Hi Jerry,

A while back you mentioned that you'd done some experiments to
investigate how idler size affects the power delivering capacity of a
rotary phase convertor. Did you write up the results? If so I'd be very
interested to see them.

Some people say that you need an idler with twice the load power rating,
some say equal, and I know of a commercial company who use idlers of
half the load power rating. So I'd be interested to know what you
discovered - it would shed some light on the mystery.

Best wishes,

Chris

Ignoramus24489 wrote:

It depends on many things besides nameplate power of the load.

For example:

1) Whether it is a hard starting load (think about a compressor) or an
easy starting load (think about a centrifugal blower)

Let's assume it's medium e.g., a hydraulic pump or something with a fair
bit of inertia like a power hacksaw. I want to decide on a fair rating
for my convertor.

2) Whether the load actually runs at nameplate power, or below (think
about a lathe that's not used to the max of its capacity)

In this case assume it runs at its nameplate power. As I said, I want to
figure out a fair rating.

3) What amount of imbalance between legs would you tolerate. Severe
duty motors, for example, may tolerate greater imbalances than CNC
machines.

I'm guessing a voltage variation of 3% is good, 5% is okay and 10% is
too much.

I have discovered that my 10 HP phase converter is not quite
sufficient to run a 200A tig welder. I mean, it runs it, but the power
in third leg sags considerably. I will soon add another idler (I am
kind of busy lately).

Did you measure the voltage drop?

I think I might just protect the motor with a thermal breaker set to
about 20% above the rated motor current (4.8 A) so that it doesn't
matter if I overload it.

Chris

On Wed, 12 Oct 2005 17:25:31 +0000 (UTC), Christopher Tidy
wrote:

Hi Jerry,

A while back you mentioned that you'd done some experiments to
investigate how idler size affects the power delivering capacity of a
rotary phase convertor. Did you write up the results? If so I'd be very
interested to see them.

Some people say that you need an idler with twice the load power rating,
some say equal, and I know of a commercial company who use idlers of
half the load power rating. So I'd be interested to know what you
discovered - it would shed some light on the mystery.

Best wishes,

Chris

I don't think Jerry is reading this group anymore, but I passed your
inquiry on to him. Jerry did a lot of experiments with idlers and
some pretty good instrumentation including an eddy-current brake.

Don Foreman wrote:
On Wed, 12 Oct 2005 17:25:31 +0000 (UTC), Christopher Tidy
wrote:


Hi Jerry,

A while back you mentioned that you'd done some experiments to
investigate how idler size affects the power delivering capacity of a
rotary phase convertor. Did you write up the results? If so I'd be very
interested to see them.

Some people say that you need an idler with twice the load power rating,
some say equal, and I know of a commercial company who use idlers of
half the load power rating. So I'd be interested to know what you
discovered - it would shed some light on the mystery.

Best wishes,

Chris


I don't think Jerry is reading this group anymore, but I passed your
inquiry on to him. Jerry did a lot of experiments with idlers and
some pretty good instrumentation including an eddy-current brake.

Thanks very much, Don.

Chris

Hi Chris

Don foreman told me that you are possibly interested in the data Don and I
collected with the eddy current dyno. No, I didnt write up the results. I
couldnt find anyone interested in knowing the facts.
I have an interesting set of curves showing how a 3 HP 3 phase motor is
capable of producing power from single phase, with - and - without an idler.
I'd be happy to send you the Excel plots and acquired data from the dyno.

It is my observation that the biggest idler provides the best 3 phase.
That is *no* surprise. What does surprise me is; the 3 phase tool motor
will deliver very nearly the same power with *no* idler as with a Big idler
when loaded to no more than 2/3 the tool motor's name plate HP. And, a 3
phase motor will deliver its Full name plate rated HP when driven by single
phase.
There is certainly limits to how the 3 phase motor will deliver full power
when fully loaded. But, the statement about a 3 phase motor being able to
produce no more than 2/3 it's name plate HP, is not accurate.

E-mail me to get copies of the Excel data on the 3 HP 3 phase motor with
and without the 5 HP idler.

Jerry








"Christopher Tidy" wrote in message
...
Hi Jerry,

A while back you mentioned that you'd done some experiments to investigate
how idler size affects the power delivering capacity of a rotary phase
convertor. Did you write up the results? If so I'd be very interested to
see them.

