GA,
it is my understanding that using a VFD with potentiometer, you can vary the speed much more infinitely, not only with gears, but also by adjust the frequency of electricity to the motor, correct?
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Pm 1340 Gt Vfd Question
- Thread starter spring5497
- Start date
GA,
it is my understanding that using a VFD with potentiometer, you can vary the speed much more infinitely, not only with gears, but also by adjust the frequency of electricity to the motor, correct?
Yes, that is correct.
Using a VFD with a 3PH motor accomplishes 2 things:
1) It allows you to run a 3PH motor from your single phase home electricity feed, and
2) It allows you to vary the Htz (cycles/second) electrical feed to the machine, to vary the speed of the motor.
Some notes on this:
The reason for a 3PH motor, as you probably have read, is to smooth out rotational torque. A single phase motor tends to have variations in rotational torque (jerking if you please, which are not noticeable most of the time)... this is due to the phase start-stop-start. With 3PH current, the phases overlap... so smooth rotational torque. When is this an issue... when running the lathe or mill at very low speeds... like threading. The difference between a rough finish and a smooth finish on larger threads... can be partly due to a single phase motor. Others have explained this in more detail.
The other note is on how slow and fast you can run the motor. While the VFD will take the motor down to a very low RPM, as well as wind it up to almost flying... the motor itself, if not rated for this behavior, will be damaged. A good rule of thumb is to keep the VFD feed between 45Htz to 75 Htz... given that 60 Htz is normal. Again, there are more thorough explanations in other posts at this forum.
For more thorough explanations... search through the PM threads for any thread that includes a VFD or setting up a new machine. Last time I did that search, I spent the entire evening reading... and I did not go back father than about a year and a half...
Sorry for the short explanations, need to run.
Best to you!
GA
It showed up as a video. I have to go do some yard work now, but in the evening, I will definitely look at that. Thank you.
Say, NoSquib, (does that mean you are 6+ feet and 200+ lbs ? or no squib in the sense shooters use the term, meaning bang every time?) have you ordered your lathe / mill yet ?
I am ready to do so (as soon as I get the spring chores done ... we are at 6500 feet and spring is just arriving here), and any specifics about what to order would be appreciated.
I have a project for the machines, of cource, but I ran across two new interesting tools that I can make with the machines. If you have any interest let me know. One is CO2 cooling, where we take advantage of sublimation of CO2 to deliver it as a gas, but take advantage of self re-solidification to deliver high density of CO2 as dry ice to the point of the heat source (none of this is my idea, by the way); And the second one is to make a RHVT, a cold/hot air gun from compressed air. Commercial guns are available, but it was invented in the 30's, patented in that time frame, and there is lots of research results published in other countries, even specific pressure and sizes of the parts to yield optimum cold air from a vortex which can then be separate cold from hot air. I am now at the stage of finding everything I can of what others have done. I would be glad to send you or post the recent interesting articles.
Anyone is welcome to join, since I am headed toward open-source (the source ideas are not mine to begin with ! ).
Say, NoSquib, (does that mean you are 6+ feet and 200+ lbs ? or no squib in the sense shooters use the term, meaning bang every time?) have you ordered your lathe / mill yet ?
I am ready to do so (as soon as I get the spring chores done ... we are at 6500 feet and spring is just arriving here), and any specifics about what to order would be appreciated.
I have a project for the machines, of cource, but I ran across two new interesting tools that I can make with the machines. If you have any interest let me know. One is CO2 cooling, where we take advantage of sublimation of CO2 to deliver it as a gas, but take advantage of self re-solidification to deliver high density of CO2 as dry ice to the point of the heat source (none of this is my idea, by the way); And the second one is to make a RHVT, a cold/hot air gun from compressed air. Commercial guns are available, but it was invented in the 30's, patented in that time frame, and there is lots of research results published in other countries, even specific pressure and sizes of the parts to yield optimum cold air from a vortex which can then be separate cold from hot air. I am now at the stage of finding everything I can of what others have done. I would be glad to send you or post the recent interesting articles.
