Breaker Devices

The circuit breakers are magneto-thermal devices that act in the protection of installations and electric motors against any overload and short circuit that may occur. These devices consist of a thermal trigger, bimetal, that acts in the situations of overload, and with an electromagnetic trigger, that acts in cases of short circuit.

Both systems are individually set to values ​​appropriate for the protection of specific loads, as well as control circuits and small motors. Some types of circuit breakers are tripped free, so if the actuator is activated in the on position, internally the circuit breaker trips, for example.

By means of a very fast cutting device, the separation of the contacts is carried out very quickly. That is, the electric arc will be greatly reduced by special construction fire-extinguishing chambers in which the alternating short-circuit current will be interrupted before it passes through zero.

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The contacts are designed with the use of special alloys based on silver, which provides a high security against the collage of the contacts and a high electrical durability. The circuit breaker needs to be specified through some well-defined quantities.


DC Motor Speed

The velocity in an electric motor of direct current is related to the electromotive force (f.e.m.) applied to the armature and to the counter-electromotive force (f.c.e.m.) generated in the armature by the magnetic field of the stator cutting the armature.

A f.m. Is the force resulting from the voltage applied to the armature being responsible for the current flowing through it. And being f.c.e.m., the force opposing f.e.m. Due to the induced voltage in the armature when it cuts off the magnetic field generated in the stator. In order for the DC motor general motor baldor to operate, both forces must be present.

As the speed of the motor depends on the voltage applied in the armature, the current in the coil and the value of the magnetic flux. Thus the engine speed tends to infinity when the flow tends to zero. Consequently, we must not take the field current in any way, as the motor “trips”.

Variable speed systems using DC motors and static converters combine large ranges of speed, robustness and precision to energy savings, which ensures optimum performance and flexibility in a variety of situations.


Main Control Functions

Among the main functions of the control of an electric motor are starting, direction of rotation, stop, speed regulation, starting current limitation, mechanical protection and electrical protection, among others. An engine only starts spinning at the moment of loading to be due, when stopped, is less than its starting torque.

In some specific applications there is a need for a rapid deceleration of the engine and the load. When turned off the power line motor uses a rotation reversing device with the engine still running. Switching off the mains motor or stopping is done by means of a device, thus preventing it from starting in the opposite direction. In the case of synchronous motors dynamic braking is counted.

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Most motors, except single-phase motors such as shaded pole and repulsion, can be used in both directions of rotation, varying only from a specific control.

Alternating current motors, with the exception of universal motors, are constant speed machines. However, it is possible to re-connect the stator coils of an induction motor so that it doubles the number of poles.


Magnetic Flux Lines

Without exception, each magnet has two poles, one north pole and one south pole, including electric motors. The invisible lines of the magnetic flux leave the north pole and go in direction to the south pole. Even if the flow lines are invisible, the effects of the magnetic field produced by them may eventually become visible.

If a sheet of paper is placed on a natural magnet or even on an electromagnet, and an iron filament is poured on it, the iron filings will be arranged along the invisible lines of the stream.

Dashed lines will indicate the path of magnetic flux lines. Already the lines of the field exist in and outside the magnet, forming thus, closed loops. The magnetic flux lines will exit the north pole and enter the south pole, returning to the north pole through the magnet.

By the time two magnets are approached, the magnetic flux around them may result in an interaction between them. If the magnets are approached with the opposite poles, they will attract and if they have the identical poles, they will repel.