Siemens SIMADYN D Manual page 484

Closed-loop thyristor current control
Pulse position
monitoring
Synchronizing
Pulse waveform
Double firing
Note
Enable
5-44
During operation the pulse position monitoring checks the difference
between the firing angle setpoint and the actual value.
If the absolute value of the deviation exceeds the limit [°], entered at input
PC6.DIL, the counter is incremented at each calculation. If the counter
status reaches the value at PC6.DIZ, the difference was too high and
directly initiates a hardware pulse inhibit and a fault message.
A line supply frequency change is mapped in the internal counter values
on the ITDC and is immediately taken into account, after transfer, in the
firing angle actual value PC6.XAS and in the 60° value of the line supply
periods PC6.X6R (refer to the Section: Synchronization and pulse
generation).
The counter status "60° of the line supply periods" is used to shift the
firing pulses.
The firing pulse waveform should be selected using input PC6.LPD and
internally changes-over the ITDC. The "7 kHz pulse chain" waveform
(PC6.LDP = 0) is selected as default, as the thyristor gating in the Sitor
sets is only designed for pulse chains. If long pulses are output to a Sitor,
this destroys the gating!
Long pulses should only be set for special thyristor gating circuits.
The length of the main pulse should be parameterized at input PC6.LMP
(1.1 [ms]) and the second pulse at input PC6.LFP (1.1 [ms]). The pulse
length may not exceed 45[°el], and must be adapted to the line
frequency. We recommend that the length data are kept the same..
Operation: Double firing results in a special status of the closed-loop
thyristor current control and is selected using the command PC6.DZ = 1.
For fault-free operation, output PC6.DZM should be set to 1. When
activated at SOL.DZM, the output voltage goes to zero and a free-
wheeling branch is therefore enabled. The first firing pulse following the
enable is continuously output with the associated firing pulse of the same
phase. This means that the DC circuit is de-coupled from the line supply
(refer to Section: Definitions).
The double firing command is directly executed. It can be switched-in at
any time in rectifier operation; this is not possible in inverter operation.
The command can be withdrawn at any time.
After the double firing has been de-activated, the firing pulses are
generated again in synchronism with the line supply.
The current controller and therefore the firing angle setpoint are tracked
(corrected) by the switch-over logic stage during double firing operation.
If the controller or pulses have not been enabled (EN=0), the setpoint
(WAF) is pre-assigned the constant firing angle of 90°.
System- and communication configuring D7-SYS - SIMADYN D
Edition 06.2002