Increasing capacity of a phase converter.
 

Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

As far as I can see it makes sense. If the idlers are always started at
separate times, you should be able to figure out a way of using the same
start capacitor to start all three idlers. Or you could just use the
three phase output from the first idler to start the others, which would
avoid some complex wiring. If your convertor uses run capacitors as
well, you'll need one for each of the idlers.

It would be really neat if you could figure out a system for starting
the extra idlers when they were needed. Perhaps you could use a system
of current or voltage relays to sense the load on the convertor and
switch in extra idlers as needed? I haven't thought out the details of
it yet, though.

One final point: try to get three identical motors if you can. It is
bound to make your convertor neater.

Best wishes,

Chris

Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

As far as I can see it makes sense. If the idlers are always started at
separate times, you should be able to figure out a way of using the same
start capacitor to start all three idlers. Or you could just use the
three phase output from the first idler to start the others, which would
avoid some complex wiring. If your convertor uses run capacitors as
well, you'll need one for each of the idlers.

It would be really neat if you could figure out a system for starting
the extra idlers when they were needed. Perhaps you could use a system
of current or voltage relays to sense the load on the convertor and
switch in extra idlers as needed? I haven't thought out the details of
it yet, though.

One final point: try to get three identical motors if you can. It is
bound to make your convertor neater.

Best wishes,

Chris

very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

Does it make sense?


phase-a-matic claims it does. They state you can parallel rotary
phase converters for large loads.

Ignoramus11916 wrote:
It would be really neat if you could figure out a system for starting
the extra idlers when they were needed. Perhaps you could use a system
of current or voltage relays to sense the load on the convertor and
switch in extra idlers as needed? I haven't thought out the details of
it yet, though.


If I go this route, I will simply use a contactor for every extra
idler and regular light switches to control the contactors. It will be
wired so that extra idlers can be started only if the contactor for
the main idler is closed.

I would be tempted to make an intelligent phase convertor. It would be
neat, but I guess it would also be something to go wrong!

One final point: try to get three identical motors if you can. It is
bound to make your convertor neater.


I do not think that I can find matching used motors, but I suppose
that neatness will be only based on appearance.

I doubt using different motors will make much difference to the
performance of the phase convertor - after all, it is only an
approximation to a balanced three phase supply - but motors of the same
power rating can have noticeably different electrical characteristics.
The old fashioned cast iron motors operate at a much lower flux density
that modern TEFC motors. One effect of this is that they require bigger
start capacitors for the same horsepower rating.

If you can't find matching motors, try to find motors which of a similar
construction and run at the same speed. For example, try to get three
finned TEFC motors, or three big cast iron motors. Having three
identical motors might also make mounting easier.

Best wishes,

Chris

Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

i


It makes sense, but get the welder and use it with the one convertor you
have now before you make any decisions. I hooked up a 600 amp Lincoln
transformer welder to my 3hp phase convertor and it worked fine at low
settings, but I could tell the convertor was maxing out around (I guess)
180 amps. Your 10hp unit should certainly keep up with reasonable
welding requirements.

John

Additional idlers brought on line should have run capacitors for best
performance.

Bob Swinney
"Ignoramus11916" wrote in message
...
On Wed, 07 Sep 2005 19:25:02 -0400, JohnM wrote:
Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

i


It makes sense, but get the welder and use it with the one convertor you
have now before you make any decisions. I hooked up a 600 amp Lincoln
transformer welder to my 3hp phase convertor and it worked fine at low
settings, but I could tell the convertor was maxing out around (I guess)
180 amps. Your 10hp unit should certainly keep up with reasonable
welding requirements.

Thanks. That makes sense. I will try it with the existing RPC. I have
a 7.5 HP motor also, should be easy to "plug in" if necessary.

i

....
If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

I have done this extact thing for my 25 hp. Mazak lathe. I used a 15 hp and
a 20 hp. idler motor. The first motor starts with start caps. After the
start caps drop out, a delay timer (set to 3 seconds) brings in the second
motor. Has worked great for two years now.

Karl

Ignoramus965 wrote:
On Thu, 08 Sep 2005 10:16:34 GMT, Karl Townsend wrote:

...

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

I have done this extact thing for my 25 hp. Mazak lathe. I used a 15 hp and
a 20 hp. idler motor. The first motor starts with start caps. After the
start caps drop out, a delay timer (set to 3 seconds) brings in the second
motor. Has worked great for two years now.

Wow, a 25 hp lathe is huge! What are the dimensions of that thing?

