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4.2.
Additional functions
4.2.1.
Softstart
This type of start can be enabled either in phase control
mode or in zero-crossing mode (ZC, BF, HSC,PA).
In the case of phase control, the increase in the conduction
angle q stops at the corresponding value of the power to be
transferred to the load.
Control of maximum peak current can be enabled during
softstart (useful in the event of a short circuit on the load or
loads with high temperature coefficients, to automatically
adjust start time to the load).
When the load shut-off time (settable) is exceeded, the
ramp is reactivated at the next power-on.
Supply
Load voltage
voltage
Initial firing angle
Figure 24 - Firing ramp with phase softstart
Figure 25 - Example of conduction angle limitation in PA mode
81900A "MHW_GPC-40/600A"_03-2021_ENG_page 77
4.2.2.
RMS current limit
The option to control the load current limit is available in all
operating modes.
If the current value exceeds the limit (settable in the nominal
full-scale range) in PA mode the conduction angle is limited,
while in zero-crossing mode (ZC, BF, HSC) the cycle time
conduction percentage is limited.
This limitation ensures that the RMS value (i.e., not the
instantaneous value) of the load current does NOT exceed
the set RMS current limit.
The illustration shows an example of limiting the conduction
angle in PA mode to comply with an RMS current limit that
is less than the nominal load current.
I
< I
rms
nom
t
t
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