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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
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me too....
thanks, Ron "Stephen Young" stephenjayyoung@netscapedotnet wrote in message ... Jim Stewart wrote: Asp3211968 wrote: i am looking to buy a vfd. i do not need a fancy box just the guts what would be a good place to start I know where you can get new older model Hitachi 1hp units for a little over $100 shipped. I have one each on my lathe and mill and am quite happy with them. If anyone wants the information, let me know and I'll dig it up and post it. I'm interested... |
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David Heidary wrote:
What is a vfd?? Volunteer Fire Department Variable Frequency Drive I'm too tired to explain. Maybe Gary C. will write you an epistle on the subject (: |
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if anybody is looking for a new vfd reasonably priced, try
www.automationdirect.com they have great deals on industrial controls in general "Asp3211968" wrote in message ... i am looking to buy a vfd. i do not need a fancy box just the guts what would be a good place to start |
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#5
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![]() Gary Coffman wrote: Note that since VFDs above about 3 hp are not designed to be run from 1 ph power, you may need to modify them to work that way, as well as also derating them. Usually this means defeating a phase loss detector in the VFD which shuts it down when a missing input phase is detected. I'm sure there are VFDs that have this feature, but I haven't run into one yet. I have run a number of VFDs from single phase, and never had any trouble with it. Defeating this circuit can be simple, difficult, or essentially impossible, depending on the design of the particular VFD. You're somewhat on your own here because you're using the VFD in a way for which it wasn't designed. Note also that high power VFDs, greater than about 3 hp, start getting expensive. If you just need to make 3 ph from 1 ph power, a home made rotary converter will be much less expensive in the higher power ranges. New, straight from the distributor, yes, they are quite expensive. But, new units that are last year's model or overstock are plentiful, and can be found on eBay all the time. I'm currently facing that dilemma. My new lathe is 7.5 hp 3 ph. That means I'll need a 11.25 hp VFD to run it on single phase. Since that's not a standard size, I have to go up to a 15 hp VFD. That's $929 from Dealer's Electric. Then I have to hope I can fool its phase loss detector into letting it run off of 1 ph power. Well, you really don't need one that big, unless you really plan on running the lathe at full power for an extended time. 7.5 Hp is a lot! Jon |
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On Thu, 10 Jul 2003 06:47:54 -0400, Brian Lawson wrote:
Hey Gary, Nice little treatise on the VFD versus rotary convertor. Thanks. Does anyone know what the IDLING current draw is for a rotary where the idler motor is in the ranges you speak of, typically 5 to 15 HP? My lathe motor is 5HP , so I expect I'll be needing a 7.5 HP rotary convertor idler motor, but it turns out a 15 HP wound rotor may be more readily available to me. I've wondered about which way to go for long term economy. My hope for the proposed new shop is that if I go rotary, that I'll "power up" the convertor sometime in the early part of the day, and it will run for hopefully 5 or 6 hours on a regular basis. I can see this helping a bit to heat the shop in the winter, but cost even more to cool it in the summer, but I'm wondering just about the costs of operating it. And so my question is, can anyone give us the amperage on their particular 220/240 line feeding their particular rotary when there is no "machine" operating from it? And some details as to what sizes everything is? Just knowing the current won't tell you the power. That's because at idle most of the current is reactive, ie the power factor is far from one. The easiest way to know the actual energy consumption at idle is to watch the watt-hour meter with everything off but the rotary. In other words, see how much the reading changes after an hour with nothing running but the idler. I think you'll be surprised at how little energy is consumed. System losses are mainly due to windage, bearing losses, and resistance losses of the wiring. Windage (air drag) is typically the largest loss. Using the lowest speed motor you can find will minimize this. Gary |
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Bryan
I have a 15hp idler running thru a 40 amp breaker. Idling it draws; L1=18 Amps L2=21 amps L3=23 amps After starting the 12.5hp motor on my harrison the amps won't change by more than an amp or so. Contact me privately if I can be of any help. John Normile jnormile (at) cswnet.com On Thu, 10 Jul 2003 06:47:54 -0400, Brian Lawson wrote: Does anyone know what the IDLING current draw is for a rotary where the idler motor is in the ranges you speak of, typically 5 to 15 HP? My lathe motor is 5HP , so I expect I'll be needing a 7.5 HP rotary convertor idler motor, but it turns out a 15 HP wound rotor may be more readily available to me. I've wondered about which way to go for long term economy. My hope for the proposed new shop is that if I go rotary, that I'll "power up" the convertor sometime in the early part of the day, and it will run for hopefully 5 or 6 hours on a regular basis. I can see this helping a bit to heat the shop in the winter, but cost even more to cool it in the summer, but I'm wondering just about the costs of operating it. And so my question is, can anyone give us the amperage on their particular 220/240 line feeding their particular rotary when there is no "machine" operating from it? And some details as to what sizes everything is? TIA. Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |
#8
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On Wed, 09 Jul 2003 11:00:58 -0700, Jim Stewart
wrote: Asp3211968 wrote: i am looking to buy a vfd. i do not need a fancy box just the guts what would be a good place to start I know where you can get new older model Hitachi 1hp units for a little over $100 shipped. I have one each on my lathe and mill and am quite happy with them. If anyone wants the information, let me know and I'll dig it up and post it. Please post it. Gunner Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli |
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