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I have an SDMO generating set with a Mitsubishi S3 L2SD engine it is supposed to run at 1500 rpm but goes up and down depending on load, if I set the rpm at no load to 1500 as soon as a load is applied the revs drop and so do the cycles from 50 to perhaps 48, if I set the revs on load, then off load the revs go up and the cycles hit 53 plus which means for example my washing machine does not want to know, I suspect the govenor on the pump but do not want to change the pump if this is within parameters for this engine, regards Rick

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Set the no load revs such that you get 51 Hz out of the generator, at 80% load this ought to give you something like 48.5 Hz with less than a 3% drop in output voltage. If not, you might have governor problems but I'd try servicing and adjusting it before replacing anything other than filters.


Posted on Dec 07, 2008

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Why does my 2005 dodge ram 1500 3.7 liter only goes up to 4000 rpm when i reve it up and it starts to sputter when in park

its the rev limiter. its suppose to do that when the engine has no load or the vehicle is stationary so you don't break the engine

Oct 09, 2016 | 2005 Dodge Ram 1500


Generator Not Producing Power - Engine Speed & Governor Control

There are 4 requirements that have to be met before a generator is able to produce power. Due to number of questions that have been asked, a Coleman PowerMate 1500-1850 with a Briggs and Stratton Engine will be used here.

1) The Engine has to be turning at correct speed
2) Field Winding (Rotor) on the alternator must be energized
3) AC Winding (Stator) must create a voltage in presence of magnetic field
4) Output passes through Safety Devices before it reaches an outlet.

This Tip will cover Engine Speed and Governor Control.

Sounds simple, but it actually goes beyond just turning. Most consumer generators are designed for an engine that turns 3600RPM for 60Hz operation. For every 600 RPM, the frequency changes by 1 Hz. Normal frequency range on a generator is about 63 (at no load) to 57 (Full Load). At half load, you should be pretty close to 60 Hz. Some generators will turn at 1800 RPM, and usually have two or more cylinders. Each 1Hz deviation is a 300 RPM change in engine speed

If you find that your engine is not turning as fast as it should, or is turning too fast, you can adjust its speed using the governor. Be careful in this area though! If you are adjusting faster, and you make too much an adjustment, the engine may over speed (red line) and be damaged. Always be ready to shut down the engine in case something goes wrong.

General Instructions on How to Adjust Speed:

It will almost be required that you have a digital multimeter that is capable of measuring frequency. You can use a AC powered clock, and compare the minute intervals with another clock, but the adjustment process will take a few hours.

Start your generator, let it run for a few minutes to warm up. Place your meter leads into the outlets, and record the frequency. This will be your No Load Frequency prior to any adjustments. Also record the voltage.

Note that depending on your meter, your voltage will likely read about 132 volts AC. If your meter is of the dollar store variety, the voltage may be reading higher (170) due to noise being present in the waveform. Don't worry about this - yet.

Now that the engine is warmed up, and your meter is indicating that the frequency is less than or higher than 63Hz, it is time to adjust the governor. Each engine will have its own method, you may have to find a owner's manual or service manual.

Start by removing any access panels that you need in order to reach the governor assembly. This will be the arm that is attached to the throttle on the carburetor via springs and rods. Look carefully near the base of the governor arm, and you will see a spring that is attached to it, and the other end is attached to a tab. The purpose of this spring is to put tension onto the governor, as well as to allow adjustment. Inverter based generators will usually have an electronic governor. The throttle is actuated by a small servo motor which is driven by the inverter / controller. These types of governors are typically not adjustable beyond replacing mechanical linkage that is worn.

Using a pair of needle nose pliers, bend the tab slightly one direction or the other (toward governor, or away from governor). Note the change in frequency. The target here, without a load, is going to be 63Hz. Once you hit this target (frequency average is 63), take a look at the voltage. It should be near 132 volts AC. If it is much higher, then lower the voltage by bending the tab slightly. Be aware that this will also lower the frequency as well.

Now that the unloaded frequency is set, connect a load that is approximate half of the generator continuous rating. For an 1800 watt generator, the continuous load is 1500 watts. Half would be 750 watts. A couple of Halogen lights will work, as well a space heater that is set on Low. Your frequency should be very close to 60Hz now. Voltage will likely be around 125 volts. Adjust the governor very slightly to reach these numbers. Your half load frequency is now set.

If you are using a space heater for a load, turn it on (1500 watts), and note the frequency reading. Also note the voltage rating as well. Frequency will likely have dropped down to about 57 or 58. This is normal. Voltage should be down around 110 to 115. Don't make any adjustments as most generators are due not carry full loads for extended amounts of time.

