O.T.

[LWD]

how big of a hydraulic pump can be driven by a 2hp electric motor? (gpm)

 

[NCmau]

If you are talking about High pressure Pump, here is what I did. I coupled a High Pressure Pump that was designed for a 3-7 HP gas engine to a 2 HP electric. It worked fine. I believe the ratio between gas and electric motor is 2.5. 1 HP electric = 2.5 HP gas.

 

[9NJoe]

LWD,

There are some formulas that you need to figure out what HP is required. Basically it depends on GPM and pressure. For pumps,

HP req. = (GPM*PSI)/1452

GPM = (DISP * RPM)/231

PSI = (disp * RPM) /RPM

Hope this helps

Joe

 

[Anonymous-0]

I thought a horse power was a horse power? One HP equals 746 watts and it don't make any difference where the HP came from.
Clearly you can get a wide range of torque from same horsepower engine (or motor) due to a number of factors such as mass of the rotating components, RPM's etc.

If it smells like a HP, and walks like a HP...it's a HP.

 

[TheOldHokie]

(quoted from post at 01:14:50 02/15/08) how big of a hydraulic pump can be driven by a 2hp electric motor? (gpm)

The HP formula 9NJoe provided will get you a basic number. Keep in mind that that formula is for "continuous" flow - so beware. For example, if you are building a logsplitter and want 12GPM and 12T force you do the math using that formula and you get a motor that's probably oversize. Why? Because you don't need 12GPM @ 12T pressure continuously. You need 12GPM for large portions of the cycle at a much lower pressure. For the brief periods you actually need the full 12T of pressure you likely need way less flow. So use Joe's formula but plug in numbers for BOTH flow/pressure combos and take the larger HP result.

TOH

 

[9NJoe]

Ooops, made a mistake, the formula for PSI

PSI = (HP *1452) / GPM

TOH is correct, these are MAX numbers.

Joe

 

[NCmau]

This is the equivalent HP. An electric motor is more efficient. It takes 2.5 HP gas to deliver the same torque as 1 HP electric. (Generally speaking).

 

[TheOldHokie]

Motor HP ratings are typically (universally) output ratings so motor efficiency is meaningless except when figuring what it's going to do to your fuel bill.

A 7.5HP gas motor produces 7.5 HP and rated torque @RPM.

A 2 HP electric motor produces 2HP and rated torque @RPM.

Electric motors often have better torque performance.

TOH

 

[OKDAD]

TOH....I thought an electric motor produced rated torque at 0 rpm (kinda like a steam locomotive). Am I wrong here?

 

[Dunk]

This HP stuff can get very convoluted, and technical.

http://en.wikipedia.org/wiki/Horsepower

And guess what, it is all relative.

Horsepower from a horse
R. D. Stevenson and R. J. Wasserzug published an article in Nature 364, 195-195 (15 July 1993) calculating the upper limit to an animal's power output. The peak power over a few seconds has been measured to be as high as 14.9 hp. However, for longer periods an average horse produces less than one horsepower.

 

[TheOldHokie]

<font color=red>TOH....I thought an electric motor produced rated torque at 0 rpm (kinda like a steam locomotive). Am I wrong here?</font>

Good question. I don't know how electric motors are rated (HP or torque) to tell you the truth. HP is nameplate data and I <font color=red>assume</font> it is at noload running RPM. Torque is not normally nameplate data. My torque comment was anecdotal - you can get great accleration using electric motors for example.

I'm sure someone knowledgable will eduacte me ;-)

TOH

 

[Dunk]

(Torque x Engine speed) / 5,252 = Horsepower

http://auto.howstuffworks.com/question622.htm

"An Electric motor at 0 RPMs makes max torque", something about that rings a bell, there are many things that can affect that too (maybe, I think), like start windings, as opposed to run windings, capacitors to assist start, etc.

A gasoline engine, makes no torque at 0 RPM, you have to apply torque to start it, it is an amazing thing what added flywheel mass can do for a shaft torque at a given RPM.

Then there is a thing called BHP, Brake Horse Power, that has do do with a constant load.

It is a science....

 

[LWD]

thanks to all.

 

[Pooh Bear]

Here is what is printed in the Northern Tool catalog.

Rule of Thumb for Hydraulic Motor Applications
For longer motor life and better performance, we recommend that
the operating pressure be kept below 1000psi by selecting the
next larger size motor.
1 HP electric motor = 1.5 HP hydraulic motor
1 HP gasoline engine = 2/3 HP hydraulic motor
1 HP hydraulic motor = 1 2/3 HP gasoline engine
1 HP hydraulic motor = 2/3 HP electric motor

HP = (Torque x RPM)/63.025

Pooh Bear

 

[TheOldHokie]

(quoted from post at 00:15:55 02/16/08) Here is what is printed in the Northern Tool catalog.

Rule of Thumb for Hydraulic Motor Applications
For longer motor life and better performance, we recommend that
the operating pressure be kept below 1000psi by selecting the
next larger size motor.
1 HP electric motor = 1.5 HP hydraulic motor
1 HP gasoline engine = 2/3 HP hydraulic motor
1 HP hydraulic motor = 1 2/3 HP gasoline engine
1 HP hydraulic motor = 2/3 HP electric motor

HP = (Torque x RPM)/63.025

Pooh Bear

While I don't know that I'd consider Northern Tool an Oracle of Physics I have no quibble with their "rule of thumb" for [b:6484e0b16e]interchange[/b:6484e0b16e] on [b:6484e0b16e]hydraulic motors [/b:6484e0b16e] vis-a-vis electric/gas motors. Also keep in mind most hydraulic motors runs slower than either gas or electric.

This chart has nothing to do with the idea a 5HP electric motor makes more HP than a 5HP gasoline motor.

TOH