6.15 Par. Group 28 - Compressor Functions
6.15.1 28-0* Short Cycle Protection
When controlling refrigeration compressors, there is often a
need for limiting the numbers of starts. One way to limit
the starts is to ensure a minimum run time (time between
a start and a stop) and a minimum interval between starts.
Parameter 28-02 Minimum Run Time can override any
normal stop command and parameter 28-01 Interval
between Starts can override any normal start command
(Start/Jog/Freeze).
None of the two functions are active if Hand On or
O
modes have been activated via the LCP. If selecting Hand
On or O, 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 parameter 28-01 Interval between
Starts is disabled.
[1] * Enabled Timer set in parameter 28-01 Interval between
Starts is enabled.
NOTICE!
This parameter can only be [1] Enabled if
parameter 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) is 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 is
disregarded until the set time has expired.
The timer starts counting following a normal
start command (Start/Jog/Freeze).
A Coast (Inverse) or an External Interlock
command override the timer.
NOTICE!
Does not work in cascade mode.
6.15.2 28-1* Oil Return Management
Insucient lubrication can be the result of oil depositing
itself in pipes and bends. Return oil deposits to the
crankcase by increasing velocity for short periods at
regular time intervals or by ensuring adequate oil return
when velocity is too low.
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. Programme the duration in parameter 28-13 Boost
Duration. The boosts are performed at
xed time intervals
(programmed in parameter 28-12 Fixed Boost Interval) or if
the compressor speed has been less than 3000 RPM (50
Hz) for too long (as programmed in parameter 28-11 Low
Speed Running Time), whichever occurs rst. Thus, the
maximum time between two consecutive oil return boosts
is as programmed in parameter 28-12 Fixed Boost Interval. A
text message on the LCP indicates oil return boosts.
NOTICE!
If parameter 4-13 Motor Speed High Limit [RPM] or
parameter 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] * O 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 xed time
intervals to complement the oil return boosts
triggered by inadequate ow speeds
(parameter 28-11 Low Speed Running Time). The
xed interval boosts ensure that oil return boosts
Parameter Descriptions
VLT
®
Compressor Drives CDS 302/CDS 303
122 Danfoss A/S © Rev. 2013-07-03 All rights reserved. MG34M422
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