Generator

rockhardhoosier · October 2023

Ok so here's my system
4 sunny island 6048 inverters
4 midnight 150 charge controllers
4 FLA 540AH batteries.
30-350w panels
10-270w panels.
Everything is working great.
Except when trying to get generator to charge the batteries. Called SMA tech support and all my settings are correct according to them.
So here's what happens. I have Kubota GL7000 generator .When I have the generator running and the inverters call for power. The master kicks open the relay and the generator starts providing power for a split second and then the inverter closes the relay or control switch because of over voltage. When measuring the voltage the voltage is 119v each leg until the generator calls for power and the voltage goes all the way up to 152v per leg. Thinking maybe this could be an AVR problem on the generator ? But if I plug in a heater to the generator the voltage stays around 119. Dont change. What's everyone's thoughts. May I add that I unhooked 2 inverters and 2 batteries from the system because I was thinking drawing to much power for this size generator. And it still done same thing.

Dave Angelini · October 2023

Borrow another generator for test. A 7 kw generator is pretty easy to find and pay for if you need a spare.

SteveK · October 2023

How about if you introduce the generator with a partial load already on it and limit the charge current in the inverter charger? It could be just noisy power and you are seeing the higher voltage for a moment as the relay falls open because of it. Inverter chargers can reject a noisy signal.

It surely doesn't stay at 152V after the relay opens, right?

Graham Parkinson · October 2023

Where and how are you measuring voltage?

BB. · October 2023

Just a couple of questions....

As SteveK asks... Have you tried placing a (relatively) small load of 100 Watts (like a filament light bulb or small electric heater) on the genset, then connect the AC inverter/charger?

Do you have a meter that can read Hz? Is the genset staying within 1% or 5% of the 60 Hz (?--You are in the USA?) line frequency (the ~100 Watt load can also stabilize frequency too for some generators).

Do you have the inverter/charger(s) wired for 120 VAC input only (I don't think the SMA supports 120/240 VAC split phase power)?

What do you have programmed for the max AC input current from the genset?

It sounds like the genset is wired for 120/240 split phase power (vs 120 VAC only) output. That is listed at 29.5 amps max... At 120 VAC split phase output, the genset can output somewhere around:

120 VAC * 29.5 amps = 3,540 Watts max (at least)
120 VAC * 29.8 Amps * sqroot (2) = 5,005 Watt (I have seen some systems single phase * 1.414 (sqroot 2) as high power limit)

So there is no chance that your genset can output anywhere near 7,000 Watts continuous (as I guess for your split phase genset setup).

-Bill

Dave Angelini · October 2023

A good way to add another inverter to the Ebay for sale list is a bad genset. Relays opening/closing under load are the source.

If you keep testing this, at least set the charge amps low and remove house loads.

rockhardhoosier · October 2023

Ok, the house load is not on it when working on this problem. inverters are calling for generator because of battery SOC%, MY charge amps are set low. Not trying to use the generator to supply house but to just charge batteries. Yes in the USA, HZ are staying anywhere from 59hz -62hz. Everything was professionally done. Even had it double checked again by another professional.I talked to SMA tech support and they went through all the settings with me. Sorry if missed some of the questions

SteveK · October 2023

My question above about adding a small load before introducing the generator to the inverter/charger was to help determine if you were experiencing frequency lock issues. A small load will sometimes help smooth out the generator. Not sure if you tried it. Not sure if you would see frequency issues with your tester.

If that shows nothing.

I would try to rewire the inverter charger so that the mains fed the generator inputs and place the inverter charger in to generator only mode via the breakers. If the inverter charger runs well in that configuration the generator must be at fault or I have connection issues between the genset and the inverter charger.

But I am using Schneider. YMMV with SMA.

Good luck!

rockhardhoosier · October 2023

Don't think can add just a small load, the inverters themselves pull I think it's around .9kw, now I took my inside electric grill like an air Fryer which pulls a good amount on start up. I plugged it into the receptacle on the generator and started it up and all the voltages were fine stayed at 118v . But its only a 120v Fryer. Like I said yesterday I turn the load off from the house. Unhooked 3 batteries and two inverters and generator still did an over voltage when inverter called for it. Might need to change out the AVR on the generator.

rockhardhoosier · October 2023

Actually I might have not thought that out ,maybe I can add a small load using the receptacle on the generator. Then let the inverter call for it . This generator operates full throttle at all times. And when the inverters call for it it drags it down pretty good.