Some people say that you need an idler with twice the load power rating,
some say equal, and I know of a commercial company who use idlers of half
the load power rating. So I'd be interested to know what you discovered -
it would shed some light on the mystery.

Best wishes,

Chris

Jerry Martes wrote:
Hi Chris

Don foreman told me that you are possibly interested in the data Don and I
collected with the eddy current dyno. No, I didnt write up the results. I
couldnt find anyone interested in knowing the facts.
I have an interesting set of curves showing how a 3 HP 3 phase motor is
capable of producing power from single phase, with - and - without an idler.
I'd be happy to send you the Excel plots and acquired data from the dyno.

It is my observation that the biggest idler provides the best 3 phase.
That is *no* surprise. What does surprise me is; the 3 phase tool motor
will deliver very nearly the same power with *no* idler as with a Big idler
when loaded to no more than 2/3 the tool motor's name plate HP. And, a 3
phase motor will deliver its Full name plate rated HP when driven by single
phase.
There is certainly limits to how the 3 phase motor will deliver full power
when fully loaded. But, the statement about a 3 phase motor being able to
produce no more than 2/3 it's name plate HP, is not accurate.

E-mail me to get copies of the Excel data on the 3 HP 3 phase motor with
and without the 5 HP idler.

Jerry

Thanks very much, Jerry. I've just sent you an e-mail.

Best wishes,

Chris

On Wed, 12 Oct 2005 19:53:28 GMT, "Jerry Martes"
wrote:


Hi Chris

Don foreman told me that you are possibly interested in the data Don and I
collected with the eddy current dyno. No, I didnt write up the results. I
couldnt find anyone interested in knowing the facts.
I have an interesting set of curves showing how a 3 HP 3 phase motor is
capable of producing power from single phase, with - and - without an idler.
I'd be happy to send you the Excel plots and acquired data from the dyno.

It is my observation that the biggest idler provides the best 3 phase.
That is *no* surprise. What does surprise me is; the 3 phase tool motor
will deliver very nearly the same power with *no* idler as with a Big idler
when loaded to no more than 2/3 the tool motor's name plate HP. And, a 3
phase motor will deliver its Full name plate rated HP when driven by single
phase.
There is certainly limits to how the 3 phase motor will deliver full power
when fully loaded. But, the statement about a 3 phase motor being able to
produce no more than 2/3 it's name plate HP, is not accurate.

E-mail me to get copies of the Excel data on the 3 HP 3 phase motor with
and without the 5 HP idler.

Jerry



Just a small postcript.

A pony started single phase driven 3 phase motor without any
phase correction easily delivers its full rated HP at a few %
lower than its rated speed.

For long term use, Brook Compton Parkinson motors data
shows that rated full load current is reached in the single phase
driven lines at roughly half full rated load. This is still below
rated full load dissipation because the current in the indirectly
energised winding is very low. For long term use roughly 2/3
rated power is a pretty fair guess.

Most of this power reduction can be recovered by a single
pahse correction capacitor chosen for best phase balance near
full load.

The Brook Compton Parkinson data is shown in the drop box
as Single phase drive.jpg

Jim

wrote in message
...
On Wed, 12 Oct 2005 19:53:28 GMT, "Jerry Martes"
wrote:


Hi Chris

Don foreman told me that you are possibly interested in the data Don and
I
collected with the eddy current dyno. No, I didnt write up the results.
I
couldnt find anyone interested in knowing the facts.
I have an interesting set of curves showing how a 3 HP 3 phase motor is
capable of producing power from single phase, with - and - without an
idler.
I'd be happy to send you the Excel plots and acquired data from the dyno.

It is my observation that the biggest idler provides the best 3 phase.
That is *no* surprise. What does surprise me is; the 3 phase tool motor
will deliver very nearly the same power with *no* idler as with a Big
idler
when loaded to no more than 2/3 the tool motor's name plate HP. And, a 3
phase motor will deliver its Full name plate rated HP when driven by
single
phase.
There is certainly limits to how the 3 phase motor will deliver full
power
when fully loaded. But, the statement about a 3 phase motor being able
to
produce no more than 2/3 it's name plate HP, is not accurate.

