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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
Hi,
I am going to make a phase converter similar to the two stage unit you have. One thing I have been unable to get a definitive answer on is sizing the ider starter (mag). So... running a 10HP ider off single phase, do you size the starter the same as if you were suppling it with 3 phase, or do you have to up size it as if you were suppling a 10HP single phase. Your set up is similar in that I what to start a 10HP idler with a size 2 starter (rated 15HP @ 230/3P or 7.5HP @ 230/1P) Any clear opinions on whether the size 2 is fine or undersized???? Thanks, Glen "Ignoramus29580" wrote in message .. . http://igor.chudov.com/projects/17.5-Phase-Converter/ I need to do a few extra things, like adding a pushbutton (which I do not have yet, I bought it on ebay yesterday), some crimpable butt splices and ring terminals, and preferably adding a second motor starter instead of a definite purpose contactor. The starter would add overload protection, which the 10 HP motor has but 7.5 HP motor does not yet. i |
#2
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
glensmith wrote:
Hi, I am going to make a phase converter similar to the two stage unit you have. One thing I have been unable to get a definitive answer on is sizing the ider starter (mag). So... running a 10HP ider off single phase, do you size the starter the same as if you were suppling it with 3 phase, or do you have to up size it as if you were suppling a 10HP single phase. Your set up is similar in that I what to start a 10HP idler with a size 2 starter (rated 15HP @ 230/3P or 7.5HP @ 230/1P) Any clear opinions on whether the size 2 is fine or undersized???? Hi Glen, You should size the starter for single phase as you have single phase entering the convertor. Presumably you have a starter with three sets of contacts, and you use two sets for single phase operation or three sets for three phase operation? The rating of the starter will be based on the current which the contacts can handle. For a single phase motor the equation giving the power in terms of line voltage V and line current I is: P = I * V For a three phase motor it is: P = 1.732 * I * V Given that I and V are the same in this case, one would expect the three phase power rating to be 15/1.732 = 8.6 hp. The manufacturer has obviously chosen a 7.5 hp, which is a nice round number. What machines do you plan to run from your convertor? Technically you should probably go for a larger starter, but if you're only going to run your convertor lightly loaded and don't insist on doing everything by the book, you'll probably get away with it. But if I was building the convertor myself I would go for a larger starter. Best wishes, Chris |
#3
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
Correction: one would expect the single phase power rating to be 8.6 hp.
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#4
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
Ignoramus4758 wrote:
snip I agree with your post, but I want to note that size 3 starters are very expensive, even used. In this case Glen should probably make his choice based on what he intends to run from the convertor. The size 2 should be fine for a 3 hp Bridgeport (say) but could be inadequate for a bad ass welder like yours :-). By the way, I like your pics of the new phase convertor. I missed the pictures when you first posted them, but just saw them now. Nice job. Chris |
#5
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
Hi,
The largest load will be a 10HP (+ 1HP feed motor) wide belt sander. It will have a heavy starting load due to the inerta of the steel rolls. I will also want to run a 3HP dust collector at the same time. The smallest load will be 1.5HP. So everything from 1.5 to 14HP at one time. For idlers I have a 15HP, a 10Hp, a 7.5, and a 5HPavailable. I believe (hoping!!) that I can get away with 15HP of idler. Have max of 60amp 240 single phase supply but I am going to try with 50amp first (much less work). Haven't decided whether a single 15HP would be the way to go or a 10/5 combo. (more complicated). Thanks, Glen "Christopher Tidy" wrote in message ... Ignoramus4758 wrote: snip I agree with your post, but I want to note that size 3 starters are very expensive, even used. In this case Glen should probably make his choice based on what he intends to run from the convertor. The size 2 should be fine for a 3 hp Bridgeport (say) but could be inadequate for a bad ass welder like yours :-). By the way, I like your pics of the new phase convertor. I missed the pictures when you first posted them, but just saw them now. Nice job. Chris |
#6
Posted to sci.engr.joining.welding,rec.crafts.metalworking
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Question on starter size
glensmith wrote:
Hi, The largest load will be a 10HP (+ 1HP feed motor) wide belt sander. It will have a heavy starting load due to the inerta of the steel rolls. I will also want to run a 3HP dust collector at the same time. The smallest load will be 1.5HP. So everything from 1.5 to 14HP at one time. In that case I would look for a larger starter. For idlers I have a 15HP, a 10Hp, a 7.5, and a 5HPavailable. I believe (hoping!!) that I can get away with 15HP of idler. Have max of 60amp 240 single phase supply but I am going to try with 50amp first (much less work). My guess is that you'll probably get away with a 15 hp idler if your convertor is well balanced. Don't take this as fact, though: ask Jerry Martes or Bob Swinney. They seem to be the phase convertor experts in this group. Of course you can also build a prototype phase convertor quickly, check that it does what you want, and then build a housing for it. Best wishes, Chris |
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