I'm building a phase converter for my son... My third one.

We're using two motors. A 5hp start unit and a 20 hp run unit for a
total of 25 hp. Using a 3 phase load center panel to distribute all
the wiring. Each of these motors will have a circuit breaker going to
a motor starter contactor and then the motor. As an aside, the load
center will make it easy for him to add machines as needed.

I'm doing the control work for him after he gets the power wiring and
panels for the above installed. So, I read up on the needed start cap
size he
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
Looks like 200 MFD will bring it right up. Note: all these plans show
a potential start relay to hold in these caps for a few seconds and
then drop out - spendy little device.

Now I want to balance voltages in the running unit using run
capacitors. An expert named Fitch gave me the attached report on
balancing. it shows I'll need around 300 to 400 MFD run caps between
each single phase leg and the "wild" leg


Then a huge simplification occurred to me. Why even use start caps?
Put the 300 or so run caps between L1 and wild in with the first five
hose motor. it will start right up.

OK, wait five seconds and start motor two, the large one. Put the rest
of the caps behind the motor start contactor on this unit.

No start caps, no potential relay. Anybody see why this won't work?

Special note, I also asked on a place that will host Fitch's .pdf. Get
it he
http://www.weaponsguild.com/forum/in...;topicseen#new



Karl

On 2013-09-16, Karl Townsend wrote:
I'm building a phase converter for my son... My third one.

We're using two motors. A 5hp start unit and a 20 hp run unit for a
total of 25 hp. Using a 3 phase load center panel to distribute all
the wiring. Each of these motors will have a circuit breaker going to
a motor starter contactor and then the motor. As an aside, the load
center will make it easy for him to add machines as needed.

I'm doing the control work for him after he gets the power wiring and
panels for the above installed. So, I read up on the needed start cap
size he
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
Looks like 200 MFD will bring it right up. Note: all these plans show
a potential start relay to hold in these caps for a few seconds and
then drop out - spendy little device.

Now I want to balance voltages in the running unit using run
capacitors. An expert named Fitch gave me the attached report on
balancing. it shows I'll need around 300 to 400 MFD run caps between
each single phase leg and the "wild" leg


Then a huge simplification occurred to me. Why even use start caps?
Put the 300 or so run caps between L1 and wild in with the first five
hose motor. it will start right up.

OK, wait five seconds and start motor two, the large one. Put the rest
of the caps behind the motor start contactor on this unit.

No start caps, no potential relay. Anybody see why this won't work?

I did the same thing. It worked well. Of course, I no longer need the
phase converter, since I moved my business to my warehouse.

i

Special note, I also asked on a place that will host Fitch's .pdf. Get
it he
http://www.weaponsguild.com/forum/in...;topicseen#new



Karl

On 9/16/2013 7:15 AM, Karl Townsend wrote:
I'm building a phase converter for my son... My third one.

Karl

snip

What is the advantage to rotary phase converters vs VFD's? I never
didn't have 3-phase so I never had to bone-up on this stuff. I just
figured that if I ever wanted equipment at home, I would get the
appropriate VFD and be done with it. Obviously, I'm missing something.

Tom Gardner Mars@Tacks fired this volley in news:0NydnV10J-Sc-
:

I would get the
appropriate VFD and be done with it. Obviously, I'm missing something.

IF you have the motors already, it's cheap. IF you can live with the
imbalance of phases that's likely to occur (usually fine when running
motors, and _can_ be tuned out) it works nicely. They usually occupy a
good deal of space (although I've converted a machine's own 3-phase motor
to run on single-phase with caps and a start relay, in the past)

VFD's tend to be noisy electrically, and more expensive than "scrap-
built" rotary converters. They're also quieter acoustically.

Rotary converters and rotary generators used to be the only way to
accomplish the task, so they stick around, and might even suit better
depending on budget and space.

Lloyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message . 3.70...
Tom Gardner Mars@Tacks fired this volley in news:0NydnV10J-Sc-
:

Obviously, I'm missing something.

No ****, Sherlocks.

On Monday, September 16, 2013 4:11:43 PM UTC-4, Tom Gardner wrote:



What is the advantage to rotary phase converters vs VFD's? Obviously, I'm missing something.

Rotary converters are much cheaper in the larger sizes. The VFD is smaller , close to the same price in small sizes, and let you vary the motor speed.

Dan

On 2013-09-16, Tom Gardner Mars@Tacks wrote:
On 9/16/2013 7:15 AM, Karl Townsend wrote:
I'm building a phase converter for my son... My third one.

Karl

snip

What is the advantage to rotary phase converters vs VFD's? I never
didn't have 3-phase so I never had to bone-up on this stuff. I just
figured that if I ever wanted equipment at home, I would get the
appropriate VFD and be done with it. Obviously, I'm missing something.


VFDs cannot operate any control systems.

i

Ignoramus14718 fired this volley in
:


VFDs cannot operate any control systems.

Not even close to true, Ig.

VFDs, with proper low-pass filtering work fine on 3ph controls.

