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RPC + machine current INTAKE??

JunkyardJ

Titanium
Joined
Oct 30, 2007
Location
Howell Mi
How much juice does your RPC draw LOADED with a machine running from the single phase input side. I'm talking ACTUAL MEASURED CURRENT using a clamp on ammeter (or better measurement if you have it). Output current would also be helpful, current drawn from the RPC by the machine. Your particular RPC design particulars would help too. Starting current would be helpful too, but not really what I'm after because I'm going with a pony motor.

I know 3 phase motors draw a LOT when starting using caps from single phase, which is why I'm going to a pony motor design. Before I go off and buy a bunch of expensive stuff, I'd like to know if I can get away with what I have for a cheapo RPC. I KNOW this isn't going to be up to the standards some of you have for doing things right, but keep in mind, this IS NOT going to be fully loaded. I'm going with an idler that's OVERKILL because there doesn't seem to be much of a penalty for idle current based on motor size. I HOPE I can get away with firing up my welder using a 20hp idler on the existing 50 amp breaker with 6ga wire. I know somebody gave a number of 1.73 x 3 phase current for single phase, but that seems a bit high. Probably about right for the size of the breaker though, so it can account for starting current and whatnot. 1.73 x 32 is 55.36 amps, which would be the MAX of what my welder would draw wide open IF that formula is correct. EVENTUALLY, I plan on wiring it all up right, just curious what the actual numbers are here. :cheers:
 
So, I'm not trying to be a PIA, just bracing you for whats to come, and maybe, just maybe helping?

Have you ever clamped your welder while welding, or cracked open the cover? Is it really pulling 3 phase? I know many do, but just as many do not. I've seen oodles of Millers that only ran on single phase. Some only use it for the wire feed, some used all 3 all the time. I've also had "family members" ruin some of grandpas nice wire feeds by reversing the phasing. (oops)

Just trying to save you a few more bucks. ;)

Doug S.
 
Look at my other thread about the welder.

I'm SURE it's 3 phase. It's an ODDBALL old lincoln dynamotor contraption. It uses a 3 PHASE MOTOR to drive a DC generator. It's probably made in the '40s. :cheers:
 
1.73 is the correct conversion factor from one phase to three phase for full load amps. if you take a look at a 5hp three phase motor at 1750rpm, the FLA would be around 14amps at 230vac...now if you look at a single phase motor with the same spec's, the FLA would be around 25amps. The conversion factor does not take into account the current draw from RPC. Since a RPC is not 100% efficient, it will also draw some amps on the single phase side ( but this number would be very low ).
I know what I am going to say, alot of guys will not like to hear...but you can run this generator type welder from a static converter. As there is really no heavy startup load, but you would need to derate the welder to about 66%. A RPC will give you about 100% on the welder.
 
We've got one of these at work and in the 35 years I've been there it's only been run on 240v 3ph and on 30a circuits, no problems. We use it for repair all over the shop and just plug it in to 30a drops. First of all you start it no load so it's just the inertia that needs to overcome and second very rarely will you use at the full 200a, ie full load. At least we don't. I would think your plan would work, although you might have to limit the max amp output to say 175. Thanks for the link I finally have a manual for it. Have had no troubles with it since I've been working there, and except for the wire welder it's the best one in the shop. Warren
 
Welcome to the forum weckelman!

I'm glad the manual helped you out. If you search Lincoln's website, there are a some more documents concerning that machine, like a parts list and whatnot. I meant to respond earlier, but our sump pump died, and right after that, our power went out :rolleyes5:. Been a kinda crappy day.
 
Went and picked up the motor for my RPC today.

It's a pretty much BRAND NEW century magnetek, looks like this one http://www.e-motorsonline.com/emotors/viewproduct_acm.php?catid=1&Pid=ACM01687 . It's not an elevator duty motor though, it's says continuous duty on it. That and the service factor is 1.15. Probably weighs about 200lbs, so at least I can pick it up by myself! I thought it was going to be one of those big cast iron frame beasts that weighs about 300lbs and that wouldn't be fun to move around without help. It draws 50 amps, spins 1795 rpm, and is allready wired for 230v. Should make a nice RPC! Need to get a pulley, I think the shaft is 1.25" or something. :cheers:
 








 
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