28-24 Warning Level
Range:
Function:
130
*
[10–
28-26 Emergency
Level
]
Selects the temperature at which a
warning shall be issued. The action
selected in
28-25 Warning Action
becomes active at this temperature.
Enter the temperature measured in
the unit selected in
28-21 Temperature Unit
.
28-25 Warning Action
Option:
Function:
Selects the action to be taken by the
frequency converter for discharge temper-
atures above the value programmed in
28-21 Temperature Unit
but below the value
programmed in
28-26 Emergency Level
.
[0]
None
No action. Only a warning will be issued.
[1]
*
Decrease
cooling
A warning is issued and the motor speed is
lowered in steps of 10 Hz every 3 minutes
until the temperature either drops below the
level programmed in
28-24 Warning Level
or
exceeds the level programmed in
28-26 Emergency Level
.
28-26 Emergency Level
Range:
Function:
145
*
[
28-24 Warning
Level
-300]
Selects the temperature at which an
alarm shall be issued. Enter the
temperature in the unit programmed
in
28-21 Temperature Unit
.
28-27 Discharge Temperature
Range:
Function:
0
*
[-2147483648 –
2147483648]
Returns the actual value of the
discharge temperature.
6.15.4 28-3* Crankcase Heating
A DC-hold Current through the motor windings can be
used as an alternative to an external crankcase heater to
keep the compressor warm when stopped.
The efficiency of the Crankcase Heating depends upon the
physical placing of the actual motor in the compressor.
If the Crankcase Heating is used together with Anti-Reverse
Protection then the drive will first brake for the set
duration followed by the heating current.
28-30 Crankcase Heating Control
Option:
Function:
Activate the DC-hold current when the motor is
stopped. The current level is defined in
28-31 Heating DC Current
.
[0]
*
Disabled
28-30 Crankcase Heating Control
Option:
Function:
[1]
Enabled
28-31 Heating DC Current
Range:
Function:
20%
*
[0 – 25%] Set the DC-hold current as percentage of the
rated motor current in
1-24 Motor Current
.
28-32 Crankcase Heating Delayed
Range:
Function:
5 s
*
[5-65534 s] This time defines the delay after a stop and
until Crank Case Heating is applied to the
compressor.
6.15.5 28-4* Anti-reverse Protection
A compressor may have a preferred rotation direction and
the instructions for cabling should always be followed, but
the consequences of a reverse rotation are normally not
fatal. The parameter group
28-4* Anti-reverse Protection
can
be set up to prevent reverse rotation at stop by injecting a
DC-brake current into the motor a few seconds after stop
followed by the eventual coast of the motor when the
discharge valve has closed.
NOTE
The DC-brake Function is not operational before any Start
Function has completed. In case of an emergency stop
before the starting sequence has completed then the
compressor may rotate reverse for a short moment after
stop. Under normal circumstances the correct sequence is
ensured by the Short Cycle Protection feature.
28-40 Reverse Protection Control
Option:
Function:
Activate a DC-brake current when the motor is
stopped. The current level is defined in
28-41 DC
Brake Current
. Not recommended for Piston
compressors.
[0]
*
Disabled
[1]
Enabled
28-41 DC Brake Current
Range:
Function:
90%
*
[0 – max motor
current ]
Set the DC-brake current as
percentage of the rated motor
current in
1-24 Motor Current
.
28-42 DC Braking Time
Range:
Function:
2.0 Sec
*
[0 – 60.0 Sec] Set the duration of the DC-brake
current.
Parameter Descriptions
Operating Instructions VLT
®
CDS302 and CDS303
120
MG34M302 - VLT
®
is a registered Danfoss trademark/Commercial Compressor
6
6