X3 Milling machine Motor Overheating and tripping house RCD

[lordedmond]

Chris

Well it's good and bad news at least you now know what's what.

It was about 48 years ago when I was in the winding dept and knowing the size it would only be a 1 hour job if the com was ok and a over night stove

But alas the charge like rhinos for small one offs

Stuart

[PK]

I burnt the motor out on my X3 in about a week. YMMV, but I don't have much time for those cheap DC motor/drive combinations.
You can see my, perfectly sensible and understated fix here: http://www.caswa.com/cncathome/X3.html

[raynerd]

Hi PK. I Actually have a .75hp inverter that I had on a motor horizontal mill once and I can get a brand new matching 3 phase motor for £110. I'll go with this if the motor goes again or controller goes. For now I'm just going to shell out and buy a new motor. Ordered it from Arc yesterday, it arrived this morning. I've hooked it up and it spins so that's a good start. However, I've had to go my inlaws and school Christmas fair so I can't tell if the problem has been cured....I will use the mill properly this evening and check but first signs look promising,

[lordedmond]

Chris

one point has made me look back through this thread.

you were cutting gears in your pic , by nature of this operation you would have been at low speed for a while. consider fitting a extra fan to help with the air flow for the motor , they blow down

the same will apply if you do go the VFD route you will need a extra fan to cool the motor , don't forget in both cases they are designed for proper cooling at rated revs not at slow speed

many large motors that have speed controllers have a large independent  fan/motor that is at full speed all the time

Stuart

[PK]

Stuart makes a good point.
Even cheaper, and this has saved me once, is the 50 cent thermister that most VFD'a have an input for. It'll stop the drive if the motor gets too hot. 

You'll think something has broken, curse and rant, then you'll touch the motor and realise that 50c just saved you $200....

[raynerd]

Stuart, pk, -  what sort OD additional fan should I be buying?

[PekkaNF]

one that fits on shroud over the motor

Visually like this:
http://www.wistro.com/index.php?co=en

Here is some commercial unit data:
www.kmmp-usa.com/products/FBI/Massblaetter/kMMp_0M_technische_Daten_2014.pdf

What is OD of your motor? Something like 63/71 motor size?

PDF, 2/3 down "Forced ventilation unit" 20W seems to get you up to 71 frme size
http://www.rotor.co.uk/forcevent.html

What sort of air duct fans there are in britain for buildings, like toilet extractor fans, or inline air duct fans? Here stadard cheap bathroom fans are not that expensive.

Found this sort of:
http://www.screwfix.eu/manrose-xf100s-20w-axial-bathroom-fan.html


There are few things to consider:
* flow must be good enough. Compuer fans are generally too small. Air is not that great conductor, therefore you need a good flow of it. Bit like a blow on angle grinder. Few wats will not do, 20W a starting point, idustrial ones seems to be 20-40w smallest sizes.
* Check that you will be not fighting agains internal fan on greater rpm.
* Air duct reducer might provide smooth transition and correct size for the shroud.

I don't know how this motor looks, i'm assuming it has internal fan and cooling air entry is at brush end, exhaust at power take out end.

Pekka

[lordedmond]

Chris

A muffin fan as used in a PCs but please fit a guard they do chop fingers , power from a 5 v Dc wall wart but you can get mains voltage ones


Stuart

[PK]

Well, right now you have no fan. So any extra air is good. If you're never going to run a VFD+motor below 50Hz, then you don't need a fan. If you are, then you might need one. 
Personally, I hate fan noise so I don't fit them. I prefer the to go up in motor power and set sensible current limits on the drives. My motors rarely get more than warm..

[raynerd]

  All up and running now!!

Is it just one of those things or is there anything I can do to stop this happening again - I.e speeds and such

[chipenter]

Not so mutch speeds but time my X1 motor got hot enugh to melt the nylon drive gear , I kept feeling the motor and iff it got to hot let it kool down , a pain when you are near the end of a job .