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micro mill electricals problems, help please!!

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BaronJ:
I agree,  rewinding an armature of that size is just not cost effective.

I see two reasonable alternatives, go for a belt conversion with an induction motor or find a treadmill with a similar (physical size) motor and use the controller from that, though it should be possible to modify the existing controller by fitting larger FET's.

pmdevlin:
thanks chaps, new fet on the way, thanks to John I know how to do that, and I got a new pot, a few quid, so worth having. Ill get the board operating as it was when it  left John.

I will tonight revisit all connections just for a last look, I fancy another look in the motor (I can now disassemble in less than 5 minutes!), then looks like its bite the bullet time with the  motor. Hopefully its not a new board after all this as they are now out of stock anyway! :hammer:

Fleming's Left Hand Rule

read it, so, in theory, if I have a circuit tester on opposing segments of the comm, the circuit should be sound, if not, its burnt out, and would this have caused the misfire I briefly experienced? Then if the motor was slow enough, or stopped on the dead segments, would that have been the short circuit, big flash, and fuse blowing?

Sounded a very clever statement by me, ha ha  :headbang:

lordedmond:
Paul
In theory yes in practice no

The resistance of the winding is so low you will not be able to tell if it's ok or a short.

First you would need to know if it's wave wound or lap wound

To give an idea on the armatures I used to rewind the coil was just a u shaped loop of 1/2 inch by 1/16 inch coper tape thing of the difference between that and a short , not so easy

That's why you do the volt drop test to pick up the difference between each seg , not a definitive reading but a consistent one across the entire commutator then it's deemed to be ok.

I do think it's the pulsed DC that causes the flash overs were a steady DC will not but the motor by your comments has not been tested on DC above 60vdc it would have been good if it could have been tested on a higher voltage for that my have shown up the fault

A point to note these controllers put the full volts on the motor but for slow speed they only turn on for say 5% of the time as you advance the pot it turn on for longer until it's on full time for full speed , so the motor always sees the full volts but in spikes

Have fun but be safe bet you know more than you wanted now , but you asked for help 😄

Stuart

steampunkpete:
In case you need it, a manual for a micro mill (which might be yours - it uses the same motor), including an exploded parts diagram is available here:


--- Quote ---http://www.boukal-naradie.sk/soubory/36498/Manual_SX0.pdf
--- End quote ---

pmdevlin:
well that proved nothing, other than its gone cold outdoors again, and the shaft circlip has disappeared to the other side of the county when I took it off :palm:

The comm has a circuit all the way round, no matter what segments I am on, don't know what that means! probably nothing :scratch: Im bored with this machine now, its time to finish my latest project which does not need a milling machine, where did that ball of wool go?

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