Anyone is welcome to join, since I am headed toward open-source (the source ideas are not mine to begin with ! ).
The fan for the motor itself is critical for slow RPM. A separate fan at constant high speed would be best, instead of a fan that is tied to the shaft of the motor.
The potentiometer sends a voltage signal to the electronics that puts out a corresponding frequency to the motor.
I am thinking of ordering the 1340GT with a 3 phase motor, but WITH the regular gear box. That way, I think there are many more operational options, as in put it in low mechanical (geared) speed, and then further slow the motor from the nominal 1700 rpm to something slower.
JPH,
I have not yet ordered mine. I'm still in the study/research phase... Since stumbling across the PM line, it appears that it's quality is unparalleled for an import. I also am almost certainly going with the 1340, but have yet to rule out the 1440. I like that is has a large diameter spindle through hole and relatively short spindle width. Turning longer material set up either with an outboard or chucked spider will be much more accurate and secure. With the GS2 VFD, you (can if you so choose) have the VFD mounted in such a way that it will not be subject to everyday beat and bang, dust, etc, but you can have the control head conveniently located, with your cyclic rate visible as well as adjustable. With that easy at your fingertips, you can simply go to a 60Hz rate (ordinary rating for most 3 phase) and use the gears just like you would w/o the VFD. I've done countless hours of research and to date, that is the most bang (no pun intended) for your buck. I also am seriously contemplating the use of the braking resistor for safety reasons. Back in the day when running a line making precision production parts for an auto manufacturer, I have seen what can happen when things go sideways... Sometimes, you need things to stop like RIGHT NOW. Lol
I like the idea of a fan set up for maximum cooling when turning at lower speeds. In my research, I have learned that some (if not the majority) have experienced some higher motor temperatures when making deep cuts at lower cycle speeds, this may help with that?
I'm certainly not an electrician, I'm simply researching machines and setups that will best fit my needs in the future. I hope folks don't think I'm trying to hijack the OP, it is not my intention, I'm just trying to bring what I have found to the table in hopes of either confirmation or critique, who knows, maybe it will help someone else!?
PS. I'm not 6+ feet and 200. LOL Good eye, good sir!
I have not yet ordered mine. I'm still in the study/research phase... Since stumbling across the PM line, it appears that it's quality is unparalleled for an import. I also am almost certainly going with the 1340, but have yet to rule out the 1440. I like that is has a large diameter spindle through hole and relatively short spindle width. Turning longer material set up either with an outboard or chucked spider will be much more accurate and secure. With the GS2 VFD, you (can if you so choose) have the VFD mounted in such a way that it will not be subject to everyday beat and bang, dust, etc, but you can have the control head conveniently located, with your cyclic rate visible as well as adjustable. With that easy at your fingertips, you can simply go to a 60Hz rate (ordinary rating for most 3 phase) and use the gears just like you would w/o the VFD. I've done countless hours of research and to date, that is the most bang (no pun intended) for your buck. I also am seriously contemplating the use of the braking resistor for safety reasons. Back in the day when running a line making precision production parts for an auto manufacturer, I have seen what can happen when things go sideways... Sometimes, you need things to stop like RIGHT NOW. Lol
I like the idea of a fan set up for maximum cooling when turning at lower speeds. In my research, I have learned that some (if not the majority) have experienced some higher motor temperatures when making deep cuts at lower cycle speeds, this may help with that?
I'm certainly not an electrician, I'm simply researching machines and setups that will best fit my needs in the future. I hope folks don't think I'm trying to hijack the OP, it is not my intention, I'm just trying to bring what I have found to the table in hopes of either confirmation or critique, who knows, maybe it will help someone else!?
PS. I'm not 6+ feet and 200. LOL Good eye, good sir!
