Skip to main content

Concentric Windings In Transformer

Figure 1.10 shows concentric windings, which are used for core-type transformers.
images
Figure 1.10 Concentric Windings
Concentric windings are classified into four following groups:
(i) Spiral windings.
(ii) Helical windings.
(iii) Cross-over windings.
(iv) Continuous disc windings.
These windings are discussed as follows.

1.5.1.1 Spiral Windings

These coils are suitable for windings to carry high currents, which are generally used or currents greater than 100 A. They are almost used for LV windings. Figure 1.11 shows double-layer spiral coils, which are wound on solid insulating former, and hence are mechanically strong.
images
Figure 1.11 Double-layer Spiral Coil
images
Figure 1.12 Helical Coils

1.5.1.2 Helical Windings

These coils are wound in the form of helix, which are generally used for low voltages 11 kV to 33 kV for large transformers. Figure 1.12 shows the cross-sectional view of helical coils where each conductor consists of a number of rectangular strips wound in parallel radially.

1.5.1.3 Cross-over Windings

These coils are generally wound on formers. Each coil consists of several layers and each layer consists of several turns. Figure 1.13 shows cross-over coils. The conductors may be of round wire with paper or cotton insulation and not suitable for currents exceeding 20 A. These coils are generally used for small transformers and for HV windings.

1.5.1.4 Continuous Disc Windings

Figure 1.14 shows disc coils. These windings consist of a number of disc and each disc consists of number of turns wound radially over one another from inside outwards and outside inwards alternately. Conductor consists of single number of rectangular strips and passes continuously from disc to disc for multiple strip of conductors. The transposition of conductors is done to ensure uniform current distribution. These windings are mechanically strong and hence can withstand stresses during short circuit conditions. These are used for HV windings of large power transformers.
images
Figure 1.13 Cross-over Coils
images
Figure 1.14 Disc Coils
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

Transformer multiple choice questions part 1

Hello Engineer's Q.[1] A transformer transforms (a) frequency (b) voltage (c) current (d) voltage and current Ans : D Q.[2] Which of the following is not a basic element of a transformer ? (a) core (b) primary winding (c) secondary winding (d) mutual flux. Ans : D Q.[3] In an ideal transformer, (a) windings have no resistance (b) core has no losses (c) core has infinite permeability (d) all of the above. Ans : D Q.[4] The main purpose of using core in a transformer is to (a) decrease iron losses (b) prevent eddy current loss (c) eliminate magnetic hysteresis (d) decrease reluctance of the common magnetic circuit. Ans :D Q.[5] Transformer cores are laminated in order to (a) simplify its construction (b) minimize eddy current loss (c) reduce cost (d) reduce hysteresis loss. Ans : B Q.[6] A transformer having 1000 primary turns is connected to a 250-V a.c. supply. For a secondary voltage of 400 V, the number of secondary turns should be (a) 1600 (b) 250 (c) 400 (d) 1250 A
4 comments
Read more

Condition for Maximum Power Developed In Synchronous Motor

The value of δ for which the mechanical power developed is maximum can be obtained as, Note : Thus when R a is negligible, θ = 90 o for maximum power developed. The corresponding torque is called pull out torque. 1.1 The Value of Maximum Power Developed        The value of maximum power developed can be obtained by substituting θ = δ in the equation of P m .        When R a is negligible,     θ = 90 o  and cos (θ) = 0 hence, . . .               R a = Z s cosθ   and X s = Z s sinθ        Substituting   cosθ = R a /Z s in equation (6b) we get,         Solving the above quadratic in E b we get,        As E b is completely dependent on excitation, the equation (8) gives the excitation limits for any load for a synchronous motor. If the excitation exceeds this limit, the motor falls out of step. 1.2 Condition for Excitation When Motor Develops ( P m ) R max        Let us find excitation condition for maximum power developed. The excitation
Post a Comment
Read more

Electrical Engineering interview questions and answers Part 17

Why star delta starter is preferred with induction motor? Star delta starter is preferred with induction motor due to following reasons: • Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses. • Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused. • In addition, starting torque is increased and it prevents the damage of motor winding. State the difference between generator and alternator Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor
Post a Comment
Read more