Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

"smitha4u" wrote in message
oups.com...
Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

1) hope the motor powers from some multiple of 6 or 12 volts.
2) lacking the above, build one MAN of a DC supply.
3) take it to a good motor shop

It would cost you more than it's worth to figure out if the torque, speed,
and stall current are within spec, if you had to build or buy the equipment.

LLoyd

its 12 V
thanks

I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha

On 9 Aug 2005 06:22:06 -0700, "smitha4u"
wrote:

Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

Assuming that such a motor has a wound field rather than permanent
magnet:

1) estimate rated field current by seeing what current results in a
steadystate temperature rise of about 20C with armature not excited.

2) With that field current applied, energize the armature with rated
voltage. Measure no-load speed and stall torque. (do the later
test quickly!) Measure armature current while stalled.

These tests are sufficient to determine the constants for the DC motor
equations describing speed and torque as fns of armature voltage,
armature current and field current.

sorry
it rated for 250-360 volts
any steps for the test
regards
smitha

On Tue, 09 Aug 2005 12:06:45 -0500, Don Foreman
wrote:

On 9 Aug 2005 06:22:06 -0700, "smitha4u"
wrote:

Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

Assuming that such a motor has a wound field rather than permanent
magnet:

1) estimate rated field current by seeing what current results in a
steadystate temperature rise of about 20C with armature not excited.

2) With that field current applied, energize the armature with rated
voltage. Measure no-load speed and stall torque. (do the later
test quickly!) Measure armature current while stalled.

These tests are sufficient to determine the constants for the DC motor
equations describing speed and torque as fns of armature voltage,
armature current and field current.


A bit difficult to second guess the field rating and this is a
problem because it has such a major effect on motor performance. Field
dissipation of 5% of rated power or 20 deg C rise is a good starting
point but a this assumption may be well removed from the manufacturers
intended rating. I would have expected a motor of this size to carry
more nameplate information.

At rated voltage, the stalled armature current of a motor of
this size is little short of spectacular! I think it would be safer
to settle for a measurement of stalled torque per amp at close to
rated full load amps together with a measurement of back EMF per
thousand RPM

Proper evaluation of a motor of this size needs pretty
substantial ancilliary equipment and a good understanding of it's
operation and limitations. For anything more than a rough test to see
if it's a dud motor it's not a task to be taken lightly. The light
hearted uncertainty on whether it's a 12 volt or 360 volt machine
doesn't engender a lot of confidence!

Jim

wrote:
On Tue, 09 Aug 2005 12:06:45 -0500, Don Foreman
wrote:

On 9 Aug 2005 06:22:06 -0700, "smitha4u"
wrote:

Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

Assuming that such a motor has a wound field rather than permanent
magnet:

1) estimate rated field current by seeing what current results in a
steadystate temperature rise of about 20C with armature not excited.

2) With that field current applied, energize the armature with rated
voltage. Measure no-load speed and stall torque. (do the later
test quickly!) Measure armature current while stalled.

These tests are sufficient to determine the constants for the DC motor
equations describing speed and torque as fns of armature voltage,
armature current and field current.


A bit difficult to second guess the field rating and this is a
problem because it has such a major effect on motor performance. Field
dissipation of 5% of rated power or 20 deg C rise is a good starting
point but a this assumption may be well removed from the manufacturers
intended rating. I would have expected a motor of this size to carry
more nameplate information.

At rated voltage, the stalled armature current of a motor of
this size is little short of spectacular! I think it would be safer
to settle for a measurement of stalled torque per amp at close to
rated full load amps together with a measurement of back EMF per
thousand RPM

Or if he has a dynamometer, hold speed constant and record a change in
torque vs a change in armature current. For the EMF constant spin the
motor with field current applied and measure the generated open circuit
voltage at the armature terminals. He should post all of the
information on the namplate as a start.

As you say, a lot depends on the equipment available...


