Hello!

We have the following problem.
We had two MM440 drives. With a power of 0.37 kw and 2.2 kW.
We replaced them with new Sinamics G 120c, 0.55 and 2.2 kW.
Both drives operate on Profibus.
I will start by describing the problem solved with the 0.55 kW drive.
The drive controls two motors in turn, i.e. it has two DDS. The motors are connected to the drive through contactors that are triggered at the right time. One of the motors has a holding brake.

The drive worked fine, but the F7807 error occurred intermittently, about 5-10 times a day.
The error ALWAYS occurred only when trying to turn on the motor. We have tried many solutions, including measuring the resistance of the motors. Found information that Siemens does not recommend installing contactors between the drive and the motor, and we changed the STEP7 program. The controller now commands the drive (motor ON) ONLY after the contactor has actually been energized (closed). This completely solved our problem. Perhaps someone will help.

Our main problem is the 2.2 kW drive.
The drive controls two motors in turn, i.e. it has two DDS. The motors are connected to the drive through contactors that are triggered at the right time. Both motors have a holding brake. A braking resistor is also connected.
Immediately after installing a new drive, error F7807 appeared every time the motors was
started. If you acknowledge this error and continue to give the command to turn on the motor, then it will start to rotate without problems. But if you stop and try to start the motor again,
error F7807 will immediately appear.
We also modified the STEP7 program as I described above. And the problem almost
disappeared. Now error F 7807 occurs 5-15 times per day. Our equipment works completely in
automatic mode without operator participation, these errors are a big problem for us.

We've tried many options. Ideas ended, please help. Thanks!

I assume that:

The run command is removed

The switch between motors is made

The DDS is switched over

The run command is made

This may be a timing 'thing', can you extend the timing between these actions, even at the expense of good operation, and see if the snag goes away, and possibly identify which action is the culprit?

Tractor

Tractor

I assume that:

The run command is removed

The switch between motors is made

The DDS is switched over

The run command is made

This may be a timing 'thing', can you extend the timing between these actions, even at the expense of good operation, and see if the snag goes away, and possibly identify which action is the culprit?

Tractor

 Hello tractor! Thanks for the answer! We have a rather long time between switching between two motors, about 2-5 seconds. Any more ideas?

I want to mention, we also deliberately made a delay between switching +0.5 seconds on a 0.55 kW drive, since we had a problem with a quick transition from forward rotation to reverse rotation.The reverse actually did not work, the current on the motor increased greatly, while the motor did not rotate.This is how we solved the problem on the 0.55 kW drive.

Need a 'think' on this one??

The timing looks ok, what are the ramp times??

Tractor

Tractor

Need a 'think' on this one??

The timing looks ok, what are the ramp times??

Tractor

Ramp up = 0.8s

Ramp Down = 0,5s

We previously changed the ramp within significant limits.The PLC allows you to do this, since the PLC calculates the speed with some steps and limits.I want to note that the speed reference from the PLC never reaches 100%.The maximum reaches 70-80% or less of the rated speed.Acceleration starts with small speed references from the PLC.

Tractor

If the system will function with longer ramp times, I would extend both up and down to see if improves the situation as a temporary measure.

Failing that...not sure?

have you tried operating in V/F?

Can anyone, make a suggestion for this??

Tractor

 have you tried operating in V/F?  -----> I don't quite understand what do you mean?

New question published by Alex A223 is split to a separate thread with the subject Is it needed to specify the power of the resistor in the parameter?.

Best regards
Jen_Moderator