SMAR LC700 - Page 176

LC700 – Users Guide
4.8
Second Transformer
The power supplies have circuits that suppress electromagnetic interferences generated by other
equipments. However, the isolation among the circuits of the output modules, the power supplies,
and the input circuits helps to prevent output transients from being induced in the power supplies
and in the inputs. In many applications the energy is supplied to the input circuits and to the power
supplies through a second transformer (Figure 4.6).
Incomming
ac
L1
L2
L3
Disc
1FU
2FU
3FU
H1
Suppressor
H1
L1
L2
L3
To Moto
r
Starters
X1 X2
Step-down
Transformer
H1 H4
X1
X
2
Isolation/
Constant - Voltage
Transformer
To power supplies
and in
p
ut circuits
To output circuits
Figure 4.6 – Power Supplies and Input Circuits Receiving Energy through a Separate
Transformer
NOTE
To minimize the generation of temporary EMI when the energy is interrupted by the interruption
key, connect a suppressor beside the transformer’s primary
.
Surge Suppression
Transient EMI (electric noise) can be generated during the commutation of every inductive electric
load. In many cases, the noise interferes directly on the origin of the commutation command and
until may damage electronic components. Those transient peaks have a time of ascent very fast,
generating a high induced tension where the automation wiring system works as the signal
transmitter and receiver due to their capacitance.