Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Mechanical & Electrical

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 10-13-2010, 07:28 PM
dubby's Avatar
dubby dubby is offline
Director: Apprentice Gatekeeper
 
Join Date: Apr 2006
Location: Lubbock, TX
Posts: 9,441
Default Determining just how much RPC is needed...

I took my questions to the local RPC expert today, a fine gentleman who has much experience and has even built his own... He said ask you guys . We had fun talking about it though


I've only got about half the needed information so I am hoping someone can come along and fill in the blanks as to how to figure out how much of a rotary phase converter is needed, how much is overkill, and if multiples are better than singles.

What we're looking at is a shop which will house various pieces of 3-phase equipment serviced by a 200amp panel. This is shared service, so it is possible that both sides could be pulling a lot of juice at once and neither side really know about it. The main equipment will be the Haas VF2 CNC machine, compressor, and supporting devices. Others in the shop will be a bridgeport, possible bandsaw and cutoff saw. I'm sketchy on what will actually be single and what will be 3ph.

Now, the CNC I know is a 30hp motor, and I'd heard it's ideal to have 30-50% more RPC than the highest rated tool. I'm not certain on the Bridgeport but cutter went out on a limb to assume 1.5-2hp.

The owner originally had planned a 50hp converter, but has now been told to change to two 40hp units instead. The reasoning again I'm unsure of, but could only guess that the CNC needs a dedicated supply in case of voltage drops and to keep the cleanest, smoothest power possible going to the machine? I'm again unsure of the brand of RPC's being purchased, but most 40's seem to require a minimum 60amp, max 200amp breaker.

My questions are:
1) Would it be better to have a single converter handle all machines in the shop? Cheaper obviously, but having adequate power is more important.

2) Are we likely to have issues with only the 200amp service? What should we expect to realistically be able to run?

3) With added in shop lights, computers, various hand tools, compressors, etc. kicking on and off will that affect the performance of the CNC if there should be a sudden surge in usage on the line?


The feller has already ordered the equipment, so it's too late to do anything about it now. But since there is a good chance it could be my problem to resolve should it come up, I'd like to be ahead of the game when it comes time to get things running 'right' instead of 'right now'.
__________________
I've always had more time than money.

Wade's Custom Kydex
Reply With Quote
  #2  
Old 10-13-2010, 08:42 PM
Matt Shade's Avatar
Matt Shade Matt Shade is offline
Made From Scratch
 
Join Date: Jan 2007
Location: Ohio
Posts: 2,762
Default

What voltage is that 200 amp panel? I think that will be the determining factor on what you can run. Even if it is 480, I think you will wish it was bigger.
I don't know much of anything about sizing RPC's but I worked in a cabinet shop doing equipment maintenance and operating machines. We had a 16hp CNC router with a 5x10' vacuum table that was fed with a 40hp rotary screw pump. I seem to recall both of these machines drawing in the neighborhood of 100 amps at 480v. The router may have only had a 16hp spindle but you also have to account for all 3 axis motors, cooling fans and all that. I would expect your mill to be the same situation.

The router was somewhat touchy about power, it had an older control panel that was prone to freezing. Also had a large internal variable frequency drive that did burn up at one point, but we never figured out why. We never tried running it during thunderstorms.
The edgebander was also CNC and was much newer. It has a windows based operating system and seemed to be less touchy, but occasionally required a reboot. Never really linked it to a particular cause though.
__________________
Handcrafted Leather
Reply With Quote
  #3  
Old 10-13-2010, 09:11 PM
dubby's Avatar
dubby dubby is offline
Director: Apprentice Gatekeeper
 
Join Date: Apr 2006
Location: Lubbock, TX
Posts: 9,441
Default

I hadn't even taken any voltage into my figurings yet. I thought amp draw would be the first thing to come into play. It is kinda out in the boonies, so it very well may have voltage limitations as well.

Thunderstorms, high wind, and hurricanes are good factors to consider and I'm glad you put them in my mind.
__________________
I've always had more time than money.

Wade's Custom Kydex
Reply With Quote
  #4  
Old 10-13-2010, 11:55 PM
terry lingle's Avatar
terry lingle terry lingle is offline
Something's Fishy ...
 
Join Date: Aug 2004
Location: Birch Island, BC, Canada
Posts: 5,352
Default

Since this is about an RPC the panel voltage is either 208 (good) or 240 (Bad).
208 is a three phase voltage and means that three phase is close by 240 is standard single phase and means no easy fix.

200 amps 240 volts is about 64 hp max input to the panel.

Subtract for lighting and other loads then derate for operating losses and you have a max actual running load of about 45 hp available.
that is probably enough to run 75 to 100 connected hp as only seldom will a motor run at rated output.

For the CNC machine I would want a dedicated RPC rated at least 35% above the CNC machines HP because the controller in that machine will demand compliance from the machine and the power must be available or it will not work.

For the rest of the shop a 40 hp unit will run a lot of machines and if set up correctly (sequenced) can use the running loads as part of the RPC to start larger loads. The limit here is that you quickly exceed that 200 amp supply and it gets dark in the shop.

You will note that the sum of the two will exceed the available hp from the supply. This will ensure good starting performance and smooth operation.

You will also note that when running that CNC machine will dominate the available supply.

Add a couple of manual machines and the compressor at the same time and you get close to tripping the main breaker.
__________________
Life beats the alternative hands down.
Reply With Quote
  #5  
Old 10-14-2010, 05:42 AM
Matt Shade's Avatar
Matt Shade Matt Shade is offline
Made From Scratch
 
Join Date: Jan 2007
Location: Ohio
Posts: 2,762
Default

Quote:
Originally Posted by dubby View Post
I hadn't even taken any voltage into my figurings yet. I thought amp draw would be the first thing to come into play. It is kinda out in the boonies, so it very well may have voltage limitations as well.

