Pillar drill motor change - too much power?!

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Dokkodo

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My old meddings' 3 phase motor decided to stop getting along with the cheapo chinese inverter that had served it pretty well for a few years. Rather than blow loads of cash on a better inverter seems to be sensible to just get a 240v replacement and do away with the faff the inverter brings.

There are a few second hand ones going soon that i have my eye on, including one with twice the HP of the original 3ph one. This appeals to me because on the inverter it always lacked gumption and would too easily get jammed up in big cuts. However, is there such a thing as too much power? will it not just mean more torque and no mercy on its subjects/my fingers?
 
The problem you are likely to have is that the motor shaft will be bigger and the distance for the mounting feet to the centre of the shaft (aka Frame Size in mm) will likely be larger for a more powerful motor. See the appendices in my motor paper referred to below.
These are not insurmountable but will need certain skills and metalworking machinery to sort out.
The reason your inverter set up seemed gutless was that either the inverter did not have a sensorless vector mode or you had not enabled it. Also to work properly, the inverter needs to go through a calibration process to measure the motor parameters.
 
Great, thanks.

I will check re: shaft size, theres a fair bit of travel on the motor tensioning travel rods so i think that might be ok.

More interesting to know about the inverter though, i wonder whether it had the capabilities all along. It was only a £50/60 jobby so i dont expect it had bells and whistles but i will have another look at it in case.

It worked well for a few years as I said, but recently it became completely gutless and also the motor was making audible crackling noises, so i thought id better retire the whole setup before anything got permanently ruined/caught fire... I was curious as to why the sudden change though, now I wonder whether a long period without power might have caused a reset in the inverter, or the prolonged use had worn down the motor
 
Hi there

I had a meddings single phase and swaped out the motor for a three phase with no problems, and some time later helped a freind out who brought a cheap three phase machine by giving him my old single phase motor. A lot of cheap invertors do not produce true sine waves, instead they produce modified or quassi sine waves and a lot of harmonics but should not be an issue for a motor, can damage electronic equipment though.
 
You don't say which Meddings you have, the power of the original 3-phase motor or what you mean by a big cut, but my Fobco Star with a 250W 1-phase motor will drive a 35mm Forstner (the biggest I've tried) through hardwood without complaint. If your Meddings/inverter setup was baulking at that sort of cut, there was surely something wrong from the outset. Apologies if I'm teaching granny, but presumably you changed the motor connections from star to delta when you fitted the inverter? Just a thought, because if not you would get loss of torque and eventually burn out the windings, which seems a possible explanation for the symptoms you're seeing/hearing.

On the 'is there such a thing as too much power' question, I probably wouldn't worry about it on sturdy beast like a Meddings. The trouble comes when the motor is too powerful for the machine and could damage it if things go wrong. I have a lathe which would take my arm off without pausing for breath if I let it - the thing is not to let it! I personally wouldn't be happy with with a drill press that was so weedy it couldn't do me an injury!

I'd go for a 1-phase replacement if it can be fitted without major mods - an inverter on a drill press seems a bit OTT IMO.

Best, Bob.
 
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