Electrical Motor Questions.

I am trying to finish off putting my S7 Myford together and I would
like some advice please. I have a few questions on the electrical
1. The Lathe doesn't have a no-volt release switch. Should I source
one with overload and reverse capabilities. (The single phase motor I
have is a gryphon 370 - with all windings at the terminal plate).
Will the chuck come off the spindle if the motor is operated in reverse
2. What is a resilient-mounted motor? Is it just rubber mounts between
the face base and mount plate on the lathe. Or something more.
3. I have another motor a Crompton 370W 3 phase which has star or delta
terminals -either mode is available. I am better getting a 240Vac
single phase to three phase inverter instead of using the single phase
motor. Which gives me variable speed and soft start and On/Off. Are
they any good - I have heard they have poor low speed torque and can
be unreliable and interfere with the TV reception.
Sorry for the dumb questions but it this hobby has a steep learning
curve - which can be expensive if the wrong decisions are made.
Thanks. Ian.
Reply to
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I would go the VFD/3-phase motor route (using the motor mentioned below), and fit a no-volt release to the VFD.
If you don't properly tighten the chick, and/or if you try cutting metal when in reverse, it will come off no problem at all.
However, with the VFDs there is usually a soft start feature so the motor cannot be slammed from fast forward to fast reverse, so if you tighten the chuck properly there is no problem.
Rubber mounts.
I hace a very similar setup on my ML7 - works just fine and I don't have a TV in my workshop anyway
If I was doing it again I would probably go for a larger motor than the 1/2 horse motor I have, but for most purposes it is OK as is.
The VFD that I have was supplied by the Newton-Tesla guys (they advertise in MEW and ME from time to time) - I got them to increase the max speed to more than double the motor RPM - the VFD kicks out 120 Hz 3-phase at max speed, so the motor spins at 2.4 times its nameplate RPM at top whack. This means that I very rarely have to change the belt position on the pulleys - I get from dead slow to max speed (in forward or reverse!) just on the VFD controls.
You can get mains RFI filters that are wired between the VFD and the mains supply that will stop the VFD from injecting nasties back down the mains - this should fix the problem if there is one.
Regards, Tony
Reply to
Tony Jeffree
No need as the VFD if programmed correctly won't restart from a mains failure. The VFD will also act as overload.
That's the nice thing with a VFD it replaces all those weird pressed steel and burnt electrical smelly bits.
-- Regards,
John Stevenson Nottingham, England.
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Reply to
John Stevenson
Yep - brain fade there. Thinking about it, the Newton-Tesla setup doesn't have a NVR but it does have one of those big red STOP buttons that kills the power to the VFD & needs two twists to the left, one to the right, and a sprinkling of Eye of Newt to turn it back on. Probably a smart move to have one of them fitted.
Spoils all the fun though
Regards, Tony
Reply to
Tony Jeffree
Thanks for the reply gents... Seems like VSD 3 phase motor is the best idea. Now.. Anyone want to buy a Gryphon (0.5hp) 370W Brook Crompton motor, only ever seen 2 hours use in its life - looks like new. It has capacitor start with internal centifugal switch.
Reply to
Using a bush I guess :-)
No but I do have a vacancy for a 1/2 hp 3ph Cub - the smoke escaped...
Reply to
Roland Craven
Can't you buy some new smoke?
Anyone know what usually fails on inverters, ie is there a pattern? Are they ever worth repairing (in 'home shop' sizes)?
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
Reply to
Tim Leech
At a guess, probabilites are o/p switching mosfets, main reservoir capacitors and input resctifer. If the boards are fried then probably not worth the trouble.
Reply to
Andrew Mawson
You won't regret it. I put a Telemecanique ATV11 (cheap + easy to set up) and 3 phase motor on my ML7 a few weeks back and my only regret is not doing it years ago.
Reply to
Duncan Munro

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