There have been several very useful threads on how to replace and program the VFD on your lathe, mostly focused on Powermatics. I've just replaced 2 of them and while that doesn't make me any kind of expert, aspects of this experience may prove helpful to others who face the task. The lathes are all in our local high school wood shop, which has been a major factor affecting the installations.
One of the 3 Powermatic 3520 lathes had a VFD fail about 3 years ago. It took about 9 months to get a school district electrician to add 220/240 wall outlet for the new lathe, and then when we first mounted and wired the replacement, we couldn't get it to work. With access issues (like Summer vacation) it took another long time to figure out that the electrician who wired the 220/240 wall outlet had done it incorrectly, or at least it didn't match the plug. Once we understood that, it was pretty simple for us to change the wires in the power supply plug to match the outlet.
When replacing a VFD, the new one will usually not be the same size as the old one, and if it is, the mounting holes will be in the wrong place. It's desirable to mount the VFD to the metal of the headstock, rather than a plywood intermediary, for electrical conductivity reasons that are above my head. I ended up reusing the heat sink that had been attached to the old vfd as an interface. It's aluminum, so I could easily drill screw holes where needed and it would provide the conductivity. The currently available VFDs tend to have fans built in to dissipate heat and don't need the heat sink.
This installation was on a 3520B, which required the addition of a wire between headstock controls and the VFD, which is easy to do, and covered in one of the forum posts. (https://www.aawforum.org/community/threads/powermatic-3520b-vfd-replacement.14784/) Once we got juice, it still wouldn't run properly. It would trip and generate an over current error code with changes in speed and forward/reverse, and sometimes wouldn't turn on with the on/off button. I replaced the on/off switch and the potentiometer, and between the access issues and me having to learn how to solder and use a multi-meter, that took a long time, too.
I programmed the VFD with the parameters used by one of our club members when he installed the same model VFD on the same model lathe with success. I checked and rechecked parameters trying to find where I'd input a wrong number, and couldn't find anything. With everything wired properly and the multi-meter suggesting all the parts were working, I threw up my hands and called the VFD seller and begged for mercy. After 3 years, they really had no requirement to help, but they did. A wonderful technician called and had me check and/or change a bunch of different settings while he scratched his head. (I could hear this over the phone. honest) He had me doing this so fast, I lost track of what changes we made, but momentarily, It Worked! In hindsight, I believe the parameter which told the VFD where and in what order to get information was set incorrectly.
While I was on the phone feeling buoyant, one of the other lathes had it's VFD give up. Still high on our success, I was confident we could get it up and running without difficulty. Silly me.
(Aside. About this same time, the third Powermatic lathe's VFD started acting up. This VFD was a replacement done by an electrical engineer, so it was a surprise. Long story short, he had put a plywood shelf over the VFD to keep shavings from getting into it. The VFD was overheating due to the shelf impeding the vertical dissipation of heat from the fan. I removed the shelf and it's run fine ever since.)
The second lathe is a Powermatic 3420A and did not require the extra wire. We had no issues with the power supply. Once again, I was able to repurpose the heat sink for mounting the new VFD, and got it wired just the same as the first installation. We had some current overload trips and error messages, so I reset the parameters for ramp up and slow down speeds. If the on-off button was in the off position, the potentiometer would increase and decrease the Hz displayed on the VFD, but if it was turned on and spinning, it would only go at a constant speed. This time I didn't wait 3 years, and contacted the same technician as before. He walked me through checking and resetting parameters, eventually resetting ramp up and ramp down speeds to very extended times (60 seconds). Switching from forward to reverse still tended to trip an overload condition, but as long as it was strictly in one or the other, it would run and we could change speeds, albeit very slowly. This allows us to use the lathe in the high school shop, as the students mostly do spindle projects and never use reverse.
I had heard that the lathe wouldn't need the braking resistor since the VFD has the feature built in, so left that unwired. With the problems encountered, I wired it up, but haven't had a chance to see if this made a difference.
The conclusion of the technician is that the motor is old and when changing speeds, and apparently when the spindle changes directions, it generates excess resistance and the VFD senses it. (If any of you electrical engineers reading this has a better interpretation, I'd love to hear it)
The main points I have to add to the "Replacing a VFD on a Powermatic Lathe" discussion are these:
1. The resources available here by searching and on Doc Green's web site are very helpful.
2. Make sure your wiring is correct and, if possible, that your control switches are working. Powermatic uses cheap but readily available parts.
