If there's anyone out there with Total Recall, you might remember I've had a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp of
mechanical resistance and know I have that much load.

Karl

"Karl Townsend" remove .NOT to reply wrote
in message ink.net...
If there's anyone out there with Total Recall, you might remember I've had
a lot of trouble with my irrigation well. Its a 20 hp single phase and
they aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under load. I have a 30 hp motor, I'm looking for ideas on how to create
30 hp of mechanical resistance and know I have that much load.

Karl

If you figure out a way of creating the resistance, which I suppose could be
some type of braking device if you don't have a load to drive, you could
have your VFD display the load parameters and see how many HP you're putting
out, either directly or by converting other readings.

If it's a 30HP pump can't you just hook it up to a tank of water and
throttle the output with a gate valve? As Karl noted you should be able
to get load info from the VFD.

Pete C.


Karl Townsend wrote:

If there's anyone out there with Total Recall, you might remember I've had a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp of
mechanical resistance and know I have that much load.

Karl

"Karl Townsend" remove .NOT to reply wrote
in message ink.net...
If there's anyone out there with Total Recall, you might remember I've had
a lot of trouble with my irrigation well. Its a 20 hp single phase and
they aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under load. I have a 30 hp motor, I'm looking for ideas on how to create
30 hp of mechanical resistance and know I have that much load.

Karl






Got a old car around? Steal disk brake assembly and master cylinder and
cobble together a brake mechanism on the 30 HP motor.
Greg

On Sun, 06 Mar 2005 16:52:53 GMT, "Karl Townsend"
remove .NOT to reply wrote:

If there's anyone out there with Total Recall, you might remember I've had a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp of
mechanical resistance and know I have that much load.

For how long? 30 HP is over 22 KW, a fair amount of heat.

For short-duration tests, you might use an automotive drum or disc
brake. You can measure torque with a spring scale. At 1750 RPM,
torque would be about 90 lbf-ft so a 1-foot arm and a 100 lb spring
scale would be about right. Stopping a car going 60 mph in 14.5
seconds dissipates about 30 HP in the brakes, so one brake could
probably take it for some seconds before it started to smoke.

A large induction motor excited with DC can produce plenty of drag
torque. It doesn't take much DC, either, because the "slip" speed is
1750 RPM rather than the few RPM it sees as an induction motor.
It'll get hot fairly quickly, though. You could adjust the drag
torque by adjusting the DC excitation to the drag motor; all you'd
need would be a bridge rectifier and a Variac.

--Maybe make a "prony brake"?

--
"Steamboat Ed" Haas : Blah blah blah blah
Hacking the Trailing Edge! : blah blah blah...
http://www.nmpproducts.com/intro.htm
---Decks a-wash in a sea of words---

"Karl Townsend" remove .NOT to reply wrote
in message ink.net...
If there's anyone out there with Total Recall, you might remember I've had
a lot of trouble with my irrigation well. Its a 20 hp single phase and
they aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under load. I have a 30 hp motor, I'm looking for ideas on how to create
30 hp of mechanical resistance and know I have that much load.

Karl

Karl

Why did you decide to not pump water? I'd have expected that you have
old or surplus water pumps around.

Jerry

A large induction motor excited with DC can produce plenty of drag
torque. It doesn't take much DC, either, because the "slip" speed is
1750 RPM rather than the few RPM it sees as an induction motor.
It'll get hot fairly quickly, though. You could adjust the drag
torque by adjusting the DC excitation to the drag motor; all you'd
need would be a bridge rectifier and a Variac.

Ideally, I'd like to run it an hour. My pump can run 24hrs a day if its dry,
I want to make sure nothing in the drive is stressed as much as possible.
That's why I went so oversize. My thinking is that if it will run an hour,
it should run a month.

I do have a 540 rpm PTO irrigation pump that could be connected to a three
phase motor. Any reason that testing at or near 540 RPM wouldn't be valid
for results at 3600 RPM (submersible well pump RPM).

Karl

"Karl Townsend" remove .NOT to reply wrote
in message ink.net...
If there's anyone out there with Total Recall, you might remember I've had
a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp
of
mechanical resistance and know I have that much load.

