Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGCOIL AND CORE ASSEMBLYFigure 20-21,— Single-phase transformer.147.125for gunfiring circuits, special signal lights, andhigh-voltage ignition circuits.The typical transformer has two windingswhich are electrically insulated from each other.These windings are wound on a common magneticcircuit made of laminated sheet steel.The principal parts are the core , which providesa circuit of low reluctance for the magneticflux; the primary winding , which receives theenergy from the a-c source; and the secondarywinding , which receives the energy by mutualinduction from the primary and delivers it tothe load.When a transformer is used to step up thevoltage, the low-voltage winding is the primary.When a transformer is used to step down thevoltage, the high- voltage winding is the primary.The primary is always connected to the sourceof the power; the secondary is always connectedto the load. It is common practice to refer to thewindings as the primary and the secondary,rather than as the high-voltage and the lowvoltagewindings.The operation of the transformer is basedon the principle that electrical energy can betransferred efficiently by mutual induction fromone winding to another. When the primary windingis energized from an a-c source, an alternatingmagnetic flux is established in the transformercore. This flux links the turns of bothprimary and secondary, thereby inducing voltagesin them. Because the same flux cuts bothwindings, the same voltage is induced in eachturn of both windings. Hence the total inducedvoltage in each winding is proportional to thenumber of turns in that winding. That is,'1 NiE2where E-^ and E2 are the induced voltages in theprimary and secondary windings, respectively,N2508