governor sensitivity in generators

[maicael]

I have been looking at some generators for a while and I noticed that in the governor arm where a spring is usually attached to control the output voktage ,it consist of 3 holes and I was wondering what would be the effect of changing what hole the spring is attached to.
Why multiple holes as option and is there relation between what hole the spring is put and fuel economy.
Anyone with more experience than i.
.
One more thing.I know this might sound stupid but I noticed that this small portable 650w generators do not have voltage regulation like the standard bigger types and so I was wondering if it was possible to construct a circuit to attach to the geneartor output that would maintain constant voltage whether load is plugged in or removed.we then take the output from the circuit into the household.
Hope am not talking nonsense. Haha
Thanks

 

[crutschow]

Changing the governor spring connection will affect how much the generator changes speed under load. Moving the spring to a hole further along the arm (spring moves more for a give arm movement) should result is less change with load.
The downside is that such a connection may result in speed "hunting" (continually varying slightly up and down) under light or no load). So that's the trade-off.

There is no simple way to regulate the output voltage of a generator without built-in regulation.

 

[maicael]

[/QUOTE]Moving the spring to a hole further along the arm (spring moves more for a give arm movement) should result is less change with load.
The downside is that such a connection may result in speed "hunting" (continually varying slightly up and down) under light or no load). So that's the trade-off.
[/QUOTE]
So a lesser change of speed under load is a good thing right?

 

[KeepItSimpleStupid]

The force on a spring is -kx and the air velocity is applied against the spring.

So, I would expect some sort of possible hunting at idle with a large moment arm.

You really can't regulate voltage unless there is a coil that can be modulated. If the generator just had fixed magnetics, all bets of external regulation would be off.

Frequency is proportional to RPM
Voltage regulation occurs because the magnetic field of the rotor is modulated.

In generators without a battery to start, residual magnetism is used to generate a small voltage to kick start the regulator.

 

[tcmtech]

Getting a mechanical governor on a generator to have good stability and response characteristics without it going into a surging mode is a bit of a trial and error process.

Ideally when I am working on a generator I try to set the governor for about 5% over frequency at no load and 5% under at full rated load so if you are on a 60 Hz system ~63 Hz no load and 57 Hz full load is good.

 

[debe]

If you are refering to the 650W 2stroke generators, then this is the circuit. The voltage is fixed by the size/value of the capacitor 13.5Uf 250V. If you alter this capacitor you alter the voltage. Engine RPM also alters the freq & the voltage , but should be set at the freq you require 50/60 Hz. These generators are notorious for exess voltage if you let them run out of fuel with a load on them as the engine rpm varies a lot. I do use one but im careful how I use it.

 

[Tony Stewart]

Control system stability in load step response is affect by bias and gain.

I was just overhauling my 5.5hp lawnmower today, which has the same adjustments for spring biased RPM and, inertia lever arm hole for throttle gain. Thus time I adjusted or minimum RPM to handle the load but maximum gain (leverage hole with largest radius. I liked the results.

 

[crutschow]

.....................
So a lesser change of speed under load is a good thing right?

Yes.
You just can't go beyond the point where it starts to hunt at light load.

 

[atferrari]

Many++ years ago I worked with the local representative of Governors America (USA). I had the oportunity to watch their technician adjusting governors recently installed, basically on fast engines.

While not invovled in the technical part, I had a (long and deep) peek at their manuals which helped me to understand the basics. Maybe, that could help you.

 

[maicael]

Many++ years ago I worked with the local representative of Governors America (USA). I had the oportunity to watch their technician adjusting governors recently installed, basically on fast engines.

While not invovled in the technical part, I had a (long and deep) peek at their manuals which helped me to understand the basics. Maybe, that could help you.

Do you still have the manual.
Maybe I could learn a thing or two.

 

[atferrari]

Google them. Still in business, IIRC, based in Awagam.

Search for "analog governors".

 

[dr pepper]

Depends if its a synchronous or inverter generator, a inverter gen does control engine speed to govern o/p voltage, a synchronous one does not, as implied the speed of the engine/gen sets the o/p frequency.
The holes in the arm are probably to setup the gen from new, there will be slight variances from gen to gen so the manufacts will select the best position for that set.
Or if you were to run the set from lpg, or diffrent grade fuel then you could use a diffrent position to compensate, a gen set run on lpg can hunt, as lpg is a gas and has a diffrent calorie rating when it burns, upsetting the performance of the governor making it hunt.

 

[atferrari]

The holes in the arm are probably to setup the gen from new, there will be slight variances from gen to gen so the manufacts will select the best position for that set.

Yes, from what I recall, the "hole selection" was aimed to a final geometry of the mechanical parts that would allow any adjustment (tweaking) and dynamic change when in actual service.

 

[maicael]

Just want to clarify, if a generator carrying a load at 220v output, current at 2A(440W).
My question is will a generator consume more fuel if the output voltage of the generator is lowered to say 180v or 190v meaning that it draws a current of 2.31A now.
Does drawing more current due to lowering output voltage cause more fuel consumption.
I ask because I noticed a norm where a lot of people lower this typical 2 stroke generators even the bigger generators all in a bid to reduce fuel consumption or something like that.

 

[dr pepper]

The generator itself draws mechanical power from the engine depending on the wattage consumed, lowering the voltage and increasing the ampage in theory is the same power draw, ie the engine turns slower but the torque will be higher to increase the current, requiring more throttle so fuel burned isnt much diffrent.
There will be some savings as friction losses in the engines bearings will have an effect, and the dynamics of the engine burning the fuel can be tuned to be effcient at certain speeds, you can fit stub stacks to the carby to do this, however the actual energy savings will most likely be very slight and probably not worth the effort.

 

[crutschow]

If you lower the speed to lower the voltage, that will also lower the AC output frequency which can be bad for some loads such as refrigerators and other motor loads.

 

[maicael]

Yes you are right about it affecting motors and refrigerators.
One mor thing, I see that this small 2 stroke gennys come with I think 12uf/350vac caps(I think) but what some locals do is replace that with a 24uf or even 30uf cap and they say this helps to boost output.
I read caps play a big part in this gennys but a won't mind a clearer explanation on the their role.

 

[debe]

You don't have to increase the cap value by mutch to put the voltage way too high.

 

[dr pepper]

In post 12 I reffered to synchronous and inverter gen's, the freq of an inverter gen isnt affected by the engine revs, as the generator is DC, the inverter generates AC, and is probably crystal controlled.