Karl


A large automotive radiator fan will present quite a load when driven at the
proper speed...

Another thought would be an eddy current brake. Essentially a driven
disk with a magnetic field so eddy currents are generated in the disk.
You would want an aluminum disk. According to someone that I knew a
long time ago that was using one for a car dyno the results are not all
that linear. He thought that at high power levels the magnetic field
was being deflected so less of it went through his disk. He was
wanting something that would present a couple of hundred hp load. or
more.

Dan

"Don Foreman" wrote in message
...
On Sun, 06 Mar 2005 16:52:53 GMT, "Karl Townsend"
remove .NOT to reply wrote:

If there's anyone out there with Total Recall, you might remember I've had
a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp
of
mechanical resistance and know I have that much load.

For how long? 30 HP is over 22 KW, a fair amount of heat.

For short-duration tests, you might use an automotive drum or disc
brake. You can measure torque with a spring scale. At 1750 RPM,
torque would be about 90 lbf-ft so a 1-foot arm and a 100 lb spring
scale would be about right.

Most VFD's will read out torque, current draw, etc.. I suppose it's all
derived from the speed and current draw, in any case there should be enough
information to determine whether the VFD/Transformer combo can handle the
load. I would monitor the voltage output of the transformer during the test.
You can reduce the voltage output from the VFD, within its range. I don't
know if it would react quickly enough to stabilize dips in the transformer
output.

On Sun, 06 Mar 2005 18:52:56 GMT, "Karl Townsend"
remove .NOT to reply wrote:

A large induction motor excited with DC can produce plenty of drag
torque. It doesn't take much DC, either, because the "slip" speed is
1750 RPM rather than the few RPM it sees as an induction motor.
It'll get hot fairly quickly, though. You could adjust the drag
torque by adjusting the DC excitation to the drag motor; all you'd
need would be a bridge rectifier and a Variac.

Ideally, I'd like to run it an hour. My pump can run 24hrs a day if its dry,
I want to make sure nothing in the drive is stressed as much as possible.
That's why I went so oversize. My thinking is that if it will run an hour,
it should run a month.

I do have a 540 rpm PTO irrigation pump that could be connected to a three
phase motor. Any reason that testing at or near 540 RPM wouldn't be valid
for results at 3600 RPM (submersible well pump RPM).

Induction motors want to run pretty close to rated speed, which would
be about 3450 RPM in a motor intended to drive something near 3600
RPM. If you speed-reduced it to 540 RPM with belts, pulleys or gears
then that might make a good load. You'd still measure torque at the
motor; perhaps a hinged mount with a torque-measuring arm. Ask
Jerry Martes for photos of his dynomometer setup.

On Sun, 6 Mar 2005 15:30:50 -0500, "ATP*" wrote:


"Don Foreman" wrote in message
.. .
On Sun, 06 Mar 2005 16:52:53 GMT, "Karl Townsend"
remove .NOT to reply wrote:

If there's anyone out there with Total Recall, you might remember I've had
a
lot of trouble with my irrigation well. Its a 20 hp single phase and they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440 three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp
of
mechanical resistance and know I have that much load.

For how long? 30 HP is over 22 KW, a fair amount of heat.

For short-duration tests, you might use an automotive drum or disc
brake. You can measure torque with a spring scale. At 1750 RPM,
torque would be about 90 lbf-ft so a 1-foot arm and a 100 lb spring
scale would be about right.

Most VFD's will read out torque, current draw, etc.. I suppose it's all
derived from the speed and current draw, in any case there should be enough
information to determine whether the VFD/Transformer combo can handle the
load. I would monitor the voltage output of the transformer during the test.
You can reduce the voltage output from the VFD, within its range. I don't
know if it would react quickly enough to stabilize dips in the transformer
output.

I forgot about the VFD. I don't think you'll get anywhere near 30 HP
out of a nominally 30HP motor slowed that much with a VFD. It's
current (and current-produced heat) that determines the power rating
of an induction motor. You can run it slower by dropping the
frequency, but since torque is proportional to current the torque
can't rise much -- so you have less power because power = torque *
speed.

