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Step pulley drill press VFD conversion: Continuous boost function

rbmgf7

Aluminum
Joined
Oct 18, 2017
So I had spare time/money to convert my 20" Jet drill press from step pulley to VFD.

Running a 4.5" pulley on the motor to the what I measure 7.5" step (bottom) on the spindle pulley. RPM range is fine for what I need but would like a little more grunt on the lower RPMs.

I'm using a Siemens V20 2HP VFD. I found the continuous boost parameter which is defaulted to 50%. At low RPMs, it would stall using my step drill but once I boosted it to it's full 200%, it's able to drill through the entire step drill without stalling. I have a Gates belt on there and it's sticky. At lower boost, I could stall the motor without belt slip.

From what I gather, it raises the voltage a little on the lower Hz? Just wanting to figure out if there are any downfalls to doing this (but just for short run, hobby stuff. Not production)? Not entirely VFD/motor savvy. It's going to an inverter rated 1.5HP Siemens motor.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
How low are you running the motor? Frequency wise I mean. If you overuse the boost function at very low RPM. you may cook the motor unless it has an external cooling fan that runs independent of motor RPM. Some of the "inverter rated" motors can handle lower speed better. Check your motor's manufacturer provided spec's.
 

mmurray70

Hot Rolled
Joined
Jan 11, 2003
So I had spare time/money to convert my 20" Jet drill press from step pulley to VFD.

Running a 4.5" pulley on the motor to the what I measure 7.5" step (bottom) on the spindle pulley. RPM range is fine for what I need but would like a little more grunt on the lower RPMs.

I'm using a Siemens V20 2HP VFD. I found the continuous boost parameter which is defaulted to 50%. At low RPMs, it would stall using my step drill but once I boosted it to it's full 200%, it's able to drill through the entire step drill without stalling. I have a Gates belt on there and it's sticky. At lower boost, I could stall the motor without belt slip.

From what I gather, it raises the voltage a little on the lower Hz? Just wanting to figure out if there are any downfalls to doing this (but just for short run, hobby stuff. Not production)? Not entirely VFD/motor savvy. It's going to an inverter rated 1.5HP Siemens motor.

You need a smaller pulley on the motor. You can get away with very small pulleys if you use the cogged v belts, they flex better.

Aim for at least around 3.5:1 reduction, or as close as you can get to that. You get lots of torque at this ratio, and you can double the speed of your motor and still get 1000rpm which is plenty for metalworking drill press.
 

Strostkovy

Stainless
Joined
Oct 29, 2017
I'm generally of the opinion to gear down the motor for the torque you need and overspeed it at reduced V/Hz and power. I never need full torque at full speed.
 








 
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