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2. FEATURES – Advanced MCCB Design Technol-
ogy & Performance
2.1 Arc-Extinguishing Device –
I
STAC
Mitsubishi has developed an epoch-making
I
STAC
technology to realize an improved current-limiting and
breaking performance within a smaller breaking space.
Introduction of
I
STAC technology upgrades the cur-
rent-limiting, selective-breaking, and cascade-break-
ing performance. The maximum peak let-through cur-
rent
I
p
decreases to about 80% (compared with
Mitsubishi’s 100AF). The passing energy
I
2
t de-
creases to about 65% (compared with Mitsubishi’s
100AF). The smaller breaking space has led to an
improved function, a smaller size, and a standardiza-
tion of the breakers.
Triple forces accelerating
The triple forces generated by a newly designed cur-
rent pass and the Vapor Jet Control (VJC) insulat-
ing materials which makes up a slot-type breaking
construction accelerate the movable conductor, and
separate the contacts faster than ever before in short-
breaking.
Electromagnetic attractive force which works between
a current of the movable conductor and a current of
the fixed upper conductor.
Electromagnetic repulsive force which works between
a current of the movable conductor and a current of
the fixed lower conductor.
Pressure which works on the movable conductor by
gas generated in the slot.
Lower,
fixed-contact
conductor
Repulsive
force
Movable
contact
Attractive
force
Current A
Current
Current B
Current C
Upper,
fixed-contact
conductor
1
2
Arc control by slot-breaking
The VJC of the fixed contact incorporates newly de-
veloped insulation made of ceramic fiber and metal
hydroxide. The substantially improves the VJC effect.
The arc-extinguishing gas energies to improve the
capability of extinguishing the arc.
The VJC suppresses the emergence of carbide prod-
ucts in breaking a current and contribute to the recov-
ery of insulation immediately thereafter.
The VJCs on the fixed and movable contacts work
together to forcefully reduce the arc spot and rapidly
contract the total arc being extinguished.
Fixed contact
VJC
Upper,
fixed-contact
conductor
Lower,
fixed-contact
conductor
Pressure
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Arc
Movable contact
Movable
contact VJC
Vapor jet control (VJC)
Vapor Jet Controllers made of insulating material are
arranged around the contacts where they control the
arc as follows:
1. The arc spot is forcibly reduced by the arrange-
ment of the insulating material.
2. The arc column is contracted.
3. Adiabatic expansion cools the arc.
4. The arc is transferred at the optimum moment to
the arc-extinguishing chamber by the arrangement
of the Vapor Jet Controllers.
