diesel hp VS electric hp

About powering boats with electricity

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Re: diesel hp VS electric hp-LINKS

Post by S.D.G. »

Interesting topics. Would also like to do a electric / outboard lower conversion in the future. Have a good link here. Seems to be the two HOME pages before it got into the ETEK PROJECT posted above.
http://www.mindspring.com/~jimkerr1/sebc&t.htm Some mentions to GLEN-L stuff on the front page.? .Believe electric HP rating lower than the same liquid HP engine. . My brother -in-law has just finsihed his 2nd electric truck conversion in Winter Haven ,Fla & will give the link to his stuff for deeper reading.
http://evprogress.org/ . ENJOY
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Re: diesel hp VS electric hp

Post by galamb »

I can see where the 2.5 factor came in with regards to electric motors in trying to determine the true horsepower.

Take a look at an air compressor. You will often see things on the tag like 2 horsepower peak or running, yet you look and it's powered by a 3/4 horse motor.

So is the motor producing the "equivalent" of 2 horsepower? Obviously by some description.

Small electric "marine" motors are usually rated by "thrust" rather than horsepower which further confuses things when trying to directly compare to a gas/diesel engine since thrust can not be directly converted to horsepower.

And while my math skills suck I believe horsepower is actually a linear measurement based on motion - the time it takes an object of a given weight to move a given distance = horsepower.

So by the purest definition, a jet engine, producing 40,000 pounds of thrust, but on a plane with the brakes locked (no forward motion just prior to takeoff) is producing ZERO horsepower. Yet as soon as that plane lifts off, while the engine is still only producing 40,000 pounds of thrust, we could then say it was producing 28,000 horsepower (or whatever the formula kicked out) - and the "horsepower" if plotted would be on an ascending line, as ground speed increased, while the torque line would be relatively flat.

While Zero horses is technically true, that sounds rediculous so "factors" have been created to try and give that scenario a value which can be more easily understood by the average person. In some cases, "horsepower" is just not measurement that should be used in trying to determine "what size or how much".

I believe the same type of theory has been applied to electric motors when trying to compare them to more common methods of marine propulsion...

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Re: diesel hp VS electric hp

Post by electric tug »

i have to agree with whoever said that the shaft hp might be the same as the rated hp on an elecric motor. I have done some research on this and because the torque is generally higher on a electric engine, this translated into more work and thus more efficency and therefore more hp. so the math of 2 point something per 1 hp ratio electric to combustion eniges(sorry forget the exact quote that was presented)- is probably pretty acurate- just to give an example:
if you look at the older diesels say prior to 1960. the hp was rated a lot less on those engines- but the engines produced much more torque than todays diesels. a lister ha3 put out 36-37 hp..but it had the power of a modern 100 hp engine. so the ratings were definitley different. and as someone mentioned its a marketing ploy gto say the bhp rather than the shp of a combustion engine.

The old fairbanks/morse diesels at 120 hp would outperform any 120 hp diesel today and of course they weighted 6 tons and were made to last forever- this comes from steam days when 1 hp was really 1 HORSES ability to pull something. tell me that a 1 hp briggs and stratton engine will do the same pulling power that a clydesdale could? perhaps geared to like 100:1 ratio?!
im sure you can see where i am going here...anyway electric engines are rated at lower kw's for comparable gas or modern diesel engines to do the same work. btw the formula to convert kw's to hp is 1.34 x hp- which explains why electric engines are measured more often in kw's!

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Re: diesel hp VS electric hp

Post by jcallends »

HP rating for electric motors is always at max operating speed not necessarily max speed, same is true for internal combustion engines. Electric motors do not necessarily have high torque at low speed, some have very low torque at low speeds, It's all about how they are wound.

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Re: diesel hp VS electric hp

Post by stre »

Solar power is the best for electricity

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Re: diesel hp VS electric hp

Post by Chopra »

Typically when comparing electric to gas/diesel most people figure on doubling the electric HP. A 25hp electric would be equal to a 50hp diesel. There are many people out there running sawmills off of gensets. I run a Woodmizer LT40 off of a 25kw genset. The key to doing this is to size the generator to your load. If you only need 50kw, a 250 kW generator is not going to be efficient. My 25kw Genset will run a theoretical 33HP. The mill is 15hp, which leaves me room for a 10hp edger motor, a 3hp edger feed motor, and enough left over for a hydraulic pump or blower, should we need them. As it is right now we are only running the 15hp mill motor. I haven't had the chance to calculate how much fuel it uses, but I don't think it is a lot more than the 24hp gas motor that is on the other mill I run which is a twin to the electric, and the genset runs on cheaper off-road diesel.

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