On Wed, 27 Jul 2005 13:42:02 GMT, Ignoramus23077
wrote:

SO, today I visited this junk yard called Pioneer Industrial Services.

Here's what I bought:

1. 10 HP Century 230/460V 3 phase motor, clean looking: $40

A nice surprise about this motor is that it is not that heavy, perhaps
150-180 lbs. I can handle it alone.

2. 7.5 HP U.S. Electrical Motors motor, dirty looking: $20

Both motors spin freely.

3. Five 92 mF 500+ volt oil filled run capacitors, each the size of a
vodka bottle, no PCB: $5 for all five. The owner did not know what
they were, I pretended that I did not know either. I said, these
pieces look interesting, I will give you $5 for them, maybe I will use
them for something.

4. A big Square D safety disconnect, $8

5. A contactor, possibly wrong for the application, $3

The guy is actually nice and pleasant and sensible. I also dropped off
a huge transformer that I could not get rid of otherwise.

My plans are as follows: I will make a self starting rotary phase
converter, as outlined in

http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

(see "Self Starting Phase Converter")

I will use 3 of my 92 mF capacitors, connected in parallel, between
leg 1 and leg 3 of the 10 hp idler, if I use a 10 HP idler.

I will create a web page about this project.

I have a question, is there some convention about leg numbering and
direction of the rotation of motor shafts? I do not want things to
rotate backwards and I want to do that in some conventional manner.

I really liked that junk yard, I will definitely go there again.

i
It makes no difference which way the RPC turns. And you can buy meters
which will tell you the direction of rotation by spinning the motor by
hand. But it really doesn't matter for most equipment. As each new
machine is hooked up turn it on momentarily and see if it turns the
right direction. If not, swap any two wires and it will spin
correctly. The only thing I do is to make sure I know which wire is
the manufactured leg at each machine. Some CNC equipment, especially
older equipment, can only tolerate the different voltage on one
particular leg. Fanuc controls can be this way. So you may need to
experiment. All that usually happens is that the machine will not
start. Manual machines with reversing switches work by swapping two
legs of the incoming power anyway so hooking up the machine and just
applying power momentarily should not cause any damage.
ERS

On Wed, 27 Jul 2005 07:27:32 -0700, Eric R Snow
wrote:

The only thing I do is to make sure I know which wire is
the manufactured leg at each machine. Some CNC equipment, especially
older equipment, can only tolerate the different voltage on one
particular leg


Typically L1. Not always..but typically.

Gunner


"This device is provided without warranty of any kind as to reliability,
accuracy, existence or otherwise or fitness for any particular purpose
and Bioalchemic Products specifically does not warrant, guarantee,
imply or make any representations as to its merchantability for any
particular purpose and furthermore shall have no liability for or
responsibility to you or any other person, entity or deity with respect
to any loss or damage whatsoever caused by this device or object or by
any attempts to destroy it by hammering it against a wall or dropping it
into a deep well or any other means whatsoever and moreover asserts
that you indicate your acceptance of this agreement or any other
agreement that may he substituted at any time by coming within
five miles of the product or observing it through large telescopes or
by any other means because you are such an easily cowed moron
who will happily accept arrogant and unilateral conditions on a piece
of highly priced garbage that you would not dream of accepting on a
bag of dog biscuits and is used solely at your own risk.'

....
The only thing I do is to make sure I know which wire is
the manufactured leg at each machine. Some CNC equipment, especially
older equipment, can only tolerate the different voltage on one
particular leg


Typically L1. Not always..but typically.

Gunner
....

Now I know I'm not typical. I've redone a whopping three machines where this
mattered. All three had the wild leg on L2.

Karl

Iggy sez:

"I will use 3 of my 92 mF capacitors, connected in parallel, between
leg 1 and leg 3 of the 10 hp idler, if I use a 10 HP idler."

That would be about right for a 10HP idler motor unbalanced RPC. It is
close to the rule of thumb for 30 uFd per HP. It will probably make you a
fine RPC. Now, here is where a problem may occur:

You specified a "Hanrahan" Self-starting RPC. It is unlikely a 10 HP motor
will start reliably - i.e., without excessively long spin-up time drawing
heavy current and popping breakers, etc. IMO, you will need to include a
capacitor start circuit. It doesn't have to be elaborate with voltage
sensing relays, or such. Between the same line side and 3rd leg where the
run capacitance is connected, connect a momentary push button and some
electrolytic (start) caps. You will need in the neighborhood of 700 - 800
uFd. I would suggest trying 1 of the 270 - 324 uFd nom., start caps as sold
by Grainger. That would give you around 600 uFd counting the 3 92's of run
cap you have connected. If that isn't enough to start in less than 1 second
spin-up time, increase the amount of electrolytics. Never leave this type
of RPC unattended. In the event of power failure, when power is restored,
the motor would be attempting to start with insufficient start capacitance
and might burn up and/or cause a fire.

Be careful, the voltages involved can be lethal.

Bob Swinney