PTO Generator

[Jerry Coles]

Hi all
I'm looking at purchasing a PTO generator (240 and/or 110v AC) onto my Dexta.
What sort of KVA could I get from my Dexta (newish engine).
BTW it started straight away at -4 deg here in N Somerset this morning.

Looking forward to your advice.
Cheers
Jerry
Bath
UK

[Bensdexta]

I'm looking at purchasing a PTO generator (240 and/or 110v AC) onto my Dexta.
What sort of KVA could I get from my Dexta (newish engine).

Jerry, Here's my guess:
Rule of thumb seems to be 2HP/kW. So if Dex delivers 26HP at PTO 540rpm, then a 13kW generator is about right. If the electrical load is purely resistive (eg an electric heater), then power factor =1 and 13kW=13KVA. If electrical load is not resistive, then power factor will be less than 1 and a larger KVA is possible. But the safe assumption would be to say that our Dex can power about 13KVA generator.

Useful link here: http://www.omafra.gov.on.ca/english/eng ... 00-059.htm

Let us know what you decide!

[Jerry Coles]

Hi Ben
Thanks for the link, that must be required reading for anybody considering a PTO generator. Just highlights what should be common sense if you step back and give it some thought.
The point about PTO RPM is notable as some PTO generators I've looked at have quite a low PTO RPM of 380 which drops the engine revs down the torqe band.
My old friend Bill, now sadly passed on had a concrete block mounted generator so that a tractor could back up and turn it but they had a whole range of tractors over the years but still the same old generator. One wonders how many times it was poorly aligned, wrong rev range etc.
Thanks once again, it looks like a slightly larger generator capacity but decent PTO RPM.
I ran quite a few different generators in the army (6KVA to 271/2KVA) and once had six running in parallel giving nearly 100KVA O/P. They would 'beat' as the revs varied under load and you would get a low surging whooom sound.
Jerry
Bath
UK

[russelm]

Takes me back to my Alsthom power transmission design days!

You will find a generator is always quoted in VA (or KVA if its larger) as VA describes the generated power.

If you consider the real work you can do you measure it in watts and clearly with something that has a poor power factor, you need to generate considerably more VA to get the required watts out.

[Jerry Coles]

Loking at the manufacturers websites it's the PTO RPM as well as the KVA that has to be considered.
As the load will mainly be resistive PF shouldn't be a problem. I don't think many small generators have PF meters and would take a bit of a leap for most to try and introduce PF correction.
I'll keep looking
Jerry
Bath
UK