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It contains application, types and advantages and disadvantages
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What is a Switch? An electrical switch is a controlling device, which interrupts the flow of current or changes the direction of current in a circuit. In simple words, a Switch can make or break an electrical circuit. Every electrical and electronics application uses at least one switch to perform ON and OFF operation of the device. So, switches are a part of the control system and without it, control operation cannot be achieved. A switch can perform two functions, namely fully ON (by closing its contacts) or fully OFF (by opening its contacts).
This is a simple ON/OFF switch. It is also called as a “One Way” or “Single Way” Switch (known as Two-Way Switch in the US). When a user presses the button of the switch, then the plates of the switch connect with each other and the current starts to flow in the circuit and vice versa. SPDT (Single Pole Double Throw) SPDT switch has three pins (terminals). One pin among three is used as common and called a Two-Way Switch (known as Three-Way Switch in the US). We can send two different signals to the same pin by using this switch. Because of this functionality, this switch is also known as selector switch. Types of Switches
DPST (Double Pole, Single Throw) This switch is basically two SPST switches in one package and can be operated by a single lever. This switch is mostly used, where we have to break both ground and lines at the same time. DPDT (Double Pole Double Throw) This switch is equivalent to two SPDT switches packaged in one pack. This switch has two common pins and four signal pins. Total four different combinations of singles can be applied to the input pins of this switch. 2P6T (Two Pole, Six Throw) It is a type of the changeover switch with a common (COM) which may be connected to six lines with a second two pole switch, which controlling and the operation of the switch is same.
ADVANTAGES OF SWITCHES
Application of Switches Electrical switches are used in myriad applications in every industry—such as aerospace, automotive, chemical, communication, marine, medical, military, petrochemical, and transportation—as well as in the commercial and residential sectors. A ubiquitous technology, switches can be found as part of the user interface for nearly every electrical and mechanical product. Door Bell: A doorbell is a signaling device typically placed near a door to a building's entrance. When a visitor presses a button the bell rings inside the building, alerting the occupant to the presence of the visitor. Although the first doorbells were mechanical, activated by pulling a cord connected to a bell, modern doorbells are electric, operated by a push button switch. Modern doorbells often incorporate intercoms and miniature video cameras to increase security. Hydraulic Pressure Switch: Hydraulic Pressure Switch are used to regulate or measure the flow of hydraulic fluids. Typically, hydraulic pressure switches are designed for handling of the majority of hydraulic fluids. Airplanes are designed with hydraulic systems to power things like the control surfaces on the plane’s exterior or the landing gear. These systems use pressure switches and sensors to ensure the actuators have the pressure to move parts of the plane when needed to turn, maneuver, or land.
What is a Fuse? A fuse was patented by Thomas Edison in 1890 as part of his electric distribution system. A fuse is an electric / electronic or mechanical device, which is used to protect circuits from over current, overload and make sure the protection of the circuit. Fuses are the protectors, these are the safety devices which are used to protect the home appliances like televisions, refrigerators, computers with damage by high voltage. The fuse is made up of thin strip or strand of metal, whenever the heavy amount of current or an excessive current flow is there in an electrical circuit, the fuse melts and it opens the circuit and disconnects it from the power supply. Also, it works as a circuit breaker or stabilizer which protects the device from damage. The fuse is made up of a material which has high resistivity and low melting point, so that it melts down due to overheating of the wire during high current flow. Their strips are made up of aluminum, copper, zinc & it is always connected in series with the circuit to protect from overcurrent in the running cables. The thickness of the fuse wire is determined based on the amount of current flow in the circuit. Normally an alloy of tin and lead is used as the fuse wire, as it has high resistivity and low melting point. The resistance of fuse wire is greater than that of live wire. FUSE CIRCUIT DIAGRAM
TYPES OF FUSES
Fuses can be divided into two main categories according to the type of input supply voltage. AC fuses On the other hand, i.e. in the AC system, voltage with 60Hz or 50Hz frequency changes its amplitude from zero to 60 times every second, so arc can be extinct easily as compared to DC. Therefore, AC fuses are a little bit small in sizes as compared to DC fuses. DC fuses In a DC system, when the metallic wire melts because of the heat generated by the over current, then Arc is produced and it is very difficult to extinguish this arc because of DC constant value. So in order to minimize the fuse arcing, DC fuse are little bigger than an AC fuse which increases the distance between the electrodes to reduce the arc in the Fuse.
Expulsion Type HV HRC fuse This type of fuse is an escapable fuse in which the expulsion effect of the gases produced by internal arcing results in current interruption. The fuse link chamber contains boric acid. Therefore, an internal arcing helps in the protection of feeders and transformers. Liquid Type HV HRC Fuse A liquid fuse (for high currents) consists of a glass tube filled with carbon tetrachloride and sealed with brass caps at both ends. The fuse wire covers sealing at one end and fixing by strong phosphor bronze spiral spring at another end of the glass tube. The liquid acts as an arc extinguishing medium. The fuse blows out when the current exceeds the maximum limit. Liquid type HRC fuse protects transformer and circuit breakers. They withstand current upto 100A on systems up to 132kV.
Low Voltage Fuse Low voltage fuses are very common in electrical systems and they come in different shapes and designs. Low voltage fuses have a voltage rating of less than or equal to 1,500V. Cartridge Fuses Cartridge fuses are used to protect electrical appliances such as motors, air-conditions, refrigerator, pumps etc., where high voltage rating and currents are required. They are available up to 600A and 600V AC and widely used in industries, commercial as well as home distribution panels. There are two types of Cartridge fuses.
D – Type Cartridge Fuse D-Types fuse contains an adapter ring, base, cap and cartridge. Fuse base is connected to the fuse cap where the cartridge is inside the fuse cap. The circuit is completed when the tip of the cartridge makes contacts though the fuse link conductor. The breaking capacity of the fuse is increased by using two or more silver wire in parallel. This type of fuse is very reliable and divided into two types: Blade type fuses and Bolt down type fuses. Blade fuse are also known as spade or plug-in fuse. Automotive OEMs use this fuse for vehicle circuit protection and withstand high temperatures. Bolt down fuse are special-purpose ones suitable for diesel vehicles and not appropriate for automotive trucks.
Dropout Fuse Drop out fuse is an expulsion type fuse to protect the transformers. When the fuse element melts, it falls due to gravity, hence providing additional isolation. Switch Fuse Switch fuse is used for low and medium voltages circuit. They can safely break depending upon rating currents of the order of 3 times the load current. Sticker Fuse This type of fuse has a mechanical indicator or striker pin that protrudes through the fuse cap upon operation of the fuse. This provides visual identification of a blown fuse and acts as a trigger for external devices. It can be used for short circuit protection of medium voltage motors. Rewireable Fuse Re-wirable fuse is also known as a kit-kat fuse. It is a simple and cheapest form of a fuse. This fuse is suitable for domestic wiring for e.g in houses. Moreover, when the fuse blows out, it is easy to replace and reuse. It consists of a fuse base and a fuse carrier. The construction of fuse element in the fuse carrier uses tinned copper, lead or aluminum and porcelain for the base.
