F030 fault in DC drive Simoreg 6RA70:dc master

Problem:

During running condition DC motor tripped showing “F030” fault.

Description:

I work in a Steel mill. And it is one of the renowned Steel mills in my country. Previously it was 18 stand mills but after some correction it is now 20 stand mill and for this purpose we changed one of DC motor named shear#2 or flying shear. We replaced it with 250KW DC motor. Previously it was 170KW. After changing this we faced with this new problem. It some times tripped in running condition especially in 3X12mm rolling showing F030 fault. We used DC drives from siemens and the model was Simoreg 6RA70.

The fault code was 2.

Analysis:

From simoreg DC master 6RA70 manual we see  F30 means the followings

From fault code we see the root cause of this fault trigger is “The current crest curve breaks upwards” as our fault code is 2 (two).

Now the interesting part, from this we understand that this problem must related to some monitoring function. As Shear#2 does not run all the time and only used for cobble chopping and optimization chopping, it is probable that it may take some extra current for very short time.

Then we found the particular monitoring parameter. It is U580 (2580) “Control word for commutation monitoring”.

By this parameter we define which commutation monitoring criteria the drive will use. In our drive it was select in 4. So Decision criterion 3 that means maximum current actual value is evaluated. That’s the reason as it was reaching the limit as it tripped.

Then we changed the parameter from 4 to 7 means all three criterion will be used.

Then the problem solved.

Regarding the manual and figure: 2

Each decision criterion has a numeric code.

If more than one decision criterion is to be evaluated, the sum of the relevant digits must be entered.

There also rules for selecting the parameter. If u select 0 then “none of the three criteria are evaluated” will be selected. If u select 1 then “Decision criterion 1 (sufficient voltage time area for commutation) is evaluated” will be selected. If u select 2 then “Decision criterion 2 (curvature of the current crest curve) is evaluated” will be selected. If u select 4 then “Decision criterion 3 (maximum current actual value) is evaluated” will be selected.

Now if you want to select both criterions 1 & 2 then enter value 3. If you want to select both criterions 2 & 4 then select 6. If you want to select all of the criterions then select 7, the sum of all codes.