Power Factor Correction Systems
Commissioning and Maintenance
The current counter readings can be accessed via the control re-
lay: when capacitor stages are switched in manually, the number
of switching cycles appears briey in the display (multiply reading
by 1000).
Wear and tear of the switching contacts has an adverse effect on
the service life of the capacitors!
Temperature monitoring
Power factor control relays have a built-in temperature switch in-
terlocked with the control system. If a build-up of heat causes the
interior temperature of the enclosure to rise above 60 °C +/- 3 K,
the system shuts down.
Note: The evaluation of the alarm contact from the control relay
will inform the user. The temperature switch has to be reset ma-
nually.
If the system comprises several cabinets, the temperature inter-
lock is looped through all of them.
Discharge resistors
The discharge resistors are tted to the capacitor terminals for
safety reasons in compliance with VDE (German Association of
Electrical Engineers) regulations. In addition to their safety func-
tion, they are also indispensable for problem-free operation of the
system and must on no account be removed. Attention must be
paid to this point particularly when capacitors are replaced!
Choked systems
Choked systems have been specially designed for operation in
networks that are highly distorted by harmonics.
The lter circuit chokes have a strong self-heating tendency and
can reach temperatures in excess of 100 °C. They are, however,
designed for these temperatures and have a built-in temperature
switch. This switches off the contactor associated with the choke
for a long enough time until the latter has cooled down again.
Ventilation / heat dissipation
For correct ventilation ensure that there is no handicap at the air
input and also at the air output. Also ensure that the switch board
cabinet at the bottom is closed especially the area around the in-
coming cables for clean air and dened air directions. Depending
on the air pollution at the installation location, the air input and the
air output system has to be cleaned frequently.
Fan
Power factor correction systems with high power losses are equip-
ped with fans. The fan motor is interlocked in the control circuit
with a fuse and a thermostat, adjusted to 30 °C.
Capacitors
The capacitors must be checked visually during the annual ins-
pection for any mechanical changes. Any variation in capacitance
or distortion by harmonics can be inferred from the operating
currents measured. If any irregularities are detected, please con-
tact your local FRAKO representative or call us directly (Tel. +49
7641/453-0).
General
Please ensure that the system is kept clean at all times, if neces-
sary having it cleaned by skilled personnel. During the annual ins-
pection the system must be given a visual check by an electrician
to verify its good working order (sound electrical contacts, no evi-
dence of overheating, etc.).
Troubleshooting
If the power factor correction system does not operate as expected, please
investigate the following points systematically:
No reaction, no display at all on control relay.
Cause: No voltage at control relay
Action: Check voltage at terminals L1, L2, L3 and N,
check control circuit fuse,
check temperature switch.
Contactors do not close even though the capacitor stage display on
the control relay indicates switched-in stages.
Cause: No control voltage or N at contactor If four-wire supply,
no jumper installed between N and PE
Action: Check control fuses and cabling.
Contactors do not close. Cap is indicated in the display, even though
the load is inductive.
Cause: Current transformer installed in spur to capacitors
Action: Install current transformer in the main supply line,
as shown at page 4, Fig. 1.
The message “U = 0” ashes in the control relay display.
Cause: No voltage or wrong voltage connected to control relay
for measurement
Action: Check whether the voltage being measured at
the control relay is at the correct level.
The message “I = 0” ashes in the control relay display.
Cause: No current or too little current in
the current transformer circuit
Action: Check current transformer (I
min
≥ 0.02 A) and cabling.
The message “C = 0” ashes in the control relay display.
Cause: The control relay has not detected any capacitances despite
carrying out the calibration procedure. No capacitor current is
registered by the current transformer. See page 4, Fig. 2.
Action: Install current transformer in main supply line
as shown at page 4, Fig.1.
Control relay switches all stages in, but does not switch them out
when the load reduces.
Cause: Current transformer registers only the load current without
the capacitor current.
Action: Install current transformer in main supply line
as shown at page 4, Fig.1.
The reactive power control relay does not terminate the automatic
calibration procedure.
Cause 1: Fault in control circuit (contactors not closing)
Action: Check control circuit fuse and cabling.
Cause 2: Very unstable network (wide cos ϕ uctuations).
Action: Wait for stable network conditions or enter C / k and type of
connection manually (see control relay operating manual).
Cause 3: No current in current transformer circuit
Action: Check current transformer and cabling.
Reactive current consumption too high even though all capacitors are
switched in
Cause 1: Capacitor power rating inadequate
Action: Check whether all contactors have closed.
Check fuses and capacitor currents.
Review the calculation of the required capacitor rating.
Cause 2: Spur to capacitors is connected before the instrument
transformer for the utility company’s meter.
Action: Relocate the connection.
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