17
AB243586442172en-001401
Electrical data, connections and wiring
Winding resistance is the resistance between
phases at 25°C (resistance value +/- 7%).
Winding resistance is generally low and it
requires adapted tools for precise measurement.
Use a digital ohm-meter, a “4 wires” method and
measure under stabilised ambient temperature.
Winding resistance varies strongly with winding
temperature. If the compressor is stabilised
at a different value than 25°C, the measured
resistance must be corrected using following
formula:
a + t
amb
R
tamb
= R
25°C
_______
a + t
25°C
t
25°C
: reference temperature = 25°C
t
amb
: temperature during measurement (°C)
R
25°C
: winding resistance at 25°C
R
amb
: winding resistance at tamb
Coefficient a = 234.5
The max. operating current is the current when
the compressor operates at maximum load
conditions and 10% below nominal voltage
(+15°C evaporating temperature and +68°C
condensing temperature).
Max Oper. A can be used to select cables and
contactors.
In normal operation, the compressor current
consumption is always less than the Max Oper. A.
value.
Winding resistance
Max. operating Current
The inrush current for the Danfoss SH scroll
compressors with motor code 4 (400V /3ph
/ 50Hz or 460V / 3ph / 60Hz) can be reduced
using the Danfoss soft starter. MCI and 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.
Danfoss MCI soft-start
controller
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.
Upon starting, the controller gradually increases
the voltage supplied to the motor until full-line
voltage has been reached.
For MCI15C, MCI25C and 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
60 Hz
70%
0.5
0
Input controlled soft start
Initial torque
ramp-up
ramp-down
Time
U
Compressor model
Soft start reference
Ambient max. 40°C
Soft start reference
Ambient max. 55°C
SH090
MCI15C
MCI15C
SH105-120
MCI25C
MCI25C
SH140-161
MCI25C
MCI25C *
SH180-SH184
MCI50CM
MCI50CM
SH240
MCI50CM
MCI50CM *
SH295-380
MCI50CM *
MCI50CM *
SH485
MCD201-055
MCD201-055
* by-pass contactor K1 is required
Application Guidelines
Summary of Contents for SH485
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