Electronic Governor

[abg]

I have taken one project-- Assembly of LPGas fired generator set of 50KVA capacity using old petrol engine and LPG conversion kit, and alternator of adequate capacity.
Now the hitch is how to control the firing thereby saving LPGas if the load is not 100%. However there is a limit for lower side i.e. idleling consumption. It needs electronic governor using micro contollers+stepper motors and solenoid valves. This electronic governor has to work according to the variation in load only. Infact this governor also should be suitable to either 25kva or 100kva too. Means designing is irrespective of generating capacity. OK Please help me providing circuit design. Thanks

 

[Willbe]

Governor fails = people dead or property destroyed?

 

[abg]

This is not a gas chamber.

 

[stevez]

I am not sure of what Willbe meant for sure but it is my understanding that engines can fail catastrophically with even minor interruptions to fuel or air - that might cover a concern for property damage. Let the RPM run high - that can be a big problem too. I know it doesn't address your question directly - only a strong suggestion that whatever you do - you give due consideration to safety and reliability. The power levels you mention are not small.

There have been a number of questions like this on this forum in the past - take a minute to search - as I recall the discussion was good and likely very relevant to your project.

 

[Diver300]

You don't say what the alternator is but I am guessing it will be a 50 Hz / 415 V or 60 Hz / 208 V and either 2 or 4 pole.

If so, you need to run at 1500 rpm for a 4 pole 50 Hz alternator, 1800 rpm for a 4 pole 60 Hz, 3000 rpm for 2 pole 50 Hz and 3600 rpm for 2 pole 3600 rpm.

The speed controls the output frequency. The speed should be the same from no load to full load. The alternator will have a voltage regulator to make sure that the output voltage is constant.

You need to control the throttle valve. Solenoid valves are almost always on/off so all you would want that for is to shut it off.

A good way is to have a stepper motor control the throttle. You can measure the frequency by looking at the main output voltage, via a small transformer.

Small generators up to 5 kVA often use lawn mower engines. Small generators need speed control just the same as large generators and lawn mowers need speed control to stop the blades going supersonic with no load while being able to produce maximum power when the grass gets tall and wet.

Lawn mowers usually use centrifugal or vane governors. Both have a light spring to hold the throttle open, which is closed as the engine speeds up by either weights moving out due to centrifugal force, or air from the cooling fan blowing on the vane. Either of those methods would be fine and might be easier to get working.

With a 50kVA alternator you should look at something to kill the ignition if it goes too fast. It would be a lot worse than an lawnmower going mad.

 

[mneary]

Many cars come with a cruise control that contains some of the safety features you need.

 

[crutschow]

The design of such a control system is not trivial since this is a closed-loop servo system that has a high potential for instability if not correctly designed, especially if you need reasonably tight control of the generator output frequency.

A general control method would be to use a microcontroller to measure the frequency of the generator output and send out the appropriate control signal to adjust the engine speed. This has the advantage of allowing easy software adjustment of the control loop parameters to stabilize the system.

A Fuzzy Logic control loop may be appropiate for this. I think that it's more intuitive and appropriate for a microprocessor than trying to do some form of PID control which generally requires some serious mathematical analysis of the loop parameters. A tutorial on this is at https://www.fuzzy-logic.com/. A demo of a Fuzzy Logic control system is at **broken link removed**.

Have you checked this forum https://www.electro-tech-online.com/threads/engine-speed-governor.26944/.

 

[Leftyretro]

This is a classic application for a PID controller, https://en.wikipedia.org/wiki/PID_controller . Your process variable (PV) would be output frequency of the alternator. Your setpoint (SP) will be the fixed desired alternator frequency and your output (OP/error signal) will be used to position the engine throttle control. The hardest part will most likely be the design and construction of the throttle control. It needs to be linear and have adequate power to manipulate the throttle with no slop or backlash (hysterisis). The idea posted about using a standard auto speed control acutator might be the best solution. You should also have some electrical protections to prevent overload conditions.

This in not an easy project and much could be learned if you could get a hold of commercial generator manuals to see how the pros accomplish the several tasks required.

 

[Willbe]

This is not a gas chamber.

That was last month's design. . .

On one forum a guy wanted advice on how to repair his own gas line leading into his house. That's fine if he only blows himself up, but suppose others are injured?
A real gas fitter wanted probably $300 for the job. If medical expenses could be $10K for the burned homeowner, a "rational person" should only attempt this job if his/her chance of failing is less than 300/10K = <3%.
The gas fitter himself probably has a higher failure rate than this.

Another project had us designing a device that could have affected the stability of a 3500# car; same concerns. There are PhdME's, and that ain't me, who spend their whole life studying vehicle dynamics.

 

[stevez]

A couple of thoughts:

1. Ideally the RPM of the generator would be fixed - to fix the alternator frequency. Use of a tachometer separate from the alternator might make it easier to "see" changes in RPM that are real - rather than having noise/fluctuations falsely signal a change.

2. A look at the electrical load might allow a faster response - rather than waiting for shaft RPM to change your control system can begin to react sooner.

You might combine this information with the other ideas presented.

 

[koi_62_las]

I have taken one project-- Assembly of LPGas fired generator set of 50KVA capacity using old petrol engine and LPG conversion kit, and alternator of adequate capacity.
Now the hitch is how to control the firing thereby saving LPGas if the load is not 100%. However there is a limit for lower side i.e. idleling consumption. It needs electronic governor using micro contollers+stepper motors and solenoid valves. This electronic governor has to work according to the variation in load only. Infact this governor also should be suitable to either 25kva or 100kva too. Means designing is irrespective of generating capacity. OK Please help me providing circuit design. Thanks

hey buddy can i hav a look at ur project as i m using similar components dat u are so to b certain will u give me ur project to have a look hope u dont mind my mail adress is daskailash62@yahoo.com