CB-100-1
62
"Hold time after start at minimum frequency"
After the compressor start in temperature-controlled
systems with only one compressor there may be signi-
ficant pressure drops in the low-pressure circuit. The
reason for this is that, due to the high setpoint devi-
ation, the compressor is powered up too fast so that the
pressure cannot be regulated quickly enough by the ex-
pansion valve. This can be avoided by setting a time in-
terval after the start during which the minimum fre-
quency of the compressor is maintained before the
compressor switches to normal operation. As standard,
the value of 0 s is set.
Operation at 50 Hz (Force)
In case of long pipelines and rising lines or a not optim-
ally dimensioned suction gas line, there is a risk of oil
migration during the long partial load phases. If the fre-
quency and therefore the mass flow is increased, the
oil can be circulated back and a compressor shut off
can be avoided. This can be realized by the "Force"
function of the VARIPACK frequency inverter. If a lack
of oil in the oil tank or compressor is reported, the di-
gital input DI2 of the VARIPACK frequency inverter can
be activated to operate the compressor at least 50 Hz.
"Resonances avoidance"
If vibrations which cannot be eliminated easily occur in
a specific range of operating frequencies, these fre-
quencies can be avoided. For this, two frequency
ranges can be defined in which the compressor does
not remain during operation. When the setpoint ex-
ceeds the defined initial value, the frequency remains
constant until the setpoint has exceeded the end value
and the frequency range is skipped. When shutting
down, the frequency is maintained accordingly until the
setpoint has fallen below the initial value.
Automatic limitation of the maximum frequency
During operation in the field weakening mode, the
VARIPACK frequency inverter limits automatically the
operating frequency as soon as the maximum operat-
ing current of the compressor or the VARIPACK fre-
quency inverter is reached. This allows an economic di-
mensioning of the combination of compressor and
VARIPACK without running the risk that the VARIPACK
frequency inverter under exceptional operating condi-
tions (high condensing temperature, start-up or start
after a long standstill) switches to fault due to thermal
overload.
Fig. 16: Graphical representation of the general control functions
Содержание VARIPACK FDU+12
Страница 12: ...CB 100 1 12 1 2 3 4 Abb 7 Steuremodul abmontieren...
Страница 46: ...CB 100 1 46 1 2 3 4 Fig 7 Dismounting the control module...
Страница 64: ...CB 100 1 64 Fig 17 Graphical representation of the general control functions of the extension module...
Страница 70: ...Notes...
Страница 71: ...Notes...
