What's new
What's new

large pony start RPC

Grigg

Hot Rolled
Joined
Jun 25, 2007
Location
Lexington, VA
I've been using a 15HP idler to run my 15 HP Lodge & Shipley lathe for several years now.

Started out really simple.
Two pole manual disconnect switch for the incoming 220 and idler motor.
A light switch to start the 1/4 HP pony motor that's connected with a flat belt to the 15HP motor.
Did add capacitors to balance the voltage between the legs.

Now I'm moving to a different shop and in the process of moving the converter would like to improve on it and ensure it is wired in a safe manner.

At this point I have:
The idler motor, a 15HP 900 RPM Allis-Chalmers, mounted on a bracket up on the wall out of the way with the pony motor hinged below it.
To feed the converter can use up to a 200 amp breaker, converter is just on the other side of the wall from the power meter.
Large electrical cabinet to house all the converter stuff mounted directly above the panel box.
300 amp motor starter with no overload protection.
Conduit run to the shop to feed a 400 amp Square-D buss duct system to distribute and feed the machines.

Also have a simple but perhaps over complicated controller (depends on how you look at it) that should automate the starting of the converter, and allow it to be simply turned on from the shop, and leave the converter in the garage.
Once the momentary start push button is engaged the pony motor runs gradually spinning the idler motor up to speed, about 900 RPM. When running fast enough an optical tachometer senses the speed and engages the 300 amp motor starter putting power to the idler and buss duct, at the same time turning off the pony motor.
The stop button will disengage the 300 amp motor starter and also interrupt the startup controller, allowing the stop button to cancel the startup cycle if needed.

This converter will run the whole shop, something over 50HP if everything was run at once, obviously the limit as planned is a 15HP motor, possibly 30HP total.
In the future I may add another large idler if I need more power or pick up any larger machines, the wiring from the panel to the bus duct will handle 200 amps if needed.
Could also substitute the home made converter for a phase perfect digital one if I ever need or want to.

So, I think I can make it work, but how to do it safely?
Does the idler motor need to be fused for it's name plate amps? If a fuse blows should the motor starter disengage, and how?
What might I need to do or consider to pass the electrical inspection before I move in?

Thanks in advance for any input and suggestions,
Grigg
 
Grigg,

I can't technically comment on your setup other than the enclosures and the motor mounting look pretty slick and professional. There is a picture of a contactor in a enclosure with arrows noting 'IN' and 'OUT'.

I'm not sure what these mean, but keep in mind that the line side...the 'IN' side of an electrical device like a mag or starter or disconnect a always on top and the load..the 'OUT' is on the bottom.

Those notations might just be for the flow of the wiring, huh.

Stuart
 
Hi Stuart,
I checked the notations on the contactor, the top is marked T1,T2,T3 and the bottom is marked L1,L2,L3, so I think that is right already.
If it's not right it does look pretty symmetrical top to bottom, does it matter??

Thanks,
Grigg
 
Grigg,

Being only a contactor, it would make no electrical difference which side was line and which was load. If that's how the device is labeled, far be it for me to correct them.

When an electrician sticks his paws into an enclosure, he is usually looking for line voltage on the top of the device and the switched load on the bottom.

It would be possible for someone to test the top leads, find them dead and assume the device was disconnected, when in reality it was live on the bottom.

It looks like that is an ABB contactor...I'm not an electrician so maybe I don't understand all I think I know!:)

Stuart
 
So, I think I can make it work, but how to do it safely?
Does the idler motor need to be fused for it's name plate amps? If a fuse blows should the motor starter disengage, and how?
What might I need to do or consider to pass the electrical inspection before I move in?

Thanks in advance for any input and suggestions,
Grigg[/QUOTE]

The job you did looks pretty neat. You are routing your power to machines
up out of the control box. Not the conventional direction but if you have
everything marked it might be ok. The electrical code changes every year, so
some that passes today might not tomorrow. It may not be a bad idea to get
a real good electrical guy to survey what you are about to do and pay him
for 1/2 to 1 hour of his time. Some of these guys like to look at good work.
He night even give you a few ideas on how to do something better.