Thunderstorms, high wind, and hurricanes are good factors to consider and I'm glad you put them in my mind.
Voltage dictates amp draw. Figure 1 hp at 746 watts, that makes a 30hp mill a minimum of 22380 watts. At 480V that requires 46.625 amps, at 208v you pull 107.6 amps. And I really think you will find its much higher due to all the servos and electronics running along with the sprindle.

You also may find that you need a step up transformer if you only have 208 or 240 available, as many large industrial machines require 480. I suppose there may have been an option when ordering, but the machines we had didn't have taps for multiple voltage like small equipment does.
__________________
Handcrafted Leather
Reply With Quote
  #6  
Old 10-14-2010, 06:55 AM
precisionworks's Avatar
precisionworks precisionworks is offline
American Tools Keep Americans Working
 
Join Date: Oct 2005
Location: Benton, IL
Posts: 3,177
Default

You may want to phone tech support at Phase-A-Matic and see what they recommend. PAM has been making RPC's since 1965 and makes the best unit in the business, IMO.

For hard starting machinery, like a gear head lathe without clutch (think Asian) the rule of thumb is 300% of motor hp. Easy starting loads require a minimum on 150% of motor hp.

Talk with PAM & they'll provide solid recommendations. They'll need to know the hp of all the machines, including those with multiple motors, as well as the utility supplied voltage (which is most likely 240 volts since you're in the USA). The NC machinery will require tighter voltage regulation, and PAM offers both CNC converters & voltage stabilizers.

Sizing info.

CNC converter.

Voltage stabilizers.

If you need a second opinion, phone tech support at ARCO Electric. I'd rate their products almost as good as PAM, but their tech support is designed for an Electrical Engineer or PhD type person ... and tech support is critical when your about to spend thousands on these items. ARCO website.

Lots of other choices too, and some build a decent RPC, but no company does phase converters as well as Phase-A-Matic.
__________________
Barry Milton - Please email or PayPal through PrecisionWorks.co
PM's are disabled
Reply With Quote
  #7  
Old 10-14-2010, 10:22 AM
dubby's Avatar
dubby dubby is offline
Director: Apprentice Gatekeeper
 
Join Date: Apr 2006
Location: Lubbock, TX
Posts: 9,441
Default

Good info guys... so really there is a chance that we could be looking at a shortage at some point. Always looking forward to things bigger and better, adding a second or third CNC may be near impossible.

I guess if we end up having enough business to justify more machinery, a move would be in order to a better location if the power company can't get us where we'll need to be.
__________________
I've always had more time than money.

Wade's Custom Kydex
Reply With Quote
  #8  
Old 10-14-2010, 04:59 PM
precisionworks's Avatar
precisionworks precisionworks is offline
American Tools Keep Americans Working
 
Join Date: Oct 2005
Location: Benton, IL
Posts: 3,177
Default

Quote:
Are we likely to have issues with only the 200amp service? What should we expect to realistically be able to run?
One 200a service panel may not be enough, but that isn't a big problem. Ask your utility to drop a bigger service cable from their transformer, and have your electrician install a second, third or fourth 200a panel. Multiple panels are the least expensive way to provide power for multiple RPC's (if needed).

RPC's can be cascaded to provide any amount of power you'll ever need. 1000 hp or more can be run with multiple RPC's in cascade (see photo).
Attached Thumbnails
Click image for larger version

Name:	PAMmultiple1.jpg
Views:	108
Size:	40.8 KB
ID:	66839  
__________________
Barry Milton - Please email or PayPal through PrecisionWorks.co
PM's are disabled
Reply With Quote
  #9  
Old 10-14-2010, 07:14 PM
dubby's Avatar
dubby dubby is offline
Director: Apprentice Gatekeeper
 
Join Date: Apr 2006
Location: Lubbock, TX
Posts: 9,441
Default

So through cascading, two 40's would provide more output than a single 50 if I'm seeing that right? How do the RPC's affect the amperage being drawn from the panel?
__________________
I've always had more time than money.

Wade's Custom Kydex
Reply With Quote
  #10  
Old 10-14-2010, 09:54 PM
precisionworks's Avatar
precisionworks precisionworks is offline
American Tools Keep Americans Working
 
Join Date: Oct 2005
Location: Benton, IL
Posts: 3,177
Default

Quote:
two 40's would provide more output than a single 50
Exactly

Another advantage is that the first 40hp can be started (with less draw than a 50), and that 40 is used to start the second 40.

Quote:
How do the RPC's affect the amperage being drawn from the panel?
To figure that:

Add together the total three-phase amperage (running load amperage) the machines can possibly draw. Usually shown on the machine as FLA (full load amps).

Multiply that number by 1.5 (extra single-phase needed to generate the third leg)

Add the idle current of the RPC.

Size the single phase breaker at 125% of that number, and select the wire size to carry that amperage.

Example:

Maximum full load amps is 48 (total of 20hp)

48 x 1.5 = 72 amps

72 + 13 (idle current of the PAM R-40) = 85 amps

85 x 125% = 106 amps

Install a 100 amp breaker and you should be OK, as (most likely) you will not have all the motors drawing FLA at the same time.

Phase-A-Matic says that if you plan to run the R-40 at absolute maximum output, you'll need a 250 amp single phase supply. It all depends on how you plan to use the machines, how many are running at the same time, how lightly loaded or heavily loaded they are, etc. It's worth a phone call to PAM to discuss your needs with an applications engineer.
__________________
Barry Milton - Please email or PayPal through PrecisionWorks.co
PM's are disabled
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 10:15 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.