TRANSFORMER LOSSES

In practice the output power is always lesser then the input power and hence the efficiency of the transformer is always less than 100 percent. this implies that some amount of energy is lost in the form of heat. The energy loss can be considered as copper losses, eddy current losses, hysteresis losses and flux leakage

Copper losses – when a current I flow through resistance R, an amount of power equal to i² R t watts is converted into heat. this arise in both copper coils and iron core. The copper coils possess resistance. When  current flow through this coil, electrical energy equal to i² R t is converted into heat. To reduce the loss, the current cannot be reduced because the normal operation of the transformer of the transformer will be affected. Instead the resistance of the coil must be minimized by using the wire of low resistivity wire. Therefore, thicker wire should be used as transformer coil. the optimum thickness will be decide by comparing the cost, space and saving of power. Copper is the best coil material available today and therefore is commonly used.

Eddy current losses – the iron core consisting of concentric layers of iron each acting as circuited single turn coil. hence, emf will be induced in the core. This emf will be produce currents called eddy currents. the eddy currents will give rise to i² R t losses. These eddy currents can be eliminated by making the iron core in the form of thin sheet of metal, and each sheet is insulted from its neighbor by thin layer of paper .this type of core is known as laminated core .the core is usually made up of stelloy ,an alloy of steel.

Hysteresis losses – the transformer core is the magnetic material. The core is magnetized twice in each cycle of the alternating voltage. when the direction of ac changes, the magnetization also gets reversed. During this reversal some energy is lost due to the molecular friction and the energy appears as heat. The loss of energy by molecular friction is called hysteresis loss. This can be reduced in practice by choosing a suitable magnetic material such as mumetal which has low hysteresis loss. mumetal is a ferromagnetic alloy containing 78 percent nickel,17% percent iron and 5% copper. its has high permeability.

Flux leakage  -  all the flux linked with the primary is not linked with the secondary due to leakage. this result in the loss of the energy. This can be minimized by using a shell type of core