Why the efficiency of the transformer is 100 percent? explain all losses.
Answers
Explanation:
Efficiency, Losses and Heat
An ideal transformer would have no losses, and would therefore be 100% efficient.
In practice energy is dissipated due both to the resistance of the windings (known as load loss), and to magnetic effects primarily attributable to the core (known as iron loss). Transformers are in general highly efficient, and large power transformers (around 100 MVA and larger) may attain an efficiency as high as 99.75%. Small transformers such as a plug-in used to power small consumer electronics may be less than 85% efficient.
Efficiency Dry-Type Transformers.
Transformers reduce the voltage of the electricity supplied by your utility to a level suitable for use by the electric equipment in your facility. Since all of the electricity used by your company passes through a transformer, even a small efficiency improvement will result in significant electricity savings. High-efficiency transformers are now available that can reduce your facility's total electricity use by approximately 1 percent. That's good for your company; it's also good for the environment. Reduced electricity use provides cost savings for your company; it also reduces air emissions from electricity generation.
Two types of energy losses occur in transformers: Load and No-Load losses.
Load losses result from resistance in the copper or aluminum windings. Load losses (also called winding losses) vary with the square of the electrical current (or load) flowing through the windings. At low loads (e.g. under 30 percent loading), core losses account for the majority of losses, but as the load increases, winding losses quickly dominate and account for 50 to 90 percent of transformer losses at full load. Winding losses can be reduced through improved conductor design, including proper materials selection and increases in the amount of copper conductor employed.
No-load losses result from resistance in the transformer's laminated steel core. These losses (also called core losses) occur whenever a transformer is energized and remain essentially constant regardless of how much electric power is flowing through it. To reduce core losses, high-efficiency transformers are designed with a better grade of core steel and with thinner core laminations than standard-efficiency models. As well, new transformer core designs are emerging that use amorphous metal instead of the traditional silicon steel. These amorphous core transformers, available from major transformer manufacturers including GE, ABB and Howard Transformers, offer up to 80 percent lower core losses than conventional transformers.
Total transformer losses are a combination of the core and winding losses. Unfortunately, some efforts to reduce winding losses increase core losses and vice versa. For example, increasing the amount of conductor used reduces the winding losses, but it may necessitate using a larger core, which would increase core losses. Manufacturers are developing techniques that optimize these losses based on the expected loading.
The loses arise from:
Winding resistance: Current flowing through the windings causes resistive heating of the conductors.
Eddy currents: Induced currents circulate in the core and cause it resistive heating.
Stray losses: Not all the magnetic field produced by the primary is intercepted by the secondary. A portion of the leakage flux may induce eddy currents within nearby conductive object such as the transformers support structure, and be converted to heat. The familiar hum or buzzing noise heard near transformers is a result of stray fields causing components of the tank to vibrate, and is also from magnetostriction vibration of the core.
Hysteresis losses: Each time the magnetic field is reversed, a small amount of energy is lost to hysteresis in the magnetic core. The level of hysteretic is affected by the core material.
Mechanical losses: The alternating magnetic field causes fluctuating electromagnetic forces between the coils of wire, the core and any nearby metalwork, causing vibrations and noise which consume power.
Magnetostriction: The flux in the core causes it to physically expand and contract slightly with the alternating magnetic field, an effect known as magnetostriction. This in turn causes losses due to friction heating in susceptible ferromagnetic cores.
Efficiency gains can be achieved by using materials with lower resistively or greater diameters. For example, transformer coils made with low resistively conductors, such as copper, can have considerably lower load losses than those made with other material.