Schaffner Group
User and Installation Manual
Ecosine
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10 Trap circuit disconnect
The trap disconnect jumper is an option allowing to connect a third party switch and, when required, to
add a capacitor contactor in series for the purpose of reducing the capacitive current during low load
operation. With permanently connected trap circuit, cos
φ
vs. load shows following characteristics:
Figure 33 Power factor vs. load (diode rectifier front-ends) (see section 3.13)
When the trap circuit is disconnected, cos(phi) returns to ~0.98. At the same time, the THDi will in-
crease. This may be negligible, since absolute values are low due to reduced load power.
Needed external components (not part of ecosine filter) or system functions for fully automated capaci-
tive current control:
|
Motor load (power factor) monitoring device
|
Capacitor contactor
A reduced load system status may be available as system controller output signal. In this case, only
adequate driving of capacitor contactor must be assured.
Note:
It is necessary to consider overall concept of power factor correction. A power factor correction
(PFC) system with large capacitor banks may become obsolete or massively reduced, when harmonic
filters are installed. In such cases it may not be necessary to install trap circuit disconnect functions.
0
0.2
0.4
0.6
0.8
1
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180
co
s
ϕ
Load [%]