NoSquib, and others ...JPH,
I have not yet ordered mine. I'm still in the study/research phase... Since stumbling across the PM line, it appears that it's quality is unparalleled for an import. I also am almost certainly going with the 1340, but have yet to rule out the 1440. I like that is has a large diameter spindle through hole and relatively short spindle width. Turning longer material set up either with an outboard or chucked spider will be much more accurate and secure. With the GS2 VFD, you (can if you so choose) have the VFD mounted in such a way that it will not be subject to everyday beat and bang, dust, etc, but you can have the control head conveniently located, with your cyclic rate visible as well as adjustable. With that easy at your fingertips, you can simply go to a 60Hz rate (ordinary rating for most 3 phase) and use the gears just like you would w/o the VFD. I've done countless hours of research and to date, that is the most bang (no pun intended) for your buck. I also am seriously contemplating the use of the braking resistor for safety reasons. Back in the day when running a line making precision production parts for an auto manufacturer, I have seen what can happen when things go sideways... Sometimes, you need things to stop like RIGHT NOW. Lol
I like the idea of a fan set up for maximum cooling when turning at lower speeds. In my research, I have learned that some (if not the majority) have experienced some higher motor temperatures when making deep cuts at lower cycle speeds, this may help with that?
I'm certainly not an electrician, I'm simply researching machines and setups that will best fit my needs in the future. I hope folks don't think I'm trying to hijack the OP, it is not my intention, I'm just trying to bring what I have found to the table in hopes of either confirmation or critique, who knows, maybe it will help someone else!?
PS. I'm not 6+ feet and 200. LOL Good eye, good sir!
The braking resister absorbs the energy in the system, but as thing slow down, the voltages are less, and so less energy is absorbed. This is demonstrated on one of the youtube videos: It takes seconds ... I think it took 7 seconds for a lathe to stop using the braking resistor. It's on the web. Another guy on the web put a disk brake on his mini lathe. I am now going to go see if there is any discussion of a brake for the 1340.
I read somewhere on hobby-machinist recently (within the last week) two people talking about installing braking resistors. I wonder if they are will ing to post time it takes from some RPM to stop.
My apologies to the owner, moderator of this thread, if my postings ought to go elsewhere.
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I am putting a 50 ohm/500w braking resistor on my 1340GT and will use the programming of another member here to do a tw0-stage braking: Normal braking will be about 1 second, and this will be fine for the stock chuck at any speed and larger chucks like my PBA at slow speeds. When running my 8" chuck above 1000 rpm, I will engage the second braking algorithm which Mark as proven to stop the larger chuck in about 2-3 seconds.
I have a braking resistor to mount on mine also... a 35 ohm/500W.
As I understand (reading at this forum), one can stop the lathe in 1-2 seconds (maybe not with a big heavy chuck), or a bit longer.
My plan is to set it up with the normal stop to run 4-5 seconds... and the E stop to really clamp down.
I suspect repeated quick stops (1-2 seconds) may not be the best for the motor or gearbox... and not really necessary most of the time.
As I understand (reading at this forum), one can stop the lathe in 1-2 seconds (maybe not with a big heavy chuck), or a bit longer.
My plan is to set it up with the normal stop to run 4-5 seconds... and the E stop to really clamp down.
I suspect repeated quick stops (1-2 seconds) may not be the best for the motor or gearbox... and not really necessary most of the time.
You are correct BUT, the GS2 (only one I'm familiar with) is programmable. You can make it take several minutes to a couple of seconds. I'm sorry, but I do not have formula's on spin down time. I BELIVE it's going to be dependent on the force of the spindle, weight, resistance applied from the resistor, etc... This is a lot of the equation that I'm not greatly informed on. I went to youtube.com and typed "GS2 VFD" in the search, there are several different applications that show the vfd before programming (ramp up, ramp down, etc) and after. The thing I have yet to see, is that particular VFD actually using the resistor.
at the 12:30 mark he discussed the ramp down programming (I know, not the GS2, but this is a series I keep up with and could find quickly). If I'm not mistaken, bluehands (previous youtube I posted) actually programs the GS2.
I dunno, I think we're all agreeing?! I got on a fact finding spree and lost my vision... lol Hope I've helped at least point people in the direction for sources.