Proper evaluation of a motor of this size needs pretty
substantial ancilliary equipment and a good understanding of it's
operation and limitations. For anything more than a rough test to see
if it's a dud motor it's not a task to be taken lightly. The light
hearted uncertainty on whether it's a 12 volt or 360 volt machine
doesn't engender a lot of confidence!



Jim

"smitha4u" wrote in message
oups.com...
I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha


This is not a job to be undertaken by someone who has to ask such basic
questions in a METALworking group.

It is proper engineering job for an experienced consulting engineer with
experience in this type of indstallation.


--
John G

Wot's Your Real Problem?

Ignoramus6689 writes:

If you have a suitably rated rectifier, and a good electrical
subpanel, you can rectify your 220V AC.

That will deliver more than 300 volts.

Best not to listen to casual advisors with machinery of this size.

"smitha4u" wrote in message
oups.com...
Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha


Not sure what you mean by bench testing. Do you want to determine the
characteristics or just see if it runs?

Don explained some of the methods for determining motor constants.
Depending on your use, and since it's a big motor, you may also want
to measure friction and the armature inertia

Other parameters would be armature resistance and inductance to
complete the full set of parameters.

Then you can model the DC motor...

Ignoramus6689 writes:

That will deliver more than 300 volts.

his motor is rated for 360 volts max, so I am not sure why you use
this number to make an objection.

I thought he said it was rated for 250 volts.

Looking back I see he said "it [sic] rated for 250-360 volts".

So, who knows. The OP does not project competence for this kind of
tinkering.

"Ignoramus6689" wrote in message
...
it needs 80 amps at 250 V DC to run at rated load. Probably much
less
without load, except at startup.

If you have a suitably rated rectifier, and a good electrical
subpanel, you can rectify your 220V AC.

If your motor is a permanent magnet design, it can function as a
generator. You can try spinning the shaft with anything and
measuring
voltage across leads. If it spins and produces voltage, it is
probably
good.

There are much better experts than me, so let's see what they say.

i

Drives for DC motors of this size typically use a 3 phase SCR bridge,
but motor-generator sets (Ward Leonard system) were quite popular
years ago...

"Rick" wrote in message
oups.com...
wrote:
On Tue, 09 Aug 2005 12:06:45 -0500, Don Foreman
wrote:

On 9 Aug 2005 06:22:06 -0700, "smitha4u"
wrote:

Hi Guys

Can any one suggest what are the various methods of performing
bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

Assuming that such a motor has a wound field rather than
permanent
magnet:

1) estimate rated field current by seeing what current results
in a
steadystate temperature rise of about 20C with armature not
excited.

2) With that field current applied, energize the armature with
rated
voltage. Measure no-load speed and stall torque. (do the
later
test quickly!) Measure armature current while stalled.

These tests are sufficient to determine the constants for the DC
motor
equations describing speed and torque as fns of armature voltage,
armature current and field current.


A bit difficult to second guess the field rating and this
is a
problem because it has such a major effect on motor performance.
Field
dissipation of 5% of rated power or 20 deg C rise is a good
starting
point but a this assumption may be well removed from the
manufacturers
intended rating. I would have expected a motor of this size to
carry
more nameplate information.

At rated voltage, the stalled armature current of a motor
of
this size is little short of spectacular! I think it would be
safer
to settle for a measurement of stalled torque per amp at close to
rated full load amps together with a measurement of back EMF per
thousand RPM

Or if he has a dynamometer, hold speed constant and record a change
in
torque vs a change in armature current. For the EMF constant spin
the
motor with field current applied and measure the generated open
circuit
voltage at the armature terminals. He should post all of the
information on the namplate as a start.


Of course, he could calculate counter emf at various points too, by
running the motor (if he knew the armature resistance) by measuring
armature current and applied voltage


As you say, a lot depends on the equipment available...


