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Governor for homemade generator

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Diy1995

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Hello, I'm new to this forum so I would like to say Hy to all.

I builded homemade electric generator. It's 2kw generator from Briggs&Stratton lawn mower engine (four stroke with carburator and centrifugal governor) and 1phase inductive industrial motor.
I managed to get motor to generate electricity (capacitor to magnetize the rotor), but now i need to make electronic governor to keep motor producing 240vac and 50hz (I guess 10% of tolerance would be ok).

I understand that I will need something to read voltage and frequency, steper motor to move carburator lever and controller in between.
What parts would I need, how can I make this? It need's to be as cheap as possible.
I have electronics and mechanics skills so I will be able to build it.

Thank you for your time/help.
 

MikeMl

Well-Known Member
Most Helpful Member
Seems like you need two different control loops, one to regulate frequency (modulate throttle to set speed), and the other to control the output voltage as a function of load current, normally done by varying the DC field current in an alternator. Since you dont have a real alternator, how do you control the output voltage?
 
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Diy1995

Member
Seems like you need two different control loops, one to regulate frequency (modulate throttle to set speed), and the other to control the output voltage as a function of load current, normally done by varying the DC field current in an alternator. Since you dont have a real alternator, how do you control the output voltage?
Hello, I saw some other people on internet do it. When voltage was 240v frequency was close to 50hz. In my case it can change a little, I will use generator for power tools and such, I don't need it for high tech electronics.
I just need something that will be ajdusting engine's RPM.
Thanks
 

MikeMl

Well-Known Member
Most Helpful Member
Have you ever done a project using an Arduino or other micro-controller?

So which is more important? Control frequency and let the voltage be dependent on the machine, or control voltage and let the frequency wander?
 

Diy1995

Member
Have you ever done a project using an Arduino or other micro-controller?
Hello, no I didn't. But I helped my friend once with his wifi controlled rc car with raspberry pi and motor micro controller. I can figure it out, I can learn that type of stuff fast via internet.
 

tcmtech

Banned
Most Helpful Member
What kind of B&S lawn mower engine doesn't come with its own governor system already on it?

I know of no such model that ever used a manual throttle system.
 

Diy1995

Member
What kind of B&S lawn mower engine doesn't come with its own governor system already on it?

I know of no such model that ever used a manual throttle system.
It has it's own governor, but in my case governor does nothing. Voltage is really sensitive to trottle and when I put load on generator voltage just drops, I must ajdust trottle higher by hand. Original governor just won't do the job (it's good for mowing lawn, but not for generator). Thanks
 

crutschow

Well-Known Member
Most Helpful Member
It has it's own governor, but in my case governor does nothing. Voltage is really sensitive to trottle and when I put load on generator voltage just drops, I must ajdust trottle higher by hand. Original governor just won't do the job (it's good for mowing lawn, but not for generator). Thanks
Then it sounds like to you want to adjust the throttle based upon voltage and not frequency.
Power tools and such are not that sensitive to frequency (as long as the minimum is not below its rated frequency).
You can adjust the engine based upon one or the other but not both.
So you could convert the AC to DC with a rectifier and read that with the A/D input of an appropriate micro to control a stepper motor.
The motor could adjust the spring tension on the governor that is already on the engine.
 

tcmtech

Banned
Most Helpful Member
It has it's own governor, but in my case governor does nothing. Voltage is really sensitive to trottle and when I put load on generator voltage just drops, I must ajdust trottle higher by hand. Original governor just won't do the job (it's good for mowing lawn, but not for generator). Thanks
What size and type of engine? 3.5 - 5 HP and vertical or horizontal?

Reason being I have worked on and even have one or two old small units form the 1960- 70's what are maybe 1500 1800 watt capable units which use the old 3 and 3.5 HP B&S engines on then and they have no major issues with speed or voltage control to the point of being a problem for basic work. Granted they run about 5% over nominal speed and voltage at no load and about 5% under at full rated load but that's well within common electrical devices working ranges and pretty good for ancient magnetic current transformer based voltage regulator tech.

As for using a induction motor as a generator you will never get one to stay stable in both voltage and frequency at the same time no matter what you do to the engine speed. A workable middle range of mostly acceptable is the best you will ever get.
 

