Control Functions - Bitzer VARIPACK FD+6 Instructions De Service

Fig. 22: Schematic wiring diagram HS.85 compressor, Part 2

6 Control functions

Graphical explanations of the control functions de-
scribed in the following sections, see figure 23, page
35.
Compressor start and STO
The compressor can only be started when it is released
(STO input closed), the start command is given (DI1
closed) and the "start to start interval" and the "stop to
start interval" (10 s) of the compressor have elapsed.
When controlled via an external setpoint signal and a
control characteristic ''0 .. Max'', a setpoint > 1% must
additionally be applied.
As soon as the start command is cancelled (DI1), the
compressor is shut down via the ramps.
If the release is cancelled (STO), however, it is directly
switched off.
CB-100-2
"Ramps"
To optimize the operating performance, the compressor
ramps can be adjusted. For slow reacting systems such
as water chillers or refrigeration systems with only one
evaporator, we recommend selecting slower ramp
times while compound systems may require faster
ramps. Apart from the limitation of the external setpoint,
these ramps define the frequency change for the
"Force" function.
As standard, the shortest ramps are set for the respect-
ive compressors. To start and stop the compressor,
that means below the minimum frequency, the optimum
ramps are fixed in the VARIPACK frequency inverter
and therefore ensure a safe and reliable compressor
start.
"Start to start interval" (time rate between two
compressor starts)
The compressor start activated by a VARIPACK fre-
quency inverter results in a lower mechanical stress on
the compressor drive gear and less heating of the mo-
tor compared to a direct start. By this, a higher number
of compressor starts per hour are allowed. An excess-
ive number of compressor starts, however, should be
avoided.
33