Turn the heater back to low or fan only, and let it cool for a few minutes before turning it off. Unplug the heater, and check the frequency and voltage without a load being on the generator. Again, frequency with no load should be about 63Hz, voltage about 132. A little bit of difference is acceptable here. And now you are done.

If you are not able to obtain the numbers mentioned, then there are other issues going on. Especially if voltage is out of range. See other Tips.

If you intend to use the generator primarily with a certain load (heater, well pump, charger, etc) you can optimize performance of that load by setting the generator frequency with that load, and only that load connected. Just keep in mind that when you add additional loads, your settings may not be adequate.

on Sep 12, 2010 | Electrical Supplies

1 Answer

Generator low voltage

It could be several things but it sounds like it just running too slow. I would the engine rpms first. Depending if is a two pole or four pole and if your 60hz or 50 Hz on the needed unloaded rpms.

Example: 2 pole 60 hz. Engine needs to be running at 3600 rpm loaded and 3750 rpm unloaded; unless, it has a fuel saving mode.
A 4 pole 60 hz would running half this rpm. The 2 pole producing 50hz would have the engine running at 3000 rpm loaded (about 3100 rpm unloaded)

Now in order for the 50 hz system to produce the same output voltage it requires a different alternator than the 60 hz version; otherwords, You simply can't convert a 60 hz to 50 hz version without changing the alternator by changing the engine speed.

Dec 29, 2014 | Electrical Supplies

1 Answer

Having SDMO genset V250 volvo engine with Leroy Somer Alt 60 hz.Having problem that engine Shut Down with the message Min U Alt. Can anybody help me to solve this problem

Min U is minimum voltage output. If it occurs when under load, check load types and for shorts. If it happens during no load, check voltage regulator and exciter, and diodes

Aug 17, 2014 | Electrical Supplies

1 Answer

I need the maitenance manual for your sdmo 500kva generators

I need the maintenance manual for your sdmo 500 kva with a Volvo Penta engine generator.

Aug 30, 2011 | Computers & Internet

1 Answer

I have a generac 22kw model QT02224anan that will run for a few minutes then shut down , then the over speed led is lit. It only happens when it is under load or during a power outage. it goes through...

its possible the overspeed is set to sensitive. or your rpm are to high. these are preset in the factory as a safety, check your manual to ensure your rpm speed is in the pre set area. generators will do this under load when you have a big load on them or take a load off. the governor will some times over compensate causing it to trip on overspeed.

Aug 10, 2011 | Generac Power Systems Generac QT02224 22...

1 Answer

My generator is not putting out the proper voltage? it's only putting out approx 75 volts on the 120 volt circit. i adjust the idle to full out and i get approx 112v.

Most low voltage conditions on generators are simply due to a low engine rpm. Most modern generators are 2- pole windings. So your engine rpm should theoretically run @ 3600 rpm. which will produce 120/240 volts @ 60 HZ. In actuality You want to set your rpm's @ Approx. 3720rpm no load. About 62.5 Hz. Without getting to technical this will give you your desired 120/240 volts loaded. Hope this helps.

Aug 09, 2010 | Northstar Electrical Supplies

1 Answer

My sdmo generator keeps shutting down temperature
Troubleshooting advice above link.
Sometimes it is the head gasket, check, it can be, incorrect fuel mixture, far too lean, exhaust should be a light grey color. Check enough oil in sump. ensure free flow of air all around machine.

Mar 28, 2010 | NEC Mitsubishi MGE 1800 Generator-Voltage...

1 Answer

The coleman voltage generator for 250 kva gen set

Well I assume that this generator is NOT three Phase, and delivering 440 Volts? in that case, that reading is what is called and "Open Circuit" reading, with a full load, that reading will/should come down to the nominal voltage of 250 V (+/- 10%) This generator is a 250 V AC unit? If this is so then it is operating correctly? It is 5kw UNIT. using a digital multimeter due to it's large input impedance it will often give erroneous readings if NOT loaded down with the correct.any. load.?

Mar 02, 2010 | Coleman Powermate Powermate 5000W...

1 Answer

I have a powermate 3500 and when running unloaded the output voltage is around 165VAc. When it is loaded it drops to around 145. what is causing my problem. knutgar

engine rpm is adjusted to high... I set engine rpm according to a loaded condition usually while running a power tool to puts max load or close to it on the generator. I try to get it at 125VAC loaded

Sep 15, 2009 | Coleman Electrical Supplies

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