[Kawgomoo]

I have a femco durga 25e lathe with fanuc OT control.

The machine was running fine, shut it down, came back a day later to fire it back up and it blows the breaker as soon as i hit the machine power on the 2nd time.

So as the control is going into its ready state, its tripping the breaker on the wall. Not tripping any breakers in the machine.

Also i did get it to start up and idle for several minutes before it tripped the breaker on my 3rd attempt. No alarm codes, the axis move like they should. I can't find anything wrong.

Besides kicking out the main breaker of course.

Help?

[guhl]

is there mains transformer (xxx/200V)?

[Kawgomoo]

The only "transformer" type thing i see is a line reactor that looks like one of the coils may be damaged. i attempted to test it with the meter, could not find any shorts to ground.

[guhl]

can you measure AC current via clamp meter?
or measure inductance, may be short circuit between winding

[Kawgomoo]

i can't measure current, it blows the breaker as soon as i try to power it up from the front panel, before i can make it around back. I'm also a one man show.

Will have to ask around see if someone has an LCR meter {i don't}

[cincyice58]

blowing the main disconnect, seems like that transformer is done.

[Kawgomoo]

So I'm running around poking stuff with the meter today. What i notice is that these 4 contactors at the bottom of the cabinet. The two on the left have a resistance of 2ohms between L1 and L2 terminals infinite between any terminal and L3.

Im not 100% sure what these relays control. But i believe the pair on the right wired for reversing would be the chip conveyor the other two should be hydraulic and coolant pumps.

Could this be my issue?

[guhl]

did you measure on the top of contactors? if so, there is a problem with secondary winding of main transformer

[Kawgomoo]

I circled the two pairs of contacts where I'm getting the 2ohm reading at.

My next question is what exactly is the main transformer of the machine? I will post pictures of the cabinet here shortly. There is a line reactor and also a transformer for supplying low voltage and single phase to secondary functions of the machine.

But I'm not seeing any transformers with mains sized wiring or anything like that.

[cincyice58]

the line reactor is taking the place of a main machine transformer it seems.

[Kawgomoo]

Ok plodding along. Here are some pics of the cabinet.

[Kawgomoo]

Now what I've discovered is that whatever has 2 ohms of resistance between the legs, is beneath this 5a breaker. If i take the reading at the top of this breaker it has 2 ohms, click it off, the resistance is gone. Along with the weird 2 ohms being at other places in the machine, like the gang of 4 white contactors at the bottom of the cabinet.



So that eliminates the line reactor from being the possible suspect, as it doesn't have 2 ohms across it.

I do not have the electrical diagram for this machine, and my overall skills are suspect. So I'm sort of poking in the dark here.

But from what i can tell, this 5a breaker feeds the transformer in the bottom right of the cabinet. I don't see anything visually wrong with it, no burn marks etc for what its worth. If anyone has any suggestions I'm all ears. Just poking around still trying to isolate exactly what is giving me the troubles.



I'm half tempted to fire the machine up with this 5a breaker turned off and see what happens.

[Kawgomoo]

So i isolated the transformer and took an ohm reading across the terminals {not sure this means anything}. On what i believe to be the input side of the transformer there are two pairs of terminals 0v and 220v. taking a reading across the pair i get about 3 ohms. if its not in the pair its infinite resistance. all the terminals on the right side read infinite from the terminals on the left. When i take a reading across the disconnected wires R2 and S2 i get 167 ohms. So the 2ohm reading I'm seeing at random places over the machine seems to be originating from this transformer........i think?

[Kawgomoo]

However i don't see how this would be the problem. Should it not be blowing the 5a breaker instead of the main breaker on the wall?

I don't see how this transformer could pull enough current, without melting any wires. To trip the main breaker.

[guhl]

I meant a large transformer which supply the whole machine
what is voltage of the machine?
what is voltage in your shop?

[Kawgomoo]

Machine and shop are 220v.

There is no mains transformer

[Kawgomoo]

The reason i am chasing the "2 ohms" across the legs is because ohms law tells me that 2ohm coil on 220v source is going to pull 110amps. This is more than the plaque states for max amperage of the machine, therefore in my mind. Its a problem, or at least worth exploring. The next lowest resistance i can find is 44ohm across the legs which works out to like a 5 amp draw, which seems more in line with what id expect to see.

As i said. I don't really know what I'm doing here. Just poking around with a meter and attempting to formulate some understanding of what the hell is going on inside this cabinet. Definitely over my head currently.

[guhl]

The reason i am chasing the "2 ohms" across the legs is because ohms law tells me that 2ohm coil on 220v source is going to pull 110amps. This is more than the plaque states for max amperage of the machine, therefore in my mind. Its a problem, or at least worth exploring. The next lowest resistance i can find is 44ohm across the legs which works out to like a 5 amp draw, which seems more in line with what id expect to see.

As i said. I don't really know what I'm doing here. Just poking around with a meter and attempting to formulate some understanding of what the hell is going on inside this cabinet. Definitely over my head currently.

2 Ohm of active resistance, you don't consider reactive part of complex resistance
Complex resistance Z = sqrt (Active resistance^2 + reactive resistance^2
if you measure resistance on induction motor you will get low active resistance as well, but it's inductive resistance (part of reactive resistance) is much higher
Complex Impedance

do you have transformer between mains and machine?

I guess 2 Ohms between L and L2 is the active resistance of primary winding of that small transformer from the photo

[Kawgomoo]

no, there is no transformer between the mains and the machine.

[cincyice58]

Breaker at the wall feeds machine, does the machine have a disconnect and a power on button. if so, see what is on when you switch the machine disconnect on, like cabinet fans, spindle motor fan which a lot of fanucs use 220vac, make sure all running ok. then when you push ON pb what turns on, like magnetic contactor for PSU/SPM/SVM (fanuc drives). Figure out if the breaker trips when machine disconnect is on only or when ON pb, you may even have a drives on or auxilary on pb which will turn Fanuc drives on.
Does it have a ac unit in the electrical cabinets?