GINO excitation resistors are starting resistors for magnet coils. Magnet coils are usually wound with copper conductors. Copper has a relatively large temperature coefficient of the resistance value so that a coil at operating temperature has a resistance value that is up to 20% higher than that of a cold coil. Consequently, a magnet coil usually has a lower intrinsic resistance as compared to its nominal voltage. A starting resistor, the so-called excitation resistor, adjusts the desired operating current to be achieved at operating temperature. Moreover, excitation resistors made from a suitable resistor alloy also compensate the temperature coefficient of the total resistance in a circuit. A typical example for an excitation resistor is the field resistor of d.c. machines which adjusts the excitation current and thus the speed of a motor or the voltage of a generator. Fast response resistors are starting resistors for magnet coils that alter the pickup properties of the coils. The coil is operated with a starting resistor at a higher, mostly double, nominal voltage. The starting resistor reduces the time constant of the total circuit T = L/(Rv+Ri), results in a faster current rise and thus in a faster build-up of the magnetic field. Another way to reach this objective is to excite the coil with a high current and then insert an upstream economy resistor. However, this solution is only feasible when a change of the excited magnetic circuit results in the same magnetic induction as during the starting phase. A typical example would be the power contactor with d.c. excitation.

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