VFD on the PM 3520B

[Marc Tuunanen]

Has anyone messed with the settings on their VFD to get a bit slower revs outta the machine. I understand it's not probably advisable but, I'd like to sand and finish on the lathe slower than 55 revs.

Best Regards,
Marc

[Reed Gray]

They (Jet/PM/WHM tool group) will not let you do it. The older PM3520A would go down to just about 0 before it turned off. I did call them and ask they why the change for the B model, and was told 'you will burn up your motor and fry your electronics'. I informed them that I had sanded out thousands of bowls at less than 50 rpm on my A model, and had no problems at all. I was told 'we did lab tests, and you could not have done that, your motor will over heat and you will fry your electronics'. Hmm. Well, when I upgraded to my Robust AB, I had Brent walk me through the process to get it to run that slow, and a slightly higher rpm setting (mine is 3 pulley/speed, and mid speed range was a bit slow). He cautioned me to check the motor, again worrying about it over heating. Well, I still continue to check the motor, and have found that it runs a lot cooler when sanding than it does when I turn. I do make my lathe work hard. There was a long thread on the AAW site in Tips and Techniques about the code you have to use to get into the VFD, and changing the speed ranges. This was a couple of years back.

robo hippy

[Marc Tuunanen]

Thanks Reed. I'll do a search for that if it's still there. Seems to me there is this little fan in a TEFC motor which is suppose to prevent the motor and electronics from burning out. But then again I'm not an EE so what do I know. Not much I suppose.

Regards and God bless,
Marc

PS: I ordered some of those BS blades. Diameter 2's should be the @#$#@!

[Joe Kaufman]

The early 3520's that I have seen were equipped with Baldor motors and Baldor drives. I don't know when the switch to Asian motors and Asian drives (Delta) was made, but the operating characteristics are not necessarily the same. The fan in the motor is rotating at motor speed and is of little value when the motor is operating at 5 Hz, minimum indicated speed on my 3520B. I have a little experience with VFD's in operation and looking over the shoulders of design and test engineers, it is no trivial task to get stable and smooth operation over a wide frequency range. My lathe is starting to get rough at 5 Hz.

Like Reed said there is info available from users that have changed the drive parameters and have reported satisfactory results. I am curious if the access code to drive is still the same.

[Marc Tuunanen]

Well folks, think I found some info. Looks like the VFD on our PM3520B is a so-so unit. Definitely not the quality unit of a Robust Lathe. Seems 50 rpm is the slowest stable speed of the VFD. Kinda sucks but, not surprising considering Chinese/Taiwanees quality or lack their of. Wish I could afford a Robust. Well maybe something to shoot for in the future. Thanks to all for the replies.

God Bless,
Marc

[Ken Fitzgerald]

Marc,

I am sorry for you disappointment.

Did you pay a Robust price for the PM-3520B? It's unfair to expect it function as well. I own a PM-3520B. It's good bang for the buck but no....it's not Robust but I paid a small fraction of the price of a Robust for the PM-3520B.

[Marc Tuunanen]

Don't misunderstand. The PM is a good deal of lathe for the money. Even still Powermatic could use a better quality VFD. Maybe someday I'll own a better lathe but i'm happy to have a PM3520B and will turn out some quality stuff, pun intended. And I didn't pay a fraction of a ROBUST.

Cheers all

[Harry Robinette]

I'm running 3 different VFD's all Chinese / Taiwanese and they all go to 0 rpm. The one on my Vega has been being used like that for about 10 years NO problems,the other two have been being used for around 2 to 3 years. The size for all is 2hp.
1 Toshiba
2 AutomationDirect
Just my $.02

[Duane Meadows]

Not just the VFD, but the motor used can make the difference as well!