The main purpose of insulating materials is to control, direct, limit and prevent the flow of electrical currents in electric motors. They are responsible for acting in the obstacle of the current flow of a conductor, to earth or a lower potential, the insulation material also provide a mechanical support, being able to protect the conductor from degradation caused by the environment, as well as passing heat to the environment .
The connection of two or more insulating materials applied to an electrical equipment is called an insulation system and this combination in an electric motor is based on different factors, such as wire insulation enamel, groove bottom, insulation between phases, varnish or impregnation resin and the groove closure, cable bonding and welding insulation. reelcraft A5800 EMP
Any material or component that does not spontaneously contact the coil does not make up the insulation system. Solids, liquids and gases are used in the insulation of electrical equipment, changing according to the needs of the system. The insulation systems intervene in the effective performance of the equipment directly, and in the quality of the insulation, to observe that its type influences in the weight, cost and durability of the same.
Evaluating that the induction electric motor is a strong and simple construction machine, its durability can depend almost exclusively on the life of the insulation of the winding, which is compromised by numerous factors such as humidity, vibrations, corrosive environments and others.
When we talk about reducing engine durability, we do not refer to high temperatures, but when the insulation burns and the winding is suddenly damaged. The permanence of the insulation, in terms of working temperature, well below is able to burn the material, refers to the gradual aging of the insulation, which is becoming dry, losing the insulating action until it no longer supports the applied voltage and causes the short circuit. 4600 OLP
Of all the factors, the most respectable one is undoubtedly the temperature supported by the insulating materials used. An elevation that can change on average from 8 to 10 degrees above the thermal class limit of insulation temperature, can dramatically reduce winding durability by half. For a longer life of the electric motor it is advisable to use thermal sensors to protect the winding.
Elements called fuses are most commonly used to avoid a short circuit that may occur and occur in any electrical system. Its operation necessarily takes place from the fusion of the fuse element, inserted in its interior. This fuse element is a conductor having a small cross section, when exposed because of its high resistance, to a higher heating than the other conductors when the current enters.
It impinges on a wire connected in parallel with the fusible element and that will slowly release a spring that will act on a type of plate or button, or even a screw, which is found coupled generally corporal cap. The fuses have within them, completely enclosing the element, a kind of granulated extinguishing material. Browning 2B5V74
The fuse element is essentially a blade or a wire, which may be of silver, tin, lead or alloy, nailed within a body, which is often porcelain, and must be sealed carefully . They need to contain an indicator, which can then be verified if the operation was actually performed.
Fuses are considered as the most used elements for protection against short circuits in electrical systems and their operation is based on the fusion of the fuse element, found inside. This element consists of a simple conductor of a small cross section, which in turn due to its high resistance passapor a higher heating than the other conductors in the passage of the current. reelcraft 82000OLS
The fuse element consists of a wire or blade, usually projected on materials such as tin, silver, lead or alloy, inserted into a closed porcelain body. It has an indicator, which has the function of allowing the verification whether it acted or not. It is a wire connected in parallel with the fuse element, which may release a kind of spring that acts on a platelet or screw, usually attached to the body cap.
The fuse can be found in different forms and depending on the nominal current of the fuse, it strikes one or more wires or blades in parallel with some sections of reduced section. In it, they may also contain a soldering point, in which the melting temperature will be much lower, compared to that of the element acting for long duration overloads.
The power contactors are for maximum currents up to approximately 600 A. In general, they have three main contacts of the NA type – normally open, for the operation of three-phase loads and can also be provided with coupled auxiliary contacts. An important factor to be verified in the use of the contactors is the sparks produced by the impact during the switching of the contacts, as this causes the natural wear of the contacts, besides constituting risks to human health. The intensity of the sparks can be aggravated in humid environments and also with the intensity of electric current circulating in the panel. In this way different forms of protection are applied, resulting in a classification of these elements. Basically there are four main categories of employment of contactors:
– AC1: it is applied in ohmic or little inductive loads, as heaters and furnaces the resistance;
– AC2: for drive of induction motors with winding rotor; air motor
– AC3: it is application of motors with cage rotor in normal loads like pumps, fans and compressors;
– AC4: is for heavy maneuvers, such as driving the induction motor under full load, reversing in full gear and intermittent operation.