IndexIntroductionPrinciples of operation of motors and generatorsACAdvantages of superconducting motors and generatorsConclusionIntroductionSuperconductivity is a phenomenon in which a conductor, once cooled below a certain temperature, loses all the electrical resistance and expels any magnetic fields inside it. When this state of superconductivity is achieved, the conductor will be able to transfer electrical energy without loss of power. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essayHowever, this only happens at very low temperatures. Without some form of cryogenics, reaching a superconducting state is impossible due to resistive losses that occur in the current-carrying conductor. Superconducting cables have been proven to increase the energy efficiency and power density of motors and generators and, as a result, reduce the overall volume of the machine. Due to the profitable advantages that superconducting machines bring, many have invested efforts in this field to better refine the design of these machines, in hopes of widespread implementation. The temperature required for superconductivity to occur, called the critical temperature, depends on the material used. At the time of the initial discovery, only liquid helium was capable of cooling some materials below their critical temperature. These materials, termed low-temperature superconductors (LTS), become superconductors at temperatures of around 4 K. Due to the high cost of obtaining liquid helium, this extremely low temperature has made superconductivity a relatively inaccessible area to study, not to mention implementation for industry. purposes. Fortunately, new materials have been discovered that can achieve superconductivity at higher temperatures, using only liquid nitrogen as a coolant. These are generally referred to as high-temperature superconductors (HTS). Current developments in superconducting motors and generators use HTS materials due to the lower cost of liquid nitrogen cooling. For HTS machines, the stator windings are usually made of special yttrium bismuth-based copper oxides (YBCO) instead of copper coils, cooled to temperatures ranging from 30 K to 40 K. The passage of a current continues through the windings creates a region of very strong magnetic flux. This allows HTS motors to generate large amounts of torque. For naval propulsion systems, the need for high-torque motors favors the use of superconductors over traditional copper windings. Principles of Operation of AC Motors and Generators A motor is a machine that converts electrical energy into mechanical energy. Electrical energy in the form of an electric current is passed through the armature of a motor while within the magnetic field of a pair of permanent magnets, subsequently inducing an electromotive force (emf) in the armature which creates a force which rotates the rotor. The rotation of the rotor is the mechanical energy produced. In a three-phase induction motor, the process is different. Alternating current (AC) is passed through coils øA, øB, and øC in the stator. The current in øA, øB and øC will be 120° out of phase with each other. When these coils carry separate AC currents, a rotating magnetic field is formed. The rotation speed of this magnetic field is called synchronous speed, which is directly proportional to the rotation speed of the rotor. The rotating magnetic field then causes achange in the magnetic flux connection in the rotor, and according to Faraday's law of electromagnetic induction, a force is exerted on the rotor to oppose the changes. This causes the rotor to start spinning. Since the stator coils use alternating current, the resulting magnetic field continues to rotate and keeps the rotor moving near synchronous speed. The rotor will never spin faster or at synchronous speed because if it does, the rotor armature will be stationary with respect to the rotating magnetic field. This means that there will be no change in the flow connection within the rotor and, as a result, no force will be exerted on the rotor, causing it to slow down. A slowdown would cause the change in magnetic flux to increase, putting a greater force on the armature which causes the rotor to spin faster, repeating the process. A generator uses similar principles to a motor but instead converts mechanical energy into electrical energy. For a three-phase synchronous generator, the rotor is the component that creates the initial magnetic field, rather than the stator in an induction motor. A direct current (DC) is passed through the wound wire to the rotor, "exciting" the rotor and forming a magnetic field around the rotor with the stator coils A, B, and C within the region of the magnetic field. This "excitation" current can come from an external source or from a small DC generator, connected to the crankshaft itself. The rotor is then spun and the magnetic field cuts the coils of wire A, B and C, causing the change in magnetic flux within the coils to be non-zero. As a result, according to Faraday's law, an emf is induced in the coils and a current is generated. When the magnetic field lines first "cut" the stator coil wires, the first lines to cut are downward (relative to the page) and by Lenz's law of electromagnetic induction, the resulting induced current will flow out from the page. As the field lines continue to cut the wire, the lines going up will cut the wire and induce a current flowing into the page. Due to the reverse direction of the field lines cutting the stator coil, the three-phase generator outputs an alternating current of three phases displaced by 120° from each other as shown in Fig. 4. Furthermore, the frequency of the output is directly proportional to the synchronous speed of the magnetic field, therefore, by varying the rotation speed of the rotor a variation in the frequency of the output voltage is obtained. For AC motors, the opposite is true: varying the input voltage changes the rotation speed of the rotor. Advantages of Superconducting Motors and Generators The idea of ​​using superconducting machines for industrial applications has recently gained support as more experiments are conducted to demonstrate their superiority over AC motors. conventional engines and generators. The advantages of using superconductors obviously arise from the zero resistance characteristic of superconductors for direct currents and very low losses due to hysteresis for alternating currents, which has many implications in the design of superconducting machines. The proposed advantages of superconducting machines over their conventional counterparts are its ability to carry larger electrical currents, lighter weight, and smaller volume of the machine. HTS materials are capable of carrying much higher currents for the same cross-section than copper wires, thus achieving much higher current density in wire windings with smaller dimensions. In synchronous generators.