5.3.3 Noise On CT Input
The control logic of the active filter provides robustness
against noise on CT inputs. High frequency noise, above 3
kHz, does not affect the active filter performance. But if the
amplitude of this noise is twice that of the real signal, the
input analog circuitry can be saturated. As a result, the
compensation quality of harmonics on line power can be
adversely affected. Noise on CT inputs with high
amplitude, in practical terms, is not realistic and usually
indicates CT or wiring damage.
5.3.4 Effect of EMI
While Electromagnetic Interference (EMI) related distur-
bances to filter operation are uncommon, the following
detrimental EMI effects may be seen:
•
Serial communication transmission errors
•
CPU exception faults
•
Unexplained filter trips
Disturbance resulting from other nearby equipment is
more common. Generally, other industrial control
equipment has a high level of EMI immunity. However,
non-industrial, commercial, and consumer equipment is
often susceptible to lower levels of EMI. Detrimental effects
to these systems may include the following:
•
Pressure/flow/temperature signal transmitter
signal distortion or aberrant behavior
•
Radio and TV interference
•
Telephone interference
•
Computer network data loss
•
Digital control system faults
Active Filter and the Power... VLT Advanced Active Filter AAF006 D and E Frames Service Manual
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