Diy1995

Member
Then it sounds like to you want to adjust the throttle based upon voltage and not frequency.
Power tools and such are not that sensitive to frequency (as long as the minimum is not below its rated frequency).
You can adjust the engine based upon one or the other but not both.
So you could convert the AC to DC with a rectifier and read that with the A/D input of an appropriate micro to control a stepper motor.
The motor could adjust the spring tension on the governor that is already on the engine.
Yes, voltage is more important to me. What kind of micro controller would I need? Thanks
 

Diy1995

Member
What size and type of engine? 3.5 - 5 HP and vertical or horizontal?

Reason being I have worked on and even have one or two old small units form the 1960- 70's what are maybe 1500 1800 watt capable units which use the old 3 and 3.5 HP B&S engines on then and they have no major issues with speed or voltage control to the point of being a problem for basic work. Granted they run about 5% over nominal speed and voltage at no load and about 5% under at full rated load but that's well within common electrical devices working ranges and pretty good for ancient magnetic current transformer based voltage regulator tech.

As for using a induction motor as a generator you will never get one to stay stable in both voltage and frequency at the same time no matter what you do to the engine speed. A workable middle range of mostly acceptable is the best you will ever get.
It's sprint 40 engine, 4,5hp i think and it's vertical. I will try again today, maybe something is wrong with governor. I give up on frequency. Thanks
 

Les Jones

Well-Known Member
Most Helpful Member
Many years ago I built a generator for amateur radio contests. (We would camp out on hills so we needed a power source.) We bought a proper 5 KVA alternator which had a built in voltage control system. We used a Fiat 500 petrol engine to drive the alternator. The way I tried to control the speed was to use the frequency of the ignition pulses from the contact breaker in the distributer. This went to a frequency to voltage converter and the outut from this was compared with a reverence voltage using Op amps. The signal from the comparitor drove a small geared motor coupled to the throttle. I remember I had a lot of trouble making the control loop stable. It was done by trial and error by phase lag and lead circuits and loop gain adjustments. A purely mechanical sytem using a centrifugal govener might be an easier solution.
You need to give details of the motor that you are using as an alternator so that we have some idea how to control its output.

Les.
 

Diy1995

Member
Many years ago I built a generator for amateur radio contests. (We would camp out on hills so we needed a power source.) We bought a proper 5 KVA alternator which had a built in voltage control system. We used a Fiat 500 petrol engine to drive the alternator. The way I tried to control the speed was to use the frequency of the ignition pulses from the contact breaker in the distributer. This went to a frequency to voltage converter and the outut from this was compared with a reverence voltage using Op amps. The signal from the comparitor drove a small geared motor coupled to the throttle. I remember I had a lot of trouble making the control loop stable. It was done by trial and error by phase lag and lead circuits and loop gain adjustments. A purely mechanical sytem using a centrifugal govener might be an easier solution.
You need to give details of the motor that you are using as an alternator so that we have some idea how to control its output.

Les.
Hello, it's an inductive asynchronous single phase motor, 2,2kw 220v maded by yugoslavian brand called Sever.
As motor it had only starting capacitor and no running capacitor.
In order to magnetize the rotor i wired 20uf running capacitor over common and phase.
Thats about it. Thanks.
 

tcmtech

Banned
Most Helpful Member
Hello, it's an inductive asynchronous single phase motor, 2,2kw 220v maded by yugoslavian brand called Sever.
As motor it had only starting capacitor and no running capacitor.
In order to magnetize the rotor i wired 20uf running capacitor over common and phase.
Thats about it. Thanks.
That concept has been around for a very long time and it's inherently unstable and there is not much that can be done about it.
It's basically a lossy LCR tank circuit, where L and R are independently variable with the load, with a mechanical power input to keep it going so any change in the load on the tanks circuit creates a considerable drift in its related voltage and frequency stability which in itself is not easily or accurately controllable by changing the mechanical input speed.

Tuning it to give the right output for a very narrow load power range is about as good as it gets.
 

Diy1995

Member
That concept has been around for a very long time and it's inherently unstable and there is not much that can be done about it.
It's basically a lossy LCR tank circuit, where L and R are independently variable with the load, with a mechanical power input to keep it going so any change in the load on the tanks circuit creates a considerable drift in its related voltage and frequency stability which in itself is not easily or accurately controllable by changing the mechanical input speed.