E-mail me to get copies of the Excel data on the 3 HP 3 phase motor with
and without the 5 HP idler.

Jerry



Just a small postcript.

A pony started single phase driven 3 phase motor without any
phase correction easily delivers its full rated HP at a few %
lower than its rated speed.

For long term use, Brook Compton Parkinson motors data
shows that rated full load current is reached in the single phase
driven lines at roughly half full rated load. This is still below
rated full load dissipation because the current in the indirectly
energised winding is very low. For long term use roughly 2/3
rated power is a pretty fair guess.

Most of this power reduction can be recovered by a single
pahse correction capacitor chosen for best phase balance near
full load.

The Brook Compton Parkinson data is shown in the drop box
as Single phase drive.jpg

Jim

Jim

I'm think you are right on with the above comments about the 2/3 HP
de-rating for 3 phase motors from single phase. 2/3 is a "good guess"
My interest had been to learn why the power would *drop off* after loaded
beyond 2/3 its HP rating. I was surprised to find that the 3 phase motors
would actually produce full HP when fed single phase.
My mind wants to guess that the actual "max HP" from a 3 phase motor on
single phase will be somewhat higher than 2/3 because of the conduction of
heat being related to the fans and mass of the "full HP" package.
I have no expectation that I'll ever use a 3 phase motor fed single phase.
I was just curious.

Jerry

I have no expectation that I'll ever use a 3 phase motor fed single phase.
I was just curious.

I have a 10 inch baldor pedistal grinder. It is 3ph and I have a
static phase converted hooked to it. It starts and runs but I have
never been happy with the amount of vibration. I am now wondering
if it will run smoother with a VFD. Is it worth hooking it up
to find out? or am I wasting my time.

chuck

"Chuck Sherwood" wrote in message
...
I have no expectation that I'll ever use a 3 phase motor fed single
phase.
I was just curious.

I have a 10 inch baldor pedistal grinder. It is 3ph and I have a
static phase converted hooked to it. It starts and runs but I have
never been happy with the amount of vibration. I am now wondering
if it will run smoother with a VFD. Is it worth hooking it up
to find out? or am I wasting my time.

chuck

Chuch

Motor theory (and my dyno experiments) does show that the tool motor
torque goes to zero while it is rotating and fed single phase. That results
in some "vibration" at heavy loads.
Does your grinder vibrate only when heavily loaded?

Jerry

Does your grinder vibrate only when heavily loaded?

No, it vibrates all the time.

On 13 Oct 2005 17:37:17 GMT, (Chuck
Sherwood) wrote:

I have no expectation that I'll ever use a 3 phase motor fed single phase.
I was just curious.

I have a 10 inch baldor pedistal grinder. It is 3ph and I have a
static phase converted hooked to it. It starts and runs but I have
never been happy with the amount of vibration. I am now wondering
if it will run smoother with a VFD. Is it worth hooking it up
to find out? or am I wasting my time.

chuck

Vibration could be either or both, wheel unbalance or
single phase torque variation. Unbalance vibration is
predominantly at rotation frequency. Torque variation is at
twice supply frequency. Unfortunately the ear is not good at
distinguishing between the two types of vibration and the only
sure fire check is to monitor the vibration with an oscilloscope.

A test run with a VFD would eliminate single phase
torque variation as a cause. If a VFD test shows that torque
variation is the problem you may be able to eliminate it by
tweaking the "static phase converter" Inverted commas are used
because some so-called converters are simply single phase
starters. They do not contain "run" capacitors which means that
the motor is running with 100% unbalanced drive. If this is the
case the addition of about 30uFd per horsepower of run capacitor
will improve the phase balance enough to eliminate the torque
variation problem.

Jim

In article , cas@w-
sherwood.ih.lucent.com says...
Does your grinder vibrate only when heavily loaded?

No, it vibrates all the time.


See if the vibration decreases immediately after you switch
off the power; if there's no significant change in
vibration, try running with the wheels removed.

I can switch my grinder and a few of the other tools in the
shop between a Phase-o-matic static converter and a rotary.
There's no discernible difference in the grinder's
vibration switching from one to the other.

Ned Simmons