In the case of large electric machines, other smaller motors connected in series with the armature chain should be placed between the main poles. We call these interpolates, in which their function is basically to guarantee the neutral line even under different armature currents, also called load conditions. This effect of the armature current that can affect the neutral line is called the armature reaction.
The position of the collector is located in a region called the neutral line, in which the voltage should be zero, however, as a function of the changes in the mechanical load of the motor, its armature current will be changed, and this factor allows a displacement of the neutral line. This causes larger arcs in the brushes, which can result in considerable damage to the collector, as well as excessive brush wear. qd bushed
In the case of small electric motors we find a kind of mechanical device, which can guarantee the process of moving the brushes to the new operating point, in which the zero voltage condition can occur.
Fuses are simple devices that serve as protection of electrical circuits as well as equipment. Fuses are devices used for the purpose of limiting the current of a circuit, guaranteeing its interruption in case of short circuits or long overloads. The short circuit is a virtually unstressed connection between conductors under voltage or, it may also be an intentional or accidental connection between two points of a system or electrical equipment, electric motor, or a component, through a negligible impedance. reelcraft 7600 EHP
The fuse element has physical properties in such a way that its melting point is less than the melting point of copper and copper is the material most commonly used in general purpose conductors. Under these conditions, the current acquires a value that is many times higher than the operating current through a negligible transient resistance, so that the equipment and part of the installation may have a short-term or electrodynamic endurable current or thermal stress (rated current of impulse) exaggerated. Its action is due to the fusion of an element by the Joule effect, caused by the sudden elevation of current in a given circuit.