Generator

[AccessWorkBoots]

I'm not supplying the gen, just sizing. The rest is up to the demo company

 

[Smart $]

I'm not supplying the gen, just sizing. The rest is up to the demo company

I would not go with less than a 150kVA-rated genset. I'll leave it to you to determine whether that is large enough...

BTW... assuming you are feeding an existing [and disconnected] service, what is the service OCPD rating?

 

[AccessWorkBoots]

Calculated size

Calculated size

Well, here's my numbers.
480 side W/O any diversity requires at least:......41 kw
208/120 side..................................................55 kw
Total.............................................................95 kw
So 95 kw is the bare minimum I need. I'm not taking any diversity for the distribution of loads on the 120 volt side(although I'm seriously considering a 70% derating of this number)) so I don't think I need to add in a safety factor as I already have some room. But I will kick it up to at least a 100 kw, maybe more.
jim

 

[AccessWorkBoots]

The 480 volt panel has a 600 amp main. I'm going to install a fused disconnect between the generator and the building once I get the sizing. The generator is going about 25 ft from the building and I'm going to install the disconnect at the point where the cables enter the building. Thanks for your help. How did determine the 150 kw? And why do the generator suppliers always change the kw to kva? kw is true power and that's what I need and kva is what the utility is charging me for ?

 

[Smart $]

... How did determine the 150 kw? And why do the generator suppliers always change the kw to kva? kw is true power and that's what I need and kva is what the utility is charging me for ?

Padded for unbalance and inrush guestimates.

Watts is true power and what the POCO charges for, though they may add a penalty for power factor ? kVA vs. kW. When sizing electrical, we always go by VA, because we are most concerned with current capacities, not true power.

 

[AccessWorkBoots]

Ok, thanks for your help.

 

[iceworm]

And why do the generator suppliers always change the kw to kva? kw is true power and that's what I need and kva is what the utility is charging me for ?

Generator KW is rated on how much power the driver can deliver. Power is Torque X RPM (X a constant to make the units match up) Power into the alternator ~= power out of the branch circuits (heat, light, motor shafts) *and yes there some efficiency issues

Generator KVA indicates the heat rejection capability of the alternator. The heating is based on the stator current and the rotor current. High inductive loads (light loaded morotors) draw a lot of current but don't draw much real power. Current is high, but the driver throttle is pulled back

3ph generators (normal stuff) are always rated in KW at .8pf (lagging). So, the KVA is always KW X 1.25.

So, you might say the kw is the driver limit, and KVA is the alternator limit

At 1pf, the driver will run out of horsepower before the alternator overheats
At .7pf (lagging) the alternator will overhat before the driver runs out of Hp.

ice

 

[Besoeker]

Generator KW is rated on how much power the driver can deliver. Power is Torque X RPM (X a constant to make the units match up)

P=Tw. Use SI and you don't need conversion factors....I'll convince you guys one day to get in step with the rest of the world...........

At 1pf, the driver will run out of horsepower before the alternator overheats
At .7pf (lagging) the alternator will overhat before the driver runs out of Hp.

The point I was making in post #5.
You just said it better..........:thumbsup:

 

[iceworm]

P=Tw. Use SI and you don't need conversion factors....I'll convince you guys one day to get in step with the rest of the world...........

I'll feel it was important when you guys and girls think it is important - :?:? huh?? yes we do.

Nope - you still sell beer is pints.

ice

 

[Besoeker]

Nope - you still sell beer is pints.

Yes, that's true. In pubs. But wine by the ml.
Buy beer in any store and the primary and often the only measure is ml.

We also do speed, distance and speed limits and fuel consumption in miles per hour, miles per gallon.
Yet fuel station forecourts sell fuel in litres.
Daft I know.

For engineering, everything is SI.
There is some sanity where it matters.

 

[iceworm]

Yes, that's true. In pubs. But wine by the ml.
Buy beer in any store and the primary and often the only measure is ml.

We also do speed, distance and speed limits and fuel consumption in miles per hour, miles per gallon.
Yet fuel station forecourts sell fuel in litres.
Daft I know.

For engineering, everything is SI.
There is some sanity where it matters.

You sure. The women weigh themselves in "stones" hmy: Ooookaayyy

Yes, you are correct there are a lot of strange units here:

Statute miles
nautical miles
kips
ft-lb torque
lb-ft energy
BTUs
ounces liquid
ounces weight (force)
ounces troy
Grains (weight measure gunpowder for reloading, Bullet weight for reloading)
And if one divides BTU by KW the answer is in hours (huh??)
231 in^3 in a gallon which means a pint is 28.9 in^3
The cooks are using teaspoon, tablespoon, cups.​

But we got barbecued ribs and tex-mex chile. Might be worth holding on to the screwy units just for those two.

ice

 

[GoldDigger]

Since when are we assuming that engineers are sane? Practical, yes!

Sent from my XT1080 using Tapatalk

 

[Besoeker]

You sure. The women weigh themselves in "stones" hmy: Ooookaayyy

But on anything remotely official your weight is in kg.

Yes, you are correct there are a lot of strange units here:

Statute miles
nautical miles
kips
ft-lb torque
lb-ft energy
BTUs
ounces liquid
ounces weight (force)
ounces troy
Grains (weight measure gunpowder for reloading, Bullet weight for reloading)
And if one divides BTU by KW the answer is in hours (huh??)
231 in^3 in a gallon which means a pint is 28.9 in^3
The cooks are using teaspoon, tablespoon, cups.​

Yes. the "ounces" bit gets Mrs B when she is cooking. She has a measuring jug marked in ounces, cups, pints, and ml.
"How many grams is four ounces?"
I can do the conversions but I first have to work out if that ounce is a weight or a volume.
SI has a lot to commend it.......

