Question Dive Shop Compressor Power Consumption

[iain/hsm]

Further again for comparison and contrast a 10 SCFM 3000 PSIG UK medical pure oxygen compressor
would be fitted with a 10BHP 7.5Kw motor. This would be at the very least be a EFF 3 power saving design and further power starting savings would be offered by using what is called an electronic Soft Start controlled start as opposed to the American preference of "Peddle to the Metal" light dimming the entire block D.O.L. Direct on Line starting.

Again for the numbers 10 SCFM flow at 3000 PSIG but with a 40 PSIG oxygen inlet pressure will require at full pressure a draw of 5.57 BHP 4.15Kw Again when calculated with a slightly higher 110 Deg F gas inlet temperature. Further for oxygen the RPM is reduced to 531 RPM to reduce piston speed

So again the question why is a more expensive 10 BHP EFF3 motor with soft start being fitted to a 10 CFM oxygen compressor when it only requires 5.57 BHP. Iain

 

[iain/hsm]

Going off memory, but don't electric motors start dropping efficiency as they reach there rated power? Maybe it is just the cheap crap motors? I'm going off a memory of looking at an electric motor dyno sheet from many years ago. There were several factors, torque, RPM, volts, amps... Enough you could map electrical HP (volts x amps to get watts) and mechanical HP (torque x RPM / 5252 if using ft/lb torque). It may have just been that one motor I was looking at, but things got ugly at the top of the scale.

Hey I'm doing my best here so far with with you lot. PSI and DegF is as good as it gets.
Don't start me off with this ft/lb or we're going full out war and Nm metric from now on
What next feet and inches? Give me strength.
Two nations divided by a common language.

Can't wait till we get into American wiring and power installations
Maybe better we don't go down that road. LOL Iain

 

[broncobowsher]

Hey I'm doing my best here so far with with you lot. PSI and DegF is as good as it gets.
Don't start me off with this ft/lb or we're going full out war and Nm metric from now on
What next feet and inches? Give me strength.
Two nations divided by a common language.

Can't wait till we get into American wiring and power installations
Maybe better we don't go down that road. LOL Iain

The only American thing I put into that was ft-lb to get the mechanical HP number. Daily work I torque stuff with that apple-close to a yard numbering system. At least I am not weighing stuff in "stones".

 

[MarkA]

The only American thing I put into that was ft-lb to get the mechanical HP number. Daily work I torque stuff with that apple-close to a yard numbering system. At least I am not weighing stuff in "stones"

Found this on the internet. At the beginning of the document there is a graph that shows curves. One being efficiency.

Three Phase Induction Motor Performance | Electrical Academia

Using the equivalent circuit of the three-phase induction motor and some additional information about the mechanical and core loses, one could calculate the performance of the three-phase induction motor from no-load to full-load.

electricalacademia.com

Maybe it’s better to use this
Three phase power = √3•V•I•cosØ.

As someone from a country that used the imperial system. Metric all the way for me.

 

[iain/hsm]

At least I am not weighing stuff in "stones".

Yeah but your still measuring oil in quarts

Whatever a quart is when its at home and your gallons are wrong LOL

 

[broncobowsher]

Yeah but your still measuring oil in quarts

Whatever a quart is when its at home and your gallons are wrong LOL

A quart is 2 pints

 

[iain/hsm]

Now your talking

A quart is 2 pints

Only if you're offering to get the next round in at the pub. I'll have a quart then.

Heck I would even go for cups gills pecks and bushels if only to hack the French and Canadians off.

 

[broncobowsher]

Washing machine is also an American measuring unit. Sinkhole closes northbound lanes of State Line Road

 

[CG43]

Hello joebob24

This one took me a bit to wrap my head around and calculate, but I think I finally came up with some heat output numbers that are interesting. Compressing air releases a lot of heat even if the compressor is 100% efficient. A 100% efficient compressor taking 1 cfm from atmospheric to 4000 psi releases requires 268 watts of input and releases 268 watts of heat. Any loss of efficiency does just turn into heat, so a 50% efficient compressor requires 536 watts of input per cfm and releases 536 watts of heat. Essentially compressors are also just 100% efficient space heaters.

If it has meaning for your project.

The 268 watts are the power for the istherme change of gas (air) state .
The compressed gas still has to be moved into the tank, which again
needs the works (P2 * V2) or the same size (because isothermal) (P1 * V1)
I calculated 265 w for the isotherme and 312 for all .

Greetings Rainer

 

[TrimixToo]

Now your talking

Only if you're offering to get the next round in at the pub. I'll have a quart then.

Heck I would even go for cups gills pecks and bushels if only to hack the French and Canadians off.

But your pints (and quarts) are different from ours. 16 oz. vs 20 and 32 vs. 40 oz. I mean, a quart of beer is a fair bit in either place but it's 25% more on your side of the puddle.