A fuse block for your motor is not a bad idea. Whenever a fuse goes at my
place there is always a reason. I have a few TIME-LAGE fuses with renewable
elements (FORM AS2R). They are made in Japan. The end caps are made of
brass and unscrew. When a fuse blows you just unscrew the end cap and put
in another element.
 
The job you did looks pretty neat. You are routing your power to machines
up out of the control box. Not the conventional direction but if you have
everything marked it might be ok. The electrical code changes every year, so
some that passes today might not tomorrow. It may not be a bad idea to get
a real good electrical guy to survey what you are about to do and pay him
for 1/2 to 1 hour of his time. Some of these guys like to look at good work.
He night even give you a few ideas on how to do something better.

Thanks,
I already have a good electrician on board, he's doing much of the work.
As far as the rules go there doesn't seem to be any problem with letting the power flow up and over to the machines. The other two boxes on the lower right are disconnects for two other panel boxes elsewhere in the shop/house, both have power coming in the back and out the top.

I've read through these papers and plans that I gathered from this forum, and forwarded them to the electrician.
This one covers the why and how better than most.
http://www.metalwebnews.com/howto/phase-converter/phaseconverter2.pdf
This one has a diagram very similar to what I would like to use.
http://www.paragoncode.com/shop/rotary_converter/
This one shows a capacitor start converter instead of the pony motor, but the writeup is helpful and explains how to add capacitors.
http://www.practicalmachinist.com/FitchWConverter.pdf

No doubt y'all have already read them too..

I don't think any of them address fuses and such that may or may not be necessary??

Really I come here for advice to try and keep this reasonably simple while still "passing code", which I think means; how can I do this safely and simply by using common sense?

I think without some good suggestions and info from me on how this works and how to make it safe it could get complicated and even more expensive. I trust the electrician to do his job, but if I know what I'm talking about too that job may be simpler.
Next time we'll both know what to do, but this time we're both learning a little.

I'm meeting with the electrician tomorrow at 1:00 to go over the converter again, I want to be prepared and try to understand what he says, and suggest some solutions too if needed.

Thanks,
Grigg
 
Talked to the electrician today,
We had a good discussion, he knows what's going on and we were already on the same page. Earlier I had some doubts but turns out it was just confusion and info lost in translation between him and me by way of his helpers..

For now the whole thing will be run off a 60 amp breaker, which protects the idler motor.
If in the future I add more idlers or a larger one I'll need to change that breaker, about 3' of wire, and add separate overload protection for the different idlers.

He also has a surplus phase monitor of some sort that can be used to turn off the main contactor if a phase is lost by either the power company or the converter. If it looks like it will work and is useful we'll use it.

This is exciting, can't wait to get it done and all the machines moved in,
Grigg
 
Talked to the electrician today,


He also has a surplus phase monitor of some sort that can be used to turn off the main contactor if a phase is lost by either the power company or the converter. If it looks like it will work and is useful we'll use it.

This is exciting, can't wait to get it done and all the machines moved in,
Grigg

You can avoid this if you get a 3 phase contactor with a adjustable overload
control which has integrated phase loss detection. They are quite nifty and
not that expensive. Most circuits I have seen do not have phase loss protection
and that means home-brew electricians get what they deserve when something
goes wrong. You are not one of those.
 
Have made a lot of progress on the converter off and on over the past several months. Have most of the shop up and running now.

Converter runs with a controller to allow one button start. Also have a remote start and stop button in the shop (converter in garage).

Still need to add capacitors to balance the legs.
Fine tune the controller, it has a couple hiccups but works fine if you (because I) understand them.

I'll take some pictures this evening of the mostly complete setup and the controller.

Still have a question on fuses. Right now the whole system is on a 50 (or is it 60?) amp breaker. Last time I had this idler set up as a converter we used a 90 amp breaker.
I can easily trip the breaker when starting the big lathe, and usually can get by with first starting the mill, then the lathe; not a permanent solution.
If I step up to a 90 amp breaker do I need to fuse the leads to/from the idler?
The system is sized for 200 amps all except the short leads from breaker to main contactor and the idler motor leads.

Using a buss duct setup after the converter to feed the machines, and fusing the drop boxes for each machine/load.

