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View Full Version : Old Woodfast lathe with a 3 phase motor.



Avery
22nd December 2012, 05:37 PM
I recently scored an old Woodfast lathe at an auction. It is mounted on a steel cabinet and has all the basics. The headstock and tailstock line up perfectly, the bearings seem sweet and the tailstock quill is smooth and stable. It needs a good clean up (half done) and some paint. I think it will be a very good addition to my workshop.

It has a .5 HP 3 phase motor, also in seemingly good condition. I don't have 3 phase power.

Should I change the motor to a new single phase unit, or should I get something like this

Variable Speed Drive 240 VAC, 0.7 kW Single Phase Input :: Variable Frequency Drives :: Motor Drivers & Controllers :: Welcome to Ocean Controls (http://www.oceancontrols.com.au/DEM-003.html)

to drive it?

Will a .5 HP motor be strong enough?

Suggestions please.

Mobyturns
22nd December 2012, 06:09 PM
Avery,
Have a look at this post as we discussed some VFD options there talking about upgrading lathes & buying second hand. http://www.woodworkforums.com/f8/time-upgrade-162345/

If the motor is original on the Woodfast one would imagine it had sufficient power to start with? I'm no expert on VFD's but as I understand them the 3 phase motor has to be wired in delta (whatever that means) to be suitable for the VFD's. I guess you would need the assistance of an electrical mechanic to program the VFD & to set it up efficiently if you decide to purchase and set one up yourself.

I purchased the Woodfast 2hp VFD which is the same drive from the new 910's for my Woodfast 908. Its essentially a bolt on option, pre programmed VFD with 3ph motor ready to plug into a std 10 single phase GPO & start turning. If you purchase another motor & VFD just check mount & shaft sizes as they are different on the various size motors.

malb
22nd December 2012, 06:23 PM
There is a lot of discussion of 3phase motors, VFD/VSD modules and single phase supplies in the metalwork section.

Basically, electricity is generated commercially and distributed in 3 phase. Typical single phase household suppy is derived by connecting between one of the three phases and neutral, which is the common reference point for the phases. Three phase supply utilises all phases, and the typical input voltage is 415VRMS measured phase to phase, which equates to 240VRMS any phase to neutral.

VFD/VSD modules take a single phase or three phase input, convert it to DC and then generate a three phase output with a user controlled frequency. Since induction motors (as per your lathe) operate at speeds controlled by the input frequency, varying the frequency varies the motor speed. The output voltage of the VFD is normally proportional to the input voltage, so 240V in gives 240 V out, 415 in gives 415 out. There is one family of units available from UK which features a step up function and will give 415V out from 240V input, but these units cost more than double normal units.

3 phase motors can be connected in two configurations for either 240V or 415V supply, but many smaller (<5HP) motors come from the factory wound for 415V only. I believe that the Woodfast motors were wound this way. However many of these motors can have the windings modified to operate properly from 240V. They will run in 415V configuration with a 240V supply, but are limited to about half their rated power, which is insufficient for many turning situations.

Options available to you include (in order of preference, versatility versus cost).

Have the motor modified (or do it yourself) and run with a 240V VFD.
Obtain a 240V to 415V VFD from he UK and use it to operate the standard motor.
Use a 240-240VFD like the unit you linked to drive the standard motor with reduced power capacity, might be Ok for smaller spindle work but would not use the the lathes capability/flexibility to the max.
Replace the motor with a single phase unit of similar or higher power. Single phase motors don't have the starting torque that 3phase ones have, and you would be totally dependant on belt changes for speed selection.
Buy a cheap 4KVA 3 phase generator to run the lathe with standard motor and maybe a dusty to 2HP as well. Would not provide variable speed.

BobL
22nd December 2012, 06:40 PM
Options available to you include (in order of preference, versatility versus cost).

Have the motor modified (or do it yourself) and run with a 240V VFD.
Obtain a 240V to 415V VFD from he UK and use it to operate the standard motor.
Use a 240-240VFD like the unit you linked to drive the standard motor with reduced power capacity, might be Ok for smaller spindle work but would not use the the lathes capability/flexibility to the max.
Replace the motor with a single phase unit of similar or higher power. Single phase motors don't have the starting torque that 3phase ones have, and you would be totally dependant on belt changes for speed selection.
Buy a cheap 4KVA 3 phase generator to run the lathe with standard motor and maybe a dusty to 2HP as well. Would not provide variable speed.

Another option is to just buy a more powerful 3Ph motor and use a 240 V VFD.
In my case it was cheaper to buy a used 3Ph 1HP motor than to get the original 1/2 HP modified.