Users Guide
85
On the other hand, you must know that copper, like almost all materials, increases its
resistivity with temperature, being able to increase the resistance of the circuit up to 5%
with the subsequent drop in available power. It is therefore advisable, when this factor is
decisive to obtain the current, for you to leave the cables to cool down.
The minimum cross-section recommended for the secondary winding is 4mm
2
/ A for the
permanent regime, 8mm
2
/A for 3 minute and 16mm
2
/A for 3s.
Parasitic inductance.
It is common to find that operators worry considerably about the resistance of the circuit
but they forget about the inductance, which, as you know, is vectorially added to obtain
the impedance. Well, this reactance, after dealing with the issue of the cross-section, is
what has the greatest influence on not being able to reach the necessary current values.
The only action you can carry out to improve (decrease) the inductance is to care for
geometry of the path. The area covered by the turn left by the outgoing conductor with
the return conductor must be reduced to a minimum, reducing to a minimum the area of
the turns, if any, wound around the raptor system to configure the secondary.
Join the cables of both sides with insulating tape or with clamps, and keep them joined
together, to reduce the space between them as much as possible, along their entire
length. Interlace the outgoing cables with the return ones is one of the best tactics.
To reduce to a minimum the parasitic inductance generated when configuring the pass-
through winding with the Raptor system, it is recommendable to acquire high current
ultra-flexible cables, supplied by SMC, as optional elements, measuring 3, 6 and 9 m
long.
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