New toy for Christmas

[Curt Harms]

Santa brought me a new toy. Well, it wasn’t a sleigh with 8 tiny reindeer, it was a brown truck. I have an Taiwanese Delta Radial Drill press and I was happy with except for the minimum speed, about 550 RPM. That’s not really slow enough for large diameter cutters like forstner bits and fly cutters. A VFD seemed like the cleanest solution short of a new drill press. I’d heard about Dealer’s Electric here so ventured to their site. They do sell VFD/Motor packages but they also sell new surplus motors and open box VFDs. I bought a 230 volt 1 H.P. Teco-Westinghouse L510 drive and ½ H.P. Century 3 phase motor for a little less than $200 delivered. I’m hoping upsizing the motor from 1/3 H.P. to 1/2 H.P will help offset the loss of torque at low motor R.P.M.s. A few hours after purchasing I found I was going to be gone for a few days so there’d be no one here to deal with a heavy-ish package. Adam Benner at Dealer’s Electric agreed to hold the package until I was back. He was as good as his word and the package arrived as scheduled.

I have limited experience with 3 phase electrics. The manual for the VFD is pretty understandable though I have no idea how most of the functions described are used. The manual did seem pretty complex until I got the hardware and started poking at it. Then it mostly made sense. I had two concerns when I began considering this project. One was a pulley for the motor. The original setup is two step pulleys. The motor pulley’s bore is smaller than 5/8”, I think it’s it’s 15 mm. The second concern was motor mount. The motor on the drill press had very little info – volts, amps and that was about it. I thought about an adapter and even purchased a piece of steel in anticipation. When I got the motor it fit like it was purpose made, it has an LA56 frame. The drill press has had an annoying vibration since it was new. The original pulley had 3 divots drilled into the outside for balance. I tried foam weatherstripping where the two halves of the belt shield come together. That helped but didn’t entire fix the problem. I couldn’t reuse the OEM step pulley so used an online pulley speed calculator and decided on a single 3.25” motor pulley. No more vibration. The driven step pulley has internal splines so replacing that is impractical. I figure I have about 180 R.P.M. at 10 Hz and 1580 at 60 Hz at the chuck.

Now comes a question for those who know more about these things than me (a low bar). The VFD has a frequency output range of 0 to 650 Hz. If my math is correct, 650 Hz. would spin a 4 pole motor at 19,500 R.P.M.:eek: That doesn’t sound like a great idea, hot rodder’s delight though. Any thoughts on what would be reasonable? 75 Hz yielding 2250 R.P.M? 90 Hz. yielding 2700 R.P.M? As I understand it, motor specs are limiting factors, rotor balance and bearings. I imagine Century would say 60 Hz. as labeled. Thanks for reading and any thoughts.

[Bill Dufour]

I recommend 30-90 Hz maximum range. You can go under for short jobs but too long and you need to add constant speed motor cooling fans. If the motor is old the top rpm should not go too high.
On my little mill/drill I replaced the single phase motor with a 3-phase American made motor. The step pulley was metric and I had to ream the pulley to fit. I used an "adjustable piloted reamer" bought from the bay. I would of had to do this on a lathe if the pulley had a keyway. I could not find a metric shaft motor that fit my budget.
Bill D

[John K Jordan]

This has some general definitions: http://www.vfds.in/vfd-parameters-setting-381662.html

My only experience is with programming a VFD for a lathe. I remember studying and puzzling for some time over the parameters and comparing with other VFDs in my shop.

[Curt Harms]

I recommend 30-90 Hz maximum range. You can go under for short jobs but too long and you need to add constant speed motor cooling fans. If the motor is old the top rpm should not go too high.
On my little mill/drill I replaced the single phase motor with a 3-phase American made motor. The step pulley was metric and I had to ream the pulley to fit. I used an "adjustable piloted reamer" bought from the bay. I would of had to do this on a lathe if the pulley had a keyway. I could not find a metric shaft motor that fit my budget.
Bill D

Hi Bill

The motor is new and I'm not going to mess with the max speed yet, I'm just trying to get a feel for how high I can go if necessary. It sounds like 90 Hz. is reasonable for a top end which would make a 1800 R.P.M. motor turn at 2700 R.P.M. ignoring slip. I can see where cooling could become an issue with extended high torque low RPM operations but I don't see running for more than a couple minutes at a time at low RPM. If need be I'll add a small fan to supplement the motor's fan.

[Curt Harms]

This has some general definitions: http://www.vfds.in/vfd-parameters-setting-381662.html

My only experience is with programming a VFD for a lathe. I remember studying and puzzling for some time over the parameters and comparing with other VFDs in my shop.

I too was slightly intimidated by all the parameters but they made a little more sense once I got the device and started poking at it. I'm still clueless about what 75% of the manual addresses, A lot of the content is intended for industrial controls. I've been able to get it to do what I want it to do so far; I'm able to use the drill presses switch for on/off, use the knob for speed control, set the 'torque boost', etc. etc. The only thing I haven't been able to do is get the digital readout to show R.P.M. instead of frequency. I'll pursue that once the Holiday madness has ended.

[John K Jordan]

I too was slightly intimidated by all the parameters but they made a little more sense once I got the device and started poking at it. I'm still clueless about what 75% of the manual addresses, A lot of the content is intended for industrial controls. I've been able to get it to do what I want it to do so far; I'm able to use the drill presses switch for on/off, use the knob for speed control, set the 'torque boost', etc. etc. The only thing I haven't been able to do is get the digital readout to show R.P.M. instead of frequency. I'll pursue that once the Holiday madness has ended.

What helped me was to get lists of the parameters actually used for a couple of lathes (the reason for me installing a VFD). I looked at the VFD manuals for both the new VFD and for two existing lathes and marked where the lathe maker had changed the parameters from the defaults. I tried to figure out the reason for the change. After some puzzling things started to make more sense, especially when I could understand where they used different names for the same parameters.

It sounds like you have things well under control (pun intended!) If you can't get the RPM on the display you might do what I did on my milling machine with variable speed but no readout: I drew some lines on the dial and labeled them 250, 500, 1000, etc. The precise speed is rarely if ever important to me but the approximate speed often is. (I measured the actual RPM with an optical tachometer, this one: https://www.amazon.com/gp/product/B004Q8L894)

JKJ

[Curt Harms]

As you say, the exact RPM isn't critical. I may make a frequency / RPM table and tape it somewhere on the drill press. Larger diameter no-name Forstner bits drilling oak sure seem to work better at around 250 RPM than they do at 550 RPM though.