On 6 Mar 2005 11:59:31 -0800, wrote:

Another thought would be an eddy current brake. Essentially a driven
disk with a magnetic field so eddy currents are generated in the disk.
You would want an aluminum disk. According to someone that I knew a
long time ago that was using one for a car dyno the results are not all
that linear. He thought that at high power levels the magnetic field
was being deflected so less of it went through his disk. He was
wanting something that would present a couple of hundred hp load. or
more.

LOTS of heat. That brake had better be water cooled!

An eddy current brake should be quite linear, but if the disc heats up
its resistivity would change which would change its behavior.

Another large induction motor excited with DC could be the brake at
3450 RPM if it could be sufficiently cooled: forced air perhaps.

im digressing but most car dynos use water as a load.

"Don Foreman" wrote in message
...
On Sun, 6 Mar 2005 15:30:50 -0500, "ATP*" wrote:


"Don Foreman" wrote in message
. ..
On Sun, 06 Mar 2005 16:52:53 GMT, "Karl Townsend"
remove .NOT to reply wrote:

If there's anyone out there with Total Recall, you might remember I've
had
a
lot of trouble with my irrigation well. Its a 20 hp single phase and
they
aren't made or serviced anymore. I have to move up to three phase.

I've bought a 50 hp VFD drive and a 75KVA transformer to produce 440
three
phase. Before I buy and install a new 30 hp. pump, I want to test this
under
load. I have a 30 hp motor, I'm looking for ideas on how to create 30 hp
of
mechanical resistance and know I have that much load.

For how long? 30 HP is over 22 KW, a fair amount of heat.

For short-duration tests, you might use an automotive drum or disc
brake. You can measure torque with a spring scale. At 1750 RPM,
torque would be about 90 lbf-ft so a 1-foot arm and a 100 lb spring
scale would be about right.

Most VFD's will read out torque, current draw, etc.. I suppose it's all
derived from the speed and current draw, in any case there should be
enough
information to determine whether the VFD/Transformer combo can handle the
load. I would monitor the voltage output of the transformer during the
test.
You can reduce the voltage output from the VFD, within its range. I don't
know if it would react quickly enough to stabilize dips in the transformer
output.

I forgot about the VFD. I don't think you'll get anywhere near 30 HP
out of a nominally 30HP motor slowed that much with a VFD. It's
current (and current-produced heat) that determines the power rating
of an induction motor. You can run it slower by dropping the
frequency, but since torque is proportional to current the torque
can't rise much -- so you have less power because power = torque *
speed.

I wasn't thinking of dropping the speed with a VFD, just using the
information from the VFD to determine the load. Most of them have all sorts
of data available.

Another thought would be an eddy current brake. Essentially a driven
disk with a magnetic field so eddy currents are generated in the disk.


I had never heard of these. Just did a good read on Google. Looks expensive,
or is there a way to get one of these reasonable? A search on Ebay gave 0
hits

Karl

Magtrol is the king of the eddy current brakes;
www.magtrol.com

Stuska is the king of water brakes
http://www.stuskadyno.com/brakes.htm

Karl Townsend wrote:
Another thought would be an eddy current brake. Essentially a driven
disk with a magnetic field so eddy currents are generated in the disk.



I had never heard of these. Just did a good read on Google. Looks expensive,
or is there a way to get one of these reasonable? A search on Ebay gave 0
hits

Karl

If the pump goes dry, the load goes away, right? That's no duty at all on
the VFD. You can do a crude test for infant mortality( the most likely
failure mode) by just running it at 60 Hz. into an unloaded motor in a 100°F
environment. If it runs 48 hrs, it will probably go 10-15 years or so until
the electrolytic caps start to dry out.

30 HP load on a 50 HP VFD means the power semiconductors are loafing.
However, the rest of the circuitry(also where the most likely failure would
occur) is working just as hard as if it was loaded to 50 HP. So, the
apparent safety margin is not so great.

