Can't remember if it was this list. The question was raised,
does compressor amperage decrease as pressure increases. I
set up an informal test, using equipment on hand. Plugged in
a Kill A Watt meter, and set it to read watts consumption.
Plug in my 3 HP Harbor Freight pancake compressor.

I turned on the compressor, and noted the reading as the
pressure went from 0 PSI to 100 PSI. The readings are as
follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing
else, it used a few minutes of my afternoon.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..

On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an informal
test, using equipment on hand. Plugged in a Kill A Watt meter, and set
it to read watts consumption. Plug in my 3 HP Harbor Freight pancake
compressor.

I turned on the compressor, and noted the reading as the pressure went
from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing else, it used
a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor and an
induction motor -- as the pressure goes up the compressor shaft would
require more torque to turn to move the air, for an induction motor
higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. I'm not
entirely straight on all the details, but put your hand over the vacuum
cleaner hose and you can hear the motor run faster -- I think it's
because the turbine is suddenly just spinning the air inside it's
housing, instead of moving it through.

--
www.wescottdesign.com

Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an informal
test, using equipment on hand. Plugged in a Kill A Watt meter, and set
it to read watts consumption. Plug in my 3 HP Harbor Freight pancake
compressor.

I turned on the compressor, and noted the reading as the pressure went
from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing else, it used
a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor and an
induction motor -- as the pressure goes up the compressor shaft would
require more torque to turn to move the air, for an induction motor
higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. I'm not
entirely straight on all the details, but put your hand over the vacuum
cleaner hose and you can hear the motor run faster -- I think it's
because the turbine is suddenly just spinning the air inside it's
housing, instead of moving it through.

yup- it's doing less work (moving air, or really not moving work when
blocked) and just speeds up as it sees less load.

squirrel cage blowers act the same, and you can see in data sheets that
running some without any sort of choke will overheat/burn them out.

On Thu, 10 Dec 2009 21:53:30 +0000, Cydrome Leader wrote:

Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an
informal test, using equipment on hand. Plugged in a Kill A Watt
meter, and set it to read watts consumption. Plug in my 3 HP Harbor
Freight pancake compressor.

I turned on the compressor, and noted the reading as the pressure went
from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100) 100 - 250

Hope the information is of some use to someone. If nothing else, it
used a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor and
an induction motor -- as the pressure goes up the compressor shaft
would require more torque to turn to move the air, for an induction
motor higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. I'm not
entirely straight on all the details, but put your hand over the vacuum
cleaner hose and you can hear the motor run faster -- I think it's
because the turbine is suddenly just spinning the air inside it's
housing, instead of moving it through.

yup- it's doing less work (moving air, or really not moving work when
blocked) and just speeds up as it sees less load.

squirrel cage blowers act the same, and you can see in data sheets that
running some without any sort of choke will overheat/burn them out.

I've thought this would make a good way to do a home-brew dynamometer --
hook the motor up to a turbine pump or blower, and choke it off more or
less to tune the load.

I wonder if something a brain-dead as a propeller would work for the
turbine, if you had a way to shut off the air to it (my interest is in
model engines, so a prop would be a natural thing to hang on the end of
one of them).

--
www.wescottdesign.com

On Thu, 10 Dec 2009 21:53:30 +0000, Cydrome Leader wrote:

Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an
informal test, using equipment on hand. Plugged in a Kill A Watt
meter, and set it to read watts consumption. Plug in my 3 HP Harbor
Freight pancake compressor.

I turned on the compressor, and noted the reading as the pressure went
from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100) 100 - 250

Hope the information is of some use to someone. If nothing else, it
used a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor and
an induction motor -- as the pressure goes up the compressor shaft
would require more torque to turn to move the air, for an induction
motor higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. I'm not
entirely straight on all the details, but put your hand over the vacuum
cleaner hose and you can hear the motor run faster -- I think it's
because the turbine is suddenly just spinning the air inside it's
housing, instead of moving it through.

yup- it's doing less work (moving air, or really not moving work when
blocked) and just speeds up as it sees less load.

squirrel cage blowers act the same, and you can see in data sheets that
running some without any sort of choke will overheat/burn them out.

I've wondered if this wouldn't be a good way to make a dynamometer for
small motors -- some sort of blower or turbine pump, with a variable
restriction on inlet and/or outlet.

In fact, it just now occurs to me that this may even work if the
'turbine' is a model airplane propeller; if you shrouded it completely
the resistance should go way down, and you'd certainly have an easy
selection of different turbines for different motors...

--
www.wescottdesign.com

On Dec 10, 4:22*pm, Tim Wescott wrote:
On Thu, 10 Dec 2009 21:53:30 +0000, Cydrome Leader wrote:
Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an
informal test, using equipment on hand. Plugged in a Kill A Watt
meter, and set it to read watts consumption. Plug in my 3 HP Harbor
Freight pancake compressor.