Proper evaluation of a motor of this size needs pretty
substantial ancilliary equipment and a good understanding of it's
operation and limitations. For anything more than a rough test to
see
if it's a dud motor it's not a task to be taken lightly. The light
hearted uncertainty on whether it's a 12 volt or 360 volt machine
doesn't engender a lot of confidence!



Jim

On Wed, 10 Aug 2005 10:34:51 +1000, "John G"
wrote:


"smitha4u" wrote in message
roups.com...
I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha


This is not a job to be undertaken by someone who has to ask such basic
questions in a METALworking group.

It is proper engineering job for an experienced consulting engineer with
experience in this type of indstallation.

How do you suppose engineers become trained to do such consulting?
That's why schools have labs.

I'm glad there are still students working with real machines in a real
laboratory rather than with 'puter sims. You can't simulate the
experience of a 50 HP DC motor drawing a gazillion amps of armature
current at stall, or if the field comes loose. Ya gotta see it in
person, after duly noting the motor bits still embedded in the bricks
from previous oopsies.

Unscheduled experiment: how fast can a twit lab TA dive under a
bench? Open field on big DC motor running with rated armature
voltage, time the twit when he hears it accelerating rapidly toward
kaboom. (Do close the field pretty quick. Forget about killing
armature current at that point; opening the switch results in a big
green arc)

The show is well worth the ensuing loud lecture endured with
simulated contrite humility. Your grade may partly depend on the
quality of your simulation....

"Don Foreman" wrote in message
...
On Wed, 10 Aug 2005 10:34:51 +1000, "John G"
wrote:


"smitha4u" wrote in message
groups.com...
I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha


This is not a job to be undertaken by someone who has to ask such
basic
questions in a METALworking group.

It is proper engineering job for an experienced consulting engineer
with
experience in this type of indstallation.

How do you suppose engineers become trained to do such consulting?
That's why schools have labs.

I'm glad there are still students working with real machines in a real
laboratory rather than with 'puter sims. You can't simulate the
experience of a 50 HP DC motor drawing a gazillion amps of armature
current at stall, or if the field comes loose. Ya gotta see it in
person, after duly noting the motor bits still embedded in the bricks
from previous oopsies.

Unscheduled experiment: how fast can a twit lab TA dive under a
bench? Open field on big DC motor running with rated armature
voltage, time the twit when he hears it accelerating rapidly toward
kaboom. (Do close the field pretty quick. Forget about killing
armature current at that point; opening the switch results in a big
green arc)

The show is well worth the ensuing loud lecture endured with
simulated contrite humility. Your grade may partly depend on the
quality of your simulation....

Yes students do need labs with big machines and yes they do leave an
indelible impression .

Many years ago I was in a lab group that shut down the whole Physics
school of a large college 3 times doing an experiment with a big machine
where a careless technician (not a student) had reversed the wiring of a
Synchroscope. but the lab was designed and built by experienced
engineers and so no-one was hurt.
The OP in this thread is asking questions that are obviously beyond his
current (sic) level of expertise and this is not the place to learn that
sort of stuff.
He will get bits and pieces of advice and never know till after the fire
that he didn't ask all the relevant questions and so did not get all the
answers.


--
John G

Wot's Your Real Problem?

Hi
Thank you all I agree with after reading all the messages that i really
did not think of all the measures and questions. Could some body
educate me what more i need to know.
before testing I think i need to prepare a test plan/procedure and what
all will i calculate and how i will show my demonstration. If they
agree my experience with dealing large machines is not sufficient
atleast they would see my test plan and do the test with some
expeerienced.
Hope i get some help and appreciate all for the info provided.
Regards
smitha

Heh, heh. A man after my own heart!!

I'm currently developing various lab exercises for ME students in
machine design. Trying to do 'real' stuff in this day of computer
simulations is a challenge. And getting across the message that flaws in
your simulation have nasty effects in the real world is best done with
things like 20hp motors and 10:1 gear boxes. Only issue is how to get it
impressive but still safe for udergrads who's idea of a big power supply
is a 300 watt ATX box for their computer.

