Hi all,

Soon I should have most of the components necessary to build my phase
convertor. I'd like to do a few trial runs in which I wire the
components together and test the convertor's performance before I go to
the time and expense of building a metal chassis to mount it on.

So today I was wondering how I could create a variable load in the range
0.5 to 2 hp. Has anyone done this before? The only three phase workshop
machine I have is a power hacksaw with a 1 3/4 hp motor. This runs
through a static phase convertor I built and I don't really want to
disturb the wiring if I can avoid it.

Ideas I had are as follows, with some disadvantages listed:

Motor bolted to wooden board. Insert 2" x 4" under pulley and lever
upwards to create load. Load control is a bit crude, as is the whole
setup, but I've used it before and it works after a fashion. Sets fire
to wood, too.

Motor bolted to board with slightly more sophisticated homebrew braking
system, possibly allowing weights to be loaded onto a lever. Still
crude, but a bit more controllable.

Motor driving variable pitch propeller in small tank of liquid. Neat,
but I don't know where to get a variable pitch propeller for little
money, or how to match it to the motor.

Bolt car brake disc/drum to motor pulley. Use hydraulic calipers to
apply load. Could be quite neat, but it would be a faff to build because
of needing a reservoir, flaring pipes etc. I'm also not sure how to
regulate the pressure. Plus car parts dealers in our area charge big $$$
for car parts.

I rather like my final idea. A while back a friend offered my a
hydraulic pump from a concrete crusher (i.e., a test rig for measuring
compressive strength). I think it has a 2 hp three phase motor and is
the kind where the motor is mounted vertically on top of the pump, with
the pump hanging down into the reservoir. So I thought I could cut a 47
kg propane cylinder in half, make a plate to cover the opening and mount
the motor/pump unit on top. Then I could have the oil circulating
through a needle valve which regulates the load. Plus I'd need a
pressure relief valve, contactor etc. It sounds like a neat idea but I'm
unsure how much the hydraulic bits would cost.

Any thoughts? Has anyone done this before? I don't want to spend too
long on this, because I want to put my effort into the phase convertor,
but it would be nice to have a controllable load.

Best wishes,

Chris

Ignoramus26924 wrote:

snip

Sounds like too much trouble...

All you need, basically, is to test voltages under no load and under
high load. Both should be acceptable. If that is the case, what will
be under intermediate loads, should also be acceptable.

I guess that makes sense, but it would be nice to know what happens at
intermediate loads. It would give a more complete picture. Maybe I
should do this after I build the convertor, but I want to get the
convertor right.

Chris

I have been told that large gensets are tested with a tank of salt
water? and the electrodes connected to the phases are lowered to
increase the surface area and therefore current passing through the
fluid and so increasing the load. Maybe you could do something on these
lines with a large car alternator.

Christopher Tidy wrote:

Hi all,

Soon I should have most of the components necessary to build my phase
convertor. I'd like to do a few trial runs in which I wire the
components together and test the convertor's performance before I go
to the time and expense of building a metal chassis to mount it on.

So today I was wondering how I could create a variable load in the
range 0.5 to 2 hp. Has anyone done this before? The only three phase
workshop machine I have is a power hacksaw with a 1 3/4 hp motor. This
runs through a static phase convertor I built and I don't really want
to disturb the wiring if I can avoid it.

Ideas I had are as follows, with some disadvantages listed:

Motor bolted to wooden board. Insert 2" x 4" under pulley and lever
upwards to create load. Load control is a bit crude, as is the whole
setup, but I've used it before and it works after a fashion. Sets fire
to wood, too.

Motor bolted to board with slightly more sophisticated homebrew
braking system, possibly allowing weights to be loaded onto a lever.
Still crude, but a bit more controllable.

Motor driving variable pitch propeller in small tank of liquid. Neat,
but I don't know where to get a variable pitch propeller for little
money, or how to match it to the motor.

Bolt car brake disc/drum to motor pulley. Use hydraulic calipers to
apply load. Could be quite neat, but it would be a faff to build
because of needing a reservoir, flaring pipes etc. I'm also not sure
how to regulate the pressure. Plus car parts dealers in our area
charge big $$$ for car parts.