Chris

Ignoramus965 wrote:
On Thu, 8 Sep 2005 11:47:07 +0000 (UTC), Christopher Tidy wrote:

Ignoramus965 wrote:

On Thu, 08 Sep 2005 10:16:34 GMT, Karl Townsend wrote:


...


If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

I have done this extact thing for my 25 hp. Mazak lathe. I used a 15 hp and
a 20 hp. idler motor. The first motor starts with start caps. After the
start caps drop out, a delay timer (set to 3 seconds) brings in the second
motor. Has worked great for two years now.

Wow, a 25 hp lathe is huge! What are the dimensions of that thing?


I saw it on his webpage, it is a real monster.

Cool. Do you have the address?

Chris

As with any RPC, multiple motor RPC's will exhibit sagging voltage as the
load is increased. Put enough of them on line and voltage drop may not be
an issue, the same as with single idler motor RPC's.

Bob Swinney
"Ignoramus11916" wrote in message
...
On Wed, 7 Sep 2005 22:59:29 -0500, Robert Swinney
wrote:
Additional idlers brought on line should have run capacitors for best
performance.

That's interesting and a little counterintuitive. That said, I do not
mind doing so if it is necessary.

i
Bob Swinney
"Ignoramus11916" wrote in message
...
On Wed, 07 Sep 2005 19:25:02 -0400, JohnM wrote:
Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase the
capacity of my RPC. My own thought is to add two more 10 HP idlers (at
very little cost). They would be switched on (if necessary), one after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

i


It makes sense, but get the welder and use it with the one convertor
you
have now before you make any decisions. I hooked up a 600 amp Lincoln
transformer welder to my 3hp phase convertor and it worked fine at low
settings, but I could tell the convertor was maxing out around (I
guess)
180 amps. Your 10hp unit should certainly keep up with reasonable
welding requirements.

Thanks. That makes sense. I will try it with the existing RPC. I have
a 7.5 HP motor also, should be easy to "plug in" if necessary.

i





--

Correct. Esp. if you are starting (additional) idlers after the first one,
as Karl has suggested.

Bob Swinney
"Ignoramus965" wrote in message
...
On Thu, 8 Sep 2005 08:12:27 -0500, Robert Swinney
wrote:
As with any RPC, multiple motor RPC's will exhibit sagging voltage as the
load is increased. Put enough of them on line and voltage drop may not
be
an issue, the same as with single idler motor RPC's.

Can I try to paraphrase what you said? A parallel motor RPC will work
as well as a single motor RPC. A parallel motor RPC would, however, be
easier to spin up than a RPC single motor whose horsepower is the same
as the sum of HPs of motors in the parallel RPCexample. Is that
correct?

i

Bob Swinney
"Ignoramus11916" wrote in message
...
On Wed, 7 Sep 2005 22:59:29 -0500, Robert Swinney
wrote:
Additional idlers brought on line should have run capacitors for best
performance.

That's interesting and a little counterintuitive. That said, I do not
mind doing so if it is necessary.

i
Bob Swinney
"Ignoramus11916" wrote in message
...
On Wed, 07 Sep 2005 19:25:02 -0400, JohnM wrote:
Ignoramus11916 wrote:
I have a rotary phase converter with a 10 HP idler.

If I was to run a serious 3 phase welder, I would need to increase
the
capacity of my RPC. My own thought is to add two more 10 HP idlers
(at
very little cost). They would be switched on (if necessary), one
after
another, after the first idler properly spins up. Once they are
running, I could turn on the load. That's better than one 30 HP
idler
because

1) They do not strain the breakers at startup
2) It would require a lot less starting capacitance
3) I could regulate how much idler power I am using

Does it make sense?

i


It makes sense, but get the welder and use it with the one convertor
you
have now before you make any decisions. I hooked up a 600 amp Lincoln
transformer welder to my 3hp phase convertor and it worked fine at
low
settings, but I could tell the convertor was maxing out around (I
guess)
180 amps. Your 10hp unit should certainly keep up with reasonable
welding requirements.

Thanks. That makes sense. I will try it with the existing RPC. I have
a 7.5 HP motor also, should be easy to "plug in" if necessary.

i









--

Wow, a 25 hp lathe is huge! What are the dimensions of that thing?

Mazak M4 22"x72" dual turrent CNC lathe.


I saw it on his webpage, it is a real monster.

Cool. Do you have the address?

I don't have a web page.


Karl

Robert Swinney wrote:
Correct. Esp. if you are starting (additional) idlers after the first one,
as Karl has suggested.

Bob Swinney
"Ignoramus965" wrote in message
...

On Thu, 8 Sep 2005 08:12:27 -0500, Robert Swinney
wrote:

As with any RPC, multiple motor RPC's will exhibit sagging voltage as the
load is increased. Put enough of them on line and voltage drop may not
be
an issue, the same as with single idler motor RPC's.

