I like to do bench grinders

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MRA

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Spaceba! I have a book on how to do this - I think I need to read it again. I think I remember that the size (uF) of C1 is proportional to the load on the motor - I imagine that the thing gets unhappy if you load the motor too heavily, if it runs well with no load? People here used to use a very large 3-phase motor on 'idle', run with capacitors like your scheme, and then take the 3 phases from that motor's terminals, to drive the smaller lathe, milling machine etc. Some people use a flywheel on the big motor, but I imagine the rotor itself adds plenty of inertia. The Japanese VFD is very nice, but it is a complete box of mystery - if it breaks, I have no chance. I can't even see most of the components, or count the legs on the computer chips inside it :)
 

h7eh7e

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I select the working capacitor C1 for this. 4 microforada per 100 watts of electric motor power. This is how I do it on all my machines. Starting capacitor C2 needs 2-3 times more. Alternatively, you can supply a DC motor. I saw on YouTube even put on a treadmill.
 

MRA

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That's interesting, and a useful guide figure - thanks. Do you know if (in general) VFD is unhappy if the 3 output legs are unevenly loaded? I imagine a bridge rectifier between 2 legs, leaving the third floating, might not be a good idea - but I am guessing. I have a variac - this (again plus bridge rectifier or 4 fat diodes) would be a cheaper way to go to DC, but you have to be careful not to go over the maximum current for the rating of the brush.
 

MRA

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That's interesting, and a useful guide figure - thanks. Do you know if (in general) VFD is unhappy if the 3 output legs are unevenly loaded? I imagine a bridge rectifier between 2 legs, leaving the third floating, might not be a good idea - but I am guessing. I have a variac - this (again plus bridge rectifier or 4 fat diodes) would be a cheaper way to go to DC, but you have to be careful not to go over the maximum current for the rating of the brush.
By the way, I was lucky 4 years ago to enjoy a camping / motorcycle holiday (with kids and sidecars) in SW Ukraine. A beautiful country, and resourceful people. We ended up buying bike spares in a big market in Kamianets Podilsky - if I had not been travelling with a Polish linguist, I would have been in some trouble!
 

h7eh7e

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MRA

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I like the latest device! Mounted on the cross-slide of a lathe, you could use that to sharpen end-mills held in the (not-moving) chuck - and also perhaps for sharpening knives from woodwork planer/thicknesser machine, since you can set the angle at which it cuts.

I select the working capacitor C1 for this. 4 microforada per 100 watts of electric motor power. This is how I do it on all my machines. Starting capacitor C2 needs 2-3 times more.
Meanwhile - thanks to your information, I have had a small success, so thank you from Manchester UK!
 

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