Skip to main content

TRANSFORMER WINDINGS

There are two types of windings usually used in a transformer. The winding receiving electrical energy is known as primary winding, whereas the winding delivering electrical energy is called secondary winding. Windings are usually made of high grade of copper. Standard conductors are used for carrying higher current. To avoid the each turn to come in contact with each other, the windings are provided with insulation. In addition to inter-turn insulator, bare copper wires are provided with enamel coating. Usually single- or double-layer cotton is used. Sometimes press board or cotton insulation is also used to support the windings. Usually additional insulation is provided for line end turns for their protection from lightning and switching over voltages. During transient disturbances, the distribution of voltage is not uniform along the windings and 80 per cent of voltage at that time appears across the first 10 per cent of turns from line end. Heat generation occurs due to energy loss, which is proportional to the volume of the material in which the losses occurs. The heat dissipation is proportional to the surface area of the same material and the tank. The ratio of heat generated to heat dissipated is approximately proportional to the ratio of volume of the material for conductors and the core to the surface area of the material for conductors, the core and the tank, which must approach to unity to limit the temperature rise. This can be achieved by corrugating the surface area of the tank. To get effective cooling, the radiators are used shown in Figure 1.18 later on.
The following are the most important requirements of transformer windings:
  • The windings must be economical.
  • The heating conditions of the windings should satisfy standard requirements.
  • The windings must have good mechanical strength to combat the force that originates due to short circuit.
  • The windings must have the necessary electrical strength during over-voltage. The following are the two different types of windings: (i) Concentric windings and (ii) sandwich windings.
Labels:

Comments

Post a Comment

Comment Policy
We’re eager to see your comment. However, Please Keep in mind that all comments are moderated manually by our human reviewers according to our comment policy, and all the links are nofollow. Using Keywords in the name field area is forbidden. Let’s enjoy a personal and evocative conversation.

Popular posts from this blog

Practical Commutation

The e.m.f. induced in each coil of armature is alternating in nature. If load is connected, the current flowing will also be alternating. But the flow of current in a d.c. generator must be undirectional. This can be achieved by the use of commutator. When the armature conductors are under the influence of one pole they carry current in one direction whereas the current is reversed when the conductors are under the influence of other pole. This reversal of current takes place along the magnetic neutral axis. Fig. 1 Note : The reversal of current is likely to take place in short interval when a coil is short circuited by a brush so that transfer of current from one direction to other is carried out without any sparking. This process is called commutation.        Thus a process by which current in the short circuited coil is reversed while it crosses the MNA is called commutation. The time during which the coil remains short circuited is known as...
1 comment
Read more

Demagnetising and Cross Magnetizing Conductors

The conductors which are responsible for producing demagnetizing and distortion effects are shown in the Fig.1. Fig. 1        The brushes are lying along the new position of MNA which is at angle θ  from GNA. The conductors in the region AOC = BOD = 2θ  at the top and bottom of the armature are carrying current in such a direction as to send the flux in armature from right to left. Thus these conductors are in direct opposition to main field and called demagnetizing armature conductors.         The remaining armature conductors which are lying in the region AOD and BOC carry current in such a direction as to send the flux pointing vertically downwards i.e. at right angles to the main field flux. Hence these conductors are called cross magnetizing armature conductors which will cause distortion in main field flux.        These conductors are shown in the Fig. 2 Fig. 2  ...
Post a Comment
Read more

Armature Voltage Control Method or Rheostatic Control of dc motor

Speed Control of D.C. Shunt Motor (Part2)  2. Armature Voltage Control Method or Rheostatic Control        The speed is directly proportional to the voltage applied across the armature. As the supply voltage is normally constant, the voltage across the armature can be controlled by adding a variable resistance in series with the armature as shown in the Fig. 1. Fig. 1 Rheostat control of shunt motor        The field winding is excited by the normal voltage hence I sh is rated and constant in this method. Initially the reheostat position is minimum and rated voltage gets applied across the armature. So speed is also rated. For a given load, armature current is fixed. So when extra resistance is added in the armature circuit, I a remains same and there is voltage drop across the resistance added ( I a R). Hence voltage across the armature decreases, decreasing the speed below normal value. By varyi...
Post a Comment
Read more