Lloyd

BQ340 fired this volley in news:523799df$0$63180
:

no plug-reversing motors with VFD's for one

That's a matter of planning, rather than a specific advantage or
disadvantage. The application matters.

VFD's decelerate then re-accelerate when switch-reversed.

RPCs do it more rapidly, but NOT instantly, which might be wanted in some
applications. They also severely stress everything while doing it.

Lloyd

On 2013-09-17, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
BQ340 fired this volley in news:523799df$0$63180
:

no plug-reversing motors with VFD's for one

That's a matter of planning, rather than a specific advantage or
disadvantage. The application matters.

VFD's decelerate then re-accelerate when switch-reversed.

RPCs do it more rapidly, but NOT instantly, which might be wanted in some
applications. They also severely stress everything while doing it.

And if you plug reverse a big enough motor with a big enough inertia,
it may happen that the motor will keep the rotation, but the phase
converter idler willr everse.

i

Ignoramus14718 fired this volley in
:

nd if you plug reverse a big enough motor with a big enough inertia,
it may happen that the motor will keep the rotation, but the phase
converter idler willr everse.



Yup! G
But I don't know (off-hand) of a VFD that will reverse its phase
arbitrarily, load or no.

Lloyd

On Mon, 16 Sep 2013 15:49:02 -0700 (PDT), "
wrote:

On Monday, September 16, 2013 4:11:43 PM UTC-4, Tom Gardner wrote:



What is the advantage to rotary phase converters vs VFD's? Obviously, I'm missing something.

Rotary converters are much cheaper in the larger sizes. The VFD is smaller , close to the same price in small sizes, and let you vary the motor speed.

Dan

#1 advantage is you can run multiple devices off one (1) rotory
converter.

#1 DISadvantage of VFDs is you can only run one (1) device off a vfd.

Gunner

"The socialist movement takes great pains to circulate frequently new labels for its ideally constructed state.
Each worn-out label is replaced by another which raises hopes of an ultimate solution of the insoluble basic
problem of Socialism, until it becomes obvious that nothing has been changed but the name.
The most recent slogan is "State Capitalism."[Fascism] It is not commonly realized that this covers nothing more
than what used to be called Planned Economy and State Socialism, and that State Capitalism, Planned Economy,
and State Socialism diverge only in non-essentials from the "classic" ideal of egalitarian Socialism. - Ludwig von Mises (1922)

On Mon, 16 Sep 2013 19:52:59 -0400, BQ340
wrote:

On 9/16/2013 4:11 PM, Tom Gardner wrote:


What is the advantage to rotary phase converters vs VFD's? I never
didn't have 3-phase so I never had to bone-up on this stuff. I just
figured that if I ever wanted equipment at home, I would get the
appropriate VFD and be done with it. Obviously, I'm missing something.


no plug-reversing motors with VFD's for one

MikeB

On machines with multiple motors such as a horizontal mill...you need
multiple VFDs to operate.


"The socialist movement takes great pains to circulate frequently new labels for its ideally constructed state.
Each worn-out label is replaced by another which raises hopes of an ultimate solution of the insoluble basic
problem of Socialism, until it becomes obvious that nothing has been changed but the name.
The most recent slogan is "State Capitalism."[Fascism] It is not commonly realized that this covers nothing more
than what used to be called Planned Economy and State Socialism, and that State Capitalism, Planned Economy,
and State Socialism diverge only in non-essentials from the "classic" ideal of egalitarian Socialism. - Ludwig von Mises (1922)

"Karl Townsend" wrote in message ...
I'm building a phase converter for my son... My third one.

We're using two motors. A 5hp start unit and a 20 hp run unit for a
total of 25 hp. Using a 3 phase load center panel to distribute all
the wiring. Each of these motors will have a circuit breaker going to
a motor starter contactor and then the motor. As an aside, the load
center will make it easy for him to add machines as needed.

I'm doing the control work for him after he gets the power wiring and
panels for the above installed. So, I read up on the needed start cap
size he
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
Looks like 200 MFD will bring it right up. Note: all these plans show
a potential start relay to hold in these caps for a few seconds and
then drop out - spendy little device.

Now I want to balance voltages in the running unit using run
capacitors. An expert named Fitch gave me the attached report on
balancing. it shows I'll need around 300 to 400 MFD run caps between
each single phase leg and the "wild" leg


Then a huge simplification occurred to me. Why even use start caps?
Put the 300 or so run caps between L1 and wild in with the first five
hose motor. it will start right up.

OK, wait five seconds and start motor two, the large one. Put the rest
of the caps behind the motor start contactor on this unit.

No start caps, no potential relay. Anybody see why this won't work?

Special note, I also asked on a place that will host Fitch's .pdf. Get
it he
http://www.weaponsguild.com/forum/in...;topicseen#new


Karl, if you are going to run several machines off of the same converter buss then probably best to first balance your idler under no-load condition and then add correction capacitors at each machine on an as-needed basis.