Thyristor Blocking Voltage Calculation - Siemens SINAMICS DCM Operating Instructions Manual

Descriptions of functions

10.20 Thyristor blocking voltage calculation

10.20 Thyristor blocking voltage calculation
The SINAMICS DCM converter offers the possibility of continually determining the voltage
available at each individual thyristor of the armature converter. The voltage is used to identify
which armature thyristors are presently conducting and which are presently blocked.
This information is available via BICOs (see function diagram 6950).
This information is used for the following functions as input variable:
● Inverter commutation fault detection and initiation of the CCP
● Torque direction changeover (sequential logic module)
The voltage at the armature thyristors is determined from the following measured values:
● 2 phase-to-phase line supply voltages (UV, VW)
● Voltage at a thyristor (for 4Q: Anti-parallel thyristor pair) (X13/X26)
● DC voltage (Va)
Selecting the thyristor blocking voltage calculation using p50166:
The thyristor blocking voltage calculation is only really required in just a few applications and
requires approx. 5% processor utilization; this is the reason that it is deactivated in the
factory setting.
p50166 = 0 Thyristor blocking voltage monitoring not active (factory setting)
Activation is recommended if a motor is not connected to the armature converter, but a very
large inductance.
Note
The thyristor blocking voltage calculation function is available from the version of module
C98043-A7117-L1-5 onwards (voltage sensing). You can find this information on the bar
code label of the module.
Note
The thyristor blocking voltage calculation only functions for armature voltage sensing via
A7117.
412
The thyristor that is relinquishing the current must assume the blocking voltage,
otherwise, commutation was unsuccessful.
Before a thyristor of the new torque direction is triggered, all thyristors associated with the
old torque direction must be blocked. The condition is evaluated in addition to the Ia=0
message.
= 1 Thyristor blocking voltage monitoring active
SINAMICS DCM Control Module
Operating Instructions, 06.2010, C98130-A7067-A1-02-7619