I turned on the compressor, and noted the reading as the pressure went
from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100) 100 - 250

Hope the information is of some use to someone. If nothing else, it
used a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor and
an induction motor -- as the pressure goes up the compressor shaft
would require more torque to turn to move the air, for an induction
motor higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. *I'm not
entirely straight on all the details, but put your hand over the vacuum
cleaner hose and you can hear the motor run faster -- I think it's
because the turbine is suddenly just spinning the air inside it's
housing, instead of moving it through.

yup- it's doing less work (moving air, or really not moving work when
blocked) and just speeds up as it sees less load.

squirrel cage blowers act the same, and you can see in data sheets that
running some without any sort of choke will overheat/burn them out.

I've wondered if this wouldn't be a good way to make a dynamometer for
small motors -- some sort of blower or turbine pump, with a variable
restriction on inlet and/or outlet.

In fact, it just now occurs to me that this may even work if the
'turbine' is a model airplane propeller; if you shrouded it completely
the resistance should go way down, and you'd certainly have an easy
selection of different turbines for different motors...

--www.wescottdesign.com

Why limit it to an air pump?

I see the same thing on an irrigation pump when the intake screen gets
plugged.

Paul

Stormin Mormon wrote:
... 3 HP Harbor Freight pancake compressor. ...

PSI -WATTS
...
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250
....

It's interesting that at max load your "3 HP" compressor is only using
250 watts, about what a 1/4 HP motor would use fully loaded. Either
your compressor is way over powered, or its motor is not really 3 HP.

Bob

On Thu, 10 Dec 2009 16:41:18 -0800, wrote:

On Dec 10, 4:22Â*pm, Tim Wescott wrote:
On Thu, 10 Dec 2009 21:53:30 +0000, Cydrome Leader wrote:
Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:

Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases. I set up an
informal test, using equipment on hand. Plugged in a Kill A Watt
meter, and set it to read watts consumption. Plug in my 3 HP Harbor
Freight pancake compressor.

I turned on the compressor, and noted the reading as the pressure
went from 0 PSI to 100 PSI. The readings are as follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100) 100 -
250

Hope the information is of some use to someone. If nothing else, it
used a few minutes of my afternoon.

This certainly makes sense with a positive-displacement compressor
and an induction motor -- as the pressure goes up the compressor
shaft would require more torque to turn to move the air, for an
induction motor higher torque = higher current.

This isn't the case with the blower in a vacuum cleaner. Â*I'm not
entirely straight on all the details, but put your hand over the
vacuum cleaner hose and you can hear the motor run faster -- I think
it's because the turbine is suddenly just spinning the air inside
it's housing, instead of moving it through.

yup- it's doing less work (moving air, or really not moving work when
blocked) and just speeds up as it sees less load.

squirrel cage blowers act the same, and you can see in data sheets
that running some without any sort of choke will overheat/burn them
out.

I've wondered if this wouldn't be a good way to make a dynamometer for
small motors -- some sort of blower or turbine pump, with a variable
restriction on inlet and/or outlet.

In fact, it just now occurs to me that this may even work if the
'turbine' is a model airplane propeller; if you shrouded it completely
the resistance should go way down, and you'd certainly have an easy
selection of different turbines for different motors...

--www.wescottdesign.com

Why limit it to an air pump?

I see the same thing on an irrigation pump when the intake screen gets
plugged.

Well, in the first paragraph I wasn't, even though I didn't explicitly
state that 'some sort of' included 'any fluid, gas or liquid'.

Clearly the second paragraph limits things severely, but as I'd be mostly
interested in seeing what a model airplane motor could do, a model
airplane propeller is a natural.

--
www.wescottdesign.com

On Dec 10, 4:15*pm, "Stormin Mormon"
wrote:
Can't remember if it was this list. The question was raised,
does compressor amperage decrease as pressure increases. I
set up an informal test, using equipment on hand. Plugged in
a Kill A Watt meter, and set it to read watts consumption.
Plug in my 3 HP Harbor Freight pancake compressor.

I turned on the compressor, and noted the reading as the
pressure went from 0 PSI to 100 PSI. The readings are as
follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing
else, it used a few minutes of my afternoon.
--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

Trying something new- see

http://spreadsheets.google.com/ccc?k...VFzN UE&hl=en

Dave

My apologies. The compressor is 3 galons. I have no idea the
HP rating.

Since a HP is 746 watts.....

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Bob Engelhardt" wrote in
message ...
Stormin Mormon wrote:
... 3 HP Harbor Freight pancake compressor. ...

PSI -WATTS
...
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250
....

It's interesting that at max load your "3 HP" compressor is
only using
250 watts, about what a 1/4 HP motor would use fully loaded.
Either
your compressor is way over powered, or its motor is not
really 3 HP.

