Three Phase; Internal Motor Protection; Phase Sequence And Reverse Rotation Protection; Voltage Imbalance - Danfoss MLM Series Application Manuallines

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PPLICATION UIDELINES

Three phase

Suggested wiring diagram
with "one shot" pump down
cycle and safety lock-out relay
Control device ................................................. TH
Optional short cycle timer (3 min) ........180 s
Control relay .................................................... KA
Liquid Line Solenoid valve ....................... LLSV
Compressor contactor ................................. KM
Phase monitor ................................................ PM
Safety lock out relay .......................................KS
Pump-down control low pressure switch .LP
High pressure safety switch ....................... HPs
Fused disconnect ............................................ Q1
Fuses ................................................................... F1
Compressor motor ...........................................M
Discharge gas thermostat......................... DGT

Internal motor protection

Phase sequence and reverse
rotation protection

Voltage imbalance

20
E ,
LECTRICAL DATA CONNECTIONS AND WIRING
CONTROL CIRCUIT
F1
MLZ/MLM scroll compressors are equipped with
an internal line break protector mounted on the
motor windings. The protector is an automatic
reset device, containing a snap action bimetal
switch.
Internal protectors respond to over-current and
overheating. They are designed to interrupt mo-
The compressor will only operate properly in a
single direction. Use a phase meter to establish
the phase orders and connect line phases L1, L2
and L3 to terminals T1, T2 and T3, respectively.
For three-phase compressors, the motor will run
equally well in both directions. Reverse rotation
results in excessive noise; no pressure diff erential
between suction and discharge; and suction line
warming rather than immediate cooling. A serv-
ice technician should be present at initial start-up
to verify that supply power is properly phased
and that compressor and auxiliaries are rotating
in the correct direction.
For three-phase applications the voltage meas-
ured at the compressor terminals for each phase
FRCC.PC.015.A4.02
F1
KM KA KA
A1
A3
KS
180 s
A2
TH
LP
KS
KM KA LLSV
Wiring diagram with pump-down cycle
tor current under a variety of fault conditions,
such as failure to start, running overload, and fan
failure.
If the internal overload protector trips out, it must
cool down to about 60°C to reset. Depending on
ambient temperature, this may take up to several
hours.
MLZ/MLM015-038 scroll compressors are de-
signed to operate for a maximum of 150 hours in
reverse, but as a reverse rotation situation can go
unnoticed for longer periods, phase monitors are
recommended.
For compressors MLZ/MLM048 and larger, phase
monitors are required. The selected phase moni-
tor should lock out the compressor from opera-
tion in reverse.
At brief power interruptions, reverse rotation can
occur with single phase compressors. In this case
the internal protector will stop the compressor.
It will have to cool down and will restart safely
afterwards.
should be within ± 2% of the average for all
phases.
L1 L3 L2
Q1
KM
KA
KS
PM
T1 T2
HPs
T3
M
DGT
KS