Re: Increasing Motor RPM via VFD
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I thought they also have fan control so fan can run appropriate speed at low RPM.
Imran
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On Jan 30, 2021, at 11:43 AM, Brian Lamb <blamb11@...> wrote: ? I don¡¯t think balance is the issue, the VFD rated motors are heavier windings and shellac on the windings, the higher frequencies tend to break down the insulation on the motors and overheat them.
On Jan 30, 2021, at 9:23 AM, David Kumm < davekumm@...> wrote:
That brings up the question, are inverter duty motors balanced for higher speeds than regular motors?? The standard is 125% of rated speed for 2 pole motors or 75 hz.? 4 pole motors are generally balanced to the same specs as 2 pole so in effect to 150 hz.?
My 1800 rpm motor is rated to 6000 rpm, but that is noted on the plate.? Dave
VFD rated motors can generally run up to 200hz, CNC router motors up to 400hz. Torque does drop dramatically over about 90hz.?
OK, I¡¯ll probably start a war¡ but you don¡¯t need huge rpm on router bits or on these mortisers. You can¡¯t manually move the cutters at a rate that justifies all this rpm, all you will get is burning. Now, on a CNC router, different story, it
has the capability to move the cutters at 500-1000ipm and can make use of all that rpm. I have machined mortises on my old Deckel mill and routinely done them at 1200 rpm and they come out great.?
On Jan 30, 2021, at 7:54 AM, David Kumm < davekumm@...> wrote:
Given the FD is direct drive, I would think the speed is closer to 3400 in the 60 hz market.? Generally you can overspeed a 2 pole motor to about 90 hz assuming the motor is decent quality.? Downside is that torque will be reduced because you aren't maintaining
the volts/hz ratio.? The benefit and need for higher speed is really for small diameter bits so the reduction in torque might not be a big deal.? 5/8" bits are not a great choice for more speed and less torque.
4 pole or 6 pole motors are good for higher hz and vector duty motors are good for something like 5000-6000 rpm or up to 240 hz.? When you do that you usually oversize the motor to compensate for the loss of torque on the high end.? You also need to realize
you may have way more torque on the low end than what the machine is designed for so care must be taken.??
Thank?Brian for straightening me out on this years ago when we had a discussion here about Rong Fu mills.? Dave
After realizing that people have used end mills on their mortising attachment, I was curious if there is a way to increase the RPM of FD250. The bit on morticing attachment is likely running around 5000 RPM, whereas FD250 is around
3000 RPM.
This article says it can be done as long as motor does not exceed it¡¯s FLA, is not electrically overloaded and operating with it¡¯s mechanical design limits.
Anyone got an idea how much more speed might be possible?
Electrical parts can be measured but I have no clue on mechanical side of what margin might exist.
This may not result in anything meaningful but I like to learn. One thing leads to another ....
Imran
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imran