Problem with Markon SL105G Generator

[yttrill]

Hi, now i have my genset motor running I'm having a lot of variation in the generator power output. It's a Markon SL105G, 7Kva, rigged for 230V. The battery current sensors report charging changing from say 40 through 60 amps (20A variation). My 800W microwave light flickers wildly. The charger itself has an LED display which goes up and down. I always had this problem but it's worse now.

I do not believe its the motor because the pitch changes with load, eg if I put on the microwave or domestic water heater but otherwise sounds stable, the rotational inertia is too high for the frequency of oscillation I'm observing.

So I was about to pull out the AVR unit according to the instructions in the manual (yea, RTFM). Which clearly says the grey wire should be connected to F1 or the generator won't work. If connected the wrong way, it has to be redone the right way after "flashing" the system with a battery (to get the residual magnetism required for starting the excitation circuits going).

Well great! The grey wire is connected to F2. There's a white one connected to F1. Of course that doesn't matter if the OTHER ends are swapped around also. But I have no idea how to tell. Anyone have any clues?

[The only part i can probably test is the bridge rectifier since all the rest is mysterious electronics .. ]

[Cap Erict3]

If it's putting out it doesn't need flashing.

Watch the Hz and voltage while u load it. It sounds like an engine problem. If the Hz drop before the voltage it's an engine issue.


------------------------------
Looking for another pretty place to work on the boat.

[yttrill]

Originally Posted by Cap Erict3

Watch the Hz and voltage while u load it. It sounds like an engine problem. If the Hz drop before the voltage it's an engine issue.

Yes, but i don't think this could be an engine problem. I do not have a working Hz meter at the moment. I doubt a voltage measurement would tell me much: the power output, which is visually apparent, is fluctuating on almost every individual cycle (i.e. at least 10Hz). I have a good eye for that because I have worked on software for triac based lighting control systems (phase controlled dimming).

The motor crankshaft and generator rotor are too heavy for the rotational speed to vary as much as the output is. IMHO. Could be wrong of course

[smac999]

is the changing current coming from an AC charger? I doubt the gen alt is putting 60a into your batteries.


the microwave and current issue likely both from a voltage or freq issue.

[a64pilot]

Try checking any grounds, that "flickering" your getting could just possibly be a loose connection? Grounds always seem for some reason to be the worst.
Especially since you've had this problem, but it's getting worse, just sounds like a loose connection somewhere.

[yttrill]

Originally Posted by smac999

is the changing current coming from an AC charger? I doubt the gen alt is putting 60a into your batteries.

Yes, it's an inverter/charger.

the microwave and current issue likely both from a voltage or freq issue.

Right. I suspect voltage. That is, the generator AVR is not working right for some reason.

[yttrill]

Originally Posted by a64pilot

Try checking any grounds, that "flickering" your getting could just possibly be a loose connection? Grounds always seem for some reason to be the worst.

AC isn't grounded. Of course yes, it could be a loose connection responding to the vibration from the generator engine. Quite possibly the on/off switch! I'll check it out, thanks!
[/QUOTE]

[CdS2 Roland]

Hello,
Your problem is due to faulty capacitors. Got the same issue with Mastervolt Whiper 6.
Verifiy if you fuel line has no air intake and the engine runs without RPM variations.
RPM controls the frequency (50Hz = 3000RPM). If you have not 50Hz set the RPM to 3060RPM. Capacitors regulate the voltage, to high voltage or voltage variations indicate worn out capacitors.


On some genset, like Mastervolt, you don't have any governor, so the RPM are all time the same.


Good luck

[colemj]

The Markon SL105 heads are AVR-controlled, not capacitor-controlled.

It is the BL105 heads that use capacitors.

Mark

[ex-12m-guy]

According to the manual, the SL series of alternator
employs slip rings.

Have you checked the rings and brushes?

[a64pilot]

Originally Posted by yttrill

AC isn't grounded. Of course yes, it could be a loose connection responding to the vibration from the generator engine. Quite possibly the on/off switch! I'll check it out, thanks!

[/QUOTE]


I don't understand AC isn't grounded?
You do have both a neutral and a ground don't you?


Sent from my iPad using Cruisers Sailing Forum

[Cap Erict3]

Originally Posted by yttrill

Yes, but i don't think this could be an engine problem. I do not have a working Hz meter at the moment. I doubt a voltage measurement would tell me much: the power output, which is visually apparent, is fluctuating on almost every individual cycle (i.e. at least 10Hz). I have a good eye for that because I have worked on software for triac based lighting control systems (phase controlled dimming).

The motor crankshaft and generator rotor are too heavy for the rotational speed to vary as much as the output is. IMHO. Could be wrong of course

I worked on this type of thing many years and yes, a voltage and Hz reading will tell you much.

I bet it's not a software nor a flux capacitor problem.

A cheap digital multimeter will read freq and emf.


------------------------------
Looking for another pretty place to work on the boat.

[yttrill]

Originally Posted by ex-12m-guy

According to the manual, the SL series of alternator
employs slip rings.

Have you checked the rings and brushes?

Nope, that's next. I'm taking all the bits off one by one. I don't have a frequency meter at the moment. I can't do any measurement on the running device since its in pieces

Damaged brushes would certainly cause flickering!

The bridge rectifier seems OK: 630 Ohms across each diode and 1300 Ohms across the bridge (weird .. it should be 630 Ohms... two diodes in series rigged in parallel should be the same resistance as a single diode). Although I have to connect use minus probe of multimeter on + terminal of rectifier.

Since, contrary to the manual, the Grey wire is connected to F2 instead of F1, I am going to have to trace the wire from the AVR to the rectifier. They're on opposite sites of the chassis. It's a bit hard to get at stuff, I need a torch and a mirror and 3 more pairs of hands.

[yttrill]

I don't understand AC isn't grounded?

There is no ground in the electrical circuit so a loose ground
connection is relevant only if there is also a short, which my RCD devices would pick up immediately.

You do have both a neutral and a ground don't you?

The boat is ground. It's a steel boat. There is a single point of attachment for the ground cable (to avoid earth loops). Unfortunately engines use chassis as negative so the battery negative is grounded. (in principle -ve should be isolated from ground). But that's 12V stuff.

[yttrill]

Originally Posted by Cap Erict3

I worked on this type of thing many years and yes, a voltage and Hz reading will tell you much.

I'm trying to get hold of a CRO. I would like to visually inspect the waveform. I suspect it is all over the place. The output power variations suggest loose or broken something. They're random. I can't see how the motor can vary that much, too much inertia is involved. The power fluctuations seen on the battery charger are just averages, they've been smoothed, but they flicker about too. The microwave runs directly off the generator when it is going.

To me this has to be either voltage variation in the output, or, random connect/disconnect in either a terminal, wire, or the electronics. For example a diode will cascade (allow current in the wrong direction) at a certain voltage, and if one is cooked, it might do so randomly, making the voltage applied to the rotor random. Still .. there's a choke in the circuit that should smooth that out.