Im about ready to finish up my 10hp rotary converter (pony motor
start) and need a source and some info, for balanceing (run) caps.

My single phase 220 service tends to run right at 240 volts most of
the time. Im the only person on the transformer in the back 40.

During my test runs when it was bread boarded, I was getting :

L1 =240vac
L2 = 221vac
L3 = 197 vac

L3 is the wild leg.

Measurements from L1 as (common)

(going from my rapidly failing memory..sigh)

Im assuming Ill need about 150 MF between L1 and L3, and nearly the
same between L2 and L3, based on various posts here in the past.

Id not care much about the L1-L3 differnce if I were only running 3 ph
motors..but this thing was built to run a Airco PhaseArc 350 amp Mig
welder (3 phase) that Id rather not blow up. Ive run the Mig on the
breadboard for a little bit, beautiful spray transfer arc with .045
wire and CO2, but I dont want to strain it until it breaks. It would
be beucoups dollars to have it fixed..if parts can be found.


What increments of caps should I be looking for? Id assume that
getting a couple 150s and sticking them in is not a good idea, but a
handful of various ratings would be better in order to do a proper
balance? Id rather not buy 20 different (cant afford to, actually)
caps and futz around.
370 volt caps I assume, are proper?

And where do I scrounge them? Ive been checking Ebay with little
sucess, unless I want to fill the cap box with 12 mf caps..which could
get messy and expensive.

Hey Bruce B.....

Do you know if Apex would be a good source to check? Ive not been in
there in some time..and never did look for caps there.

And lastly...and most importantly...

how do I tell the difference between a run cap, and a start cap?
Start are generally not oil filled, and run are?

I have about 10 or so 17mf 600 volt steel can caps, but I suspect I
dont have anywhere close to enough capacitance for this purpose.

The rpc is pretty primative, being nothing more than a momentary
pushbutton started 1/2hp 3600 rpm motor wired 220, that spins up the
10hp 3600 rpm idler, at which time I close the Big Frankenstein Switch
to engage the power feeding the 10 hp motor. and release the momentary
switch running the pony. Transmission is via 1:1 pulleys I made, and a
V belt. To shut it down, I open the Big Switch (a 60 amp disconnect)

Id much rather had a 1725 rpm motor, just for the quieter
sound..shrug..but I didnt have one in my Stuff.

I already have a commercial 5 hp rotary, but it smoked (fortunatly
easily fixed) when I tried to run the welder on it. Shrug.

Thanks

Gunner


"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

I hate to disillusion you, but what you have there is not a rotary
converter, but a cobbleded up static converter.
It will still work, just won't stay balanced under varying loads.
The running caps are the big can type metal cans, 6-8" tall rated for
your PEAK voltage, not rms. You should have a bank of them with clip-on
jumpers to adjust the phase angle to get optimum balanced current &
voltage.
The inductor in a static converter normally has taps to vary the
inductance too. Your pony motor is a fixed inductance.
Bugs

In article , Gunner Asch says...

And lastly...and most importantly...

how do I tell the difference between a run cap, and a start cap?
Start are generally not oil filled, and run are?

Start capacitors are typically electrolytic and housed in plastic
covered cases. They give a lot of mfds per volume, but are only
momentary rated. They blow up if run continously.

Oil filled ones are used for run capacitors and are often found
in steel cans. Though as an electronics tech I can say that one
can find electrolytics with that form as well. I only mention
this as if you scrounge you might well come across some like
that. Folks who source from motor repair shops can pretty much
depend on the electrolytics being in insulated housings.

Often the oil-filled ones will say this, stamped on the side.

The 17 mfd 600 volt ones might be usefull during the tuning phase.

If based on the hanrahan site you will need about 150 then I would
dither that value in units of maybe 1/4 of 150, or so. Something
like 40 or 50 mfds per change.

Typically the voltages are listed as:

L1-L2

L2-L3

L3-L1

You had just L1, L2, L3 listed. But if you spec them by
pairs (because that's how you are measuring, one hot leg
to another) then it makes it clearer.

Peter Haas has a good diagram he

http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=3;t=001360;p=0

But notice that he calls the incoming line L1 and L2, the generated leg
(which I think you are calling the wild leg) he calls L3. I *think* that
is the convention in general, don't be confused by it.

So the balancing capacitors are C(1 to 3) and C(2 to 3). Power factor
correction is by C(1 to 2).

I take the belt off my pony motor once the thing's running.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Bugs wrote:
I hate to disillusion you, but what you have there is not a rotary
converter, but a cobbleded up static converter.

Gunner's phase converter includes a 10 hp idler motor with pony motor to spin it
up. In what sense is that static?

It will still work, just won't stay balanced under varying loads.
The running caps are the big can type metal cans, 6-8" tall rated for
your PEAK voltage, not rms. You should have a bank of them with clip-on
jumpers to adjust the phase angle to get optimum balanced current &
voltage.
The inductor in a static converter normally has taps to vary the
inductance too. Your pony motor is a fixed inductance.
Bugs

In article , Grant Erwin says...

Gunner's phase converter includes a 10 hp idler motor with pony motor to spin it
up. In what sense is that static?

Hmm. Lemme think.....

None.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article , Ignoramus11255 says...

Jim, can you help me clarify a power factor correction question?
Assuming wild leg == L3, I have caps on L1-L3 and L2-L3. That greatly
cuts down on vibration and humming noise. Just awesome. What I am
wondering about is whether I would cut down on stray currents (power
factor) if I added some capacitance on L1-L2. Which I could do,
although I am space limited.