I rather like my final idea. A while back a friend offered my a
hydraulic pump from a concrete crusher (i.e., a test rig for measuring
compressive strength). I think it has a 2 hp three phase motor and is
the kind where the motor is mounted vertically on top of the pump,
with the pump hanging down into the reservoir. So I thought I could
cut a 47 kg propane cylinder in half, make a plate to cover the
opening and mount the motor/pump unit on top. Then I could have the
oil circulating through a needle valve which regulates the load. Plus
I'd need a pressure relief valve, contactor etc. It sounds like a neat
idea but I'm unsure how much the hydraulic bits would cost.

Any thoughts? Has anyone done this before? I don't want to spend too
long on this, because I want to put my effort into the phase
convertor, but it would be nice to have a controllable load.

Best wishes,

Chris

Consider this: Get 3, 220 V "variacs" (variable autotransformers) or a
single 3-phase, ganged, 220 V variac. Connect each of your 3 phases
through each of the variacs to 3, 220 V, 200 Watt lamps, 3 in parallel, to
each variac. At full brilliance, the 9 lamps would be "drawing" nearly 3
HP.

Bob Swinney

"David Billington" wrote in message
...
I have been told that large gensets are tested with a tank of salt water?
and the electrodes connected to the phases are lowered to increase the
surface area and therefore current passing through the fluid and so
increasing the load. Maybe you could do something on these lines with a
large car alternator.

Christopher Tidy wrote:

Hi all,

Soon I should have most of the components necessary to build my phase
convertor. I'd like to do a few trial runs in which I wire the components
together and test the convertor's performance before I go to the time and
expense of building a metal chassis to mount it on.

So today I was wondering how I could create a variable load in the range
0.5 to 2 hp. Has anyone done this before? The only three phase workshop
machine I have is a power hacksaw with a 1 3/4 hp motor. This runs
through a static phase convertor I built and I don't really want to
disturb the wiring if I can avoid it.

Ideas I had are as follows, with some disadvantages listed:

Motor bolted to wooden board. Insert 2" x 4" under pulley and lever
upwards to create load. Load control is a bit crude, as is the whole
setup, but I've used it before and it works after a fashion. Sets fire to
wood, too.

Motor bolted to board with slightly more sophisticated homebrew braking
system, possibly allowing weights to be loaded onto a lever. Still crude,
but a bit more controllable.

Motor driving variable pitch propeller in small tank of liquid. Neat, but
I don't know where to get a variable pitch propeller for little money, or
how to match it to the motor.

Bolt car brake disc/drum to motor pulley. Use hydraulic calipers to apply
load. Could be quite neat, but it would be a faff to build because of
needing a reservoir, flaring pipes etc. I'm also not sure how to regulate
the pressure. Plus car parts dealers in our area charge big $$$ for car
parts.

I rather like my final idea. A while back a friend offered my a hydraulic
pump from a concrete crusher (i.e., a test rig for measuring compressive
strength). I think it has a 2 hp three phase motor and is the kind where
the motor is mounted vertically on top of the pump, with the pump hanging
down into the reservoir. So I thought I could cut a 47 kg propane
cylinder in half, make a plate to cover the opening and mount the
motor/pump unit on top. Then I could have the oil circulating through a
needle valve which regulates the load. Plus I'd need a pressure relief
valve, contactor etc. It sounds like a neat idea but I'm unsure how much
the hydraulic bits would cost.

Any thoughts? Has anyone done this before? I don't want to spend too long
on this, because I want to put my effort into the phase convertor, but it
would be nice to have a controllable load.

Best wishes,

Chris

Use a water pump, and a valve to adjust the flow. For a proper job, mount
the pump on bearings so it can rotate, restrained by a spring balance,
which is the basis for a Heenan and Froude water brake engine dyno.
Geoff

Robert Swinney wrote:
Consider this: Get 3, 220 V "variacs" (variable autotransformers) or a
single 3-phase, ganged, 220 V variac. Connect each of your 3 phases
through each of the variacs to 3, 220 V, 200 Watt lamps, 3 in parallel, to
each variac. At full brilliance, the 9 lamps would be "drawing" nearly 3
HP.

