Although the official description is rather academic, the real situation in the field usually cannot be separated from the following:
1. A/D conversion circuit aging or failure
This is the most common reason for us.
This is the most common reason. The A/D chip is getting old, the temperature is high for a long time, and the power grid fluctuates instantly, all of which may cause it to start reading inaccurately.
Typical symptoms of A/D problems:
* The machine just turned on the jump
* Higher temperature jumps
* Measured current waveform is not symmetrical
* Running on the test bench for a few minutes and then reporting errors
2. Current detection element bias
Many Mitsubishi drives rely on Hall elements or shunt resistors to measure current internally.
Whenever there is a slight deviation of these things, the driver will "mistakenly” think that the current is not right.
We have seen:
* Shunt resistor value drift
* Hall elements getting wet
* A burned out power section that biases the detection loop
3. Poor wiring contacts
This is really the big one for field failures.
Common culprits:
* U/V/W oxidized.
* Deformation of the encoder wire under tension
* Oil or iron dust in the plug
* Poor grounding
The most annoying thing about these problems is - it may come and go, and then jump again when your people leave.
4. Shorted power module (IGBT/IPM)
If the power module is shorted, the current must be abnormal and the drive just pulls the trigger.
This type of problem is generally accompanied by:
* Obvious burn marks
* Jumping at the moment of energization
* "Popping” sound of the machine
5. PCB aging, void soldering, corrosion
We receive a few PCB aging every month for drives that have been around for about 10 years.
Common conditions:
* Cracked solder joints
* Capacitor leakage
* moisture into the board
* Localized yellowing and blackening
All of these may make the feedback circuit out of the problem.
How to Determine the Scene?
If you encounter Alarm 17 in the field, you can simply follow our usual way of thinking:
① Record the alarm and model number first
The MDS-A, MDS-B and MDS-D series are quite different, and the specific model number is important.
Some generations are not so sensitive to alarm mechanisms, while others are particularly picky.
② Check all wiring after stopping
Include:
* Motor three-phase wires U/V/W
* Encoder feedback line
* CN connector
* Grounding
* Plug oxidation, oil, etc.
We have encountered countless cases of "the plug is not plugged in properly”.
③ Measure the motor
Although Alarm 17 is most likely a drive problem, the motor if:
* Insulation is off
* The windings are short
* The cable is torn
The drive will also suspect that "you're not getting the right current” and raise an alarm.
④ Put the drive on the test platform to run
This is the most effective way to determine.
Our own Mitsubishi test platform can:
* Simulate the load, run high-speed
* Look at the current waveform
* Detect whether the A/D circuit is drifting
* Check if the power module is normal
If Alarm 17 jumps on the test platform, then it is 100% internal problem of the driver.
⑤ Then judge whether to repair or replace
Internal problems are usually focused on:
* Bad A/D chip
* Shunt resistor bias
* Hall sensor bias
* IGBT/IPM short circuit
* The board is blackened
* Capacitor aging
These are the ranges we often fix.
Alarm 17 How to Solve the Most Stable?
According to the hundreds of repaired cases in our hands, generally the following methods:
* Replace the A/D related circuits.
This is the highest probability solution.
* Repair or replace the power board
Module is shorted, burned black, power segment is bad - direct replacement of the board is the least troublesome.
* Clean up the wiring, redo the grounding
This category costs almost nothing, but solves a lot of "field intermittent alarms”.
* Repair the motor if it is short-circuited.
As long as the motor current is abnormal, the drive must alarm, regardless of whether the drive itself is normal.
* Drive is too old, corrosion is serious → recommend directly replace it
More than ten years of drive, sometimes repair is just "painkiller”, not as good as a direct replacement of the refurbished.
How to Avoid Jumping Alarm 17 in the Future?
Our own customers if the equipment environment is relatively harsh, are recommended:
* The cabinet should be blown out once every six months
* Re-grounding
* The wire harness should not be immersed in oil
* Plugs should be unplugged and cleaned once in a while
* Capacitors should be replaced once every 5-8 years (this is really critical)
The cost of prevention is very low, but it can make the drive last for several more years.
