Siemens GEAFOL Neo Operating Manual page 17

6.4.2 Installation wiring without enclosure
The high voltage side cable can be connected to the transformer after layout in the bottom cable tray or after layout
the top cable tray. Cable or bus bar can used for the low-voltage side connection. If the bus bar connection is used, soft
connection transition is recommended to avoid mechanical impact on the low-voltage winding and reduce noise level
due to structural reasons.
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Warnings:
• The reliable support for cables and busbar shall be ensured to avoid obvious external force acting on the connection of transformer.
• High-voltage cables are not allowed to pass through the high-voltage connecting rod (delta connection) of the transformer.
6.5 Bolts fastening
6.5.1 Contact surface preparation
Before bolting or terminal joining, the oxide layer (weak conductor) that is not visible on the contact surface must be
cleaned. If the contact surface is rough and required to be polished (such as brushing, grinding stone, etc. If any of the
contact surfaces is disassembled, the contact surfaces must be cleaned again before bolting.
If the transformer is installed in a room that is prone to condensation or contains more corrosive gases, the aluminium-
copper contact area needs to be painted to protect the entire contact area, especially the contact edges. If this moisture-
proof measure is not taken, aluminum-copper composite foil (cupal) shall be installed between the contact surfaces, so
that the aluminum surface is connected with the aluminum bar, and the copper surface is connected with the copper bar.
6.5.2 Bolt requirements
Corrosion-resistant parts must be used for bolt connections, and it is
recommended to use strength grade: galvanized bolts not be less than 8.8
and stainless-steel bolts not less than A2-70 hexagonal bolts. To transfer
the bolt tightening pressure to the largest possible contact surface, a
high-strength anti-loosening washer shall be used on the contact surface.
Conical cushion is recommended (DIN6796).
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1 Flat washer ISO 7093
2 Hexagon bolt, ISO 4014 or ISO 4017
3 Hexagon nut, ISO 4032
4 Conical cushion, DIN 6796
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