Electrical data, connections and wiring
The inrush current for the CH scroll compressors
with motor 380-415V / 3ph / 50Hz can be
reduced using the Danfoss digitally-controlled
MCI compressor soft starter. MCI & MCD soft
starters are designed to reduce the starting
current of 3-phase AC motors; they can reduce
the inrush current by up to 40%, thereby
eliminating the detrimental effects of high
starting torque surges and costly demand
charges from the resultant current spike. Upon
starting, the controller gradually increases
the voltage supplied to the motor until full-
line voltage has been reached. All settings,
such as ramp-up time (less than 0.5 sec) and
initial torque, are preset and do not require
modification.
When the control voltage is applied, the
MCI50CM soft starter will start the motor,
according to the settings of the ramp-up time
and initial torque adjustments. When the control
voltage is switched OFF, the motor will switch off
instantaneously.
On CH compressors, by pass contactor K1 is
required by means of the built-in auxiliary
contact (23-24) the by-pass function is easily
achieved, see wiring diagram beside.
No heat is generated from the MCI. As the
contactor always switches in no-load condition
it can be selected on the basis of the thermal
current (AC-1).
Danfoss MCI soft-start
controller
Upon starting, the controller gradually increases
the voltage supplied to the motor until full-line
voltage has been reached.
For MCI50M, all settings such as initial torque,
ramp-up time (less than 0.5 sec) and ramp-
down time are preset and do not require any
modification.
For MCD201-055, the following settings have to
be adjusted to ensure a maximum inrush current
reduction as well as a starting time less than
0.5 sec.
Frequency
Initial
torque
(%U)
Ramp-up
(seconds)
Ramp
down
(seconds)
50 Hz
60%
2
0
Compressor model
Soft start reference
Ambient max. 40°C
Soft start reference
Ambient max. 55°C
CH290
MCI50CM *
MCI50CM *
CH485
MCD201-055
MCD201-055
* by-pass contactor K1 is required
When the control voltage is applied to A1 - A2,
the MCI soft starter will start the motor, according
to the settings of the ramp-up time and initial
torque adjustments. When the control voltage
is switched OFF, the motor will switch off
instantaneously.
Input controlled soft start
By means of the built-in auxiliary contact (23-24)
the by-pass function is easily achieved, see wiring
diagram beside.
MCI with by-pass contactor
Initial torque
ramp-up
ramp-down
Time
U
15
FRCC.PC.026.A4.02
Application Guidelines