Randy

"Karl Townsend" remove .NOT to reply wrote
in message news
Another thought would be an eddy current brake. Essentially a driven
disk with a magnetic field so eddy currents are generated in the disk.


I had never heard of these. Just did a good read on Google. Looks
expensive,
or is there a way to get one of these reasonable? A search on Ebay gave 0
hits

Karl

"R. O'Brian" wrote in message
news7PWd.23596$Az.8787@lakeread02...
If the pump goes dry, the load goes away, right? That's no duty at all
on
the VFD. You can do a crude test for infant mortality( the most likely
failure mode) by just running it at 60 Hz. into an unloaded motor in a
100°F
environment. If it runs 48 hrs, it will probably go 10-15 years or so
until
the electrolytic caps start to dry out.

30 HP load on a 50 HP VFD means the power semiconductors are loafing.
However, the rest of the circuitry(also where the most likely failure
would
occur) is working just as hard as if it was loaded to 50 HP. So, the
apparent safety margin is not so great.

Randy


Good points. I'll set it up and run the motor without load. Use this time to
learn the control. The manual is a small book.

I still want to test it under load. I'm feeding single phase 440 into the
VFD. Some have told me "no problem" just derate. Others have said "won't
work"

Karl

"R. O'Brian" wrote in message
news7PWd.23596$Az.8787@lakeread02...
If the pump goes dry, the load goes away, right? That's no duty at all
on
the VFD. You can do a crude test for infant mortality( the most likely
failure mode) by just running it at 60 Hz. into an unloaded motor in a
100°F
environment. If it runs 48 hrs, it will probably go 10-15 years or so
until
the electrolytic caps start to dry out.

30 HP load on a 50 HP VFD means the power semiconductors are loafing.
However, the rest of the circuitry(also where the most likely failure
would
occur) is working just as hard as if it was loaded to 50 HP. So, the
apparent safety margin is not so great.

Randy


I think the input is single phase so the derating has to be taken into
account.

Most full service tractor dealerships have a PTO dyno they hook to a tractor
PTO. These are usually portable. All you would need is the coupling for your
"motor".

"Erik Litchy" wrote in message
news:HPKWd.100243$4q6.62933@attbi_s01...
im digressing but most car dynos use water as a load.

At least the cheap ones do.

The ones I ran were 500 HP GE DC dynamometers : )

He claimed that the magnetic field caused by the eddy currents caused
the magnetic field he was generating to not go thru the disk. Instead
it went around the disk or at least a lot of it did.

Dan



Don Foreman wrote:


An eddy current brake should be quite linear, but if the disc heats
up
its resistivity would change which would change its behavior.

Karl Townsend wrote:
A large induction motor excited with DC can produce plenty of drag
torque. It doesn't take much DC, either, because the "slip" speed is
1750 RPM rather than the few RPM it sees as an induction motor.
It'll get hot fairly quickly, though. You could adjust the drag
torque by adjusting the DC excitation to the drag motor; all you'd
need would be a bridge rectifier and a Variac.


Ideally, I'd like to run it an hour. My pump can run 24hrs a day if its dry,
I want to make sure nothing in the drive is stressed as much as possible.
That's why I went so oversize. My thinking is that if it will run an hour,
it should run a month.

I do have a 540 rpm PTO irrigation pump that could be connected to a three
phase motor. Any reason that testing at or near 540 RPM wouldn't be valid
for results at 3600 RPM (submersible well pump RPM).
Running a 30 Hp 3450 RPM motor at 540 RPM will give 4.5 HP! The torque
output stays constant at the lower speed, so you get 15% of rated output.

Jon

wrote in message
oups.com...
He claimed that the magnetic field caused by the eddy currents caused
the magnetic field he was generating to not go thru the disk. Instead
it went around the disk or at least a lot of it did.

Dan



Don Foreman wrote:


An eddy current brake should be quite linear, but if the disc heats
up
its resistivity would change which would change its behavior.


I used to have some 200 HP eddy current dynamometer performance curves at
work. If I find them I'll scan one and post...