SteveK · October 2023

If I read you correctly you said you have no house loads connected and you reduced charge current to a minimal amount. I am confused why there is such a large load on the generator if the above is true. I mean, you own one helluva nice generator there. It's not $100 2-Stroke.

That heavy drag on the generator concerns me with supposedly miniscule charging currents set in the inverter charger and no house loads. I don't think there is initial inrush current of that magnitude to worry about but I could be wrong here.

I'd move to low value breaker protected grid power on the generator inputs to eliminate the generator from suspicion but I won't tell someone else to do it. Like Dave said above every time those relays open under enough load (like you described by the engine loading) is like playing Russian Roulette with your inverter's health.

Does that generator have some form of "ECO" switch by chance? If it does the RPM's may be too low for startup and by switching it off will allow the generator to spool up higher.. Common problem with inverter type generators not that yours is.

rockhardhoosier · October 2023

SteveK said:

If I read you correctly you said you have no house loads connected and you reduced charge current to a minimal amount. I am confused why there is such a large load on the generator if the above is true. I mean, you own one helluva nice generator there. It's not $100 2-Stroke.

That heavy drag on the generator concerns me with supposedly miniscule charging currents set in the inverter charger and no house loads. I don't think there is initial inrush current of that magnitude to worry about but I could be wrong here.

I'd move to low value breaker protected grid power on the generator inputs to eliminate the generator from suspicion but I won't tell someone else to do it. Like Dave said above every time those relays open under enough load (like you described by the engine loading) is like playing Russian Roulette with your inverter's health.

Does that generator have some form of "ECO" switch by chance? If it does the RPM's may be too low for startup and by switching it off will allow the generator to spool up higher.. Common problem with inverter type generators not that yours is.

Yes, this is why I am confused. There is no house load. I had SMA tech support on the line and they had me to change the settings on the inverters and have them call for the gen, and every time it would shut the relay down due to over voltage. I just installed a new AVR and that wasn't the problem. This generator operates at full throttle at all times. I called kubota to make sure this was correct and it is. I am stumped at this point.

rockhardhoosier · October 2023

SteveK said:

How about if you introduce the generator with a partial load already on it and limit the charge current in the inverter charger? It could be just noisy power and you are seeing the higher voltage for a moment as the relay falls open because of it. Inverter chargers can reject a noisy signal.

It surely doesn't stay at 152V after the relay opens, right?

Sorry , did not see this question. Relay kicks out within about 3-4 secs of it calling for the generator, because of over voltage.

BB. · October 2023

When you say runs at "Full Throttle"... Exactly what do you mean?

Typically, a standard genset (gasoline/desiel/etc. motor driving a standard alternator--Not an Inverter-Generator like a Honda or Yamaha type)--The genset runs at a fixed RPM (speed control governor). In the case of this genset (guessing):

https://generator.kubota.com/products/60hz/gl_7000.html

This is a two pole alternator, so the genset runs at 3,600 RPM for 60 Hz (you are in the US?). The throttle (fuel demand) for the engine should vary on engine load... Light throttle when little or no load, and more throttle when driving heavier loads. All based on the governor keeping the engine at 3,600 RPM +/- a couple percent.

For example, if the engine was using "full throttle" with little to no electrical loads, the engine would over speed (much faster than 3,600 RPM) and the line frequency would be well over 60 Hz. (60 cycles per second AC power * 60 seconds per minute = 3,600 RPM with two pole alternator).

The genset only has a volt meter on the main panel... Do you have a DMM (digital multi-meter) that can read frequency?

You can also get current clamp meters that can measure voltage/frequency/AC (or DC current--depending on meter type) current... A nice AC/DC Current Clamp DMM is really nice for debugging power (you only need an AC only current clamp meter for 120/240 AC work--But the DC current clamp function is really nice for solar/battery/etc. DC power system wiring):

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (inexpensive AC+DC clamp DMM)
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid-priced AC+DC clamp DMM)

Or you can even get a nice panel meter to wire into your system:

https://www.amazon.com/s?k=AC+power+meter+frequency&i=industrial&crid=3TR1JYXJYALXW&sprefix=ac+power+meter