Don Foreman wrote:

On Wed, 10 Aug 2005 10:34:51 +1000, "John G"
wrote:


"smitha4u" wrote in message
groups.com...

I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha


This is not a job to be undertaken by someone who has to ask such basic
questions in a METALworking group.

It is proper engineering job for an experienced consulting engineer with
experience in this type of indstallation.


How do you suppose engineers become trained to do such consulting?
That's why schools have labs.

I'm glad there are still students working with real machines in a real
laboratory rather than with 'puter sims. You can't simulate the
experience of a 50 HP DC motor drawing a gazillion amps of armature
current at stall, or if the field comes loose. Ya gotta see it in
person, after duly noting the motor bits still embedded in the bricks
from previous oopsies.

Unscheduled experiment: how fast can a twit lab TA dive under a
bench? Open field on big DC motor running with rated armature
voltage, time the twit when he hears it accelerating rapidly toward
kaboom. (Do close the field pretty quick. Forget about killing
armature current at that point; opening the switch results in a big
green arc)

The show is well worth the ensuing loud lecture endured with
simulated contrite humility. Your grade may partly depend on the
quality of your simulation....

Smitha

Would it be OK for me to ask what kind of school you are attending?? It
is difficult to consider that there is a school that would present you with
a 25 HP DC motor without first acquainting you with the the fundamentals.

Perhaps English isnt your first language.

When you ask this News Group to educate you, it seems that you have no
instructions available from that school.

I's suspecting this is a prank post. How about you supply a little more
background on what you are doing and maybe where you are.

Jerry

"smitha4u" wrote in message
ps.com...
Hi
Thank you all I agree with after reading all the messages that i really
did not think of all the measures and questions. Could some body
educate me what more i need to know.
before testing I think i need to prepare a test plan/procedure and what
all will i calculate and how i will show my demonstration. If they
agree my experience with dealing large machines is not sufficient
atleast they would see my test plan and do the test with some
expeerienced.
Hope i get some help and appreciate all for the info provided.
Regards
smitha

"Don Foreman" wrote in message
...
On Wed, 10 Aug 2005 10:34:51 +1000, "John G"
wrote:


"smitha4u" wrote in message
roups.com...
I believe i can bulid in my school lab.
Aprreciate if you can expalin it in detail
Thanks
Rgards
smitha


This is not a job to be undertaken by someone who has to ask such
basic
questions in a METALworking group.

It is proper engineering job for an experienced consulting engineer
with
experience in this type of indstallation.

How do you suppose engineers become trained to do such consulting?
That's why schools have labs.

I'm glad there are still students working with real machines in a
real
laboratory rather than with 'puter sims. You can't simulate the
experience of a 50 HP DC motor drawing a gazillion amps of armature
current at stall, or if the field comes loose. Ya gotta see it in
person, after duly noting the motor bits still embedded in the
bricks
from previous oopsies.

Unscheduled experiment: how fast can a twit lab TA dive under a
bench? Open field on big DC motor running with rated armature
voltage, time the twit when he hears it accelerating rapidly
toward
kaboom. (Do close the field pretty quick. Forget about killing
armature current at that point; opening the switch results in a
big
green arc)

The show is well worth the ensuing loud lecture endured with
simulated contrite humility. Your grade may partly depend on the
quality of your simulation....

Have to agree-the only computer simulation I ever did was a second
order system patch wired on a General Dynamics analog computer.
Everything else was lab work...

"smitha4u" wrote in message
ps.com...
Hi
Thank you all I agree with after reading all the messages that i
really
did not think of all the measures and questions. Could some body
educate me what more i need to know.
before testing I think i need to prepare a test plan/procedure and
what
all will i calculate and how i will show my demonstration. If they
agree my experience with dealing large machines is not sufficient
atleast they would see my test plan and do the test with some
expeerienced.
Hope i get some help and appreciate all for the info provided.
Regards
smitha


As you have seen from the replies, there's various ways to determine
motor constants.You need to tell everyone what you DO know about DC
motors first. Are you familiar with the basic DC motor equations? What
are the capabilities of the lab-any equipment to measure large torques
and currents?

