Transformer – Electromagnetic Induction

ABNT, through its technical standard NBR 5458 (1981), defines the transformer as: “A device that, through electromagnetic induction, transfers electrical energy from one or more circuits (primary) to other or other (secondary) circuits, using the same frequency, but usually with different currents voltages and currents. ”

For this component of the electrical network four points must be considered: – the input voltages;

– about to leave;

– the type of winding;

– the power and shape of the core.

As for the input and output voltages, the transformer may be of the voltage lowering type or the voltage lifter. The transformer will be voltage lowering when the input voltage is greater than the output voltage, and will be voltage boost when the situation is reversed.

Protection systems in distribution networks should include the following points:

– Protection in materials and equipment against damage caused by short circuit;

– Improvement and reliability of the distribution circuit, by reducing the possibilities of the effects of a fault to the smallest possible part of the circuit in the shortest time; with this, there is the decrease of the power involved and number of consumers reached.

– Rationalization of the cost of protection schemes that should not exceed the benefits arising from their use.

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Current Variations

Among other functions, devices called inductors are widely used as a way to prevent various possible variations of electric current, as well as to form a transformer and also in filters that ignore high frequency signals, which are the low pass type filters. By understanding some concepts and definitions about the inductors, it is possible to conclude that they, like the capacitors, have in common the capacity to store a great flow of energy.          hose reels reelcraft

Like inductors, inductors often oppose alternating current. In comparison to the capacitors, it can also be said that the faster the current variation over a period of time, the greater the amount of voltage at the terminals of the inductor, and no sudden variations of current are accepted.

When it comes to the constitution, the inductors are designed as a coil of a conductive material, such as copper, for example. Thus, a ferromagnetic core, capable of increasing the inductance by concentrating the lines and bud of the magnetic field flowing through the interior of the conductive turns. With the diverse possibilities of applications, the inductors can be constructed for a specific objective like in integrated circuits.

Relationship between Electricity and Magnetism

In 1820, the Danish professor Hans Christian Oersted, realized an experience in which it demonstrated for the first time the relation between electricity and magnetism. The experiment was to place a magnetized needle parallel to a wire that would be traversed by an electric current. Thus, Oersted observed that, upon closing the circuit key, the wire was driven by an electric current, and at that instant the needle immerged deflected its north-south orientation.

This fact had already been observed when a magnet was approaching a magnet needle, when the key was opened, the current flow stopped and the needle returned to its normal position, in this way the relation between electricity and magnetism was discovered.

In the eighteenth century, the American scientist Benjamin Franklin had attempted to explain the electrical phenomena of attraction and repulsion. In his theory, he accepted that all bodies had a kind of “electric fluid,” responsible for such phenomena.

By having friction, some bodies lost that fluid, others received it and without friction, these bodies remained in their neutral state with equal numbers of negative and positive fluids. According to these ideas, since it is a matter of transferring electricity from one body to another, there would be neither creation nor destruction of electric charges, the total amount of electric fluid being constant.

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Continuous Current Motors with Composite Excitation

Compound excited electric motors are used where there is a need for constant speed with extreme load variations and in order to combine the best of the parallel connection with the best of the serial connection, for this there is the composite connection. We achieved optimum parallel engine speed regulation with the excellent starting torque of the series engine.         Browning 1VP68X

In general, we can say that depending on the application, DC drives have the greatest benefits in terms of reliability, user friendly operation and dynamic control, such as:

– operation in four quadrants with relatively lower costs;

– continuous cycle even at low speeds; high torque at start and low revs; wide variation of speed;

– ease in speed control;

– AC / DC converters require less space;

– flexibility (different types of excitation);

-relative simplicity of modern AC / DC converters.

The function of the composite motor is to make it possible to take advantage of the high torque of the series connection, without speed shots with reduced loads or no load, then apply the low speed variation of the parallel motor under different load situations.

 

The Soft-Starters

Soft-starter electronic equipment is the starting device for induction motors, all in a solid state, ie based on semiconductor switches. The principle of operation of the soft-starter is, like electromechanical systems, to reduce the initial starting voltage and how the torque is proportional to the current, and that to voltage, the electric motor will start with reduced torque. As a rule, the soft-starters have acceleration ramp adjustment. This adjustment can be done via potentiometer or HMI (Human Machine Interface). A5835 OLP

Static starters are microprocessor keys designed to accelerate or decelerate and protect three-phase induction motors and by setting the thyristor firing angle, we control the effective voltage applied to the motor. With correct adjustment of the variables, the torque and current are adequate to the needs of the load, ie, the required current will be the minimum required to accelerate the load without changes of frequency. Some features and advantages of the soft-starters are the setting of the starting voltage for a predefined time, the starting voltage pulse for loads with high starting torque, fast voltage reduction at an adjustable level, protection against phase overcurrent and undercurrent.