NewtonLaw
Senior Member
- Location
- Honesdale, PA USA
It all comes down to the accountants saving the company money! Customer service comes second.
Generator KW Rating Based Upon Engine Horsepower
- Thread starter Ravenvalor
- Start date
- Status
There's no such thing. It's an SI unit.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
emphasis per the worm
Well, yes, but perhaps not for the reasons you list.
So, the installation design is a 50hp driver connected to a 37.3KW alternator, connected to a 50hp electric motor, driving a pump, requiring 50hp input to the shaft.
Operator starts the generator, and turns on the motor.
Generator trips off-line immediately
Amazingly not only won't the motor run, it won't even start.
Hummmm .... We forgot the 6 X FLA locked rotor, plus a bit more for inrush, and the alternator %IZ is dropping the voltage under locked rotor conditions.
Is that the fault of the generator manufacturer, or the specification? The engineer told them they wanted a generator with a 50hp driver (and alternator to match). The engineer did not tell the mfg they wanted to start and run a 50hp motor.
Screech - Stop, Re-design.
Specified: 50hp driver, alternator to start and run 50hp motor
MFG supplies a 50hp driver connected to a 250kw alternator. It looks kind of funny, but that is okay.
Operator starts gen
Turns on motor.
Motor and pump come up to speed.
Operator loads up the pump to max and the generator slows down - won't hold frequency. What??
MFG: You didn't tell us that you were using a 1.15sf motor. Loaded right up that is 50 x 1.15 = 57.5. And our published alternator efficiency spec is 95%. To hit full load on the pump would require 57.9/.95 = 60.5hp
So, who is deficient: The engineer that can't read the spec? Or the MFG that sells exactly what was specified but no more?
And then the mfg throws another rock:
All you want is to drive the pump. Why didn't you just direct connect the driver to the pump? The combination would not have made 115%, but you would have made 100%. And dropped the project cost and complexity to 1/4.
WHANGGG - right between the eyes
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
(emphasis by the worm)
Yes, exactly that. Amazingly companies will build as specified for the least cost. If they can't make spec, nobody will pay. If they can't make a profit, they don's stay in business. They are going to maximize their profits.
Customer service is 2nd, 1st, 27th? That is just part of the marketing/business plan. It will be where ever it needs to be to keep their customers.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
[QUOTE="Besoeker3, post: 2564657, member: 159424"]There's no such thing. It's an SI unit.[/QUOTE]
Ahh yes, I see that, it is precisely:
9,192,631,770 periods of the radiation emitted by a caesium-133 atom in the transition between the two hyperfine levels of its ground state.
Although I also see that it has been corrected 27 times (1 second each time) since inception is 1967. Seems rather sloppy for an SI unit.
I am not advocating US Customary units are better. Nor am I advocating SI is unnecessary.
Rather, us in the US get to use which ever we want.
NASA likes SI. Which is good. No, not because of Mars Climate Orbiter (1999), and not because of the all metric Hubble (1990). But because pounds-force, pounds-mass, slugs (across the board ugly yuck) do not lend well to rocket surgery.
Fish mongers and house-husbands like USC units.
Nobody in the US is going to spend $billions$ to change road signs.
Nobody baking Grandma's sausage and pineapple sauerkraut soufflé is going to throw away their teaspoons and measuring cups and buy a gram-scale.
Contrary to the metric-centrics inherent belief that us in the US are stupid*, it is not about that. It is about the money. Nobody is going to empty their wallet to make you (as "all y'all) feel good.
*Okay, we might be stupid about some things - but not about this
Theory of Metric-Centrics
per the worm
Ahh yes, I see that, it is precisely:
9,192,631,770 periods of the radiation emitted by a caesium-133 atom in the transition between the two hyperfine levels of its ground state.
Although I also see that it has been corrected 27 times (1 second each time) since inception is 1967. Seems rather sloppy for an SI unit.
I am not advocating US Customary units are better. Nor am I advocating SI is unnecessary.
Rather, us in the US get to use which ever we want.
NASA likes SI. Which is good. No, not because of Mars Climate Orbiter (1999), and not because of the all metric Hubble (1990). But because pounds-force, pounds-mass, slugs (across the board ugly yuck) do not lend well to rocket surgery.
Fish mongers and house-husbands like USC units.
Nobody in the US is going to spend $billions$ to change road signs.
Nobody baking Grandma's sausage and pineapple sauerkraut soufflé is going to throw away their teaspoons and measuring cups and buy a gram-scale.
Contrary to the metric-centrics inherent belief that us in the US are stupid*, it is not about that. It is about the money. Nobody is going to empty their wallet to make you (as "all y'all) feel good.
*Okay, we might be stupid about some things - but not about this
Theory of Metric-Centrics
per the worm
Ahh yes, I see that, it is precisely:
9,192,631,770 periods of the radiation emitted by a caesium-133 atom in the transition between the two hyperfine levels of its ground state.
Although I also see that it has been corrected 27 times (1 second each time) since inception is 1967. Seems rather sloppy for an SI unit.
I am not advocating US Customary units are better. Nor am I advocating SI is unnecessary.
Rather, us in the US get to use which ever we want.