If you had some aluminum disks maybe 1/4 inch thick and 18 or so inches
in diameter..........And some Microwave Oven Transformers. hack saw
the transformers so you can use just the E sections and the primary
winding. Use two transformer per disk with one on each side of the
disk so the magnetic field goes thru the disk. You could probably use
AC and a light dimmer to control the magnetic field.


Dan

R. O'Brian wrote:
If the pump goes dry, the load goes away, right? That's no duty at all on
the VFD. You can do a crude test for infant mortality( the most likely
failure mode) by just running it at 60 Hz. into an unloaded motor in a 100°F
environment. If it runs 48 hrs, it will probably go 10-15 years or so until
the electrolytic caps start to dry out.

30 HP load on a 50 HP VFD means the power semiconductors are loafing.
However, the rest of the circuitry(also where the most likely failure would
occur) is working just as hard as if it was loaded to 50 HP. So, the
apparent safety margin is not so great.
The real problem here is that Karl only has single-phase 240 V mains,
and needs to run a 3-phase motor. While I recommend VFDs for doing the
phase conversion for small shop machines in this circumstance, the 24 hr
runs at full rated power sounds like a possible problem. The rectifiers
and filter capacitors in the VFD are stressed more on single-phase than
with a 3-phase supply, and will have a shorter life. The .6 derating
of using a 50 Hp VFD certainly helps, but may not quite be enough.

I don't think you'll learn anything from even a 24 hour run, unless you
monitor the temperature of the capacitor bank while you are running it.

Does the VFD manufacturer stand behind this use of the drive? Do they
have any suggestions? One other thing - it is said that long runs of
wire from the VFD to the motor can cause problems with motor insulation
breakdown, as the voltage spikes from the switching of the transistors
in the VFD cause damage to the insulation. Unless this is a shallow
well (I don't remember) that would mean long lines to the motor. Does
the pump maker have any comments on using VFDs to run their pumps?
(I'm assuming a submersible well pump, if not, then ignore this last
bit.)

Jon

I understood that hypothesis from your previous post.

On 6 Mar 2005 20:59:02 -0800, wrote:

He claimed that the magnetic field caused by the eddy currents caused
the magnetic field he was generating to not go thru the disk. Instead
it went around the disk or at least a lot of it did.

Dan



Don Foreman wrote:


An eddy current brake should be quite linear, but if the disc heats
up
its resistivity would change which would change its behavior.

....
have any suggestions? One other thing - it is said that long runs of wire
from the VFD to the motor can cause problems with motor insulation
breakdown, as the voltage spikes from the switching of the transistors
in the VFD cause damage to the insulation. Unless this is a shallow
well (I don't remember) that would mean long lines to the motor. Does
the pump maker have any comments on using VFDs to run their pumps?
(I'm assuming a submersible well pump, if not, then ignore this last
bit.)
....

I'm totally on my own here. Pump manufacturer says to only use 440 3 phase
directly from the power company. I haven't got that. I know just a three
phase motor-capacitor bank setup (to generate 3 phase) will have trouble.
Can't bring in a 30 hp motor under full load with my 200 amp 1 phase
service - the volts will drop like a rock and trip everything. Don't know
if you know this, but large pumps are actually WAY overloaded at 0 head
pressure, they move too much water. The VFD is just for the soft start
ability.

There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

Karl

If I understand your description, this is a pump shaft driver that sits
on top of the well. There are two standard ways to check the output of
the motor and pump.
Wire to water efficiency measurement is done by taking the discharge
pressure and gpm and comparing that HP with the voltage and current at
full load.
A horsepower is 550 ft. lb./second. Water weighs 8.34 lb./gal. 1 ft. of
head =0.433 psi. You must measure the flow and pressure at the well
head. Remember to add the depth of the water in the well to calculate
the lift to the well head.
Your irrigation well should have a Parshall flume or weir to measure
the flow. You need a pressure gauge at the well head, then add the lift
pressure to it.
If this is all too complicated, find an engineer who will run the test,
or a fireman who knows how to test fire pumps. They should be able to
test the well for you.
Bugs

