Elettronica Santerno SINUS K, User Manual

Page: 182 / 191

INSTALLATION
SINUS K
INSTRUCTIONS
182/ 191
14.1. Radiofrequency Disturbance
Radiofrequency disturbance (RFI) may occur where the inverter is installed.
Electromagnetic emissions produced by the electrical components installed inside a cabinet may occur as
conduction, radiation, inductive coupling or capacitive coupling.
Emissions disturbance can be the following:
a) Radiated interference from electrical components or power wiring cables inside the cabinet;
b) Disturbance and radiated interference from outgoing cables (line cables, motor cables, signal cables).
The figure shows how disturbance takes place:
M
INVERTER
S
T
U
V
W
R
Irradiated and conducted
noises
Irradiated noises
GROUND
Irradiated noises
GROUND
Figure 91: Disturbance sources in a power drive system equipped with an inverter.
The measures to be taken to suppress disturbance include: grounding enhancement; changes made to the
cabinet structure; installation of mains filters on the line and installation of output toroid filters on the motor
cables; optimization of the wiring and cable screening.
Always restrict as much as possible the area exposed to disturbance, so as to limit interferences with the other
components in the cabinet.
Grounding
Disturbance occurring in the grounding circuit affects the other circuits through the grounding mains or the
casing of the connected motor.
Disturbance may interfere with the following appliances which are installed on the machines and which are
sensitive to radiated interference, as they are measurement circuits operating at low voltage (
μ V) or current
signal levels ( μ A):
-
transducers (tachos, encoders, resolvers);
- thermoregulators (thermocouples);
- weighing systems (loading cells);
- PLC or NC inputs/outputs;
- photocells or magnetic proximity switches.
Disturbance is mainly due to high-frequency currents flowing in the grounding mains and the machine metal
components. Disturbance occurs in the sensitive sections of components (optical transducer, magnetic
transducer, capacitive transducer). Disturbance may also occur in appliances installed on machines with the
same grounding or metal and mechanical interconnections.
A possible solution is to enhance the inverter, motor and cabinet grounding, as high-frequency currents flowing
in the grounding between the inverter and the motor (capacity distributed to the ground of the motor cable and
casing) may cause a strong difference of potential in the system.