Bob

After reading my post, it's clear I keyed in a couple
things wrong. 3 HP should read 3 gal, and the watts
at 90 PSI is 244. I should spend more time proo-
freeding. I do apologize.

Can't remember if it was this list. The question was
raised, does compressor amperage decrease as
pressure increases. I set up an informal test, using
equipment on hand. Plugged in a Kill A Watt meter,
and set it to read watts consumption. Plug in my
3 galon Harbor Freight pancake compressor.

I turned on the compressor, and noted the reading as the
pressure went from 0 PSI to 100 PSI. The readings are as
follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 244
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing
else, it used a few minutes of my afternoon. And
demonstrates
that I am lousy at transcribing information from sheet to
keyboard.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..

I am trying a couple things new.
* Correct the terms. 3 gal not 3 HP. 12 disciples, not 10.
* Transcribe the numbers accurately off the page. 90 PSI is
244 watts; 10 commandments, not 12.

Sorry, folks, it makes a lot more sense when I copy
accurately.
--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Dave__67" wrote in message
...

Trying something new- see

http://spreadsheets.google.com/ccc?k...VFzN UE&hl=en

Dave

On Dec 10, 1:42*pm, Tim Wescott wrote:
On Thu, 10 Dec 2009 16:15:18 -0500, Stormin Mormon wrote:
Can't remember if it was this list. The question was raised, does
compressor amperage decrease as pressure increases.


This certainly makes sense with a positive-displacement compressor and an
induction motor -- as the pressure goes up the compressor shaft would
require more torque

I think there's a detail that is still missing; a piston displacement
compressor has a 'dead volume'; when at max pressure, the
motor compresses the dead volume, opens the valve to the tank,
and no gas flows. It then closes the valve to the tank and does
another cycle.
If the vent-to-atmosphere valve opens when the dead volume
is still at high compression, you lose that compressed air and the
FORWARD torque it applies to the motor. So, the timing of the
big-intake-valve opening is crucial here. The action on the piston
downstroke is ... unspecified, so we can't be sure if there's a
useful recovery of compression energy or not.

"Stormin Mormon" wrote:

Can't remember if it was this list. The question was raised,
does compressor amperage decrease as pressure increases. I
set up an informal test, using equipment on hand. Plugged in
a Kill A Watt meter, and set it to read watts consumption.
Plug in my 3 HP Harbor Freight pancake compressor.

I turned on the compressor, and noted the reading as the
pressure went from 0 PSI to 100 PSI. The readings are as
follows:

PSI -WATTS
10 - 198
20 - 199
30 - 211
40 - 220
50 - 229
60 - 233
70 - 237
80 - 240
90 - 255
95 - 248 (wasn't sure the compressor would make it to 100)
100 - 250

Hope the information is of some use to someone. If nothing
else, it used a few minutes of my afternoon.

Just out of curiosity, how about charting psi vs amps. Then calculate VA.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On Dec 11, 12:24*am, "Stormin Mormon"
wrote:
...And demonstrates
that I am lousy at transcribing information from sheet to
keyboard.
--
Christopher A. Young

When I have a lot to write I type it up and edit it in Wordpad and
then copy and paste into a posting, leaving the top line in the Reply
field intact to preserve the header.

jsw

On 2009-12-13, Jim Wilkins wrote:
On Dec 11, 12:24*am, "Stormin Mormon"
wrote:
...And demonstrates
that I am lousy at transcribing information from sheet to
keyboard.
--
Christopher A. Young

When I have a lot to write I type it up and edit it in Wordpad and
then copy and paste into a posting, leaving the top line in the Reply
field intact to preserve the header.

You should also try to leave the "References: " header intact to
make threading newsreaders work properly.

And my newsreader allows me to select my own choice of editor,
instead of using one built in which I may not like. I opt to use "jove"
as my editor with both mutt (e-mail client) and slrn (newsreader), both
on unix of course, so this may not be as easy on Windows.

And, with jove I can always read in an existing file to add to
the article with a "Control-X Control-i", so no cut and paste needed.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2009-12-15, Steve Ackman wrote:
In , on 14 Dec 2009 06:44:46
GMT, DoN. Nichols, wrote:

And, with jove I can always read in an existing file to add to
the article with a "Control - [shift?] X Control-i", so no cut and
paste needed.

Too many keystrokes for me. nano does it with
"Ctrl-r"

That one is already used for "reverse search", which I do more
often than insert from a file, so I prefer the less frequently used
functions to have the longer sequences.

And no -- there is no shift needed on the "Control-X", just
habit typing it as uppercase. (And actually, if I want to use an
uppercase 'X' with the Control -- it works too. (Though I could
re-assign it to serve some other function.)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---