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Meddings MF4 drill electrics

adding an inverter etc....

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Toby16/01/2017 07:33:18
117 forum posts
17 photos
Posted by Mark C on 15/01/2017 19:10:58:

Toby, the my output is better than that after a choke (I realise you are measuring the transistor drive voltage so it may well be different). I don't have any traces from the scope but the biggest error I saw was the shape of the wave (it was a little "stepped" and there was some offset or dwell at zero crossing).

A good point. Yes, to avoid confusing others, that top trace I posted is the input to the final drive stage of the inverter. The output will be filtered, either internally or effectively by the motor, so will not be anywhere near as bad as that. I just posted it to show how much electrical noise there is internal to the inverter. How much of that gets out (either to the motor or back through the supply) depends on how good the filtering is - both internal to the inverter and external in the form of EMC and output filters.

Toby

Toby05/02/2017 17:17:23
117 forum posts
17 photos

I realised I had not updated this with the latest progress - the inverter is temporarily on a bit of ply so I test everything out but wired into the original start/stop switches.

Yes, I know the wiring is not exactly to the regs but it will get done properly when I put it all in a box, honest!

After a bit of playing with the inverter settings I was ready for some drilling. First a 10mm drill through 10mm of steel, then follow that up with a very cheap 20mm blacksmith drill. The drill was visibly blunt but it didn't even break a sweat, even when leaning on the star handle I could only get the current indication on the inverter up to 1.85A (no load is 1.7A). IIRC this was on 300rpm.

I do think I need a bigger drill vice though....

drilling20mmlr.jpg

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