It's called a Prony Brake. Just an arm and brake shoe. The arm rests on
a suitable scale and the brake is clamped down until the max load is
reached. The pressure on the scale and the lever arm length will give
you the HP directly.
550 ft. lb. sec. = 1 HP.
Bugs

Well, errr, hhmmnnn, not exactly directly. The formula for calculating HP
from a "standard" Prony Brake with a 5.25 ft. torque arm is:

Brake HP = (scale pounds x RPM) divided by 1000

If the torque arm is anything other than 5.25 feet, the convenient divisor,
1000, has to be changed via the ratio of 5.25 / Torque arm length.

Bob Swinney


"Bugs" wrote in message
ups.com...
It's called a Prony Brake. Just an arm and brake shoe. The arm rests on
a suitable scale and the brake is clamped down until the max load is
reached. The pressure on the scale and the lever arm length will give
you the HP directly.
550 ft. lb. sec. = 1 HP.
Bugs

On Mon, 07 Mar 2005 13:46:17 GMT, "Karl Townsend"
remove .NOT to reply wrote:

...
have any suggestions? One other thing - it is said that long runs of wire
from the VFD to the motor can cause problems with motor insulation
breakdown, as the voltage spikes from the switching of the transistors
in the VFD cause damage to the insulation. Unless this is a shallow
well (I don't remember) that would mean long lines to the motor. Does
the pump maker have any comments on using VFDs to run their pumps?
(I'm assuming a submersible well pump, if not, then ignore this last
bit.)
...

I'm totally on my own here. Pump manufacturer says to only use 440 3 phase
directly from the power company. I haven't got that. I know just a three
phase motor-capacitor bank setup (to generate 3 phase) will have trouble.
Can't bring in a 30 hp motor under full load with my 200 amp 1 phase
service - the volts will drop like a rock and trip everything. Don't know
if you know this, but large pumps are actually WAY overloaded at 0 head
pressure, they move too much water. The VFD is just for the soft start
ability.

There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

There must be basis for this, but I wonder what it might be. Motors
are inherently inductive loads, so I can't imagine that the inductance
of a couple hundred feet of paired wire would be significant. The
transistors in the VFD must have transient protection on them to
protect them from inductive loads because that is exactly what a VFD
is designed to drive.

It is slightly conceivable that the intervening inductance and
resistance of the long wires could permit the motor to spike the wires
even though snubbed at the VFD. A remedy for that would be to put
600-volt MOV's or Tranzorbs across the lines at the load end.

It is a fact. The cure in your case is a reactor mounted at the VFD and
wired in series with the motor feeder. Top quality industrial motors can
usually handle the max. spike voltage, so spike protection is not so common
in industrial applications unless the motor is inaccessible or difficult and
time consuming to replace. Does this apply to you? BG. The reactor
should be available from the VFD manuf. as an accessory. Everything down
stream of the reactor will be protected, so your standard downhole cable is
OK.

Do you know for a fact that your VFD will run on single-phase power? Some
are internally protected from phase loss and automatically trip off when a
single-phase condition occurs.

Randy



"Karl Townsend" remove .NOT to reply wrote
in message nk.net...
...
have any suggestions? One other thing - it is said that long runs of
wire
from the VFD to the motor can cause problems with motor insulation
breakdown, as the voltage spikes from the switching of the transistors
in the VFD cause damage to the insulation. Unless this is a shallow
well (I don't remember) that would mean long lines to the motor. Does
the pump maker have any comments on using VFDs to run their pumps?
(I'm assuming a submersible well pump, if not, then ignore this last
bit.)
...

I'm totally on my own here. Pump manufacturer says to only use 440 3 phase
directly from the power company. I haven't got that. I know just a three
phase motor-capacitor bank setup (to generate 3 phase) will have trouble.
Can't bring in a 30 hp motor under full load with my 200 amp 1 phase
service - the volts will drop like a rock and trip everything. Don't know
if you know this, but large pumps are actually WAY overloaded at 0 head
pressure, they move too much water. The VFD is just for the soft start
ability.

