[Noteworthy] VFD public service announcements

[mksj]

It is clear that it is an output device failure, at this cost level they do not repair the VFD's, larger VFD's are more modular and often specialized for the application so pays to have them repaired. A new Automation Direct 2 Hp VFD are $200. It appears you are using 3 phase input model which are built for lighter duty then a single phase model. As mentioned the technology has advanced significantly, buying the same older model is probably a poor choice, you really need to be buying one with some form of sensorless feedback motor control, to be doing low speed drilling and tapping will be very taxing on the VFD/motor. I would limit the motor lower speed to 20Hz. The applied torque will still be 1/3rd of what a pulley speed reduction would be for the same spindle RPM.

 

[toprecyler]

Mksj, thanks for info. It will help my total learning/ understanding this VFD.

One note, we are imputing 110v single phase to run this drill press. The drill press motor is 1-1/2 HP 3 phase.


I found in the statement about avoiding stalling the motor. It was in Dake’s instructions.

What I find ironic is in above institutions, it says tapping is allowed, and has more instructions on following page. But it also mentions to avoid stopping under load, or stalling the motor, otherwise this can damage the electrical components.

Isn’t this what we do when tapping?

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[mksj]

Yep, kind of stupid manufacturer statement, and most likely due to the ancient type of VFD they are using. Typically you need to also oversize the motor for low speed operation. A more current VFD replacement would be the Allen Bradley 25B-V6P0N104 for 120V input and a 6A 3 phase motor output, but it is stupidly expensive. Replacing it with a 4M, you are back to where you started and will mostly likely fail over time. Just was a cheap solution at the time. Lenze, Inveteck, WEG are also worth looking at in a NEMA4 120V VFD, moving to a single phase 230V input would given many more options at less cost. You probably would also want a sealed unit, and you would be much better off going to 230V single phase input.
Invertek VFD's are very easy to install for minimalist type systems and have been reliable, I do not use them due to cost and less extensive programming options/inputs. The one below is fully contained as to speed, direction and power and could be used as a direct replacement single unit system. One could add a remote E-Stop.

VFD, 1.5hp, 5.8A, 110-115V, Single Phase Input/3 P

VFD, 1.5hp, 5.8A, 110-115V, Single Phase Input/3 Phase Output, Keypad, Potentiometer, Disconnect Switch, NEMA 4X, Outdoor IP66, General Purpose AC Drive, OPTIDRIVE E3 Series, Simple Setup with 14 Basic Parameters and Functions

www.wolfautomation.com

 

[simontrav]

In a stall the current is liable to go up dramatically. If you overrate your VFD you run the risk of cooking the motor windings, but you've probably bought yourself more time. (You can probably hit the off switch before the windings burn out).

 

[AGCB97]

I looked back here and couldn't find a motor data plate spec or picture of it. That is where I ALWAYS start.
Aaron

 

[mksj]

Newer VFD's calculate the time and current (I2T) for overload, a 300% overload results in an instantaneous (assume milliseconds) overload and shut down. This would be probably similar or less to what a motor across the line would experience on start-up (LRA). Older VFD semiconductor output devices were more susceptible to damage, newer ones in at least mainstream VFD's are more robust.

 

[toprecyler]

Update.

I programmed the new replacement VFD to minimum 30 HZ.

And I removed the bolt someone added to the motor mount plate to help tension the belt by pushing against the press housing. The bolt head was preventing the last 1/4” of motor adjustment to make changing belts speeds easily. And I switch the speed to the slowest setting.

If we get into a situation where we need to drill lots of small holes, we can now easily switch the belt speed faster to match what the drill should have.

But most of our drilling is usually 2-3 holes at a time, so slower RPMs will not really be noticeable time difference.


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