Curt Harms
12-23-2017, 9:52 AM
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.
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.