3. The number of parameters that have to be set is small. That should not be a reason to avoid the changeover.
4. Be aware that you may do everything correctly, but some factor other than the VFD and it's settings may be sabotaging the system. (power supply, switch/potentiometer)
5. Make use of the really helpful support people where you buy the VFD. (If the seller doesn't have such people, try VFDs.com, where they do)
6. In the end, there is a little voodoo involved in getting a new VFD to work on an older lathe
One of the 3 Powermatic 3520 lathes had a VFD fail about 3 years ago. It took about 9 months to get a school district electrician to add 220/240 wall outlet for the new lathe, and then when we first mounted and wired the replacement, we couldn't get it to work. With access issues (like Summer vacation) it took another long time to figure out that the electrician who wired the 220/240 wall outlet had done it incorrectly, or at least it didn't match the plug. Once we understood that, it was pretty simple for us to change the wires in the power supply plug to match the outlet.
When replacing a VFD, the new one will usually not be the same size as the old one, and if it is, the mounting holes will be in the wrong place. It's desirable to mount the VFD to the metal of the headstock, rather than a plywood intermediary, for electrical conductivity reasons that are above my head. I ended up reusing the heat sink that had been attached to the old vfd as an interface. It's aluminum, so I could easily drill screw holes where needed and it would provide the conductivity. The currently available VFDs tend to have fans built in to dissipate heat and don't need the heat sink.
This installation was on a 3520B, which required the addition of a wire between headstock controls and the VFD, which is easy to do, and covered in one of the forum posts. (https://www.aawforum.org/community/threads/powermatic-3520b-vfd-replacement.14784/) Once we got juice, it still wouldn't run properly. It would trip and generate an over current error code with changes in speed and forward/reverse, and sometimes wouldn't turn on with the on/off button. I replaced the on/off switch and the potentiometer, and between the access issues and me having to learn how to solder and use a multi-meter, that took a long time, too.
I programmed the VFD with the parameters used by one of our club members when he installed the same model VFD on the same model lathe with success. I checked and rechecked parameters trying to find where I'd input a wrong number, and couldn't find anything. With everything wired properly and the multi-meter suggesting all the parts were working, I threw up my hands and called the VFD seller and begged for mercy. After 3 years, they really had no requirement to help, but they did. A wonderful technician called and had me check and/or change a bunch of different settings while he scratched his head. (I could hear this over the phone. honest) He had me doing this so fast, I lost track of what changes we made, but momentarily, It Worked! In hindsight, I believe the parameter which told the VFD where and in what order to get information was set incorrectly.
While I was on the phone feeling buoyant, one of the other lathes had it's VFD give up. Still high on our success, I was confident we could get it up and running without difficulty. Silly me.
(Aside. About this same time, the third Powermatic lathe's VFD started acting up. This VFD was a replacement done by an electrical engineer, so it was a surprise. Long story short, he had put a plywood shelf over the VFD to keep shavings from getting into it. The VFD was overheating due to the shelf impeding the vertical dissipation of heat from the fan. I removed the shelf and it's run fine ever since.)
The second lathe is a Powermatic 3420A and did not require the extra wire. We had no issues with the power supply. Once again, I was able to repurpose the heat sink for mounting the new VFD, and got it wired just the same as the first installation. We had some current overload trips and error messages, so I reset the parameters for ramp up and slow down speeds. If the on-off button was in the off position, the potentiometer would increase and decrease the Hz displayed on the VFD, but if it was turned on and spinning, it would only go at a constant speed. This time I didn't wait 3 years, and contacted the same technician as before. He walked me through checking and resetting parameters, eventually resetting ramp up and ramp down speeds to very extended times (60 seconds). Switching from forward to reverse still tended to trip an overload condition, but as long as it was strictly in one or the other, it would run and we could change speeds, albeit very slowly. This allows us to use the lathe in the high school shop, as the students mostly do spindle projects and never use reverse.
I had heard that the lathe wouldn't need the braking resistor since the VFD has the feature built in, so left that unwired. With the problems encountered, I wired it up, but haven't had a chance to see if this made a difference.
The conclusion of the technician is that the motor is old and when changing speeds, and apparently when the spindle changes directions, it generates excess resistance and the VFD senses it. (If any of you electrical engineers reading this has a better interpretation, I'd love to hear it)
The main points I have to add to the "Replacing a VFD on a Powermatic Lathe" discussion are these:
1. The resources available here by searching and on Doc Green's web site are very helpful.
2. Make sure your wiring is correct and, if possible, that your control switches are working. Powermatic uses cheap but readily available parts.
3. The number of parameters that have to be set is small. That should not be a reason to avoid the changeover.
4. Be aware that you may do everything correctly, but some factor other than the VFD and it's settings may be sabotaging the system. (power supply, switch/potentiometer)
5. Make use of the really helpful support people where you buy the VFD. (If the seller doesn't have such people, try VFDs.com, where they do)
6. In the end, there is a little voodoo involved in getting a new VFD to work on an older lathe