But we got barbecued ribs and tex-mex chile. Might be worth holding on to the screwy units just for those two.

We have had a lot of what you might consider strange or not so strange units here.
I'm an old fellow and was taught Imperial units at school. To that extent I'm mostly comfortable with either. Distance measured in yards and miles, horse races in furlongs, height in feet and inches, beer in pints, vital statistics in inches, land in acres, and yes, weight in stones and pounds. Chains and links. Did those too. The gill, fathom, cable, the ell (good word for Scrabble players) and the peck.

Some of the more obscure units, maybe not so much. I'm a farmer's boy. My father could work out bushels per acre for granulated fertiliser and set up the spreader to dispense the right amount.

SI has a lot to commend it.......
How's my sales pitch?



Back to that genny.

P=Tw.
The prime mover determines the power limitation.
The generator (alternator) kVA determines the maximum current that can be drawn.

Steady state values of course.
Transients outside the power limitation can be supplied from the ke of the rotational inertia and overcurrent from the thermal inertia of of the machine windings. But voltage regulation is another matter.

 

[Phil Corso]

Gentlepeople,...

Since this topic has morphed into one where "anything can be professed", has anyone heard of the following three legitiment process measurements:

a) Firkens per Fortnight?

b) Rubber-Ball Bounces?

c) Aluminum-Ball Seconds?

Regards, Phil Corso

 

[GoldDigger]

Well, A is pretty standard and "obvious" but B and C seem to need some explanation. Same way that the "light year" is a perfectly good unit but requires an explanation.

PS: Who maintains the standard rubber and aluminum balls? Or is that not a factor in the measurement?

Sent from my XT1080 using Tapatalk

 

[Besoeker]

Well, A is pretty standard and "obvious"

If you assume firkins rather than firkens, then yes it can be quantified depending on which firkin measure you take as a firkin measure.

For example, it could be 41 litres.
So, in process terms, a firkin/fortnight would amount to about 2.9 l/day.

Perhaps that's, on average, how much fuel a small standby genny might use for test purposes.

 

[Phil Corso]

Gentlepeople...

"FpF" or Firkins-per-Fortnight" was the outut of an LNG-to-Gas plant in Italy! The Brit-gineers in our Global startup team, representing 11-nations, came up with it during a 4-year startup delay! The firkin-unit was related to butter production!

"AbS" or Aluminum-Ball-Seconds was a measurement used by Lab-Techs of Celanese Plastics Company, to measure the viscosity of melted cellophane!

"TbB" or Tennis-Ball-Bounces was a dimensional unit used in the LNG-to-Gas plant (above) to monitor the leak-rate in a cryogenic heat-exchanger's perlite filled "cold-box" enclosure. It consisted of welding an appropriately sized close-nipple and gate-valve to the enclosure, plugging the outlet with a tennis ball, and then count the number of bounces the ball took when the valve was quickly opened. The plant was shutdown when count reached 11-bounces! Oh, yes the count was made and officialy recorded every shift!

Another unit concocted in the same gas plant was "MTBF" for Mean-Time-Before-Flare!

Finally, let me know if anyone is interested in a very unsual Synchronizing scheme!!

Phil

 

[Phil Corso]

GD...

I'm unable to access MHF Private message line! What do you need or want to know!

Phil

 

[John120/240]

Gentlepeople...

"FpF" or Firkins-per-Fortnight" was the outut of an LNG-to-Gas plant in Italy! The Brit-gineers in our Global startup team, representing 11-nations, came up with it during a 4-year startup delay! The firkin-unit was related to butter production!

"AbS" or Aluminum-Ball-Seconds was a measurement used by Lab-Techs of Celanese Plastics Company, to measure the viscosity of melted cellophane!

"TbB" or Tennis-Ball-Bounces was a dimensional unit used in the LNG-to-Gas plant (above) to monitor the leak-rate in a cryogenic heat-exchanger's perlite filled "cold-box" enclosure. It consisted of welding an appropriately sized close-nipple and gate-valve to the enclosure, plugging the outlet with a tennis ball, and then count the number of bounces the ball took when the valve was quickly opened. The plant was shutdown when count reached 11-bounces! Oh, yes the count was made and officialy recorded every shift!

Another unit concocted in the same gas plant was "MTBF" for Mean-Time-Before-Flare!

Finally, let me know if anyone is interested in a very unsual Synchronizing scheme!!

Phil

Phil, Lets hear it. I find units of measure interesting. This is the kind of knowledge that wins bar bets.

 

[Phil Corso]

Ok John, since you asked... (Finally someone on this forum with, I hope, a sense for humor!)

Some time ago I was Manager of the Electrical, Instrument, and Power departments of Celanese Plastics Company. The plant was located in the Iron-Bound district of Newark, New Jersey. It was called Iron-Bound because the area was surrounded by railroads.

One day, a neighborhood representative visited for a favor. He asked, "Could you have your steam plant 'sound' the steam whistle as a wake-up alarm for those people that worked in various Iron-Bound plants.."

Neighborhood PR was high on the agenda in those days, so I arranged for the Power Plant operators to activate the steam whistle every morning at 6:30am. Furthermore, so that we were in sync with the neighbors, I advised the operators that they were to use the very large (10-15 ft dia) clock visible on the Ballantine Brewery's tower. Within a 1/2 mile of our plant, it was also visible to many in the neighborhood.

One morning, about a year later, I received an early morning call from Ballantine's Chief Engineer. He asked, "Is your plant down?" I replied "Yes, why do you ask?" "Because" he responded, "we use your whistle to set the clock on our tower!"

Phil