Thyristor Blocking Voltage Calculation - Siemens SINAMICS DCM Operating Instructions Manual

10.23

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
The thyristor that is relinquishing the current must assume the blocking voltage,
otherwise, commutation was unsuccessful.
● Torque direction changeover (sequential logic module)
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.
The voltage at the armature thyristors is determined from the following measured values:
● Two 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
This parameter is only evaluated once during power up, i.e. a change only takes effect after
a restart or power up with saved parameters (p0976 = 11).
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 rather
a very large inductance.
Note
The thyristor blocking voltage calculation function is available as product version 5 of the
"Voltage measurement" module. You can find this information on the bar code label of the
module.
Note
The thyristor blocking voltage calculation only functions for the armature voltage
measurement via the "Voltage measurement" module.
If the thyristor blocking voltage calculation is activated with p50166 = 1 when the hardware
version of the power interface is not suitable, fault message F60058 with fault value
r0949[0] = 6 appears after the next power-up with the saved parameters.
SINAMICS DCM Control Module
Operating Instructions, 12/2018, A5E34888669A
= 1 Thyristor blocking voltage monitoring active
Descriptions of functions
10.23 Thyristor blocking voltage calculation
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