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2.3 Burst-firing operation for transformer loads and loads with a
high positive temperature coefficient TC (mixed operation)
H
Soft start
H
Power units 05.01
It is not possible to change over to phase-angle control in this
mode of operation.
For the first switch-on of the thyristor power unit, or after being switched off by
inhibiting the firing-pulses, after a supply line interruption, or if the setpoint
was switched off for more than 8seconds, there will always be a short phase-
angle controlled start (area a in the diagram).
After this soft start, the controller switches over automatically to burst-firing
operation if the given setpoint is larger than the minimum setpoint + 10% of
the setpoint range (area b in the diagram).
Example:
Setpoint range 2 — 10V
The changeover to burst-firing operation takes place at
2V + 10% of 8V = 2V + 0.8V = 2.8V
After this changeover, the power output is regulated to follow the setpoint in-
put provided.
If the power unit runs into current limiting
controlled start, then the output is regulated according to the maxi-
mum current given by the curent limit setting, even for low levels of
the setpoint input.
1. with extra codes TR/TO
2 Operating modes
1
during the phase-angle
15
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