3HP 1P motor tripping RCD tripping

[BobL]

Fellow member LarryM brought around the motor from his Jet Thicknesser yesterday for me to have a look at that was tripping his shed RCD.

On opening it up this is what we found.

http://www.woodworkforums.com/attachment.php?attachmentid=337403&stc=1
The white fibreglass sleeve covering a junction had poorly located so that it been rubbing on the rotor and had worn through to the conductor

Here is a close up of the rub point - here you can see that has been rubbed in two places.

http://www.woodworkforums.com/attachment.php?attachmentid=337404&stc=1

I replaced the sleeve and tied it back down and fixed it in place with some HT silicone.
http://www.woodworkforums.com/attachment.php?attachmentid=337405&stc=1

[dinosour]

Good recovery,
bit hard to tell from photo, but a word of caution as to a possible reduction in cross section of the wire. If it has worn through it may creat a hot spot with load. This may lead to the wire burning through. Hind sight is great and it's easy to say things after the event, but I would have applied some solder to the injury and then insulated the repair. Just trying to support not criticise.

[dinosour]

Should have added this to previous reply,
This shows the advantage of having a RCD on the circuit, without it the damage could have been a lot worse, probably a replacement or rewind of the motor.
The RCD does not only protect us but as seen it helps reduce damage to our equipment

[BobL]

Well spotted, It sure does look burned in the photo but under a 10X loupe it looked like a lump and it felt like a lump when prodding it with a scalpel tip. The more I look at the photo the more it looks like a burn and now you have me worried. It won't be too be too difficult to cut the silicone off with a scalpel and fix it.

[BobL]

I opened it all back up again and burnt away the resin and now can clearly see it is a small depression but it's small in comparison to the diameter of the wire.
I estimate that it's at most 5% reduction in the cross section area of the wire at that point so it probably would have been OK as it was.


http://www.woodworkforums.com/attachment.php?attachmentid=337442&stc=1

But just to play it safe, I put a dob of solder on it.
http://www.woodworkforums.com/attachment.php?attachmentid=337443&stc=1

[dinosour]

T for team, well done for taking the time to check the damage. Looking at the most recent pics your probably right, minimal copper loss.
Well done