-Bill

rockhardhoosier · October 2023

Ok, maybe someone has adjusted the governor up to much, but the current volts it is putting out, at current RPM, is 118 or 234-236. My inverter measures the hertz coming from the generator and I noticed last night it was reading 64.3hz. But if i adjust the RPM at all the volts start dropping down on each leg. Maybe I could adjust down one volt at a time and see when the relay doesn't kick out for over voltage. Just a thought. I am no expert,lol . It really seems like there is a big draw on it when the inverter calls for it, because it drags the generator down. for a couple of seconds. Just a FYI my batteries are hooked in parallel. Which I figure is normal . I am going to order one of the testers. I know I probably did not answer anything you was asking or talking about. LOL

Ralph Day · October 2023

Ive had my generator for years, it's old and I make it run. If; the frequency is over 62hz unloaded (about 60hz loaded) it will have high voltage and flakyness. Utility power is usually 250vac; or so, the generator 240vac. I don't use it much anymore with utility power.

rockhardhoosier · October 2023

BB. said:

When you say runs at "Full Throttle"... Exactly what do you mean?

Typically, a standard genset (gasoline/desiel/etc. motor driving a standard alternator--Not an Inverter-Generator like a Honda or Yamaha type)--The genset runs at a fixed RPM (speed control governor). In the case of this genset (guessing):

https://generator.kubota.com/products/60hz/gl_7000.html

This is a two pole alternator, so the genset runs at 3,600 RPM for 60 Hz (you are in the US?). The throttle (fuel demand) for the engine should vary on engine load... Light throttle when little or no load, and more throttle when driving heavier loads. All based on the governor keeping the engine at 3,600 RPM +/- a couple percent.

For example, if the engine was using "full throttle" with little to no electrical loads, the engine would over speed (much faster than 3,600 RPM) and the line frequency would be well over 60 Hz. (60 cycles per second AC power * 60 seconds per minute = 3,600 RPM with two pole alternator).

The genset only has a volt meter on the main panel... Do you have a DMM (digital multi-meter) that can read frequency?

You can also get current clamp meters that can measure voltage/frequency/AC (or DC current--depending on meter type) current... A nice AC/DC Current Clamp DMM is really nice for debugging power (you only need an AC only current clamp meter for 120/240 AC work--But the DC current clamp function is really nice for solar/battery/etc. DC power system wiring):

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (inexpensive AC+DC clamp DMM)
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid-priced AC+DC clamp DMM)

Or you can even get a nice panel meter to wire into your system:

https://www.amazon.com/s?k=AC+power+meter+frequency&i=industrial&crid=3TR1JYXJYALXW&sprefix=ac+power+meter

-Bill

So, I went in on the generator and lowered the RPM, I finally got the inverter not to kick out by lowering the rpm down until the voltage was at 113-114v, and the hertz was at 57-58hz, when the load kicked in the hertz drop to around 55hz, and volts stayed the same. I measured what amps the inverters were calling for and it was 20amps on each line. But that is a setting in the inverter. I still think something not quite right

BB. · October 2023

Sorry to keep asking the details... Getting power (whether solar, generator, or grid) correct depends on the details.

On the genset--It appears it has a "series/parallel" switch for the AC windings... In series, you have 120 VAC between "black line and neutral", and "red line to neutral"... And 240 VAC between Black and Red Lines (actually, this genset may be rated for 110/220 VAC--Not really a "deal breaker" US/North America power). And a maximum of 29.5 amps (at 220/240 VAC) on either Black or Red (or Line 1 and Line 2 "hots").

You can also flip a switch/setting for parallel AC windings (I believe) that will give you 110 or 120 VAC only output:

https://absolutegenerators.com/media/blfa_files/Kubota_LowBoy_II_Diesel_Generator_GL7000_GL11000_GL_Series_-_Service_Manual.pdf

Rated voltage 120 / 240 V 110 / 220 V
Rated current 54.2 / 27.1 A 59.1 / 29.5 A

So it does appear that there are both 110 and 120 VAC versions of the genset available...

The reason I am asking details about the genset... Depending on the exact model you have and how you have it configured (110 VAC single phase only, or 110/220 VAC split phase)--The max output of the genset current is either (roughly) 27,1 per "hot lead" (black red, Line 1 or Line 2--Or if set for 110 (or 120) VAC only, a maximum of around 54-59 amps @ 120/110 VAC (just Line 1 or Black lead--However that genset is labeled/color coded).

You say your inverters are 20 Amp maximum on Each Line... Again, trying to be crystal clear--Is that 20 Amps from each inverter-charger, or 10 amps from each, added together for 20 amps total @ 110 VAC.

If you are measuring 20 amps on both the Hot (Line) and the Neutral (typically white) on a 120 VAC system, they will be the same (or something is wired wrong).

