The line supply voltage, line current as well as the armature voltage are continually sensed in the SINAMICS DC MASTER.
A possible commutation fault (inverter commutation fault - inverter shoot-through) is detected from these quantities, which results in the following measures being initiated:
1. The firing pulses are immediately disabled in the SINAMICS DC MASTER
2. The converter sends a "turn-off command" to SIMOREG CCP (via the serial interface).
3. SIMOREG CCP turns off the thyristors by connecting the pre-charged quenching capacitors anti-parallel to all thyristors. As a consequence, the current commutates from the converter into SIMOREG CCP. The quenching capacitors are initially discharged by the currents that they accept and they are then charged with the reverse polarity. The armature current starts to decrease as soon as the voltage of the quenching capacitors has reached the value of the motor EMF. However, the armature voltage continues to increase. As soon as it has reached the limit value, resistors are switched-in, which absorb the energy fed back from the motor during the remaining time of the current reduction phase.
4. A fault message is initiated in the SINAMICS DC MASTER.
5. The SIMOREG CCP re-charges the quenching capacitors with the reverse polarity so that a new quenching operation is possible.
Each time that the line supply voltage is switched in (e.g. via a line contactor), SIMOREG CCP requires approximately 3 s until it is ready for use as the quenching capacitors must first be charged up.
After a quenching operation, SIMOREG CCP requires a certain time until it is ready for use again. The duration depends on the operations during the quenching process and immediately afterwards. On one hand, the quenching capacitors in SIMOREG CCP must be charged to the required value with the reverse polarity (approx. 10 s). On the other hand, the chopper resistors, that convert the energy into heat when the armature current is reduced, require a cooling time calculated using a algorithm in the software. Depending on the amount of energy that was dissipated, this can take up to approx. 20 min.
SINAMICS DC MASTER has setting and monitoring parameters for commissioning, operation, monitoring and diagnostics of the SIMOREG CCP. The state of the SIMOREG CCP is signaled via connectors and the triggering of the SIMOREG CCP or erroneous states are signaled using fault and alarm messages.
Data is exchanged between the SINAMICS DC MASTER and SIMOREG CCP via the serial interface.