6.15 Parameters: 28-** Compressor
Functions
6.15.1 28-0* Short Cycle Protection
When controlling refrigeration compressors, often there
will be a need for limiting the numbers of starts. One way
to do this is to ensure a minimum run time (time between
a start and a stop) and a minimum interval between starts.
This means that any normal stop command can be
overridden by
28-02 Minimum Run Time
and any normal
start command (Start/Jog/Freeze) can be overridden by the
28-01 Interval between Starts
.
None of the two functions are active if
Hand On
or
Off
modes have been activated via the LCP. If selecting
Hand
On
or
Off
, the two timers will be reset to 0, and not start
counting until
Auto
is pressed and an active start
command applied.
28-00 Short Cycle Protection
Option:
Function:
[0]
Disabled Timer set in
28-01 Interval between Starts
is
disabled.
[1]
*
Enabled Timer set in
28-01 Interval between Starts
is
enabled.
NOTE
This parameter can only be
[1] Enabled
if
25-00 Cascade
Controller
is set to
[0] Disabled
.
28-01 Interval Between Starts
Range:
Function:
300 s
*
[0 - 3600 s] Sets the time desired as minimum time
between two starts. Any normal start
command (Start/Jog/Freeze) will be
disregarded until the timer has expired.
28-02 Minimum Run Time
Range:
Function:
12 s
*
[0 - par.
28-01]
Sets the time desired as minimum run time
after a normal start command (Start/Jog/
Freeze). Any normal stop command will be
disregarded until the set time has expired.
The timer will start counting following a
normal start command (Start/Jog/Freeze).
The timer will be overridden by a Coast
(Inverse) or an External Interlock command.
NOTE
Does not work in cascade mode.
6.15.2 28-1* Oil Return Management
Insufficient lubrication can be the result of oil depositing
itself in pipes and bends. The oil deposits can be returned
to the crankcase by increasing velocity for short periods at
regular time intervals or when velocity is too low to ensure
adequate oil return.
With Oil Return Management, these two oil return
mechanisms can be programmed into the Compressor
Drive™. With Oil Return Management enabled, the
frequency converter performs oil return by boosting the
compressor speed to 4200 RPM (70 Hz) for a selectable
duration (as programmed in
28-13 Boost Duration
). The
boosts are performed at fixed time intervals (as
programmed in
28-12 Fixed Boost Interval
) or if the
compressor speed has been less than 3000 RPM (50 Hz) for
too long (as programmed in
28-11 Low Speed Running
Time
), whichever occurs first. Thus, the maximum time
between two consecutive oil return boosts is as
programmed in
28-12 Fixed Boost Interval
. Oil return boosts
are indicated by a text message on the LCP.
NOTE
If
4-13 Motor Speed High Limit [RPM]
or
4-14 Motor Speed
High Limit [Hz]
is set to the boost speed 4200 RPM an oil
boost may cause unwanted staging or destaging if
parameter group
25-** Cascade Controller
is active.
28-10 Oil Return Management
Option:
Function:
[0]
*
Off
No function
[1]
On
Oil return mechanism is active.
28-11 Low Speed Running Time
Range:
Function:
60 min
*
[1 –
1440
min]
Running at low speeds for extended periods
may result in inadequate oil return to the
compressor crankcase. Set this parameter to
the maximum running time the compressor
is allowed to run at a speed below 3000
RPM/50 Hz. An oil return boost is performed
each time the compressor has been running
at a low speed for this maximum time.
28-12 Fixed Boost Interval
Range:
Function:
24 h
*
[1 –
168 h]
An oil return boost is performed at fixed time
intervals to complement the oil return boosts
triggered by inadequate flow speeds
(
28-11 Low Speed Running Time
). The fixed
interval boosts ensure that oil return boosts
are performed even when no boosts have
occurred due to low flow speed (
28-11 Low
Speed Running Time
).
28-13 Boost Duration
Range:
Function:
30 s
*
[10 – 120 s ] This parameter controls the duration of oil
return boosts.
Parameter Descriptions
Operating Instructions VLT
®
CDS302 and CDS303
118
MG34M302 - VLT
®
is a registered Danfoss trademark/Commercial Compressor
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