If you are measuring on 220/240 VAC Split Phase power, the Black and Red (or Line 1 and Line 2) will not always be the same--Especially if you are driving separate 110 VAC loads. The White or Neutral, will be (roughly) the difference between L1 and L2 (i.e., 23 amps on L2, 20 amps on L2, then 3 amps on Neutral).

Single phase 110 VAC wiring:

Example of 110/220 VAC split phase circuit (the center wire is White/Neutral):

Image: https://www.generatorsource.com/getattachment/Services/Voltage-Changes/Figure1a.JPG.aspx

I believe your genset can be set do do either above... But note that the maximum current is 1/2 on the 110/220 VAC split phase vs the 110 VAC single phase configuration...

So understanding the wiring/configuration, and the loads (i.e., 20 amps total @ 110 VAC, or 20 amps per inverter @ 110 VAC or what) is important here. Need to match with the capabilities/configuration of the genset.

-Bill

Graham Parkinson · October 2023

Just as a minor contribution to this discussion:

There are typically two controls on non-inverter generators: An RPM governor sets the frequency whereas the voltage is controlled via the AVR unit (Automatic Voltage Regulator). The service manual that BB linked to shows a non-adjustable AVR unit in those Kubotas. Normally the AC voltage is factory set in the AVR by trimming the value of the electrolytic capacitor to get the exact working voltage required under load. If the generator is somewhat old it is possible that the capacitor has deteriorated and is causing an incorrect voltage at the desired RPM. These capacitors are easy to replace (there is a photo in the manual of the AVR and capacitor).

Right after poor contacts, capacitor failure is the most typical cause of electronic equipment failures.

rockhardhoosier · October 2023

BB. said:

Sorry to keep asking the details... Getting power (whether solar, generator, or grid) correct depends on the details.

On the genset--It appears it has a "series/parallel" switch for the AC windings... In series, you have 120 VAC between "black line and neutral", and "red line to neutral"... And 240 VAC between Black and Red Lines (actually, this genset may be rated for 110/220 VAC--Not really a "deal breaker" US/North America power). And a maximum of 29.5 amps (at 220/240 VAC) on either Black or Red (or Line 1 and Line 2 "hots").

You can also flip a switch/setting for parallel AC windings (I believe) that will give you 110 or 120 VAC only output:

https://absolutegenerators.com/media/blfa_files/Kubota_LowBoy_II_Diesel_Generator_GL7000_GL11000_GL_Series_-_Service_Manual.pdf

Rated voltage 120 / 240 V 110 / 220 V
Rated current 54.2 / 27.1 A 59.1 / 29.5 A

So it does appear that there are both 110 and 120 VAC versions of the genset available...

The reason I am asking details about the genset... Depending on the exact model you have and how you have it configured (110 VAC single phase only, or 110/220 VAC split phase)--The max output of the genset current is either (roughly) 27,1 per "hot lead" (black red, Line 1 or Line 2--Or if set for 110 (or 120) VAC only, a maximum of around 54-59 amps @ 120/110 VAC (just Line 1 or Black lead--However that genset is labeled/color coded).

You say your inverters are 20 Amp maximum on Each Line... Again, trying to be crystal clear--Is that 20 Amps from each inverter-charger, or 10 amps from each, added together for 20 amps total @ 110 VAC.

If you are measuring 20 amps on both the Hot (Line) and the Neutral (typically white) on a 120 VAC system, they will be the same (or something is wired wrong).

If you are measuring on 220/240 VAC Split Phase power, the Black and Red (or Line 1 and Line 2) will not always be the same--Especially if you are driving separate 110 VAC loads. The White or Neutral, will be (roughly) the difference between L1 and L2 (i.e., 23 amps on L2, 20 amps on L2, then 3 amps on Neutral).

Single phase 110 VAC wiring:

Example of 110/220 VAC split phase circuit (the center wire is White/Neutral):

I believe your genset can be set do do either above... But note that the maximum current is 1/2 on the 110/220 VAC split phase vs the 110 VAC single phase configuration...

So understanding the wiring/configuration, and the loads (i.e., 20 amps total @ 110 VAC, or 20 amps per inverter @ 110 VAC or what) is important here. Need to match with the capabilities/configuration of the genset.