Bob Swinney

It's a nice idea, but a three phase variac will cost big money. At least
round here it will. I've seen them sell on eBay for £100+.

Chris

Geoff M wrote:
Use a water pump, and a valve to adjust the flow. For a proper job, mount
the pump on bearings so it can rotate, restrained by a spring balance,
which is the basis for a Heenan and Froude water brake engine dyno.
Geoff

Thanks for the suggestion. I don't have a water pump, but I've been
offered a 2 hp hydraulic pump/motor unit free. I don't see a problem
with using this, do you?

Best wishes,

Chris

Might be worth playing with an alternator by connecting it to an
electric motor and placing some electrodes in a salt solution to see how
the load varies with surface exposure. I don't see the variacs are
required. IIRC the test set-up I mentioned didn't produce gassing due to
the AC nature and the O2 and H2 gases apparently recombined at the
electrodes. If done outdoors then the alternator may be able to be used
as standard DC output otherwise you would have to get at the internals
and the internal 3(or more in some cases) phase in the alternator.

Christopher Tidy wrote:

Robert Swinney wrote:

Consider this: Get 3, 220 V "variacs" (variable autotransformers) or
a single 3-phase, ganged, 220 V variac. Connect each of your 3
phases through each of the variacs to 3, 220 V, 200 Watt lamps, 3 in
parallel, to each variac. At full brilliance, the 9 lamps would be
"drawing" nearly 3 HP.

Bob Swinney


It's a nice idea, but a three phase variac will cost big money. At
least round here it will. I've seen them sell on eBay for £100+.

Chris

Ignoramus19652 wrote:
how about: buy 3 adjustable room heaters from your local store (or
borrow from friends), put one heater on each leg, and vary heat
setting to simulate varying loads.

I thought about using a heater as Xpelair heaters with three phase
wiring are quite common here. But I'm doubtful as they're primarily a
resistive load and won't behave in quite the same way as a motor.

Return after use.

I think that's slightly too cheeky even for me. I did it one time I
urgently needed a landline telephone (I had ordered one but it was
taking ages to arrive) and another time I needed a camera flash
extension lead for one evening, but I'd be reluctant to do it with a
heater. Mind you, some guys I know did it with a big TV during the 2002
World Cup.

Chris

David sez:
"I don't see the variacs are required."

You also must not have seen where Chris wanted a variable load.

Bob Swinney

Used to have a 3 phase log taper version for lighting. But it was needed in a project...
Now a 'baby' ballet has a wonderful light control panel.
Had to get singles with toggle handles not hand knobs.

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder



Robert Swinney wrote:
David sez:
"I don't see the variacs are required."

You also must not have seen where Chris wanted a variable load.

Bob Swinney



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I did see that a variable load was required. That is where varying the
exposed surface of the electrodes comes in altering the current flow and
so the load.

Robert Swinney wrote:

David sez:
"I don't see the variacs are required."

You also must not have seen where Chris wanted a variable load.

Bob Swinney

On Fri, 23 Sep 2005 22:42:14 +0000 (UTC), Christopher Tidy
wrote:

Geoff M wrote:
Use a water pump, and a valve to adjust the flow. For a proper job, mount
the pump on bearings so it can rotate, restrained by a spring balance,
which is the basis for a Heenan and Froude water brake engine dyno.
Geoff

Thanks for the suggestion. I don't have a water pump, but I've been
offered a 2 hp hydraulic pump/motor unit free. I don't see a problem
with using this, do you?

Hydraulic pump should work well. Most hydraulic pumps have some
"drag" even with no hydraulic load -- which is OK because most loads
you'll have on your converter will also have some minimum drag.

You probably know that the fluid will get hot with extended testing.
Your "brake" power is being converted to heat. No problem for short
tests or with plenty of fluid.

The hydraulic approach is considerably easier than a prony brake if
you want any torque measurement. The primary downside is that
hydraulics can be messy.

Car brakes, disc or drum, tend to chatter. You don't notice a little
chatter when decelerating the mass of a car, but you sure do in
something like this! Torque data has a lot of noise in it. (Been
there, done that.)

