Troubleshooting alert 18345 - Coolant Motor Overload

Hey everyone--

Have an early 90's Cincinnati Sabre 1000 with Acramatic 850sx control. Working well and I'm digging into the machine nicely.

Machine has an intermittent coolant motor overload alert - number 18345. Coolant tank/conveyor has a typical 3 ph motor in it. Cleaned crud out of tank (screens at motor looked great), checked wiring harness from motor back to connector, including the pins at the connector. Pump always turns on fine when overload breaker is reset and alert is cleared. Seems to run fine- no weird noises and pump housing stays cool. Usually trips the alert when I use an M5 to turn off spindle and pump at the same time. Sometimes it'll trip when I use an M9 or the Coolant Stop button on the control. Very rarely goes while the mill is cutting or pump is turning on-- just when I want to turn it off.

So from those symptoms I'm leaning away from the motor being an issue and focusing more on the contactor and the overload breaker. Have a spare off ebay that I was thinking of swapping in. Given the age of the mill, I assume it's reasonable for a contactor and/or overload breaker to wear out? Anything else I should look at? Can call an electrician if needed, but unsure if that's going to be a big help at this point, with the relatively simple circuit I'm working with.

Also has a "murrelektronik" 23050 mounted on the side of it, which a quick search says is a motor surge suppressor. Looks clean and in good shape, at least as much as a potted plastic box with three wires sticking out of it can!

Here's a photo of the contactor and breaker, in case you're aware of issues/suggestions for them.
http://www.cnczone.com/forums/attach...d=338298&stc=1

Thanks for any help or info you can provide!

--John

The first thing is to take the contactor apart and clean the contacts on each phase you also may want to replace the 3 phase suppressor Go to Home Depot and buy a clamp on AC amp probe ($100) with a peak hold feature. Check each phase when starting and stopping the coolant motor on peak hold. Last is to replace the overload unit.


MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

Took the contactor apart, cleaned everything thoroughly with contact cleaner spray and some elbow grease. Had some carbon on both sides of all six contacts, as well as a bit of tacky dried coolant vapor on magnet assembly that's now gone.

Used my multimeter to check the suppressor diodes but had OL on all of them, so it's either fried or that's how they read at low voltage?

Put all back together and it seems to be working well. Cycled pump a half dozen times along with the spindle motor and no issues. Will assume it's fixed. If it comes back I'll swap in the replacement suppressor that I ordered.

Thanks for the help!
--John

I don't think there are diodes in a suppressor package it should only be a R-C combination to reduce arching on the contactor contacts.

MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

Ah- makes sense. Suppressor looks like this:

Attachment 338732

I incorrectly thought it was three diodes, kinda like a rectifier circuit. Explains why the multimeter would be OL on a diode test. The hazards of a little bit of electrical knowledge :-)

Thanks again!
--John

That is a 3ph snubber made up of three caps and three resistors.
It should measure open circuit between leads.
If you have to reset the O/L below the contactor, it could be bad contact on the O/L. if it is not actually the motor itself.
But the fact it shows up when turning off tends to point to the O/L.
Al.

Thanks Al. Cleaning the contactor seems to have sorted it for now. Now have spares on hand for all three components so can substitute each incrementally if problem reappears. (And of course will check the motor with an ammeter at that point too.)

--John