KRB-5404
86
6-2-2. Arc chambers
The following describes how to replace arc chambers.
1) Make preparations for parts replacement. Refer to section 6-2-1.
2) Carefully lay the breaker body on spacers with the backside down as shown in Fig. 75. The spacers must be at least 7-cm high to
prevent deformation of protrusions on the breaker body backside, and have the size and strength that allow the breaker body to
be safely laid on them. Take care to keep the main circuit contacts clean of dust.
Fig. 75 Laying the breaker body on spacers
3) Turn the arc chamber mounting screw eight or ten turns to loosen as shown in Fig. 76. (The arc chamber mounting screws are of
captive type and cannot be removed from the arc chamber.)
Arc chambers (at the top)
Arc chambers (at the bottom)
Fig. 76 Arc chamber mounting screws
4) Holding the arc chamber mounting screw, remove the arc chamber.
5) Reinstall each part or component in reverse order of removal after inspection.
Fig. 77 shows a removed arc chamber.
Fig. 77 Arc chamber
Spacer
7 cm or higher
Breaker body
Arc chambers (6 - 8)
Arc chamber mounting screw
(captive),
Pan head M6 (12 - 32)
with spring and flat washers
Tightening torque: 4.7 - 5.9 N·m
Arc extinguishing grids
Arc chamber mounting screw