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I was talking about the drill press I own and how it has the ability to swing very low RPMs in another thread. With this ability comes a small problem.The maximum RPM is 1200. This is not really fast enough for small drill bits. The motor is a three phase 3/4hp rated at 1200 RPM on the name plate running off a VFD.
My question is could the motor stand to be rotated faster?
If I doubled the hertz to 120 I would double the motor RPM to 2400. This is still slower than many AC motors out there. I know I would have to pay attention to the bearings for excess noise, heat, or vibration but could the rotor take it?
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(07-21-2021, 10:54 AM)KyleD Wrote: I was talking about the drill press I own and how it has the ability to swing very low RPMs in another thread. With this ability comes a small problem.The maximum RPM is 1200. This is not really fast enough for small drill bits. The motor is a three phase 3/4hp rated at 1200 RPM on the name plate running off a VFD.
My question is could the motor stand to be rotated faster?
If I doubled the hertz to 120 I would double the motor RPM to 2400. This is still slower than many AC motors out there. I know I would have to pay attention to the bearings for excess noise, heat, or vibration but could the rotor take it?
Almost certainly yes. Bearings would be the same or similar to a 2-pole motor spinning 3600 rpm. Rotor is the same or similar and has no moving parts (except itself).
BUT it's most likely not a VFD rated motor, so keep the power down at high speeds. Use the lowest operating frequency you can set the VFD for - louder, but the voltage peaks due to harmonics will be lower. And since it's not a continuous-duty application like a pump or fan, it will probably last forever anyway.
Tom
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Thanks for your knowledgeable opinion TDKPE.
Any use at a higher RPM would be for small drill bits so high loads should never be a problem.
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07-21-2021, 09:11 PM
(This post was last modified: 07-21-2021, 09:11 PM by TDKPE.)
(07-21-2021, 08:03 PM)KyleD Wrote: Thanks for your knowledgeable opinion TDKPE.
Any use at a higher RPM would be for small drill bits so high loads should never be a problem.
It won’t have much torque up there, either, as the windings were designed for 60Hz, not 120 Hz, so the magnetic fields won’t have enough time to fully develop with each half cycle. It will probably run under constant power above 60Hz, and with the speed-up belt drive, it’ll be wimpy. If the VFD can even go that high.
Tom
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I have my ear to the ground and hope to find a bench top drill press that has the RPM range for smaller bits. Until then I will probably not mess with the VFD. Small holes can be drilled at 1200 RPM with just a little bit of patience.
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