MM440 DC-Link

Hi,

I have 2 drives, 2 MM440's, 4kW.

The DC-links are coupled via 15Amp sitor fuses.

The main supply is connected via thermistor.

The drives are connected to a PLC (profibus). So no physically I/O.
The profibusmodules have 24V supply (always)


The thermistors do not have contacts, so I do not know when one of the thermistors does not function, why ??


well, when one drive has no main supply, it doesn't stop funtioning, because it can take it's voltage from the DC-Link of the drive that still has main supply.


Is there a parameter, or something I can do to stop the drive when it has no main supply (if it takes voltage/current from the other MM440) ?


Regards

no help ?

no help ?


please ?

Why are the DC busses connected together? What are you calling "thermistors"? A circuit breaker, Fuses,?

By thermistor are you referring to a motor temperature sensor? The MM440 does have motor thermal protection capabilities. If yes, then you should set P601 and P604. See "MicroMaster 440 Operating Instructions" (6SE6400-5AW00-0BP0), pages 87 and 158.

Or, are you using some type of regenerative braking? While I have not used this, I understand that braking can be integrated in the DC link. Maybe someone here can help if this is what you are doing and need help setting this up. See "Micromaster 440 Operating Instructions" (6SE6400-5AW00-0BP0), page 136. This section explains a couple of methods of decelerating when the drive receives an OFF1 or OFF3 command. Perhaps this is what you are after?

Does the following picture show what you are doing?

english

bad anglish from me...

Not thermistor, but circuit breaker, brbrbr

When I wrote that, i must have been Silly...


What I do is I have 2 drives, the power supply is connected via Circuit breakers. But the DC-Link is also coupled to reduce the kWh (the usage on the net).

BUT, when a circuit breaker is out, one drive gets no power supply. It keeps functionning because it is still feeded via the DC-Link of the other drive...

Is there a bit in the drive that says that the power sypply is okay or not ? Why do I ask this, well, the circuit breakers have no contacts that are connected to the PLC.

Greetz

Well, right off the bat, I'd say GET AUX CONTACTS ON THE CIRCUIT BREAKERS FEEDING THE DRIVES. If either breaker trips, or is shut off, you need to disable the drives. Seriously.

There are status bits in Siemens drives to indicate if Line Power is available, but they are (on AC drives) derived off of the DC Bus, so in your case, as long as one drive is fully powered up, both will read healthy.

There are several valid reasons for paralleling the DC bus on AC drives, one of the most common being where you have a two drive payoff-rewind system. In that case, the payoff is almost always in a regenerative mode. Rather than just dumping all that power into a resistor bank, you let it go to the drive that is actually motoring. This saves the cost of regenerative front ends.

The problem with this scheme is that unless you shut down both (or all) drives in the event of a fault on one (like one main breaker opening), you require the front end rectifier of the remaining drive to source all power required by both. If the remaining drive is of a much larger capacity, you may be okay (mostly). If the two are of the same capacity, you risk damaging the input rectifiers on the functioning drive.

Aux contacts for breakers aren't that expensive, compared to drives.