14.4 Soft Start with Burst Firing
This is an additional function to the Burst
Firing. The unit start in phase angle mode
with a ramp starting from zero up to the full
tension in the cycles number set in the
parameter.
When the ramp is over, the thyristor unit will
stay in conduction at full voltage up to the end
of cycles of
burst. The S+BF firing is used to control small
inductive loads to avoid inrush surge current
and to reduce the electromagnetic interfer-
ences.
The example show the firing with Burst
cycles =4 and start ramp half cycles=3.
Voltage Supply (V)
Load Voltage (V)
25%
50%
75%
100%
ON
OFF
Voltage Supply (V)
Load Voltage (V)
25%
50%
75%
100%
ON
OFF
Voltage Supply (V)
Output Voltage (V)
ON
OFF
Setpoint Value (%)
Load Voltage RMS (V)
Ramp Up
Ramp Down
14.5 Phase Angle
The Phase Angle firing allow the control
of the power on the load, for this firing
the thyristor can be in conduction only
for a part of the voltage cycle.
This part of the voltage cycle is
adjustable in function of the input signal
from 0 at 100%.
The PA firing is normally used for control
the inductive loads, and is also possible
control a primary of transformer
coupled with the cold resistances like:
Superkanthal, Molybdenum, Platinum,
Tungsten or Quartz Lamp. The only
disadvantage with phase angle is the
possible generation of interferences
that however can be reduced with opportune
filters.
14.6 Soft Start with Phase Angle
This is an additional function to the
Phase Angle. The firing angle of the
thyristor increase or decrease up to the
final setpoint value.
The Soft start ramp is an important
feature to reduce the inrush current
with transformers during the during
the cycle of magnetization or with cold
resistance that are near to the short
circuit when they are supplied.
Setpoint Ramp Up / Setpoint Ramp
Down.
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