-Bill

Ok, mine is 120/240. So, on the gen wires going to the inverters, you have a red and black hot, one goes to master and slave2 and one goes to slave 2 and slave 3. Each one of those lines are pulling like 20.3 amps, and 21 amps. because that is what the gen is calling for. With the setting i have it on And like Graham said above I learned that the governor adjusts the hertz not the rpm. So right now, the generator is running at 116v each leg and when the inverter calls for it , it is staying engaged. I did adjust the hertz down from 64 to 59. But the voltage shoots up to 132 per leg when the inverter calls for the gen And about the switch from parallel to series i have no knowledge of it. I will read up. This gen is a 2017-2018 model.
Hey and believe me I appreciate everyone's help. And I try to answer back with what knowledge I have,LOL.

BB. · October 2023

To clarify... The governor only controls Engine RPM (revolutions per minute) and (for "standard alternator gensets) the Frequency or Hz or CPS (cycles per second.

Hz (frequency in cycles per second) * 60 Seconds per Minute = RPM (revolutions per minute):

54 Hz (CPS) * 60 seconds per minute = 3,240 RPM

Now the RPM (frequency) of the genset is not supposed to affect output voltage--But some have better AVRs (automatic voltage regulators) than other gensets...

The reality is that RPM does affect the "efficiency" of mechanical to electrical conversion... And the AVR may do a "less than perfect" job of voltage regulation.

Regarding the 120 vs 120/240 switch--All of the photos I have found are pretty low resolution--So I cannot really read the front panel setup... An example of the switch (random photo online):

Image: https://us.v-cdn.net/6024911/uploads/editor/08/h5e46jbnwu23.png

Your genset may or may not have this switch, or it may be completely different from this random photo I found.

Another photo:

Image: https://us.v-cdn.net/6024911/uploads/editor/1v/ggeuwbxdxcuq.png

In any case--You have a 120/240 (or 110/220) VAC @ 60 Hz genset. If there is a problem, the AVR sounds like it is less than ideal in its voltage control.

The issue is that "large step loads" are difficult for any genset to "absorb". The output voltage can under or overshoot depending on load conditions and AVR/Genset/Alternator design. Some brands/models of inverter-chargers may have a "soft start/soft ramp" configuration when drawing current for charging.

If you can do something like having "Group 1" inverter+slave turn on first, and the second turn on a few seconds (or minutes) later--That would be a big help.

From an "owner's manual". #12 "full power" switch (120 only output vs 120/240 output). Page 17 of manual:

https://www.nppi.com/wp-content/uploads/2018/04/GL-Series-GL-7000-GL11000-Operators-Manual.pdf

Image: https://us.v-cdn.net/6024911/uploads/editor/5w/dybglso8oml4.png

Vs a different GL7000 models. Page 18 of manual:

Image: https://us.v-cdn.net/6024911/uploads/editor/dx/2obx4mf5nd9s.png

The Line 1 and Line 2 (black and red) terminals are a maximum of 27 (or 29) amps (depending on model) when configured for 120/240 VAC... So 20 amps per Line is fine.... Note the Neutral/White line will have somewhere between 0 and 20 amps (0 amps if both L1 and L2 are 20 amps, or 20 amps if L1 is 20 amps and L2 is 0 amps (just as an example). For a general statement, a property wired 120/240 VAC split phase system--You don't worry about White Wire current (assuming everything else is OK--We can talk more if you wish).

In general, it sounds like your genset is correctly wired to your loads... And you may have issues with the AVR ore other internal alternator issues (there are multiple windings in the alternator that can be used as part of voltage regulation--I am not expert here). Changing governor (frequency/RPM) values a little bit should not be affecting the AC output voltage this much (the spec is 5% output variation between zero and full load--5% of 110 volts is 5.5 VAC output variation spec... I.e. 110 vac full load to 116.5 volts zero load--If all is working to specifications).

-Bill

BB. · October 2023

I should add... You would typically use the 110/120 VAC only output voltage is typically used when you have a single large 110 VAC load (over 27 amps) and need "full power" of 7,000 kWatts for a single large 110 VAC AC load.

Since you have two (two sets?) of relatively matched 110 VAC loads (around 20 amps each)--Then you run 1/2 the loads from Line 1+Neutral and the other 1/2 of the loads from L2+Neutral--And since your maximum current is now 27 amps or so (round up to 30 amps), you can use smaller AC AWG Wiring (easier to pull through conduit, less voltage drop, etc.)... VS a 60 Amp circuit with much heavier copper cables (harder to pull through conduit and such)...

Obviously, if you have 220 VAC loads, then you need the 110/220 VAC split phase power to give you the power for your dedicated 220 VAC load(s).

-Bill

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