Adjusting frequency and voltage?

[jakester]

Hello,
I have a chinese yanmar knock off 5KW 120/240v diesel generator and it runs fine, other than being very load, but my no load voltage is 116 at 62.5 Hz.  When i raise the speed, the voltage and frequency both up, how do i get the voltage up and still keep the frequency below 63?  I changed the capacitor in the head but that didnt change the readings.
Help!
Jake

[TimSR2]

What's your loaded stats? Fully  loaded voltage droop and frequency?  Sounds like you are within the acceptable tolerance now. If you can hold 108v at 59 hz with a 5kw resistive load the unit will probably serve well, as long as it is located close to the load.

Check to see if your alternator field has a tapped resistor for voltage adjustment. If so, you can get independent control of voltage.

[Ronmar]

What Tim said.  What does it do under load?  As you pull current out of it feeding a load, the capacitive regulation should add to the field to attempt to maintain output voltage.  You need to check it loaded to confirm the regulator is working properly.  There also may as tim mentioned be an adjustable resistor to set the voltage starting point.   

The RPM will droop as load increases, so around 62HZ with no load is a good starting point as it will settle toward 60HZ as load is increased...

[jakester]

I will test it under load again to get some firm numbers, but as I recall the voltage dropped off enough to affect lights, blower fan.... It doesn't appear to have any adjustment other than throttle.  I replaced the capacitor with the same 16uf 450v unit and the voltage and Hz dropped just as bad.  I don't understand capacitive regulation, but have noticed that other similar sized units appear to have larger capacitors in them.  I am toying with the idea of putting a 24uf unit it to see if my voltage will improve relative to frequency.

[jakester]

Well i ran some tests at results by changing the AVR  capacitor and it made a much larger difference that i thought.
The hz under no load were all over from 62 to 80 hz, so i guess doubling the stock capacitor was too much.
as follows
16uf no load 120v 62.5 hz
32 uf no load 135v 64hz initial with fresh capacitor
adjusted speed down

32 uf no load 129v 62 to 80hz
the slightest resistive load dropped the Hz back to a steady 62
32 uf 12 amp 125v 60 hz
32 uf 18 amp 123v 59.5 hz
as much as i hate trial and error for a $50  half moon capacitor. I guess i will settle for a  22 to 24uf AVR cap.

[Ronmar]

Those last numbers don't look to bad.  How are you measuring frequency?  That 80hz sounds like an artifact that is effecting your freq counter, especially since it goes away with load.  ANother question is how is your generator output wired/how are you applying that 18A of 120V load?  If you are wired for 120V output only(both 120V legs in parallel, that is approaching half load on a 5KW head.  IF you are wired for 240, and applying that load to one 120V leg, it is still approaching 1/2 the generators output, but it is approaching full load for that single 120V leg...  That voltage drop dosn't sound too bad for nearly half load, but the RPM droop 62 down to 59.5 seems a little much for less than half load.  All the load on one leg might make it appear to have more load than it does though.  Was the engine all the way warmed up when you made these tests?  Fully warm might improve the governor response...  These generators output is RPM dependent. If the RPM maintains better with load application, the voltage will also not droop as far.

[jakester]

I measure frequency with a Kill-A-Watt meter. The test were with the generator switched to 120V only, vs the 120/240v. Since i didn't have any spare 240v twist lock plugs, it was easier than tapping into my patch cord. 
I agree the loaded value didn't look bad, but i wasn't sure if running unloaded at 129v and applying a light load would be a good idea, and the swinging Hz value was unsettling.  This only showed up after the generator had run a few minutes.  Any thought on a final uf rating? 

[Ronmar]

129 unloaded isn't terrible.  Most UPS's start to think about swapping at around 127.  129 on the line won't hurt anything but I would guess that even the slightest load applied will knock it down a few volts.  As for capacitance, I cannot reccomend a size.  basically you want a size that will give you an acceptable droop across your load range without going much higher than the 129 you are seeing now. 

IF you were getting 120 from the plugins, you may have been only loading half the generator windings. A better way to gauge voltage and RPM droop(governor performance) would be to apply 240V.  that way you know you are loading the generator windings equally.