Three Phase Electrical Characteristics - Danfoss MLM116 Application Manuallines

Application Guidelines
Three phase electrical
characteristics
LRA (Locked rotor amp)
MCC (Maximum continuous
current)
Max. operating current
Winding resistance
Danfoss MCI soft-start
controller
Electrical data, connections and wiring
Compressor model
Motor voltage code 4
MLZ/MLM116
380-415 V/3 ph/50 Hz
Locked Rotor Amp value is the higher average
current as measured on mechanically blocked
compressor tested under nominal voltage. The
LRA value can be used as rough estimation for
The MCC is the current at which the motor
protection trips under maximum load and
low voltage conditions. This MCC value is the
maximum at which the compressor can be
The max. operating current is the current when
the compressor operates at maximum load
conditions and 10% below nominal voltage.
Max Oper. A can be used to select cables and
contactors.
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 stabilized ambient temperature.
Winding resistance varies strongly with winding
temperature. If the compressor is stabilized
at a different value than 25°C, the measured
resistance must be corrected using following
formula:
The inrush current for the Danfoss MLM/MLM116
compressors with motor code 4
380-415 V/3 ph/50 Hz can be reduced using
the Danfoss soft starter. MCI soft starters are
designed to reduce the starting current of
Compressor model
MLM/MLZ116
* by-pass contactor K1 is required
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.
LRA MCC Max. operating current Winding resistance
A A
175 39
the starting current. However in most cases, the
real starting current will be lower. A soft starter
can be applied to reduce starting current.
operated in transient conditions and out of
the application envelope. Above this value, the
electronic module will cut out the compressor to
protect the motor.
In normal operation, the compressor current
consumption is always less than the Max Oper. A.
value.
a + t
amb
R = R _______
tamb 25°C
a + t
25°C
t : reference temperature = 25°C
25°C
t : temperature during measurement (°C)
amb
R : winding resistance at 25°C
25°C
R : winding resistance at tamb
amb
Coefficient a = 234.5
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.
Soft start reference
Ambient max. 40°C
MCI50CM
U
ramp-up
Initial torque
Single compressors
A Ω
35 0.914
Soft start reference
Ambient max. 55°C
MCI50CM *
ramp-down
Time
FRCC.PC.035.A5.02
13