Issue February 2002
Document Number: 13124
- 6 -
The circular switching mode distributes the load uniformly on all elements such as contactors and
capacitors. A further advantage of this mode is that a capacitor step, when switched out, has enough
time for discharging before it is switched in again.
The advantages of the circular switching sequence are also applicable for the so-called hunting
programs. With the switching sequence 1:2:2:2:2:2, for example, the "double-size" steps are likewise
switched in circular switching sequence. The "single-size" step will then be used only for fine tuning.
With the switching programs of equivalent hunting steps, e.g. 1:1:2:2:4, the hunting steps of same size
(1:1 or 2:2) will also be switched alternately.
2.5. Optimized switching performance
The
ESTAmat PFC
Controller
measures continuously the demand for reactive power and the
variations of it and, due to the optimized switching performance, switches in or out the largest possible
capacitor step. In case of, for example, a power factor correction equipment of 25 : 25 : 50 : 50 : 50
kvar, the
ESTAmat PFC
Controller
will immediately switch in a step of 50 kvar instead of gradually
switching in steps of 25kvar. This way, the number of switching operations is reduced, which results
in an increased life expectancy of both the capacitors and the contactors.
2.6. Generator operation (4-quadrant operation)
The increasing use of renewable energy sources (e.g. wind, solar, biogas) and thermal regeneration,
as also the application of emergency power supply systems, require that state-of-the-art power factor
controllers operate trouble-free in case of a feed-back of active power into the general supply mains
(generator operation). In both cases of energy supply and of energy feed-back, the
ESTAmat PFC
Controller
can identify correctly the inductive reactive power and compensate it.
2.7. Switching delay time
The period between lighting-up of one of the light-emitting diodes (LED) ("
ind
","
cap
") and the
switching in or out of capacitor steps is defined as switching delay time. The switching delay time can
either be determined by the
ESTAmat PFC
Controller
as a function of load, or preset by the
operator.
2.8. Blocking delay time for re-switching
The period between switching out a certain capacitor step and the earliest possible re-switching in
of the same step is defined as re-switching blocking delay. With the
ESTAmat PFC
Controller,
this
blocking delay for re-switching can be either 20, 60, 180 or 300 seconds. This period is necessary in
order to allow the voltage existing at the capacitor after the switching-out to reduce to an acceptable
level. The blocking delay for re-switching shall be selected in accordance with the existing
discharging device. Switching-in shall be effected only when the residual voltage is less than 10% of
the operating voltage.
2.9. Harmonic current - Root-mean-square current
By means of the FFT-analysis (
F
ast-
F
ourier-
T
ransformation), the
ESTAmat PFC
Controller can
determine harmonic currents of the 3rd, 5th, 7th, 11th, 13th, 17th and 19th harmonic. The presentation
is in percentage with regard to the current of the basic frequency. The Controller displays the
