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Bear switch fuse combines electric equipment to choose medium technical issue

From;    Author:Stand originally
  in recent years, of the protection in 10kV distribution transformer and control switch in choosing, as a result of bear switch, simpler than having a structure, operation maintains fuse combination electric equipment and breaker appearance convenient, cost is low, move to wait for an advantage reliably, make combine electric equipment to win wide application thereby. In applying actually, how to choose assorted electric equipment correctly, bear switch, fuse and transformer how reasonable anthology match parameter, it is to matter to whether play combines electric equipment function, assure the crucial question that systematic safety runs.
  
The desired result of 1 move electric current
Because combine the three-phase fuse fuse-element of electric equipment to fuse,have time to differ, after there is one photograph to disconnect above all in three-phase fuse, bump implement movement, right now the likelihood appears additional two-phase fuse have not extinguish arc leaves, and bump implement hit out form the phenomenon that cuts off fault current by bear switch, open the task to transfer bear switch to assume by what fuse assumes originally namely. The three-phase semmetry electric current when because this move electric current is,pointing to fuse and function of bear switch changeover. When be worth under this, first phase current leaves by fuse, other two-phase electric current leaves by bear switch. When be more than this value, three-phase electric current leaves by fuse only. Shifting electric current is we should notice a main index when choosing assorted electric equipment, if choose undeserved, bear switch can susceptive move electricity is not enough, cause the explosion of switch the job that assumes two-phase short-circuit current feebly.

Normally cent is bear switch general model and frequent model two kinds, the yield that is insulation medium with air enrages type and switch of bear of type of calm sb's anger to be general model, vacuum and SF6 bear switch are frequent model, different bear switch, the target that changes electric current each are not identical, general model the move electric current of bear switch is controlled in 800 ~ 1000A, frequent model can amount to 1500 ~ 3150A.

The size of distribution transformer is distinct, corresponding move electric current is not identical also, practical move electric current can undertake estimation by transformer capacity. The general S9- 800ö10 move electric current that deserves to change is 978A.

Reach those who combine bear switch to open time and character according to the definition that changes electric current, electric current of bear switch move should keep away from the biggest short-circuit current, control the 70% less than in the biggest short-circuit current, transfer electric current actually to be 978 × 70% = 685A about namely. On the foundation that analysing homebred bear switch and fuse technology coefficient, considering the disperse sex of the product, according to the checking computations outcome that changes electric current, with the experience of the our city, the capacity is in the transformer of 800kVA less than, what air of optional in order to is isolated from is general model bear switch, the capacity is in the transformer inside limits of 800 ~ 1250kVA, what choose vacuum or SF6 insulation commonly is frequent model bear switch. The capacity is more than the transformer of 1250kVA to ask to choose breaker to have protection and control. From electric equipment of our city combination old moving case looks, on the safe side, the case is good, because choose,did not appear all the time match undeserved and produce an accident.
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