Once, a customer said that his machining center jumped F30021 every now and then, stopped the machine and re-powered and good, so tossed for two months, are fast neurasthenia. At first suspected that the drive, the module is removed and sent to the test, what is not wrong. Finally, we took apart the drag chain to see, inside the power line insulation skin in a position to wear with the paper, the shaft to go to that place on a slight leakage to the ground. After replacing the wire, the alarm completely stopped. So when you come across the F30021, don't be so quick to sentence the driver to death, the real culprit is often hidden in places you wouldn't expect.
F30021 pops up on the screen, what is this alarm mumbling about?
Siemens' definition of this alarm is straightforward: the power unit has detected a ground fault. In human terms, the driver realizes that the current is not going the right way, and some of it has slipped out to the "ground” side. Under normal circumstances, the current from the drive out, through the motor around and back, the whole process is a closed loop. But once the insulation is broken, line moisture, which parts of the leakage, the current will take a shortcut directly to the ground to run. SINAMICS inside the monitoring circuit is particularly sensitive to catch such anomalies, immediately shut down and report F30021, which is why some equipment obviously still look like a turn, the driver is dead to prevent it from starting again - it is to save life. It's trying to save its life.
Eight times out of ten, the problem lies in the cable that has been tossed back and forth.
Over the years, we have encountered the most F30021 cases, not the drive itself, but the motor power cable. Especially those robots, machine tools, packaging line equipment, every day in the drag chain bending back and forth, the cable outer skin looks good, inside the insulation and copper core has long been fatigued out of cracks. The cable in the drag chain, go to a particular location before the leakage, which is the most typical characteristics of F30021.
Just like the beginning of the example, not sure when the time, power off and restart and good, basically is the problem of the line. So now as long as we see F30021, the first reaction is to suspect that a few power lines. Focus on checking the drag chain in the head, the motor outlet, the corner of the bend, and by the coolant soaked place. These four places are the hardest hit.
Motors are old and the insulation skin is as brittle as a cracker
Many factories only focus on the drive, but no one cares about the motor.
Servo motors have been dry for seven or eight years or more, and the insulation of the windings inside has long since begun to degrade. Especially high workshop temperature, moisture, vibration, coolant splash, but also frequent start and stop, these are accelerating the aging of insulation. At first, just low insulation resistance, but also to hold up; to the back of the slowly leakage to ground, drive a test, F30021 on the face of the smash.
Interestingly, this motor tends to be cold when nothing happens, turn half a clock hot up before the alarm. This is actually the insulation material a heat performance is worse, the leakage is more obvious. So if the alarm is related to the running time, don't forget to include the motor in the scope of suspicion.
That braking resistor you forgot in the corner is probably the culprit!
After repairing many F30021s, we have developed a habit: after checking the motor and wires, we must take a look at the braking resistor. This place is too easy to be overlooked. Gantry machining centers, large inertia servo, lifting equipment, lifting platforms, these systems in the braking resistor working frequency is scary. If the internal parts of the braking resistor go bad, or the wiring insulation deteriorates, it can cause a ground fault as well. But the driver will not write clearly in the alarm "ground fault from the braking resistor”, it is only a unified report F30021. We have encountered several times, and in the end to find out the end of the braking resistor terminal box, clean up, change the wire, and then it is fine.
Weather can also be the cause of F30021
There is another situation is particularly amusing: sunny days nothing at all, a rainy day on the alarm; winter morning boot report, and so on the afternoon temperature up and normal. This is mostly related to moisture condensation. A lot of electrical cabinet is not completely sealed, a big temperature difference between day and night, inside the condensation of small water droplets. Water droplets fall on the plug connector, terminal row, the naked eye can not be seen, but it formed the point of leakage current, enough to SINAMICS grounding protection to trigger.
One winter, a packaging machine reported F30021 every morning and automatically good in the afternoon. The customer thought that the drive was bad, but finally found that the motor junction box had long term condensation, and the water beads were hanging there. Installed a heater, from now on peace of mind.
Drive inside the set of "scout” failure, it is not impossible!
If the motor, cable and brake circuit are all normal, then we have to think about whether the driver's own monitoring circuit is lying to the military. SINAMICS internal current transformer to sense the current state, this transformer if bad or signal drift, it may be misjudged by the system as a ground fault. This is not often the case, but in the kind of use for ten years up, suffered a lightning strike, grid surge impact, or long time high temperature operation of the drive, indeed seen. This kind of hardware problem should be sent to the professional
Siemens test bench to check, the site basically can not be diagnosed.
When it comes to the driver itself, it is the last step!
A lot of customers see the F30021, shouting to change the driver, in fact, according to the proportion of repair down over the years, the peripheral parts accounted for a large part. Only the previous ones are ruled out, before the real turn to suspect the power module itself. For example, IGBT insulation breakdown, power board leakage, current detection circuit abnormalities, aging of the motherboard, module internal moisture. Many of these failures in the static measurement is not out, must run up with load to reveal, so you have to rely on a professional test bench. Don't come up to run to change the whole machine to go, not to mention the money spent, the problem is not likely to rely on that does not go.
Take the reset button hard to carry, carry out a big hole do not regret!
Some operators see F30021, snap a reset and continue to do, a short time is able to muddle through. But the ground fault this thing will slowly grow, at first only occasional downtime, dragged to the back may be the motor winding burned, power line overheating fire, IGBT module fried, power unit scrapped, and finally the entire production line lying down for several days. Originally a few hundred dollars to replace a cable, hard to drag into the tens of thousands of dollars of maintenance orders, this thing in the workshop is really not seen.
Everyday a little more worry, you can let F30021 less come to the door!
In fact, it is not that difficult to prevent F30021 ground faults. Regularly take the shaking table to play the insulation resistance, inspection time to take a look at the drag chain in the wire skin there is no cracks, the cabinet to keep dry, oil pollution and iron debris cleaned up in a timely manner, the braking resistor wiring tightened, the aging of the motor before it is too late to test the insulation. These things look inconspicuous, but can keep most ground faults at the door. Especially the operation of more than five years of equipment, insulation testing is best incorporated into the scheduled insurance program. Normally, a little more care, than the accident and then repair a hundred times stronger.
Finally
If the F30021 is still dead with you after checking around the site, the problem is mostly hidden inside the drive.
Songwei CNC has been doing
Siemens SINAMICS drive repair, IGBT module testing, power unit repair, motor and cable insulation testing, and special diagnosis of ground faults for domestic and foreign industrial customers over the years. New parts used parts are also available. Running a full load with a specialized Siemens test bench can dig out the fault point more accurately and help customers stop the machine for a few days less.
In the end, Siemens alarm F30021 is telling you that there is a leakage current in the system that shouldn't be there. Really repair, the most common root is the power cable, motor insulation, braking circuit, moisture, dirt and these peripheral factors, drive itself bad probability is not as high as imagined. So when it comes to F30021, don't rush to dismantle the module, and start touching the most basic wires, motors and connectors. A lot of complex ground faults, check to the end, but just a plug wet, or which wire skin worn a little bit.