NASA likes SI. Which is good. No, not because of Mars Climate Orbiter (1999), and not because of the all metric Hubble (1990). But because pounds-force, pounds-mass, slugs (across the board ugly yuck) do not lend well to rocket surgery.
Fish mongers and house-husbands like USC units.
Nobody in the US is going to spend $billions$ to change road signs.
Nobody baking Grandma's sausage and pineapple sauerkraut soufflé is going to throw away their teaspoons and measuring cups and buy a gram-scale.
Contrary to the metric-centrics inherent belief that us in the US are stupid*, it is not about that. It is about the money. Nobody is going to empty their wallet to make you (as "all y'all) feel good.
*Okay, we might be stupid about some things - but not about this
Theory of Metric-Centrics
per the worm
[/QUOTE]
And I'm not suggesting Americans are stupid by any means. My dear wife is American.
She likes to cook and bake but sometimes units need to be converted. I do that.
I'm old enough to have been taught Imperial, CGS, MKS and SI. The latter is the easiest to work with. And note, it is SI, not metric. You can't express volts in metres, a unit of length/distance.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
(emphasis per the worm)
Okay, that just officially disintegrated this discussion. Color me lost - Unless it is a condescending example of a metric-centric response.
Either way, I guarantee, metric or not (or if you pefer - "SI of not") I'm not using any Me-Trees to measure anything - not even the 1000 meter target butts at the rifle range.
I'm headed to lunch. Enjoy your evening.
Carultch
Senior Member
- Location
- Massachusetts
SI is a subset of metric. Metric is the more general term, that means powers of 10, and in addition to SI, also includes the historical variants of the concept, such as the CGS system, and some prefixes that are no longer active.
SI, whose full name is the French term that means International System of Units, is the standard of the metric system used today, which established the 7 base units of kilograms,meters, seconds, amperes, Kelvins, moles and candelas, and the powers of 10 prefixes we use today.
No. It is SI, not metric. You can buy conductors by the metre but not volts or Amps.
I disagree with this. SI is not a subset of metric since all the elements of SI are not elements of metric.
Glad someone agrees with me..........
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Very interesting comments in high detail. The other thing that happens at Altitude is the air over the radiator or any air cooled condenser is less dense and this reduces the efficienty of heat rejection on that device. The other thing that is counter intuitive is that moist air is less dense than dry air.Um, no. The definition of SAE Net Horsepower recognizes the losses incurred by "all the accessories necessary to perform its intended functions ".
SAE net horsepower definition | The Free Automotive Dictionary
SAE net horsepower according to the free Automotive Dictionary.www.automotivedictionary.org
It's not "sad", just the inherent detail-oriented nature of engineering work. There are a beezillion variables to consider, many of which are glossed over by sales & marketing people.
For example: Higher elevations result in less power being developed because each intake stroke sucks in less air. Likewise higher ambient temperatures. Except in some engines that are turbocharged and normalized. And it results in more power being available because less energy is needed to expel exhaust gasses into less-dense air and a single-speed belt-driven radiator fan consumes less energy in thinner air. Et al., et al., et al., et al., et al. ...
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
What's counter intuitive about that?
The mass of a water-vapor molecule is 18 grams per mole. A nitrogen molecule, 28 g/m. Oxygen, 32 g/m. Argon, 40. (monoatomic "molecule")
Even if that were true, who cares? So some metric units were carried over into SI when it was unified, harmonized and rationalized. The end result is a unified, harmonized and rationalized system.
They also got rid of inconsistent units, (such as the candlepower), goofy units, (such as the metric horsepower) and units that were just pain wrong from the get-go. (the kilogramme-force, which was obviously invented by someone who didn't understand the distinction between force & mass)
Last edited:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The kilogramme-force is a natural counterpart to the pound-mass for people who need to convert freely between the two systems or for physics students doing homework.
As long as you realize the definition, namely that one kilogramme-force is the force exerted on a 1 kilogramme mass by 1 normal Earth gravity, there is nothing inherently "wrong" with that unit. It is a derived unit, of which we use many for their convenience.
drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
- Occupation
- Registered Professional Engineer
Except that you're creating a derived unit from a derived unit from a variable natural phenomenon and creating a redundant & confusing unit of force.
Sure, I "realize" what a kgf is. I also realize that using or teaching it will ultimately lead to disaster.
Sure, I "realize" what a kgf is. I also realize that using or teaching it will ultimately lead to disaster.
Moosebytes
New User
- Location
- Randolph, Nj
I have always stayed with 1.5 hp for 1 KW and most OEM spec sheets agree.
Technical Specifications
Model 50 RD
50 kW Diesel Generator Set
Engine Specifications
Manufacturer Isuzu
Model 4BG1TPV
Type In line 4 Stroke
Aspiration Turbo
Cylinders 4
Displacement 264 In3. (4.3 L)
Bore and Stroke, 4.13 in x 4.92 in.
(105 mm x 125 mm)
Compression Ratio 16:1
Minimum C.C.A. at 5°C 750
RPM 1800 rpm 1500 rpm
BHP Minimum REQ"D
at Rated kW 76 68
BMEP 127 psi 136 psi
- Status