generator output measurement

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srinivasan

Member
Location
Bangalore,India
output of the generator is commonly in the unit of kva and voltage rating also available. can we say generator output rating in hp. if tell the procedure to convert kva to hp or direct calculation
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I agree. A generator has an electrical output, so its should be measured in electrical units - KW.

HP is a mechanical measurment, and is a more suitable rating for the engine that turns the generator.

Also, as soon as you say something like "The generator output is 10 HP", someone will assume it can start and run a 10HP motor.
 

kwired

Electron manager
Location
NE Nebraska
forgive me if I slip a wrong unit in here, but you could give rating as watts, horsepower, volt-amperes, tons of refrigeration, foot pounds/sec , calories/sec, joules/sec, BTU/sec, and many other units.

1 horsepower = 746 watts.
 

iwire

Moderator
Staff member
Location
Massachusetts
One horsepower is also equal to the energy expended by an average horse to raise 33,000 lbs

one foot in one minute.

An average Shetland pony or a Clydesdale? ;)

Actually one horse power is equal to the energy expended by anything to raise 33,000 lbs one foot in one minute. :)
 

mivey

Senior Member
Actually one horse power is equal to the energy expended by anything to raise 33,000 lbs one foot in one minute. :)
Good thing the force of gravity is a constant.:p

They are all considered "obsolete". Here is the list I have:

1) cheval-vapeur horsepower: HP = 745.699871581W and CV=735.498750 W (E). From James Watt in 1782 and was equal to raising 528 cubic ft of water by one foot in one minute.

2) boiler horsepower: HP = 9816.664971 W (E). Power to evaporate 34.5 lb of water at 1 atm and 100?C in one hour.

3) metric horsepower: HP = 735.498750 W (E). HP = 75_kgf_m_/s ~ 542.5_ft_lbf_/s

4) electric horsepower: HP = 746.000 W (E)

5) water horsepower: HP = 746.043 W

6) horsepower: HP = 745.699871581 W. Also 550ft_lbf_/s (E)

7) British horsepower: BHP = 745.699871581 W. Also 550_ft_lbf_/s (E)
 

Besoeker

Senior Member
Location
UK
One horsepower is also equal to the energy expended by an average horse to raise 33,000 lbs
one foot in one minute.
Actually, that's power, not energy. It's a rate. Lbs-ft/minute.
If you (or a horse) raised 33,000 lbs by one foot it would be the same energy regardless of the period of time.
 

mivey

Senior Member
Actually, that's power, not energy. It's a rate. Lbs-ft/minute.
If you (or a horse) raised 33,000 lbs by one foot it would be the same energy regardless of the period of time.
That was iwire's post and he did say "the energy...in one minute".
 

Besoeker

Senior Member
Location
UK
From James Watt in 1782 and was equal to raising 528 cubic ft of water by one foot in one minute.
FWIW a cubic foot of water weighs 62.5 lb (at STP) so 528 ft3 would be 33,000 lb

6) horsepower: HP = 745.699871581 W. Also 550ft_lbf_/s (E)
7) British horsepower: BHP = 745.699871581 W. Also 550_ft_lbf_/s (E)

We now use SI of course and it's so much simpler and more elegant.
One Newton is the force required to accelerate one kilogram at one metre per sec per sec.
One Newton through one metre in one second is one Watt.
One Amp times one Volt is also one Watt.

:D
 

Besoeker

Senior Member
Location
UK
I missed the connection. The only one I can remember is 8.3 lb/gal for water or about 8.5lb for a gallon of milk.
The UK gallon is larger.
I remember from primary school (that's up to age eleven) being taught "a pint of water is a pound and a quarter". That makes a gallon ten pounds.
Again, SI makes it simpler. One litre of water weighs one kilogram.
 

Haji

Banned
Location
India
output of the generator is commonly in the unit of kva and voltage rating also available. can we say generator output rating in hp. if tell the procedure to convert kva to hp or direct calculation

The gen set output is rated in kW or KVA and the relation is

kW=0.8*KVA

hp=0.746kW

So hp=0.8*0.746*KVA

hp=0.5968*KVA
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
The gen set output is rated in kW or KVA and the relation is

kW=0.8*KVA

hp=0.746kW

So hp=0.8*0.746*KVA

hp=0.5968*KVA

I just got bit by the assumption that kW=0.8*KVA. I found a generator with a 0.33 PF rating. KW was 0.33 * KVA.

Ouch. :)
 

kwired

Electron manager
Location
NE Nebraska
The gen set output is rated in kW or KVA and the relation is

kW=0.8*KVA

hp=0.746kW

So hp=0.8*0.746*KVA

hp=0.5968*KVA

KW and KVA are the same if power factor of the load is 100%

Power factor is not always 80% either, care to modify your formula?
 
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