Author Options:

can a 25hp diesel engine power a 25kw alternator to power a 15kw motor? Answered

I have a 25hp china single cylinder diesel engine and a 25kw alternator of 80% power efficiency. 
I have a 15kw electric motor attached to a vegetables oil expeller that I want to power.
Can I use the 25hp diesel engine to power the 25kw alternator to get 15kw out of it to power the 15kw motor?



1 year ago

746 = 1 HP

So 25 x 746=18642.5 (Thanks Google)

That's 18.642 Kw so No if you want full power out,

It may rin but not at full power.

Essentially less losses what you put in comes out the other end even if it is in a different form.


Answer 1 year ago


Essentially the 25 HP is only 18.65 KW which is Less then your 25 KW alternator !!!


Assuming your engine speed RPM is correct for the 80% eff alternator. You will get 18.65 x 0.80 = 14.92 KW almost 15 KW....

It may work if you start the oil motor unloaded until it gets to foll speed...


Answer 12 months ago

Thanks for the answer ICENG

the diesel engine (18.65KW) EFF is 100% =1

The alternator (25KW) EFF is 80% = 0.8

What will be the output in this case?


Answer 12 months ago

Shaft Input to alternator 18650 watts (25HP), less 20%,

Output AC electrical power 14.92KW " almost 15KW (two days ago)"

Still assuming the diesel engine RPM is matched to the alternator min RPM.. Otherwise no output, or the frequency could be 200 Hertz and wearout the oil expeller mechanism in minutes...


12 months ago

Josehf is correct "you are pushing it" that is why I said ;

"It may work if you start the oil motor unloaded until it gets to full speed !"

BTW a starting electric motor uses over 5 times the load current as it accelerates to full speed...

Running the vegi expeller shaft directly from the diesel engine makes a lot more sense unless you want to avoid diesel fumes from contaminating the oil..

Josehf Murchison

12 months ago

Your numbers are tight, to power the 15 kw motor with an 80% alternator you need a minimum 24.2 horse diesel engine.

15,000 / 746 = 20.1 + 4.1 = 24.2 hp for a quick calculation.

The alternator would most likely prefer a 40 to 50 horse diesel engine and then you will have the full 25 kw available, but with a 25 horse diesel you are pushing it.

Why don't you just power the vegetable oil extractor directly off the 25 hp diesel, it should have more than enough power.