Generator Voltage Problem

This sounds like a classic, normal source impedance or Thévenin's theorem problem. Without knowing the voltage drop or any of the voltage regulating possibilities your generator has I cannot say if you're being hyper critical or have a real problem. I am curious though, what is an Atmel RISC microcontroller doing in a generator? (Undefined acronyms bother me.) Have you examined the rotor brushes and rings for intermittent contact burns? Often a generator's documentation includes the rotor and stator DC wire resistances so a technician could determine if a short in either windings existed. (At least they use to provide this information.) If there were some mechanical slippage between the engine and the generator or the engine itself was just old and tired then this might account for the low power generation. Do you have any manifold vacuum readings for the motor? When was the last time you checked the air cleaner?

Bringing the engine up to speed might also help the output voltage. One thing to look at might be the fuel system (clogged filters, pump adequacy, presence of contaminants in the fuel, etc.)

Tornado

it seem the generator have low power.

1. Yes, could it be problem at fuel system..check at filters, pump till injector may need callibration.

2. Did you already check, generator rating, perhaps the setting already change under its real capacity.

3. Do not use voltage droop for this application

4. May be you adjust gain of AVR

5. Check for winding main and excite winding. Also rectifier component.

Carbon brushes are not having proper contacts. This will also damage contact wiring quickly by over heating.

Where are you checking the voltage, at the load point or on generator terminals? If you are checking at load, that probably means your wiring is not adequate enough for that kind of load,

As you said load requires 60 Hz frequency and engine is running in RPM for 55Hz. Once check the fuel injecting system and also check the gain of AVR

the engine was overholed and all spare parts changed(injectors, filters,etc..) and the voltage was taken from output cable. btw the engine is 2 cylinders , do you think thats mean the generator applicable for 50 Hz ?!!

thanks for your time

1. Please, bear in mind ! An engine have more than 5 different type injector. Let me give example, ABC type engine has range output HP from 10-50HP, ABC-1 injector is for 10HP and ABC-2 is for 20HP..etc. May be your engine has wrong ijector installed, means! your engine could be downgrade. Check for PN for sparepart !

2. Fuel Pressure is drop...problem in on engine, again ! check on fuel system

The Generator rpm determines the frequency. If your region is 60HZ (USA for example) then the governor should be adjusted to run the engine at 60Hz (1800 rpm) before doing anything with the AVR etc.

When at 1800rpm (60Hz), check the voltage with no load. If lower than the design or required value, you can adjust the AVR gain to obtain the correct voltage.

LOAD: if the rpm drops at 5kw only (generator rated at 14kW), to 55Hz, the governor and/or engine need looking at to find out which of the two is having a problem. IF the rpm remains at 58-60 Hz, and the voltage drops more than 5% of the no load, then somethibg is wrong with the AVR / Alternator system.

To help you, we need more information on the behaviour of the Genset...

I think 60Hz or 60Hz is not the problem. Output of the generator is poor for some other reason. As generator is running at constant speed. It looks there is no problem with the engine parts.

Power generator sure has problem.

Output before AVR or virgin output of the generator need to be high enough. AVR is to make the voltage output within the range if there are fluctuations.

Look for a checklist for the power output problems in the service manual and one by one search for solution.

Sorry, I should have answered earlier on this input.

There is nothing such as virgin output before AVR.

The AVR starts the ball rolling (Voltage buildup) from the start: Remanent Magnetism in the Rotor (or stator depending which is holding the field windings) will generate a little voltage which is bypassed by the AVR directly to the field to reinforce the magnetic field, ... More voltage ... more field current again... until the voltage reaches the value set on the AVR (or high enough for the AVR to start reacting to it...). The AVR is in control from the start and keep control all along to maintain the Output voltage within a certain margin +/- 3% or better or worse.

u said engine spare rplaced means injector so check abut new injctor type /size may be differnet from old one.

There's a few critical questions that still have not been answered. I know that it seems like nit picking but we don't know what the details of the 5 kW load under voltage condition. What has the single phase voltage dropped to when the 5 kW three phase load gets applied, does each phase only sag from 220VAC to 219VAC? If so then I doubt that this is a real problem. What is the current output of any of the three hot phases with this load? Is the load a reasonably balanced 3 phase load? If not what is the neutral current? (That's probably a red herring but it does show the lack of possibly pertinent information that could help.) Has the generator produced full electric power since the overhaul or is it now diminished after the overhaul? (Just because it was rebuilt does not mean that it was rebuilt correctly.)

Dear yasser gh,

Please check the Generator Name plate & the engine name plate.Are they have same RPM rating.You have said that the fr.is 55 Hz at max speed it means that you are having an engine that is rated for 1500 RPM ( 50 Hz) and the

Engine speed for 55 Hz is 1650 RPM which 1500 RPM engine can run at max speed

(10 % over speed) for non-continous operation. If you are sure that your load needs

58 to 60 Hz, Change the Engine.

Manroop.Chennai

The engine speed can be adjusted on the Governor of the engine. There is no need to change the engine for that!

If the engine rated power is too low for the intended power generation, then you can advice to change it. But as stated by the OP, he is only loading at 5kW and the engine is rated for more than twice that.