side-issue, but the Precise grinders are variable, too - off Variacs - and the Panto-engraver same again ELSE air-pressure, depending on what spindle is mounted. then all-mechanical variables with one PIV-Werner-Reimers, three Reeves vari-belted or equivalant. Four with DC drive, one strange AC series-wound motor (Electro-Mecano DP) all three lathes, two of three drillpresses, both mills, and the shaper ALL variable speed. Stepless-variable Reeves Vari-Drives O/E can still be had, new, but a bigger motor and stouter VFD should be MUCH cheaper.Īnd. I mean simple step-pulleys, AND retaining what you already have as finer-grain variable within the ranges.
Just that either of VFD or DC drive fall off their 'sweet spot" as they move away from dataplate optimal RPM. That's not a relative "efficiency" thing. finding a way to add-back another mechanical ratio or three.Ī pragmatic "rule of thumb" is that decently stable, smooth, and well-regulated under-load stepless electrically variable speed wants twice the motor HP as mechanical ratios need, same tasking, otherwise. Solving the problem "all electric" - AC OR DC- will probably cost you at least $1,000 MORE than. To regulate speed on a DC motor you just need IR compensation in the drive, whereas AC motors need some combination of voltage and frequency adjustment to keep them at a certain speed.Īlternatively, you may be able to switch between a 2 pole or 4 pole motor or vice versa if you have no control of the drive ratio.
#Pulleys timing belts full
DC motors are awesome but require good drives to work to their full capacity, which aren't as cheaply available as VFDs. If you are concerned about torque, neither of those will be your friend.
Normal variable speed motors are universal motors or a variety of capacitor start/run motors. (Not to say that the features of the VFD shouldn't be used fully, but you can certainly work without it). The motor may appear to be stalling out but is totally within its current limits, assuming it has an external fan for cooling. Now set it to 360 rpm and you will only get 210 rpm at full load.
Consider that a 3450 rpm motor has 150 rpm of slip at full load. I will say that even a drive without any of the fancy modes or tuning should give near full torque at any speed, but you will have full slip at full torque regardless of speed, so you may need to increase the volts per hertz at low speeds to account for this, but be careful. Reminds me of my old F150 that liked to hunt for a gear between fourth and fifth when driving at the speed limit. How is the motor attached? If you can, change pulley ratios that you have more rpm in low gear or less rpm in high gear. Now I can tap with leaving it in high gear and the floating head barely moves. Tuned the drive and no way can I stop the spindle at minimum speed. It was better, but still could stop the spindle. In high gear at minimum speed I could stop the spindle with my pinky. I kept breaking 1/4 inch taps in my CNC with a floating tap holder in low gear. Not a huge cut by any means compared to larger lathes, but I had the speed pot set to minimum rpm and it did not even blink. The other day I was using a 3/8 die to cut threads in some 3/8 mild steel. I leave the belt permanently on the 75% speed pulley and overspeed the motor a little. Of course proper motor parameters need to be programmed in the drive. The drive needs to be in sensorless vector mode (assuming your drive has this mode - if not its not worth owning) and auto tuned. This is not a HP issue - this is a torque issue. Certainly sounds like the drive is not set up properly.
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