why are electric motor/gas engine HP requirments different for pumps

[SPYDERLK]

Nope, horsepower is different depending on what you are talking about. 10 EBH [electric brake horsepower] is equal to 20hp from a gasoline engine. It is also equal to about 14hp from a diesel engine. Here is some more to confuse you. A Honda 20hp gas engine is stronger than a 20hp briggs. A 50hp cummins is stronger than a 50hp Isuzu. I know this from the school of hard knocks. You have to start to consider torque curves, displacement, turbocharging ect ect. Not fun to size engines for hydraulic drives with so much inconsistency. CJ

,,,,,,,,,,,,,,,,,Sorry. A horsepower is a horsepower. It is a given amt of work per unit time.

 

[bcp]

Horsepower is thunder, torque is lightning.

Thunder is good, thunder is impressive; but it is lightning that does the work.

Mark Twain

 

[SPYDERLK]

Horsepower is thunder, torque is lightning.

Thunder is good, thunder is impressive; but it is lightning that does the work.

Mark Twain

Truth in the quote. The lightening is the horsepower. The Voltage would be the torque. No power until it moves [current].

 

[LD1]

Yep. Can have all the torque in the world and get nothing done. Torque doesn't automatically imply movement. You need torque + movement to do work. Which is what HP is

 

[Deere Dude]

Hello everybody. I've been on the Surplus Center website (again!) and their tech section has a quick calculator to plug in GPM, H.P. numbers etc., and it will calculate everything from needed HP to cubic inches for you. Easily. What's puzzling me is that just under the HP calculation total is (in red letters) a statement that has me confused. Basically say's that a given HP number that is punched out by the calculator is for electric motors, and that you have to double that number if your going to use a gas engine to drive your pump. Can anyone offer a plausible explanation for this? Horsepower is horsepower, right? Thanks in advance for your input. memphismark

I have a 8HP, I believe, gas pressure washer at home that delivers 3000 PSI and 3.5 gpm approx.

After I bought and used it I decided to get a similar set-up in a factory wash operation. It has been 20 years ago but we got a 3 HP electric and hooked it to the exact same pump. I believe it was 230 volts, but it worked like a charm.

 

[LD1]

I have a 8HP, I believe, gas pressure washer at home that delivers 3000 PSI and 3.5 gpm approx.

After I bought and used it I decided to get a similar set-up in a factory wash operation. It has been 20 years ago but we got a 3 HP electric and hooked it to the exact same pump. I believe it was 230 volts, but it worked like a charm.

Were you actually getting 3000PSI and actually flowing 3.5GPM?

If so, that would require ~7HP.

Smaller electric motors "can" make WAY more than their rated HP. Their rated HP is for continuous duty and long life. If you dont worry about long life and dont operate it on a continuous basis, then you may get by with a smaller motor.

I would bet that if you put an amp clamp on that motor while running it, you would be exceeding the FLA rating of the motor by quite a bit. If not, then you either aint running 3000psi or aint delivering 3.5GPM

 

[buickanddeere]

Horse power is horse power but torque is what gets the work done. Electric motors have more constant torque.

Wrong.
HP is HP. The different between using a reciprocating prime mover vs an electric motor is the ability of each to provide momentary overload torque beyond the steady state max rated.
The ICE may have a torque rise when lugged from 0 to maybe 140% when overloaded from rated HP and rated rpm , down to max available peak torque . To carry intermitant overloads.
The electric motor on the other hand can momentarily carry 175-300% more than it's rated nameplate max , to handle momentary overloads. Of course if that 10HP is start state driving a 20HP load. It's going to not stall but trip the thermal overloads in about 40 seconds.
To the casual observer that never understood highschool physics . They will stand there and tell you that 10 electrical HP is more than 10HP from a ICE gasser.
If the load is something like a centrifugal irrigation pump where there are no overloads. A 10HP ICE will carry the load just as well as the 10HP electric motor.
It's the electric motor's available torque rise % vs the ICE 's torque rise % , not HP vs HP.

 

[buickanddeere]

Nope, horsepower is different depending on what you are talking about. 10 EBH [electric brake horsepower] is equal to 20hp from a gasoline engine. It is also equal to about 14hp from a diesel engine. Here is some more to confuse you. A Honda 20hp gas engine is stronger than a 20hp briggs. A 50hp cummins is stronger than a 50hp Isuzu. I know this from the school of hard knocks. You have to start to consider torque curves, displacement, turbocharging ect ect. Not fun to size engines for hydraulic drives with so much inconsistency. CJ

Not so. If you don't believe me ask BCP , LD1 and Spyderlink in thier posts.

 

[SPYDERLK]

Were you actually getting 3000PSI and actually flowing 3.5GPM?

If so, that would require ~7HP.

Smaller electric motors "can" make WAY more than their rated HP. Their rated HP is for continuous duty and long life. If you dont worry about long life and dont operate it on a continuous basis, then you may get by with a smaller motor.

I would bet that if you put an amp clamp on that motor while running it, you would be exceeding the FLA rating of the motor by quite a bit. If not, then you either aint running 3000psi or aint delivering 3.5GPM

Thank you!

Wrong.
HP is HP. The different between using a reciprocating prime mover vs an electric motor is the ability of each to provide momentary overload torque beyond the steady state max rated.
The ICE may have a torque rise when lugged from 0 to maybe 140% when overloaded from rated HP and rated rpm , down to max available peak torque . To carry intermitant overloads.
The electric motor on the other hand can momentarily carry 175-300% more than it's rated nameplate max , to handle momentary overloads. Of course if that 10HP is start state driving a 20HP load. It's going to not stall but trip the thermal overloads in about 40 seconds.
To the casual observer that never understood highschool physics . They will stand there and tell you that 10 electrical HP is more than 10HP from a ICE gasser.
If the load is something like a centrifugal irrigation pump where there are no overloads. A 10HP ICE will carry the load just as well as the 10HP electric motor.
It's the electric motor's available torque rise % vs the ICE 's torque rise % , not HP vs HP.

Thank you! ... Curious on the 300% above nominal torque stall point figure. - - I didnt realize stall could be forestalled beyond around 200%. :confused3:

 

[buickanddeere]

High resistance rotor motors , some triple cage motors and repulsion start/induction run motors can approach 300% before they reach the "break down" torque and rpm.