If you have a pressure gage, you can record output power as pressure *
flowrate. Flowrate will be pretty constant (displacement of pump *
speed) because induction motors only vary a few percent in speed from
noload to full load.
---

Jerry Martes once built an eddycurrent dyno for studying RPC's. It
worked extremely well, with torque easily adjustable from near zero to
about 5 HP worth at 1725 RPM. It used a thick aluminum disc and four
electromagnets made from alternator field coils. Torque was measured
by means of a torque arm and straingage loadcell, speed with an
inductive pickup. Both were recorded on a P.C. datalogger.

I designed some elex for it: a high resolution (about 200 parts per
million) speed sensor and a phasemeter that converted phase difference
between two voltages (or a voltage and a current) to an analog
voltage. I don't recall if we ever actually built either. The speed
sensor (really time per rev) was only good for average speed; it
measured counts during 1 rev from a 1 MHz clock.

Errrr, could you expound just a bit on how one would go about varying the
exposed surfaces in such a way as to calibrate the load? Your answer was
typical of a great many of those on RCM, lately. It seems like some
responders just like to see their names on the PC rather than offer any
thought-out, workable, advice. Someone asks a fairly specific question and
then they get a ration of BS from the responder. Sorta like: The man asked
how to make a wheel of a certain size and you told him to go chop down a
tree!

Bob Swinney
"David Billington" wrote in message
...
I did see that a variable load was required. That is where varying the
exposed surface of the electrodes comes in altering the current flow and so
the load.

Robert Swinney wrote:

David sez:
"I don't see the variacs are required."

You also must not have seen where Chris wanted a variable load.

Bob Swinney

Robert Swinney wrote:
Errrr, could you expound just a bit on how one would go about varying the
exposed surfaces in such a way as to calibrate the load? Your answer was
typical of a great many of those on RCM, lately. It seems like some
responders just like to see their names on the PC rather than offer any
thought-out, workable, advice. Someone asks a fairly specific question and
then they get a ration of BS from the responder. Sorta like: The man asked
how to make a wheel of a certain size and you told him to go chop down a
tree!

Bob Swinney

I can see what David's talking about. It's probably a bit more
complicated than I'd want to use for this task, but it's still a
worthwhile idea. As I see it you drive a car alternator using a three
phase motor and connect the alternator's output wires to a pair of
rectangular electrodes which can be lowered into the salt solution. The
further you lower them, the greater the current drawn from the
alternator. I assume that you measure the load by using the voltage and
current at the motor. Is that right?

Best wishes,

Chris

Don Foreman wrote:
On Fri, 23 Sep 2005 22:42:14 +0000 (UTC), Christopher Tidy
wrote:


Geoff M wrote:

Use a water pump, and a valve to adjust the flow. For a proper job, mount
the pump on bearings so it can rotate, restrained by a spring balance,
which is the basis for a Heenan and Froude water brake engine dyno.
Geoff

Thanks for the suggestion. I don't have a water pump, but I've been
offered a 2 hp hydraulic pump/motor unit free. I don't see a problem
with using this, do you?


Hydraulic pump should work well. Most hydraulic pumps have some
"drag" even with no hydraulic load -- which is OK because most loads
you'll have on your converter will also have some minimum drag.

You probably know that the fluid will get hot with extended testing.
Your "brake" power is being converted to heat. No problem for short
tests or with plenty of fluid.

I was thinking of 5 to 10 gallons of oil, which I reckon should be okay
for short tests.

snip
Jerry Martes once built an eddycurrent dyno for studying RPC's. It
worked extremely well, with torque easily adjustable from near zero to
about 5 HP worth at 1725 RPM. It used a thick aluminum disc and four
electromagnets made from alternator field coils. Torque was measured
by means of a torque arm and straingage loadcell, speed with an
inductive pickup. Both were recorded on a P.C. datalogger.

This is another interesting idea. It sounds very like the
electromagnetic retarders used on buses and trucks. I'd wondered about
something like this, but I reckon the parts will be harder for me to
acquire than the hydraulic parts. I might do a few simple tests before
building a nice convertor, then do more thorough tests afterwards, or I
might do it the other way round. I haven't decided yet.

