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Richard
14-10-2018, 04:18 PM
I have a nice Harrison M300 lathe, which I have fitted a single phase motor to.

I'd like to use all the exisiting switchgear, brake, fwd/rev lever etc.

Looking at the schematics, the contactor coils appear to run from 110v which is derived from a small transformer. This transformer has different input taps but not one for 240v, so if I replace the transformer with a 240 to 110, I should be able to use the exisiting switchgear with the single phase motor?

I haven't look at motor reversing in detail yet, but I am assuming this will need some re-wiring of the fwd/rev contactors.

24908

Anyone else done this?

Cheers!

Doddy
14-10-2018, 04:34 PM
Without spending too much time on the schematic - yeah, looks to be picking a supply off two phases and transforming this to 110V (if the markings on the schematic are to be believed - no reason not to). So, yeah, get a 220-110V transformer of sufficient rating - it'll be right.

Reversing a single-phase motor is a case of reversing the starter windings. The usual three-position motor switches (On-Off-Reverse) provide the necessary switchgear.

Richard
15-10-2018, 04:36 PM
Without spending too much time on the schematic - yeah, looks to be picking a supply off two phases and transforming this to 110V (if the markings on the schematic are to be believed - no reason not to). So, yeah, get a 220-110V transformer of sufficient rating - it'll be right.

Reversing a single-phase motor is a case of reversing the starter windings. The usual three-position motor switches (On-Off-Reverse) provide the necessary switchgear.



So this is what I think I need to reverse the single phase with the two contactors I have in the machine:24924


I took the lamp off, built like it's designed to survive a direct nuclear strike! Massive cast box with a 415v to 50v transformer, 4 fuses and isolator.

I'm sure I can replace with something simpler...

24925

Doddy
15-10-2018, 04:41 PM
The schematic - yup, though I'd be interested in the 1c1/1c2 arrangement - these are contactors?, what actuates these? a mechanical forward/stop/reverse switch? in which case this can be re-used - which is what I think you're after?

The other thing is to look to see if you can only energise the start coil whilst the run coil is energised - again, can be done with the 1c1/1c2 arrangement, depending on it's behaviour.

Doddy
15-10-2018, 04:44 PM
My bad - 1C1/1C2 are the relays shown at the bottom of the schematic?

Then use two pairs of the 1c1/1c2 contacts to provide the change-over for the start coil, and the remaining contact for both 1c1 and 1c2 wired in parallel to provide the live supply to the motor run coil.

Richard
15-10-2018, 06:04 PM
My bad - 1C1/1C2 are the relays shown at the bottom of the schematic?

Then use two pairs of the 1c1/1c2 contacts to provide the change-over for the start coil, and the remaining contact for both 1c1 and 1c2 wired in parallel to provide the live supply to the motor run coil.

Yes, 1c1 and 1c2 are the fwd/rev contactors operated by microswitches which are in turn operated by the motor control lever on the carriage. See bottom of schematic. Obviously they are never both closed!

You're right, I can use the third pair of contacts to switch the run coil on/off, which I haven't shown in my sketch.

Cheers!

Richard
15-10-2018, 06:10 PM
Yes, 1c1 and 1c2 are the fwd/rev contactors operated by microswitches which are in turn operated by the motor control lever on the carriage. See bottom of schematic. Obviously they are never both closed!

You're right, I can use the third pair of contacts to switch the run coil on/off, which I haven't shown in my sketch.

Cheers!


Updated.

24926

magicniner
15-10-2018, 08:56 PM
I have a nice Harrison M300 lathe, which I have fitted a single phase motor to.

I helped a friend to fit a VFD to his and convert the rest of the switch gear to 240, why on earth would you want to fit a motor providing "Lumpy Torque" to such a nice lathe?

magicniner
15-10-2018, 09:02 PM
I have a nice Harrison M300 lathe, which I have fitted a single phase motor to.

I helped a friend to fit a VFD to his and convert the rest of the switch gear to 240, why on earth would you want to fit a motor providing "Lumpy Torque" to such a nice lathe?

Richard
16-10-2018, 12:13 AM
I helped a friend to fit a VFD to his and convert the rest of the switch gear to 240, why on earth would you want to fit a motor providing "Lumpy Torque" to such a nice lathe?

I had a single phase 2.2kw motor handy...

Do you think I'll see the lumpy torque in the surface finish?

magicniner
16-10-2018, 10:00 AM
I had a single phase 2.2kw motor handy...

Do you think I'll see the lumpy torque in the surface finish?

You'll have to wait and see, you don't have the rubber mounts normally associated with single phase machines, they help significantly in smoothing out the bumps in the torque output.
I noticed a significant improvement in surface finish when I converted my Myford Super 7 to 3 phase, I would never go back to single phase for a lathe or mill,
Regards,
Nick

Richard
16-10-2018, 10:07 PM
You'll have to wait and see, you don't have the rubber mounts normally associated with single phase machines, they help significantly in smoothing out the bumps in the torque output.
I noticed a significant improvement in surface finish when I converted my Myford Super 7 to 3 phase, I would never go back to single phase for a lathe or mill,
Regards,
Nick

The motor is bolted to the the headstock but the drive is via belts and it's spinning a big old chuck so may not be too bad.

I'll face off some ali and see if there is any sign of uneven cut.


So when you fitted a VFD, I assume you delta the motor and wire the VFD direct to it? I read that VFD's like to be close to the motor and don't like contactors etc in the way.

Did you re-wire the fwd rev microswitches to operate the VFD or just add a control pendant/box for the VFD?

I would like to retain the fd rev lever and footbrake.

magicniner
16-10-2018, 11:32 PM
Yes, motor Delta, wired my friend's 300 to use all the standard controls, just with a speed pot added, Fwd/Rev lever works as standard as does the foot brake.
He initially wired the motor Gamma (I named it after him) where the two ends of each winding were joined and one inverter phase was connected to each closed loop! :D

Richard
07-11-2018, 02:15 PM
In the end I managed to get a rotary inverter which works great and was fairly cheap (1/3 new price). There is definatley less vibration but I didn't check surface finish with the single phase.

Nice to have original lamp and subs pump going, along with all the switchgear kept as standard.