volt light bulb, but I I'm not willing to repeat the test with an actual parallel with a fuse, if I needed a 600 v fuse, like that one mentioned, I do have access to them, I just a not ready willing to take a chance of possibly, of frying a $600-$800 inverter board, on a generator with only 105 hours on it.
I certainly understand your desire to ensure smoke only comes out of the exhaust and not the electronics :D

My guess is that with the lower resistance of the heater, the Honda will be able to track the line better by I don’t know how well it will deal with a drifty mechanically governed genset. There are reports they have successfully paralleled with stable sources like utility power but I’m not aware of anyone trying with less stable sources.

Bill
 

Zephyr7

Registered
Invert until it Hertz. Or just take the stairs.....easy now, one step at a time, don't trip. :)
Yucky stepped sine wave :(

With one more step, it would be easy to low-pass filter it to get a nice sinewave output. A lot of the older big (100+ KVA) Liebert UPSes did that. The only downside is the BIG AC capacitor banks needed, and they are a scheduled maintenance item.

Bill
 

Zephyr7

Registered
Looks like your grid has some lagging power factor loading going on, and maybe a bit of noise too. Nothing a few caps can't fix :)

Inverter output looks really clean. What kind of inverter are you using there? High frequency PWM type?

Bill
 

OnanParts

Sponsor
Last Subscription Date
06/20/2020
Looks like your grid has some lagging power factor loading going on, and maybe a bit of noise too. Nothing a few caps can't fix :)

Inverter output looks really clean. What kind of inverter are you using there? High frequency PWM type?

Bill
Negative on the HF. Got caps and lots of copper! :)
 

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Vanman

Subscriber
Last Subscription Date
07/10/2019
I know that the marketing wanks like to call them "Modified Sine Wave" inverters, but what they really mean is Modulated Square Wave. :brows: The only similarity to a sine wave is the fact that it is indeed Alternating Current. :D
 
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