Variable speed control for Super Seven

The best way, IMHO, is with a 3-phase motor and a VFD. A friend got both from eBay (separately of course) for a little over £100. With the correct motor, no mods are required other than re-wiring and mounting the VFD and controls.

Hi Nick,

4 pole 3 phase motor and an inverter is the way to go. No need to do any thing with the belts. Generally leave on a mid speed setting where you get somewhere between 1:1 and 2:1 reduction from motor to spindle. f you want to do low speed work for an extended period of time then increase the step down ratio to keep the motor speed up and hence effective fan cooling.

You should find a fair selecion of suitable motors and inverters on Ebay 3/4 to 1 hp should be fine. No need to use the standard ML7 switchery. The inverter will provide no volt release and reversing from its front panel.

One slight gotcha. You might need either a spare motor pulley or a friend to bore the exisiting one out/sleeve it to fit the new motor.

Hope this helps. Call back if you need more info

Bob

Fab, Thanks Very much. What about the inverter - is there anything to go for or avoid ?. Nick

Hi Nick,

You need a 240/440 volt motor sometime known as dual voltage or Star/delta. This will have 6 terminals and in Delta mode will run from

240 volts 3 phase. Mechanical details to suit the lathe naturally

Look for inverters that have 240 volt single phase input and 240 3 phase output. Nearly all inverters have the same input to output voltage although some are coming on the market that do the step up 240 in and

440 out. These are dearer and not what you need. Incidentally 1 hp =750 watts. An inverter with a little more capacity than the motor is Ok but too much overrating means the inbuilt protection won't be optimum for your motor. Don't be tempted to run a motor with a greater power rating than the inverter. The manufacturers go to a lot of trouble putting factory fitted smoke in these inverters and you don't want it escaping!!

Something like this perhaps

are not many cheap ones on ebay tonight but if you keep looking they do crop up every now and then. If you have deepish pockets, there are packages like this which give you all you should need.

Hth

Bob

It is not clear from the advert but this item is a 3 phase motor with varispeed control I have this one & it is brilliant The "buy it now" on ebay looks like "Newton tesla Direct" site -this is where I got it from ie Newton tesla [ usual disclaimer} see

to fit and use you wont regret it Mike