Can I try to paraphrase what you said? A parallel motor RPC will work
as well as a single motor RPC. A parallel motor RPC would, however, be
easier to spin up than a RPC single motor whose horsepower is the same
as the sum of HPs of motors in the parallel RPCexample. Is that
correct?

i

The downside of the parallel motor RPC is that three 10 hp motors will
take up more workshop space than one 30 hp motor. That is unless you do
something weird where you have one motor here, another motor here, etc.,
but that wouldn't be for me. I'd find it a pain if I ever wanted to move
to another workshop. A 30 hp motor is actually surprisingly compact -
think of a motor with roughly three times the volume of a 10 hp motor.

Chris

The upside is you can move three motors, the one bigger one maybe not.

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



Christopher Tidy wrote:
Robert Swinney wrote:

Correct. Esp. if you are starting (additional) idlers after the first
one, as Karl has suggested.

Bob Swinney
"Ignoramus965" wrote in message
...

On Thu, 8 Sep 2005 08:12:27 -0500, Robert Swinney
wrote:

As with any RPC, multiple motor RPC's will exhibit sagging voltage
as the
load is increased. Put enough of them on line and voltage drop may
not be
an issue, the same as with single idler motor RPC's.


Can I try to paraphrase what you said? A parallel motor RPC will work
as well as a single motor RPC. A parallel motor RPC would, however, be
easier to spin up than a RPC single motor whose horsepower is the same
as the sum of HPs of motors in the parallel RPCexample. Is that
correct?

i


The downside of the parallel motor RPC is that three 10 hp motors will
take up more workshop space than one 30 hp motor. That is unless you do
something weird where you have one motor here, another motor here, etc.,
but that wouldn't be for me. I'd find it a pain if I ever wanted to move
to another workshop. A 30 hp motor is actually surprisingly compact -
think of a motor with roughly three times the volume of a 10 hp motor.

Chris


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Martin H. Eastburn wrote:
The upside is you can move three motors, the one bigger one maybe not.

Igor doesn't seem to have much problem moving around big compressors and
stuff. He should be fine with a 30 hp motor :-D.

Chris

If that is the case, the large motor division of GE (IIRC) is north of Austin - they
had a longhorn steer in the front grass area of the plant. The motors required an
extra heavy rail line to the site, a very over sized metal building (NICE shop if we got the big bucks)
with a several hundred ton gantry crane. IIRC, they did the big electric motors for trains,
ships and other toys.

I think it was in economic straits about the time we moved - maybe it is up and going.

Martin
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



Christopher Tidy wrote:
Martin H. Eastburn wrote:

The upside is you can move three motors, the one bigger one maybe not.


Igor doesn't seem to have much problem moving around big compressors and
stuff. He should be fine with a 30 hp motor :-D.

Chris


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Martin H. Eastburn wrote:
If that is the case, the large motor division of GE (IIRC) is north of
Austin - they
had a longhorn steer in the front grass area of the plant. The motors
required an
extra heavy rail line to the site, a very over sized metal building
(NICE shop if we got the big bucks)
with a several hundred ton gantry crane. IIRC, they did the big
electric motors for trains,
ships and other toys.

I think it was in economic straits about the time we moved - maybe it is
up and going.

Christopher Tidy wrote:

Martin H. Eastburn wrote:

The upside is you can move three motors, the one bigger one maybe not.



Igor doesn't seem to have much problem moving around big compressors
and stuff. He should be fine with a 30 hp motor :-D.

Chris


That's Westinghouse.
All but vacant.
I wanted to run the lathe...
It could turn a complete locomotive.

Yes - I remember - it was in trouble - downturn soon after building and doing a tv special show...
Nice shop !

Martin
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



wws wrote:
Martin H. Eastburn wrote:

If that is the case, the large motor division of GE (IIRC) is north of
Austin - they
had a longhorn steer in the front grass area of the plant. The
motors required an
extra heavy rail line to the site, a very over sized metal building
(NICE shop if we got the big bucks)
with a several hundred ton gantry crane. IIRC, they did the big
electric motors for trains,
ships and other toys.

I think it was in economic straits about the time we moved - maybe it
is up and going.


Christopher Tidy wrote:

Martin H. Eastburn wrote:

The upside is you can move three motors, the one bigger one maybe not.




Igor doesn't seem to have much problem moving around big compressors
and stuff. He should be fine with a 30 hp motor :-D.

Chris


That's Westinghouse.
All but vacant.
I wanted to run the lathe...
It could turn a complete locomotive.

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----