Build your own generator

[wrooster]

with that hp.. you could go to about 11kw and be good. ie.. your 10kw head with a lil peak overhead would be safe.

with a direct drive head on that engine you will be able to get around 13KW continuous output power.

the Kubota D1005 engine is rated for continuous use at 3600RPM with an output of 16.8KW [=22.5HP]. at the datasheet spec 80% conversion efficiency at the alternator, that's 13.4KW available at the electrical end of the generator -- continuous.

a larger generator head than the 10KW unit proposed, coupled with this engine, will provide greater power in general and more importantly greater surge power for starting motor loads such as well/irrigation pumps, air conditioners/water chillers, and air compressors.

wrooster

 

[mrcaptainbob]

How does an engine set up like that keep the generator's rpm's steady under varying loads? Is the throttle response from it's governor sensitive enough to maintain the needed rpm's? Or does the power get routed through a unit that smooths out the cycles, amps, voltage stuff to prevent spikes and such?

 

[BHD]

one needs a proper governor, for maintaining the engine speed,
most use some type of mechanical governor,

the governor on my generator is the same that is used on a combine harvester of the same era as the engine manufacture,

(in my opinion having some extra engine is not a problem), as the surges do not effect the seed droop as much and the recovery of the speed,

the droop should should be less than 5% which works out to about 2 cycles, for most situations,

normally my generator keeps with in about 1% in the cycles,

for a poor mans cycle meter,
one can take a old plug in clock with a second hand, and then time it with a digital or battery unit, the longer you time say 5 Min's vs 1 min, the more accuracy your reading will be,
I usually set my generator up to about 61 to 62 with no load and when it starts to load it will set in to about 60 cycles a min,

