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3.7
n
:
oteS
uSe with inductive loadS and tranSformerS
a. When the GFW is working it is not allowed to open neither the connection between GFW and the transformer nor the connection
between the transformer and the load
b. The maximum current controllable by the device is less than the product's rated value (see technical data).
c. In ZC and BF trigger mode, use the Delay-triggering function to limit peak magnetization current.
d. In PA trigger mode, use the Softstart function.
e. DO NOT use HSC trigger mode.
f. DO NOT connect RC snubbers in parallel to the transformer primary.
g. Always set Dip-Switch 5 to ON (and run the initial configuration procedure described in paragraph 3.4)
3.8
t
rigger modeS
In power control, the GFW permits the following modes:
- modulation through variation of the number of operating cycles with "zero crossing" firing mode
- modulation through variation of the phase angle
ZERO CROSSING MODE
A type of operation that eliminates EMC interference. This mode manages load power through a series of ON operating cycles rather
than OFF operating cycles.
ZC - constant cycle time (Tc ≥ 1 sec, settable from 1 to 200 sec)
Cycle time is divided into a series of conduction and non conduction cycles in proportion to the power value to be transferred
to the load.
Figure 44
For example, if Tc = 10sec, if the power value is 20% there is conduction for 2 sec (100 conduction cycles @ 50Hz) and non
conduction for 8 sec (400 non conduction cycles @ 50Hz).
BF - variable cycle time (GTT)
This mode controls power on the load via a series of conduction ON and non conduction OFF cycles.
The ratio of the number of ON cycles to OFF cycles is proportional to the power value to be supplied to the load.
The CT repeat period is kept to a minimum for each power value (whereas in ZC mode the period is always fixed and not
optimized).
38
80999D_MHW_GFW 400-600A_07-2020_ENG
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