That would be power factor correction if you did that.

You need to obtain and read the information provided in the
jim hanrahan paper, and also what fitch williams has written
on the subject.

Because I've not ever done this I think you should hear about
it from the experts.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 18 Dec 2005 05:16:30 -0800, "Bugs" wrote:

I hate to disillusion you, but what you have there is not a rotary
converter, but a cobbleded up static converter.

Really? Odd. All those links and all the discussions here have lead
me to believe its a RPC.

It will still work, just won't stay balanced under varying loads.
The running caps are the big can type metal cans, 6-8" tall rated for
your PEAK voltage, not rms. You should have a bank of them with clip-on
jumpers to adjust the phase angle to get optimum balanced current &
voltage.
The inductor in a static converter normally has taps to vary the
inductance too. Your pony motor is a fixed inductance.
Bugs

Good to know. My commercial and plainly marked Rotary Converter,
seems to be miss marked, and doesnt have any taps.

I wonder if I should sue the maker?

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

On Sun, 18 Dec 2005 11:45:52 GMT, Gunner Asch
wrote:

Do you know if Apex would be a good source to check? Ive not been in
there in some time..and never did look for caps there.

There are tons in the North corner inside the main store building -
remember, San Fernando Road runs on a diagonal. (Stupid surveyors
always taking the easy way out...)

Go in the front door, and hang to the left along the SF Road wall,
all the way to the wall (before the "Back Room" door) - that corner.
With the Variacs and Sola Ferroresonant transformers. There's also a
center aisle that has smaller values boxed up.

Now telling the oil filleds from the regular electrolytics will be a
bit of a challenge, unless you have some old reference catalogs handy
that tell you what series numbers you want.

And you might find some PCB oil-filled models in the pile, you don't
want those. I forget the year they officially eliminated PCBs, but it
was a few years between that and when they started marking the cases
"No PCB's" leaving a grey area where they were clean but not marked.
Then you get into translating date codes...

For the usual small values I just go over to Johnstone or Grainger.
The new ones are cheap enough, you know they're run caps because
they're marketed as such, and you know they'll last at least a few
years.

Apex is better for the really odd stuff they simply don't make
anymore, or that would be radically expensive if bought new.

I've had Apex quote a price on a few used parts that approached the
current new price of an in production item like a solenoid valve, and
had to pass - if I pay full price, I want a warranty too.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

On Sun, 18 Dec 2005 11:45:52 GMT, Gunner Asch
wrote:

SNIP
Do you know if Apex would be a good source to check? Ive not been in
there in some time..and never did look for caps there.

Hey Gunner,

A year ago now, but walk in and bear right, to the end of the big rack
along your left. Turn left (you should be able to see the door to the
"back-yard" directly ahead) and on the end faces of the second or
third rack, they were about knee to waist high. Oil filled for "run"
caps. They have some others too, but I forget where, and you want
oil-filled for running anyway, not electrolytics.

Take care.

Brian Lawson,
Bothwell, Ontario.

On Sun, 18 Dec 2005 15:20:58 -0500, Brian Lawson
wrote:

On Sun, 18 Dec 2005 11:45:52 GMT, Gunner Asch
wrote:

SNIP
Do you know if Apex would be a good source to check? Ive not been in
there in some time..and never did look for caps there.

Hey Gunner,

A year ago now, but walk in and bear right, to the end of the big rack
along your left. Turn left (you should be able to see the door to the
"back-yard" directly ahead) and on the end faces of the second or
third rack, they were about knee to waist high. Oil filled for "run"
caps. They have some others too, but I forget where, and you want
oil-filled for running anyway, not electrolytics.

Take care.

Brian Lawson,
Bothwell, Ontario.


Thanks Bruce and Brian.

Gunner

"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner

You need oil filled capacitors. They should be labeled NO PCBs. A new 100
uF run cap costs $11 on ebay, see item 7572846399. It is not that
much, although you may possibly need a few. My 10 HP motor is very
nice because it starts on just 184 uF between kegs 1-3.

By the way, I tried a capacitor between legs 1-2 (for power factor
correction and reduction of idle amps). It worked great and reduced
idle current from 15-17a to just 7 A. I am very happy.

1

On Sun, 18 Dec 2005 11:45:52 GMT, Gunner Asch
wrote:


And lastly...and most importantly...

how do I tell the difference between a run cap, and a start cap?
Start are generally not oil filled, and run are?


Although oilfilled capacitors are entirely suitable as run
capacitors they're mostly a historic overhang from the days when
paper dielectric and foil electrodes was the norm. The reason for
the oil filling was to impregnated minute residual voids in the
dielectric. In DC operation these are pretty innocuous but,under
AC stress, ionisation in unfilled voids eventually leads to
failure.

With modern capacitors, AC rated plastic film types are
both cheaper and smaller. These use metalised polyester or
polypropylene film. Because they are void free, oil filling is
unnecessary.

A useful source is power factor correction capacitors for
industrial fluorescent fittings. These are typically housed in
oval or cylindrical aluminium containers with tag connections.
An alternative construction is housed in a white or grey plastic
cylindrical plastic container usually with flexible flying leads
rather than tags. 40 uF units are readily available and, since
they're pretty small it's not difficult to parallel up to the
value you need. They will feel surprisingly light because very
little metal is used in the construction and will be marked with
the VAC working voltage.

Intermittent rated AC rated start capacitors are pretty
well always mounted in black cylindrical containers usually with
tag connections. Slightly heavier for their size than plastic
film and about three times as many uF per unit volume. Best
bought new from a motor supplier.

Jim