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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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Variable Freq. Drive?
Is there any way to use a VFD to control the speed of a single (1)
phase motor? thanks, joyful |
#3
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Variable Freq. Drive?
in a nutshell no.
wrote in message ups.com... Is there any way to use a VFD to control the speed of a single (1) phase motor? thanks, joyful |
#4
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Variable Freq. Drive?
Thanks Steve. That was a pretty small nut!
But isn't it possible to just use 1 phase of the VFD, disabling the start winding/mechanism of the motor, or would this ruin the drive? For and example, let's suppose I had a VFD rated at 3HP. If I used only one phase could I drive a 1HP motor? joyful |
#5
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Variable Freq. Drive?
Thanks Tim for your reply. I really appreciate it. I had asked
another question that got on another group somehow, and that was: Does anyone know where I can get info ON THE WEB that describes/shows pictures., etc. of how to wind/rewind a 3 PH motor? One person sent me to a small site that just gave electrical diagrams. I appreciate that but, I need to know the actual congfiguraton that the wire/s are wound in that stator. The reason I'm asking is because I'm trying to avoid building something that will do the job (namely: VFD) as I know I can't come near to the quality/reliability of VFD products already out there. It would also be helpful if I could see sketches of how the magnetic fields are represented at different degrees, but I guess that would be too much too ask. Reckon if I continue in this direction I'll just have to sit down at the drawing board and figure it out myself. Any other thoughts are welcome. thanks, joyful |
#6
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Variable Freq. Drive?
wrote:
Thanks Tim for your reply. I really appreciate it. I had asked another question that got on another group somehow, and that was: Does anyone know where I can get info ON THE WEB that describes/shows pictures., etc. of how to wind/rewind a 3 PH motor? One person sent me to a small site that just gave electrical diagrams. I appreciate that but, I need to know the actual congfiguraton that the wire/s are wound in that stator. The reason I'm asking is because I'm trying to avoid building something that will do the job (namely: VFD) as I know I can't come near to the quality/reliability of VFD products already out there. It would also be helpful if I could see sketches of how the magnetic fields are represented at different degrees, but I guess that would be too much too ask. Reckon if I continue in this direction I'll just have to sit down at the drawing board and figure it out myself. Any other thoughts are welcome. thanks, joyful I did a search on 'rewind motors how to' in altavista and got this: http://www.easa.com/mo/TN-pdfs/TN35-1000.pdf. If you want to rewind a motor into a 3-phase it'll have to have the right number of stator slots, and they'll have to be even around the circumference of the stator -- these are both things that you wouldn't be able to count on from a single phase motor. Frankly I think you could flip burgers and earn enough for a 3-phase 3HP motor before you could figure out how to rewind one on your own. Unless you want to know just to know, it's a losing proposition. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ |
#7
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Variable Freq. Drive?
According to :
Thanks Steve. That was a pretty small nut! But isn't it possible to just use 1 phase of the VFD, disabling the start winding/mechanism of the motor, or would this ruin the drive? It would not *start* the motor without the start winding, and the proper frequency for that start winding and capacitor. The motor needs that start winding to get started, since it does not have any other windings to make use of the other phases from the 3-phase output of the VFD. You might be able to set the VFD for 60 Hz, and spin the motor by hand just before switching on the VFD -- but this would be quite unsafe if you were trying to run any machine tool from the motor. For and example, let's suppose I had a VFD rated at 3HP. If I used only one phase could I drive a 1HP motor? You could *drive* it -- at close to the normal speed -- if you found some other way to get it started. But you probably could not get *useful* power out of it over the range of speeds that a real three-phase motor can do. At low speeds, it is very likely to stall easily. At high speeds, the slip might be excessive, and it might stall again. Note that VFDs normally start a three phase motor at a very low frequency (speed) and ramp it up to normal 60 Hz speed at a preset rate. Even if you left the start winding and capacitor connected, the values would be wrong until you got close to the standard 60 Hz output -- and by that time, you might have fried the start capacitor, as they are not made for long term operation. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#8
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Variable Freq. Drive?
Hi Tim,
Thanks again. The old motor I have is a 3 phase I fished out of the dump. And I agree that it's cheaper to buy one. But that is not why I'm doing this. I just want to under stand how the thing actually works. It's sorta like asking the climber why he wants to waste all his time and energy climbing that mountain. No doubt he will answer: "Because it's there". Well, it's good for my mind to have a puzzle to keep it active. This just happens to be the latest one. Thanks for the link. Don't know why google didn't offer this. Looks like I've got some studying to do. Have a good day, joyful |
#9
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Variable Freq. Drive?
Thanks Don. Looks like I better go find some other wheel to reinvent!
joyful |
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