The electrical and mechanical input/output levels you will be dealing
with can be lethal. If this is for a school lab project I'd suggest
you consider a 12 volt permanent magnet motor from a car (engine
cooling fan or blower motor) and determine the motor constants.

I'd put something like 100V across the field winding and see what the output
is for the armature when turned at a speed near the rated speed.
The thing that is nice about DC motors is that the can be used easily as DC
generators, especially if the field is a magnet. The other thing about DC
motors is that they will spin on much lower voltages (10^ os rated voltage
is a good starting point for low speed operation) although the current will
be the same approximate valuee as the full speed current. Currrent, of
course, goes up with load from some value which may be 50% of the max
current.


--
Why do penguins walk so far to get to their nesting grounds?

On Wed, 10 Aug 2005 06:03:56 GMT, Ignoramus6689
wrote:



I am not sure what it is that they can learn with a 20 kW motor, that
they cannot learn with a 1 HP motor.

Respect and perspective. Ya can't get into much trouble with a 1 HP
motor. Wiring a 24-volt doorbell is not sufficient preparation for
working wtih 440V wiring, though the same theory applies to both.

In all actuality this might be a drill press from Sears. You know "Maximum
Developed HP" crap they label everything with.

Sears has really turned into a joke. Everyday I am on edge that they will
go out of business and my hand tools will be about worthless. Should I just
start buying the Chinese crap now?

I actually took a glance at a drill press at Sears. Looked at the back to
find the plate on the motor in an attempt to find the true HP. Conveniently
the plate was missing, but the 4 rivet holes where there. Nothing more
insulting.


"smitha4u" wrote in message
oups.com...
Hi Guys

Can any one suggest what are the various methods of performing bench
test for a 20 Kw(25HP) DC electrical variable speed motor.

Thank you
Regards
smitha

Jerry Martes writes:

and maybe where you are.

NNTP-Posting-Host: 12.2.142.7

resolves to:

Caterpillar, Inc. CATERPILLAR-142-0 (NET-12-2-142-0-1)
12.2.142.0 - 12.2.142.255

On Wed, 10 Aug 2005 20:57:52 -0500, Richard J Kinch
wrote:

Jerry Martes writes:

and maybe where you are.

NNTP-Posting-Host: 12.2.142.7

resolves to:

Caterpillar, Inc. CATERPILLAR-142-0 (NET-12-2-142-0-1)
12.2.142.0 - 12.2.142.255

Bingo. Troll

Gunner

The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty."
Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly
save yourself, but it is too late to save that society. It is doomed. " Lazarus Long

"Ignoramus6689" wrote in message
...
On Tue, 09 Aug 2005 23:17:22 -0500, Richard J Kinch
wrote:
Ignoramus6689 writes:

That will deliver more than 300 volts.

his motor is rated for 360 volts max, so I am not sure why you use
this number to make an objection.

I thought he said it was rated for 250 volts.

Looking back I see he said "it [sic] rated for 250-360 volts".

exactly.

So, who knows. The OP does not project competence for this kind of
tinkering.

If I got a 20 kW DC motor (shudder), I would not try to run it. It it
was a permanent magnet motor, I would try to spin it up and see if
there is DC voltage generated by the motor.

i

I would start by making sure that sucker was very securely anchored
to something fairly bit -- you set something like that on a "bench" or
anywhere else for that matter and apply power it will do 2 things:
1) take off in a hurry in some direction from the torque and
2) either rip your wires out or just twist them together for lots of
fireworks
(and 25 Hp is capable of taking a small "bench" with it when
it starts).

mikey