Assistance needed to build a small generator

[ThorUK]

Hello,
Is any one able to help?

I am trying to build a small, 200W, generator. I have a 0.5HP diesel engine and was hoping to be able to use it for my problem stated above. My problem is down to weight and cost! My engine weighs 170grms and am looking for an all up weight of less than 750grms. My final power requirements are 12V and at least 10amps.

My questions that I think need answers are:

1) Would my engine be powerfull enough?
2) Would I be better using a DC alternator to get my power or an AC alternator? I am OK converting the ac-dc...
3) Has any one had any experience in this size area?
4) Are there any obvious pitfalls or has any one any thoughts about this?
5) As mentioned before cost and weight are a major concern as this is a private project. Any non official ways are greatly appreachiated.

Hope you can help, I have tried almost everywhere!

Kind regards,

Andy

 

[EdDanzer]

Use a small car alternator, it will give 12vdc at any RPM.

 

[Heydave]

1. The power is just enough assuming typical efficiencies. RPM could be an issue. If you have to change speed, the belts, gears etc may cost too much power.
2. DC generators actually have AC in the armature and use the brushes to convert to DC. Regulation uses current through the field windings. Noise from the brushes could be a problem as could rectification of an alternator although the alternator could have multiple phases to reduce the ripple. Typical car alternators regulate using DC current in the armature supplied through slip rings.
3. Not since science fair a few decades ago. I was working in the 2 Hp range.
4. A light weight generator of this size would be an asset for camping and other recreation activities. I have considered a small steam generator using a camp fire, cooking fire, or solar reflector as a available heat.
5. Consider using any permanent magnet DC motor as a generator. For efficiency, use a switching DC-DC regulator on the output. There are a great many such regulators available in this power range. Depending on the duty, you may be able to spin a motor faster than its normal use to increase power/weight. The same motor could be used as a starter as well.

 

[mdonner]

Car alternator is ideal for this application, but bare in mind that it can not operate with no load: the voltage across the rectifying diodes will exceed diodes' breakdown voltage.

 

[BJC]

Interesting. What kind of engine do you have?
Consider the generator or altenator from an outboard. In some they built into the flywheel but I have seen some that were the size of a can of soup.

 

[Nandos]

Andy:

A solution for you is to use a DC motor used for moving the wind-shield wipers in a car or using the motor driving the fan for the radiator.

The voltage generated would be around 15 volts if yu drive them around 3 to 4000 RPM.
The current output would be the rating of the motor at full load ( 8 to 20 amps ) depending on the model.

I am quite curious about your 0.5 HP, Diesel engine, what is the RPM ?.

0.5 HP is 746/2= 373 watts and with the efficiency of the motor to be around 60 % the power available should be around 120 watts, but do not expect more than around 85 -90 watts if you want the motor to last at least 800 hurs.

Can you send to me, info on your motor via direct email = garciah@flash.net ?.

Thanks

Nandos

 

[ScottyUK]

What about a motorcycle alternator? Much smaller / lighter than car (automobile!) type, but voltage & power o/p should be about right.

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Alternators under Product or Service, which will return 97 companies to inquire about a right size alternator for your diesel engine