Need Generator experts

[zain_khan1]

Dear friends, i have john deere generator of 50kva.......specs of generator engine are shown in pictures....my generator engine power is 75KW @ 1800 RPM....according to my little knowledge, engine of 75kW can generate 100kva electricity...i saw alot of generators which are 75kW engine and produce 100kva....then why my generator is still running on 50kva ? ....its fuel consumption is also high, not like 50kva generator when i compare with my friends generator 50kva....i think the wrong dynamo is installed with wrong engine.....should i change the dynamo from 50kva to 100 kva ? .....will it work fine for me or i am just miss calculating things here.....i also need 100kva generator, if things worked it will b a great saving for me....please give me some advise as there are very few good generator experts which i hope i will find one here on pakwheels......

[ahmedk06]

how are you measuring, is your Multimeter calibrated or not

[zain_khan1]

i measured once when i purchased it.....i purchased two geneartor at very cheap price....and they are working fine.......but when i noticed the specs of engine and had done some more research on internet i find out my generator engine is too big for 50kva dynamo......which i may b wrong......but i want to confirm it 100%...u never know

[capsat]

please check the specs of dynamo if it is correctly coupled to right engine, if it is then please cross check the AVR unit most likely it is malfunctioning. also there must be a connection from AVR to throttle control engine managing engine rpm plus a cut-off switch / breaker for protection

From the posted images i can carefully say that it is a locally fabricated generator from scrap yard engine & dynamo not technically coupled with necessary monitoring gauges.

you may be needing some patience and a skilled electrician to resolve the issue plus a diesel engine mechanic to check for injector pump timing for fuel consumption

engine laga dy-numa laga saylencer FIT hona chahyea awaz kam holi ho gi teen char meter laga day soi hilni chheyay start hai 220 volt mil gaya baas generator tayaar bahar rakh dai footh path par koi girahk mil jai ga ..

[zain_khan1]

please check the specs of dynamo if it is correctly coupled to right engine, if it is then please cross check the AVR unit most likely it is malfunctioning. also there must be a connection from AVR to throttle control engine managing engine rpm plus a cut-off switch / breaker for protection

From the posted images i can carefully say that it is a locally fabricated generator from scrap yard engine & dynamo not technically coupled with necessary monitoring gauges.

you may be needing some patience and a skilled electrician to resolve the issue plus a diesel engine mechanic to check for injector pump timing for fuel consumption

engine laga dy-numa laga saylencer FIT hona chahyea awaz kam holi ho gi teen char meter laga day soi hilni chheyay start hai 220 volt mil gaya baas generator tayaar bahar rakh dai footh path par koi girahk mil jai ga ..

no bro u missunderstood me.....i want to install 100kva dynamo on this engine.......the engine is fine......all i m asking is can i run 100kva dynamo on this engine?

[capsat]

please check engine specs from OEM, if the engine is designed to run at 2000 rpm for extended hours without labouring there is nothing wrong to couple a 100kVA dynamo. see if you can get hold of cummins or a bosch dynamo

[bigmaster]

no bro u missunderstood me.....i want to install 100kva dynamo on this engine.......the engine is fine......all i m asking is can i run 100kva dynamo on this engine?

if the engine is 75KW, then obviously a 75KW dynamo should have been installed.

check for the dynamo specification written anywhere on the dynamo....see if it is 50kva or 100kva etc...

and google for the correct spec dynamo for the engine....

[zain_khan1]

please check engine specs from OEM, if the engine is designed to run at 2000 rpm for extended hours without labouring there is nothing wrong to couple a 100kVA dynamo. see if you can get hold of cummins or a bosch dynamo

yes i verified the specs from OEM.....they are same as shown in picture......thats what i thought......it is possible......100KVA dynamo should not be problem for this engine.....but there is 1 more confusion......i have another 30kva generator too.....same confusion is there too......the engine power is 45KW and dynamo is 30kva........there must be some thing why they are using big engines for such dynamos.....there is nothing written on both dynamo....no specs on dynamo....i was told by a seller that one is 50kva and the other is 30kva.....thats all what i know.....both generator are working fine and smoth

[zain_khan1]

if the engine is 75KW, then obviously a 75KW dynamo should have been installed.

check for the dynamo specification written anywhere on the dynamo....see if it is 50kva or 100kva etc...

and google for the correct spec dynamo for the engine....

there is nothing written on dynamo......how to find out if it is 50kva dynamo or 100kva dynamo ?
if 100kva can run on this engine then why 50kva dynamo is installed.......why will one do this ?
i want to read the mind behind this engineering....i have another 30kva generator too....the engine power is 45kw and dynamo is 30kva

[bigmaster]

there is nothing written on dynamo......how to find out if it is 50kva dynamo or 100kva dynamo ?
if 100kva can run on this engine then why 50kva dynamo is installed.......why will one do this ?
i want to read the mind behind this engineering....i have another 30kva generator too....the engine power is 45kw and dynamo is 30kva

this engine seems to be able to support 50 KVA.

I think the dynamos on both ur engines are very low quality, low power factor and low efficiency ones. That is the only explanation for poor economy.

Get ur dynamos checked from an expert that which model/spec it is....if u can find the model number written somewhere on it, google it to find its specs....

