In shell type construction, as shown in Fig. The application of core type transformer is preferred for high voltage ratings as they are more economical.
Since flux is an alternating one, in order to reduce eddy current losses the core is laminated. The core type has a single magnetic circuit and the shape of coils used are cylindrical in shape. We can see that the primary and the secondary winding’s are at the different limbs of the core.But practically, in a core type, a part of primary winding is on one limb of the core and other is on the other limb of the core. The shell type construction needs more specialized fabrication facilities than core type, while the latter offers an additional advantage of permitting visual inspection of coils in the case of a fault and ease of repair at substation site. Standard transformers have primary and secondary windings placed in two different directions, but in autotransformer windings, the primary and the secondary windings are connected to each other in … 10.29, the coils are wound around the two limbs of a rectangular magnetic core. In shell type transformers advantage is gained through the core being used to protect the windings from mechanical damage. The secondary output voltage is higher than the input voltage. In shell-type transformers, the core surrounds a considerable portion of the windings. But practically, in a core type, a part of primary winding is on one limb of the core and other is on the other limb of the core. 10.31, the coils are wound on the central limb of a three limb core. A core type transformer is shown in the diagram below. The core is assembled of a continuous strip or ribbon of transformer steel wound in the form of a circular or elliptical cylinder. In short, maximum linkage is provided in order to avoid the flux leakage between the primary and the secondary winding’s.The typical arrangement of the transformer is shown as: In the following diagram the low voltage winding is closest or adjacent to the iron core instead of the high voltage winding. The three-limb core-type three-phase transformer is the most common method of three-phase transformer construction allowing the phases to be magnetically linked. The coils used in the winding of 3 phase are cylindrical in shape. Power transformers are designed to have considerable greater leakage reactance than is permissible in distribution transformers because in power transformers inherent voltage regulation is not as much important as current limiting effect of the higher leakage reactance. The shell type construction gives better support against electro-magnetic forces between current carrying conductors. They are of the self-cooling type and are almost invariably oil-immersed. The iron core is rectangular in cross-section for small size transformers and circular for large size ones to reduce the quantity of copper required. These forces are of considerable magnitude under short-circuit conditions. The coils used in the winding of 3 phase are cylindrical in shape. Less insulation is required between iron core and winding. Core Type Transformer: Such kind of transformer’s core is designed to have two limbs, each contains separate winding i.e. The three phase transformer is mainly classified into two types, i.e., the core type transformer and the shell type transformer. The core is of rectangular shape. The secondary winding also has a … The medium used in the core. Iron Core Transformer Transformers Based on Winding Arrangement AutoTransformer. The thickness of laminations or stampings varies from 0.35 mm to 0.5 mm. The term is used to include all transformers of large size (250 kVA and above) used in generating stations and substations for transforming the voltage at each end of a power transmission line. This is the most common type of transformer, widely used in electric power transmission and appliances to convert mains voltage to low voltage to power electronic devices. A core type transformer is shown in the diagram below. Though the cost of manufacturing of such a cruciform core is much greater, but the circular coils that are used are easier to wind and provide more mechanical strength, especially when short-circuit occurs. primary & secondary winding.