Grigg
 
Here are some pictures of it


Does anyone know of an off the shelf controller for a pony start phase converter?
The one I'm using is "home made" but we're considering making it a little more permanent, refine the design and have some printed circuit boards made up, which is surprisingly affordable even just for a couple.

Grigg
 
Check the NEC, Article 455, has the design and installation covered.
Thanks, here's one link still trying to find one I can print..
While I understand most of the words it appears to be written in a different language, anyone care to translate for "the average guy"
The calculations and examples given in article 455 are for a commercial phase converter with a "nameplate" this being a "home made" converter it only has the original motor name plate, are these the values to use or something different?

Grigg
 
The link from the email was for a code interpretation book, not the actual code.
Interpreting the National Electrical ... - Google Books

The code is even more difficult to read. I do not know of any simple "recipe" type code book. We all just have to struggle through it.

The code is available to read at many sites but you will not be able to print it due to copyright restrictions. You can also usually access the NEC at your local building codes department.
 
Your wiring and breaker seems underrated. My 20HP converter uses a 100A 2P breaker to feed it and 3ga wire on the primary side (as sized for 100A). On the secondary it's 6ga wire feeding a disconnect switch and main panel. I don't understand what the attraction of the pony start is vs just throwing the right capacitors in there to make it self starting. My converter self starts and runs when line voltage is put across it, so no controller and no interlocks to worry about.
 
Your wiring and breaker seems underrated.
...I don't understand what the attraction of the pony start is vs just throwing the right capacitors in there to make it self starting...
They are undersized. In the old shop I had a 90 amp breaker for the same converter.. I'll swap this one out and upgrade the wire from breaker to main contactor, just a couple feet so no big deal there. The wire after the main contactor feeding the buss way is adequate, I forget the size but good for 200 amps.

When I swap the feeder breaker I'd like to use a thermal overload relay on the idler motor.

I think to each his own on the capacitor start or pony motor. I've had three different capacitor start converters, and right now I like the pony start best. Even the 10 HP capacitor start would seriously dim the lights when starting, the 15 HP pony start fed from the same panel box hardly dims the lights. Not sure if that matters or not, but seems the better of the two choices to me. On the other hand for a small converter the capacitor start doesn't bother me.

Grigg
 
You can avoid this if you get a 3 phase contactor with a adjustable overload
control which has integrated phase loss detection
. They are quite nifty and
not that expensive. Most circuits I have seen do not have phase loss protection
and that means home-brew electricians get what they deserve when something
goes wrong. You are not one of those.
Can you point me in the right direction here, I'd like to learn more about these, and see some examples
I've searched for overload relays but haven't found one with the phase loss detection.
Don't need a whole contactor, just the overload part.

Thanks,
Grigg
 
I don't understand what the attraction of the pony start is vs just throwing the right capacitors in there to make it self starting. My converter self starts and runs when line voltage is put across it, so no controller and no interlocks to worry about.
Lower starting inrush current is the reason for using a pony start.

Most of the modern motor starters without overload heaters use a microprocessor to measure current and also phase loss.

Check for IEC contactors.
 
Lower starting inrush current is the reason for using a pony start.

Most of the modern motor starters without overload heaters use a microprocessor to measure current and also phase loss.

Check for IEC contactors.

What you describe is integrated into the overload block section on modern units.
A older starter starter can be used with the same type of protection, if not more,
if you add a three phase power monitor to your RPC. Over, under voltage, phase
loss and reversal are monitored. Good thing to have if the wild leg fuse on your
RPC opens and your tool motor is subjected to single phasing. The monitors are
the size of a small contactor.
 
What you describe is integrated into the overload block section on modern units.
A older starter starter can be used with the same type of protection, if not more,
if you add a three phase power monitor to your RPC. Over, under voltage, phase
loss and reversal are monitored. Good thing to have if the wild leg fuse on your
RPC opens and your tool motor is subjected to single phasing. The monitors are
the size of a small contactor.
Yup. The power monitors may work on an RPC app if they are set up correctly but they may not have wide enough tolerances to avoid nuisance tripping.
 








 
Back
Top