Description and operation
Pole operation
(Interrupting principle)
L13--003EN/02
3/6
08--2000
E ALSTOM
Opening, continued
Operation
The table below gives the stages of opening :
Stage Description
Start of opening
When the moving contact (4) separates from the main
contacts (3), the current is switched onto the arc con-
tacts (10). The compression of the (Vp) volume cau-
ses the first r ise of pressure.
103 4 Vp
Thermal effect
When the contacts (10) separate, the arc appears and
its energy causes the pressure to rise in the thermal
expansion volume (Vt), closed by the fixed contact rod
(11) and the insulating nozzle (12).
12 10 Vt
11
Interrupting and
assistance
at opening
When the rod (11) comes out of the nozzle (12), the
thermal overpressure in the volume (Vt) is released
causing an energy blast to occur, just before the cur-
rent zero passage, ensuring final quenching of the arc.
The (Vp) volume pressure decreases to the ambiant
pressure by means of the valve (13) to allow the end
of the opening.
Vt Vp 13
11 12
Continued on next page.
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