Precautions For Connections; Maintenance And Inspections - Mitsubishi Electric NF50 Quick Start Manual

NF50 AND NF100 CIRCUIT BREAKER QUICK START MANUAL
• Do Not Block Ventilation Ports Do not block the ventilation ports.
The breaker performance could drop.
• Avoid Direct Sunlight Make sure that the breaker is not subject to
direct sunlight during use. An increase in temperature could cause
malfunctions. Sunlight could also discolor the nameplate and molded
case, etc.
• Do Not Remove the Rear Cover Do not remove the rear cover
from the back of the base.
• Do Not Wipe with Thinner, Detergent or Chemical Cloth Do
not use thinner, etc., to clean the surface of the breaker. Use
compressed air or a dry cloth to clean.
• Mounting Style Pay attention to the mounting angle of the
following models as the overcurrent tripping characteristics may
vary according to the mounting style. Use in a vertical direction is
recommended.
100%
107%
ON
ON
ON
ON
1 1 0 %
ON
ON
ON
ON
107%
100%
Rate of change of rated current by mounting angle

1.4 PRECAUTIONS FOR CONNECTIONS

• Oiling of Threads Prohibited Do not apply lubricant to the threads.
Oil will decrease the friction at threads and cause the screws to
loosen easily, and the unit to overheat. Excessive stress will be
applied on the threads even with the standard tightening torque and
can cause the screws to break.
• Connect Conductors Parallel to Each Pole Connect each
connection conductor so it is parallel to each pole.
• Do Not Deform Studs When connecting the conductors on the rear
connection type, take care not to deform the studs when tightening.
• Do Not Connect in Reverse As a rule, do not connect the power
and load in reverse. If necessary, refer to the specifications and
select a model which can be connected in reverse. An insulating
barrier should be provided on both the power and load sides of the
breakers when using a high voltage circuit where dew condenses
easily or in a circuit which has a reverse connection in the circuit.
• Securely Fix Conductors A large electromagnetic force is applied
on the connected conductor according to the accident current. Use
the conditions on the right as guide and securely fix (tighten) the
conductors.
4
Mitsubishi Electric Automation, Inc.
93%
9 0 %
93%
Electromagnetic force applied per 1m conductor
(During 3-phase short-circuit)
Current Target Value kA (Pf)
10 (0.4)
18 (0.3)
25 (0.2)
35 (0.2)
42 (0.2)
50 (0.2)
65 (0.2)
85 (0.2)
100 (0.2)
125 (0.2)
• Bar Connection When directly connecting the conductor, refer to
the outline drawings and drill the conductor.
• When connecting the conductors to a bar terminal, pay attention to
the insulating distance with the ground. A ground fault prevention
barrier is available as an option.
• Wire Retention Type Connection When directly connecting to the
terminal, insert the single strand or stranded wires in straight and
then tighten. A commercially-available crimp terminal or bar can be
connected directly.
• When using stranded wires, split them and then tighten.
• Solderless Terminal Connection Untwist the connection wires,
align the core wires and then tighten. The wires will loosen up during
use, and must be tightened during periodic maintenance.
• Do not solder or bind the end of the strands.
• Make sure not to catch the insulating sheath of the wire when
tightening.

1.5 MAINTENANCE AND INSPECTIONS

• Initial Inspections After installing the MCCB inspect the following
matters before powering the units.
Model Inspection Items
Are there any excessive screws, drilling scraps,
wire scraps or any other conductive materials
around the terminals?
Are there any cracks or damage on the cover
or base?
Common Is there any dew condensation on the cover,
base or terminals?
Measure the insulation resistance with a 500V
insulation resistance tester.
Are the connector connections tightened
securely?
Distance Between Conductors (cm)
10 20
490 245
1860 930
4410 2205
8720 4360
12545 6270
17835 8920
30185 15090
51550 25775
71540 35770
111720 55860
Criterion
All conductive material
must be removed
No cracks or breaks
allowed
No dew condensation
allowed
5MΩ or more
Must be specified
tightening torque