Tuning it to give the right output for a very narrow load power range is about as good as it gets.
Ok, thats scary as i builded generator already, getting pulley costum machined out and everything. What if I set it to get around 500vac is there any circuit that would take excess voltage and transform it to heat or something like that and when i will put load on it voltage will drop, so there will be less excess voltage to take away because it will go into my consumer (just like dc voltage regulator)?

Plus I found out that this Sever manufacturer was building generators with that type of motor. It's rare and on pictures i don't see any type of governor, there is only a box mounted on motor and I have no idea what is inside :s. Thanks
 

crutschow

Well-Known Member
Most Helpful Member
What kind of micro controller would I need?
You could use a Picaxe, programmed in the BASIC language, which is the easiest computer language to start with and learn for small projects.
Many on these forums use the Arduino but that uses a variant of the C language which, to me, has an arcane notation that is much more difficult to learn.

You likely will have to add some loop compensation in the control program to achieve a stable generator output voltage (avoid hunting or oscillation in the speed) which will require some form of PID or Fuzzy Logic (which I think is easier to use with a micro).
 

tcmtech

Banned
Most Helpful Member
The closest semi stable systems based on this concept is those that use three phase motors and have one or even two of the three separate phase windings setup as the exciter circuits. Their voltage stability is better but they still have a frequency drift that's not totally attributable to the engine RPM drift due to rotor slip effects.

That's basically how many of the low end portable generators work now by having a dedicated and specifically tuned excitor winding set separate from the output set. That and they have special wound rotor that is setup to have two dedicated poles and the windings are shorted with a diode in series so that the rotor always puts the same magnetic pole on the same side.

They are frequency stable in relation to the rotor RPM and their voltage regulation is usually within the +- 5% - 10% allowance range over their rated load capacity.

The closest you can get to that design would be to set up your start winding to be the one with the capacitor on it providing you can get the main windings to put out the right voltage range without overloading the start winding exciter circuit with too much current.

Ideally you would set your frequency to + 5% - 10% at no load adjust your capacitor value to give a similar +5% -10% voltage at that speed as well. Then hope the combined frequency and voltage drop off curve stays tolerable until you get close to the motors rated wattage output level.
 

dr pepper

Well-Known Member
Most Helpful Member
For the same reasons as above you would need to turn the motor at a higher speed tban rated (due to slip) to get the max rated output power from it.
Or accept you'll get around 70% power at 50/60hz.
I found a instructables for a arduino generator controller, it'll give you an idea of whats involved.
http://www.instructables.com/id/Generator-Governor/
 

spec

Well-Known Member
Most Helpful Member
Just one very small, and perhaps obvious point, the mechanical governor mechanisms and other exposed mechanisms on lawnmower engines tend to attract dust and also dry out. A good clean and a squirt of thin oil works wonders.:)

spec
 

Diy1995

Member
The closest semi stable systems based on this concept is those that use three phase motors and have one or even two of the three separate phase windings setup as the exciter circuits. Their voltage stability is better but they still have a frequency drift that's not totally attributable to the engine RPM drift due to rotor slip effects.

That's basically how many of the low end portable generators work now by having a dedicated and specifically tuned excitor winding set separate from the output set. That and they have special wound rotor that is setup to have two dedicated poles and the windings are shorted with a diode in series so that the rotor always puts the same magnetic pole on the same side.

They are frequency stable in relation to the rotor RPM and their voltage regulation is usually within the +- 5% - 10% allowance range over their rated load capacity.

The closest you can get to that design would be to set up your start winding to be the one with the capacitor on it providing you can get the main windings to put out the right voltage range without overloading the start winding exciter circuit with too much current.

Ideally you would set your frequency to + 5% - 10% at no load adjust your capacitor value to give a similar +5% -10% voltage at that speed as well. Then hope the combined frequency and voltage drop off curve stays tolerable until you get close to the motors rated wattage output level.
I can't do this because I have 1phase motor. I just realised that angle grinder is doing good even on 300v and 80hz, it's not heating or anything. I will just try to get as close as possible with this design. Thanks
 
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