Best wishes,

Chris

I originally just mentioned the idea as I was told that gensets can be
tested in this manner so in that case they would probably have meters
already to provide the load info on the genset. As regards using an car
alternator, I through that in as possible readily available source of an
item that could be used to provide the load for a motor. If I was using
an AC alternator for the test I would use my magnetic current
transformer to read the current off on a DVM, if DC I would have to get
a suitable hall effect current sensor or ammeter with a suitably sized
shunt. The electrodes would just be placed as necessary to provide the
required load. I wasn't intending to provide a full fledged solution as
from previous posts Mr Tidy seems very competent and could then take the
basic idea if useful and work it into a solution to suit his needs and
equipment. I only responded to your reply as it appeared you didn't
realise what allowed the load to be varied when you seemed to suggest a
variac would be required for varying the load.

Robert Swinney wrote:

Errrr, could you expound just a bit on how one would go about varying the
exposed surfaces in such a way as to calibrate the load? Your answer was
typical of a great many of those on RCM, lately. It seems like some
responders just like to see their names on the PC rather than offer any
thought-out, workable, advice. Someone asks a fairly specific question and
then they get a ration of BS from the responder. Sorta like: The man asked
how to make a wheel of a certain size and you told him to go chop down a
tree!

Bob Swinney
"David Billington" wrote in message
k...

I did see that a variable load was required. That is where varying the
exposed surface of the electrodes comes in altering the current flow and so
the load.

Robert Swinney wrote:

David sez:
"I don't see the variacs are required."

You also must not have seen where Chris wanted a variable load.

Bob Swinney

One point of caution with the hydraulic would be the presence of high
pressure fluid. Bath University in the UK has/had a hydraulic dyno rig
which used a valve to throttle the system and provide the load and
because of the potential danger if pressurised parts of the system
failed it was well shielded with no one being allowed within that area
during a test run.

Christopher Tidy wrote:

Don Foreman wrote:

On Fri, 23 Sep 2005 22:42:14 +0000 (UTC), Christopher Tidy
wrote:


Geoff M wrote:

Use a water pump, and a valve to adjust the flow. For a proper job,
mount
the pump on bearings so it can rotate, restrained by a spring balance,
which is the basis for a Heenan and Froude water brake engine dyno.
Geoff


Thanks for the suggestion. I don't have a water pump, but I've been
offered a 2 hp hydraulic pump/motor unit free. I don't see a problem
with using this, do you?



Hydraulic pump should work well. Most hydraulic pumps have some
"drag" even with no hydraulic load -- which is OK because most loads
you'll have on your converter will also have some minimum drag.
You probably know that the fluid will get hot with extended testing.
Your "brake" power is being converted to heat. No problem for short
tests or with plenty of fluid.


I was thinking of 5 to 10 gallons of oil, which I reckon should be
okay for short tests.

snip

Jerry Martes once built an eddycurrent dyno for studying RPC's. It
worked extremely well, with torque easily adjustable from near zero to
about 5 HP worth at 1725 RPM. It used a thick aluminum disc and four
electromagnets made from alternator field coils. Torque was measured
by means of a torque arm and straingage loadcell, speed with an
inductive pickup. Both were recorded on a P.C. datalogger.


This is another interesting idea. It sounds very like the
electromagnetic retarders used on buses and trucks. I'd wondered about
something like this, but I reckon the parts will be harder for me to
acquire than the hydraulic parts. I might do a few simple tests before
building a nice convertor, then do more thorough tests afterwards, or
I might do it the other way round. I haven't decided yet.

Best wishes,

Chris

David Billington wrote:
One point of caution with the hydraulic would be the presence of high
pressure fluid. Bath University in the UK has/had a hydraulic dyno rig
which used a valve to throttle the system and provide the load and
because of the potential danger if pressurised parts of the system
failed it was well shielded with no one being allowed within that area
during a test run.

Thanks for the warning. I've seen this happen and it's pretty scary. If
I were to take this route I'd certainly build a shield of some sort
around the valves and pipework.

Chris