There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down
the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

Karl

In article ,
says...
On Mon, 07 Mar 2005 13:46:17 GMT, "Karl Townsend"
remove .NOT to reply wrote:


There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

There must be basis for this, but I wonder what it might be.

I ran across this while shopping for a VFD last week. It's
the best explanation I've seen for both the problem and the
solutions.

http://www.yaskawa.com/site/dmdrive.nsf/(DocID)/MNEN-
5JFQPL/$File/AD4079.pdf

Ned Simmons

In article gx0Xd.23611$Az.20036@lakeread02,
says...
It is a fact. The cure in your case is a reactor mounted at the VFD and
wired in series with the motor feeder. Top quality industrial motors can
usually handle the max. spike voltage, so spike protection is not so common
in industrial applications unless the motor is inaccessible or difficult and
time consuming to replace. Does this apply to you? BG. The reactor
should be available from the VFD manuf. as an accessory. Everything down
stream of the reactor will be protected, so your standard downhole cable is
OK.

It's best for the motor if the reactor is at the motor end
of the wiring, but at the VFD is better than nothing. I get
reactors from these folks, generally cheaper than from the
drive manufacturer.

http://www.transcoil.com/

Ned Simmons

Ned Simmons wrote:

In article ,
says...
On Mon, 07 Mar 2005 13:46:17 GMT, "Karl Townsend"
remove .NOT to reply wrote:


There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

There must be basis for this, but I wonder what it might be.

I ran across this while shopping for a VFD last week. It's
the best explanation I've seen for both the problem and the
solutions.

http://www.yaskawa.com/site/dmdrive.nsf/(DocID)/MNEN-
5JFQPL/$File/AD4079.pdf

Ned Simmons

That sure seems to cover it, interesting stuff. It also specifically
mentions deep well pumps. Seems to indicate that a reactor at the VFD
output is good for up to 300' of wire to the motor.

Pete C.

Karl Townsend wrote:

...

I'm totally on my own here. Pump manufacturer says to only use 440 3 phase
directly from the power company. I haven't got that. I know just a three
phase motor-capacitor bank setup (to generate 3 phase) will have trouble.
Can't bring in a 30 hp motor under full load with my 200 amp 1 phase
service - the volts will drop like a rock and trip everything.

That's probably due to poor power factor. Most VFD's, especially big
ones have
pretty good power factor. Of course, running the VFD on single phase
may hurt
the PF a bit. But, it probably is better than either a motor or most
rotary phase
converter schemes.

200 A 240 V should yield 48 KVA, so if the reactive component is not
excessive,
you shouldn't get a voltage dip.

Don't know
if you know this, but large pumps are actually WAY overloaded at 0 head
pressure, they move too much water. The VFD is just for the soft start
ability.

Yes.

Well, the pump motor should be pretty safe if you get the output reactor
for the
VFD. Of course, if the motor croaks, you could have a problem getting
it replaced.
How many hours/year are you planning on running this thing? If you are
expecting
to run it thousands of hrs/year, I'd start to worry about the life of
the VFD. However,
blowing the capacitors in the VFD may only be a couple hundred $ repair
every
couple of years, even in that case. When the capacitors die, it
hopefully will not
damage the VFD, and shouldn't harm the pump.

Jon

On Mon, 7 Mar 2005 13:28:13 -0500, Ned Simmons
wrote:

In article ,
says...
On Mon, 07 Mar 2005 13:46:17 GMT, "Karl Townsend"
remove .NOT to reply wrote:


There's risk no matter which way I go. Now, I've not heard of the voltage
spike issue. Is this rumor or fact? My motor leads will be 225 feet down the
hole. Anyplace I can go to investigate this problem? I'm thinking special
wire would be prudent.

There must be basis for this, but I wonder what it might be.

I ran across this while shopping for a VFD last week. It's
the best explanation I've seen for both the problem and the
solutions.

http://www.yaskawa.com/site/dmdrive.nsf/(DocID)/MNEN-
5JFQPL/$File/AD4079.pdf

Makes sense. Thanks, Ned!