Vfd and motor change

rimfire1903

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May 25, 2018
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need help, i would like to have a vfd on my clausing 8520 mill in very good condition, (but) it has a 3/4hp dc. with belt drive with pulley set up, i am a gunsmith and need to cut dovetails in slides and barrels, and run in a slow speed around 6-700 rpms,, herd i need a 3ph induction motor and a vfd, i dont have 3 ph. home shop 110/220
so what do i have to do to achieve this i wouldn't mind a 1 hp or even the 3/4hp is ok with me, can you explain exactly what i need to do including motor type and hp,vfd type for the motor i need,, wright i am running 110, i would like to avoid changing belts but if the cost is out of my ball park, i would like to modernize the older we get the lazier we get,,,, i get,,, please be specific thank you for your time
 
You don't need 3 phase power in the shop. Part of the job of the VFD is to take your single phase power and convert it to 3 phase. You can run a 1hp 3 phase motor using your 110V shop power. You just plug your VFD into a 20A outlet and wire the VFD's 3 phase output to your 3 phase motor. Its that simple. You didn't mention what kind of VFD you were looking at, but I strongly recommend the KB Electronics KBAC-27D model. These are pricey, but come in a nema 4X/IP65 enclosure which is watertight with watertight knob and switches as well. This controller will drive up to a 1.5hp motor on a 110 volt line, and up to a 2hp motor if you wire it to a 220V line. Alternatively, you can go with a much less expensive Chinese import and build your own enclosure for it. There are plenty of folks that have done that with apparently decent results.
 
You might want to try and find a 900 or 1200 RPM 3 Phase motor if you are planning to run that slow most of the time. The problem with running the typical 1800 RPM motor that slow with a VFD is cooling. Another option may be to add an external fan. If your mill uses a 56 frame motor, finding a slower motor may be challenging.
 
thank you both for all the help, i don't run slow most of the time just for dovetails thank you for your help, have a great day, does the motor have to be induction motor? or ac
 
You say you currently have a dc motor? With speed control or without? Or did you mean ac motor?
Mark
 
dc motor, via belt and pulleys for speed control, not ac motor, dc motor thank
 
You can get a open frame dc drive from automation direct for 136, need an enclosure and potentiometer, good for up to 1 hp at 90vdc.Probably even cheaper deals around.
Keep your present motor.Potential for dynamic braking, forward reverse , etc.
Others can tell you about the torque curve, ease of use and installation.
 
Post details of your existing DC motor. DC motor is variable speed, if you vary the voltage to it. Not sure why your machine would come with a DC motor and fixed DC voltage. DC was the old way to get variable speed, before the proliferation of cheap VFDs. DC is still a good way to go, and if you have a DC motor already then it probably makes more sense to get a cheap DC drive for it and leave the motor alone.

I'm half-ass suspecting you actually already have a DC drive buried in there somewhere, even if there's no exterior speed control knob, as I can't come up with a reason they would use a DC motor for fixed speed.
 
This is a causing 8520 3/4 hp all there is a on and off switch. Only way to change speed is by changing v belt on several step pulleys.
 
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