Vacuum Interrupter
Vacuum interrupters offer the advantages of enclosed
arc interruption, small size and weight, longer life,
reduced maintenance, minimal mechanical shock,
and elimination of contact degradation caused by
environmental contamination.
In the closed position, current flows through the
interrupter moving and fixed stems and the faces
of the main contacts. As the contacts part, an arc is
drawn between the contact surfaces. The arc is rapidly
moved away from the main contacts to the slotted
contact surfaces by self-induced magnetic effects. This
minimizes contact erosion and hot spots on the contact
surfaces. The arc flows in an ionized metal vapor and as
the vapor leaves the contact area, it condenses into the
metal shield which surrounds the contacts.
At current zero, the arc extinguishes and vapor
production ceases. Very rapid dispersion, cooling,
recombination, and de-ionization of the metal vapor
plasma and fast condensation of metal vapor causes the
vacuum to be quickly restored and prevents the transient
recovery voltage from causing a restrike across the gap
of the open contacts.
Vacuum Interrupter Assembly
Each interrupter is assembled at the factory as a unit
to assure correct dimensional relationships between
working components. The interrupter assembly consists
of a vacuum interrupter, a molded glass polyester stand-
off insulator, upper and lower clamps, flexible shunts,
bell crank, operating rod, and contact load spring. The
vacuum interrupter is mounted vertically with a fixed
stationary stem and a moving stem to open and close
the contacts. The upper and lower glass polyester
stand-off insulator and clamps support the interrupter
and are fastened to the circuit breaker’s stored energy
mechanism frame. Upper and lower flexible shunts
provide electrical connections from each interrupter to
the circuit breaker’s primary bushings while providing
isolation from mechanical shock and movement of the
interrupter’s moving stem. The operating rod, loading
spring, and bell crank transfer mechanical motion from
the circuit breaker’s operating mechanism to the moving
stem of the interrupter. A vacuum interrupter contact
erosion indicator is located on the moving stem of
the interrupter. It is visible when the circuit breaker is
withdrawn and is viewed from the rear of the circuit
breaker.
Vacuum
Interrupter
3
EATON
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Visual Instruction Booklet Essentials | 150VCP-W 25kA 1200A | January 2017