[YamahaYB100]

This engine is coupled with right size alternator
And engine advertised power is 75kwm mechanical) on 1800 rpm which is gross power
But when mechanical power is converted to electrical power and there's is some power loss because nothing is ideal on universe
In Pakistan we run genset on 1500 rpm
Now your engine generates 75kw on 1800 rpm and max torque is

75*5252?1800=218.83 lb-ft
Now calculate power on 1500 rpm
218*1500?5252=62.5 kw
Multiply it with 0.8
62.5*8=50kw
If you still have confusion download Cummins and cat gensets pdf everything is mentioned their even BSFC

[YamahaYB100]

If I'm not wrong your max fuel consumption should between 11 to 14 liter per hour

[bigmaster]

This engine is coupled with right size alternator
And engine advertised power is 75kwm mechanical) on 1800 rpm which is gross power
But when mechanical power is converted to electrical power and there's is some power loss because nothing is ideal on universe
In Pakistan we run genset on 1500 rpm
Now your engine generates 75kw on 1800 rpm and max torque is

75*5252?1800=218.83 lb-ft
Now calculate power on 1500 rpm
218*1500?5252=62.5 kw
Multiply it with 0.8
62.5*8=50kw
If you still have confusion download Cummins and cat gensets pdf everything is mentioned their even BSFC

there are different dynamos available which are rated for different rpms...

I have a generator that runs on 3000rpm, for example.

It's not a problem getting a dynamo for 1800rpm...

Also, your calculation assumes a flat torque-rpm curve.

you ignored dynamo efficiency which is usually around 90%+.

So the 75kw engine coupled with a decent dynamo can take a 65kw load at 1.0 power factor at max.

so it should be able to run a 75kva dynamo. look for a dynamo that produces 50hz/230V at 1800rpm. or the same at 2000rpm, then you can go upto around 100kva

[zain_khan1]

If I'm not wrong your max fuel consumption should between 11 to 14 liter per hour

no......max fuel consumption is 5/6 liter per hour for 50kva and 2.5/4 for 30kva..........when i put too much load on both generator, the engines seems to be effortless and relax.....it doesnt sounds like too much load on engines.....it means engines have more then enough power... ...there are dynamo avaliable for 1800rpm.....i think 100 kva dynamo should work fine on this engine....

[zain_khan1]

there are different dynamos available which are rated for different rpms...

I have a generator that runs on 3000rpm, for example.

It's not a problem getting a dynamo for 1800rpm...

Also, your calculation assumes a flat torque-rpm curve.

you ignored dynamo efficiency which is usually around 90%+.

So the 75kw engine coupled with a decent dynamo can take a 65kw load at 1.0 power factor at max.

so it should be able to run a 75kva dynamo. look for a dynamo that produces 50hz/230V at 1800rpm. or the same at 2000rpm, then you can go upto around 100kva

yes 1800rpm dynamo are avaliable for 75kw engine power which is exactly 100kva.......@YamahaYB100 has a point to ponder....... when mechanical power is converted to electrical power and there's is some power loss

[YamahaYB100]

there are different dynamos available which are rated for different rpms...

I have a generator that runs on 3000rpm, for example.

It's not a problem getting a dynamo for 1800rpm...

Also, your calculation assumes a flat torque-rpm curve.

you ignored dynamo efficiency which is usually around 90%+.

So the 75kw engine coupled with a decent dynamo can take a 65kw load at 1.0 power factor at max.

so it should be able to run a 75kva dynamo. look for a dynamo that produces 50hz/230V at 1800rpm. or the same at 2000rpm, then you can go upto around 100kva

your 3000 rpm generator has 2 pole alternator
4 pole alternator generates 50 hz on 1500 rpm and will also work on 1800 rpm but frequency will 60 hz
read this for pole and rpm calculation
Alternator - Wikipedia, the free encyclopedia
torque calculations is based on power which is written on name plate ( in 1st photo)
i didnt ignored efficieny and in last line 0.8 figure is multiplynga factor for power loss
till now i have seen alternators with 0.8 pf
can you source a decent dynamo with unity pf

no......max fuel consumption is 5/6 liter per hour for 50kva and 2.5/4 for 30kva..........when i put too much load on both generator, the engines seems to be effortless and relax.....it doesnt sounds like too much load on engines.....it means engines have more then enough power... ...there are dynamo avaliable for 1800rpm.....i think 100 kva dynamo should work fine on this engine....

5 to 6 liter is good but i told you max con. on 70 to 75 amp on each phase it should be more than 11

[bigmaster]

your 3000 rpm generator has 2 pole alternator
4 pole alternator generates 50 hz on 1500 rpm and will also work on 1800 rpm but frequency will 60 hz
read this for pole and rpm calculation
Alternator - Wikipedia, the free encyclopedia
torque calculations is based on power which is written on name plate ( in 1st photo)
i didnt ignored efficieny and in last line 0.8 figure is multiplynga factor for power loss
till now i have seen alternators with 0.8 pf
can you source a decent dynamo with unity pf

oh ur right about the rpm thing...so the engine was designed for use with 60hz....btw its not that big a deal if you use 60hz instead of 50hz, cuz most of the appliances are rated for a range of frequencies (50-60hz). The only thing that can be damaged is the fan regulator. Don't know about industrial loads. He should check with all his equipments ratings, make sure nothing blows up lol..

u calculated torque at 1800rpm. And used that same torque figure to calculate power at 1500rpm. How do you know torque is same at 1500rpm and 1800 rpm, it may be different. That was my point...The torque may drop significantly, lowering power output significantly, maybe that's the reason why it has a smaller dynamo than what engine ratings seem to suggest. And that must be the reason for bad fuel economy as well, since the engine is running at an rpm other than what the manufacturer designed it to be most efficient at.

power factor and alternator efficiency are different things...

power factor depends on load. It's a difficult thing to understand. I don't fully understand it.

[bigmaster]

yes 1800rpm dynamo are avaliable for 75kw engine power which is exactly 100kva.......@YamahaYB100 has a point to ponder....... when mechanical power is converted to electrical power and there's is some power loss

do tell us what equipment are you running on the generators?