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 the 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
Winding resistance
The inrush current for the Danfoss WSH scroll
compressors with motor code 4 (400V /3ph /
50Hz or 460V / 3ph / 60Hz) can be reduced using
the Danfoss digitally-controlled MCI compressor
soft starter. MCI 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.
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.
Input controlled soft start
Compressor model
Soft start reference
Ambient max. 40°C
Soft start reference
Ambient max. 55°C
WSH090
MCI15C
MCI15C
WSH105
MCI25C
MCI25C
WSH120
MCI25C
MCI25C
WSH140
MCI25C
MCI25C *
WSH161
MCI25C
MCI25C *
WSH184
MCI25C
MCI25C *
* 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).
13-14 contact not applicable with MCI 25C.
MCI with by pass contactor
13
FRCC.PC.028.A5.02
Application Guidelines