but try to keep it in the 55 to 65 cycles out put, other wise you will stress the electrical equipment you have,

~~~~~~~~~~~~~~~~~~~

if the engine does not have a built in governor like a tractor or combine or small engine, one will need some type of exterior governor added on to control the engine speed,

 

[Soundguy]

with a direct drive head on that engine you will be able to get around 13KW continuous output power.

the Kubota D1005 engine is rated for continuous use at 3600RPM with an output of 16.8KW [=22.5HP]. at the datasheet spec 80% conversion efficiency at the alternator, that's 13.4KW available at the electrical end of the generator -- continuous.

a larger generator head than the 10KW unit proposed, coupled with this engine, will provide greater power in general and more importantly greater surge power for starting motor loads such as well/irrigation pumps, air conditioners/water chillers, and air compressors.

wrooster

I'm sure that looks great on paper and the spec book.

since we all live in a different place.. IE.. the real world.. I'd realistically plan on a lil over 11kw of sustainable load on a 22.5 hp rated engine.

soundguy

 

[RonMar]

I'm sure that looks great on paper and the spec book.

since we all live in a different place.. IE.. the real world.. I'd realistically plan on a lil over 11kw of sustainable load on a 22.5 hp rated engine.

soundguy

Yep, a very well proven rule of thumb for SUSTAINABLE power output is 2HP per KW of electric load. Pretty much any generator spec/rating you are going to look at will bear this out. The ST heads are OK, but quality can vary quite a bit as they are made all over china, kind of a cottage industry... Unfortunatly for your project, they do not make a 3600 RPM version. As far as I am aware, they are all built 4 pole for direct coupling to an 1800 RPM engine. I use one with belt drive off of a 650 RPM slowspeed diesel engine.

Your biggest issue will be speed control. There are 3 basic diesel throttle configurations:
1. Basic throttle lever where throttle lever directly controls fuel rack/input. This will need a governor to operate as a generator prime mover.
2. basic governor as part of the injector pump. This is a narrow band governor often found on tractors and such. Throttle lever controls bias spring on spinning flyweight/ball governor. Makes the throttle lever basically a speed selector. This will mostly work as a generator, but due to the governors small band of fuel control, it will not respond well to large generator load changes. This is the biggest issue with running a generator off of a tractor 3PH.
3. Generator configured governor which has FULL throttle authority, and can respond to any load change automatically within the engines HP ability...

 

[wrooster]

I'm sure that looks great on paper and the spec book.

since we all live in a different place.. IE.. the real world.. I'd realistically plan on a lil over 11kw of sustainable load on a 22.5 hp rated engine.

soundguy

go on.

in the "real world" that you are talking about, Kubota's generator division uses the D1005 engine to power generators spec'd for 14KW prime (continuous use) / 15.4KW intermittent output.

see, for example,
KUBOTA GENERATORS | PRODUCTS | Specifications : J Series : Other 60Hz. J318

blanket statements that start with "in the real world..." should probably have some "real world" information as back up. using 2HP of engine output per 1 KW of generator output is a nice rule of thumb, but it is not entirely accurate.

if the OP couples his Kubota D1005 engine to a 10KW generator head, it will work fine. he just needs to realize that he is leaving >40% additional capacity (>4KW) on the table, and that's a lot of headroom. that headroom may or may not be useful to the OP, but it's useful for him to know when planning a alternator head purchase.

wrooster

 

[Iplayfarmer]

Does a larger generator head use up more energy than a smaller one. I'm speaking about if both are unloaded. I'm wondering if there is any advantage other than purchase price for using a smaller head.

 

[wrooster]

Does a larger generator head use up more energy than a smaller one. I'm speaking about if both are unloaded. I'm wondering if there is any advantage other than purchase price for using a smaller head.

IMHO, this decision is quite application dependent.

if you have primarily resistive loads, like a lot of incandescent/flourescent lights used to illuminate a indoor horse ring or such, you could probably save some money with the smaller generator head. total up the steady state watts you need, and buy a unit.

on the other hand, if you have loads with high starting wattage requirements -- such as a deep well pump, air compressors/air conditioners, processing/handling motors for grain conveyance or such -- then you should opt for the larger head. the added mechanical inertia of the larger rotor and additional power output capacity will prevent voltage sags and possible motor damage when these high inrush loads start up.

wrooster

 

[Soundguy]

I said it exactly as I inteded to say it.

it's a good rule of thumb because history has proven it out.

the OP leaving a lil KW capability on the table may help him in the large load pickup department where the engine will stay in it's power band because it has a few hp to spare to keep the gennerator at correct speed. There's no 'real' downside to having more head than engine, or more engine than head. if you have more engine than head, the engine will not stall on large loads near max output. when you have more head than engine, you pickup some thermal and overlaod protection for the head when running at max.. with either case you have a marginof something unused.. no biggie.

If I was generating over 25kw I might start tuning that 2hp per kw down a bit to get closer to true hp to kw exchange, still allowing for mechanical losses and effeciency.

soundguy

go on.

in the "real world" that you are talking about, Kubota's generator division uses the D1005 engine to power generators spec'd for 14KW prime (continuous use) / 15.4KW intermittent output.

see, for example,
KUBOTA GENERATORS | PRODUCTS | Specifications : J Series : Other 60Hz. J318

blanket statements that start with "in the real world..." should probably have some "real world" information as back up. using 2HP of engine output per 1 KW of generator output is a nice rule of thumb, but it is not entirely accurate.

if the OP couples his Kubota D1005 engine to a 10KW generator head, it will work fine. he just needs to realize that he is leaving >40% additional capacity (>4KW) on the table, and that's a lot of headroom. that headroom may or may not be useful to the OP, but it's useful for him to know when planning a alternator head purchase.

wrooster

 

[RonMar]

Does a larger generator head use up more energy than a smaller one. I'm speaking about if both are unloaded. I'm wondering if there is any advantage other than purchase price for using a smaller head.

In answer to your question, yes, a larger head consumes more static energy. A larger head is built to deliver it's rated power under a large temperature range. A larger head makes more heat so therfore has a larger blower and moves more air. If the generator head is lightly loaded, it makes little heat, but the air is being pumped anyway. This requires more HP to pump that air. A larger generator has a larger field winding and will require a little more excitation current to maintain rated voltage. That energy has to come from somewhere, which is in the form of added magnetic load/drag on the spinning rotor. Peak generator efficiency is typically found somewhere between 50-75% of max rated load. In most cases, you want your generator head sized to meet your load in this range.

A diesel engine typically achieves it's best efficiencies when loaded in excess of 75% of it's capacity. When these rules are followed, you have a generator that is about as efficient as you are going to get, and with a little bit of surge load capacity to help deal with starting larger inductive loads such as A/c, well pumps, compressors, ect. Especially in the case of smaller gensets, a heavy flywheel that stores inertia also helps out a great deal for starting inductive loads and in general frequency stability. That is probably why 3PH driven generators even operate acceptably with the narrow bandwidth governors typically found on tractors. you have all the added weight of flywheel, clutch gearbox and PTO spinning shafts adding to the overall inertia to help stabilize the output RPM.