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Build thread: 30HP Balanced RPC/Pony Start

jonesturf

Cast Iron
Joined
Aug 4, 2012
Location
PA
Starting a new thread instead of continuing my other one. Thanks for everyones help so far. Sitting here watching the Super Bowl and trying to design my circuit. Have a couple of questions first and some specs.

30HP idler
Pony start
Have up to 200 Amps in the house but will try running this initially from a 100 amp feed in the garage.
Going to be used for a Hardinge Conquest 42 CNC lathe with a 10HP spindle. Might add my 1HP surface grinder to it later on but I'm not worried about it now.

1. Looking at contactors. Leaning towards a Size 4. Since I'm only applying 2 phases to the idler do I need a 3 phase contactor or is there a cheaper/simpler contactor like a single phase contactor I can use? I'm also having a hard time finding used ones that activate with 24 volt.

2. With the pony start do I need a potential relay?

Will hopefully have a circuit design up by tomorrow. Thanks
 
A 30 Hp is too much for your needs. I know its tempting to use what you already have but a 15 or 20 would be enough.

1. Most contactors have removable coils for AC voltages. You may have to buy the contactor and 24 coil separately.
You should get the 3 pole and a auxiliary contact for this type of hookup. The generated leg from the idler motor
is connected to the third set of contacts. The picture does not show the auxiliary set of points (a small little box)
that is attached to the contactor used for push button start/stop control.

DSC_0739.jpg

2. With a 15 Hp you won't need a pony motor.
If you did use the 30 Hp and a pony start motor, how are you going to disengage the drive belt?
 
I do also have two three phase servos drawing 7.6fla each. I had read previously it's best to go at least double if not triple for cnc. I know it's big...actually huge. I may source something else but now I want to see this thing run and nothing in my area for a fair price any smaller.

If I go pony I was going to let it free spin after the idler picks up until I go over and release it. Probably a hinge/lever of some sort to take the tension off or maybe a sliding base like on some 80/20 extrusions I have laying around.

Thanks for the pic. Didnt have time to finish my diagram tonight. What's the Agusta monitor do? Is that a worthy investment? I was considering put volt/amp led readouts on the panel for each phase.
 
Pic of servo tag.
27126fc50237bb7c7c650e43e9be5dbc.jpg
 
I notice now that says "stall" for amps. Is that different than fla? The other servo I had laying around didn't say it that way. Now I'm a little confused.
 
What's the Agusta monitor do? Is that a worthy investment? I was considering put volt/amp led readouts on the panel for each phase.
The Agastat continuously monitors phase voltage balance, under-voltage, phase loss, and phase reversal. Stops the the RPC on any of those.
This one cost $35. The part number is PMBLBSL. There is one on Ebay for $195, which is not worth it. You can do better.
I think a volt/amp read out is a waste of money sometimes, other times I want to build one. So I'm on the fence for the readout.

DSC_0803.jpg
 
A few thoughts. You don't need a size 4 contactor, a size 3 will do just fine. You may want to reconsider using 24 volts for the coil, the inrush coil burden is 1100 VA, at 24 volts that is 46 amps. The sealed burden is 85 VA or 3.5 amps. If you want to stay with 24 volts, I would use a relay and run the coil at line volts.

For simplicity, you might want to hard couple the pony to the main, just deenergize it.

Tom
 
I already got rid of the idea of using 24v. Just another thing I need in the box. Going for either a 110v or 220v coil. Going to be ordering parts tonight. Will let everyone know how it goes.
 
Here is my rough draft.

Do I really need the fuses before the CNC? I'm guessing it wouldn't hurt but I'm not sure if its redundant.

30hp RPC.jpg
 
That looks pretty clean. My only concern would be your indicator light should be picking up natural legs. The blue leg is generally reserved for wild/ generated. Any contactors there after should as well use the natural legs for a coil. Never run a generated leg to a coil.

It looks like you are switching the generated leg through that contactor. There's no need for that. Once the idler comes online, the distribution block has full voltage. That switching is kind of redundant.

Your Black line start circuit needs a hold contact jumping from your L1 distribution block to the line between the start button and the stop button. In this situation you would need another fuse. But, if you add one of the little snap on Control contacts. You can stick with one fuse.
 
Matt

First off thanks for the help before.

I figured I might get one with overload protection on it that's the only reason I did that but now looking at it it doesn't make sense to run it back through the contactor.

I will take a look at the switches again and update.

I just figured for the light it would show I would actually have the third leg going but again that's kind of silly with the meters.

TO

That makes sense. Was thinking maybe sense the cnc has a circuit breaker it wouldn't be needed.
 
I guess I should make both fuses the same before the contactor and after the caps on the way to the cnc?
 
Also I forgot to mention wire sizes I the drawing. I will update that as well. Do I need to stay the same wire size the whole way through, for example 2 ga, on the main lines or can I break some of that down until I get to the end? Seems like it would be hard to work with inside the box. Like three 6 GA for example as long as the amp ratings total what the larger wire would be?
 
Ya youre right. I was in a hurry and its my first time using Visio although its not very hard.

Quick question regarding overload protection on a contactor. I found a good deal on a size 4 contactor...a couple actually. One comes with a thermal overload relay attached and is adjustable up to 80A. It's a 3 phase contactor. Would it still work with the overload circuit in single phase? Is it benefical to have that even though I have everything fused? I was hoping to find something to protect the CNC equipment from overload and single phasing. Seems like it would be more approriate on its way out to the CNC versus before the idler. Thoughts?
 








 
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