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Rectifier Transformers
Published in K.R.M. Nair, Power and Distribution Transformers, 2021
The ampere-turn balancing and eddy current losses of the windings of a rectifier transformer are affected by the winding geometry and design. The ampere turns are balanced in a 2-winding transformer (excluding the effect of no-load current). If harmonics are produced in the secondary winding, the ampere turns are balanced on the primary winding in equal magnitude. Due to this, the eddy losses on the primary and secondary have almost the same per unit magnitude. When the transformer has two or more secondary windings, the harmonic generation depends on the winding placement and coupling.
Direct Current (dc) Electronics
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
The magnetic strength of an electromagnet depends on three factors: (1) the amount of current passing through the coil, (2) the number of turns of wire, and (3) the type of core material. The number of magnetic lines of force is increased by increasing the current, by increasing the number of turns of wire, or by using a more desirable type of core material. The magnetic strength of electromagnets is determined by the ampere-turns of each coil. The number of ampere-turns is equal to the current in amperes multiplied by the number of turns of wire (I × N). For example, 200 ampere-turns are produced by 2 A of current through a 100-turn coil. One ampere of current through a 200-turn coil produces the same magnetic field strength. Figure 1-84 shows how the magnetic field strength of an electromagnet changes with the number of ampere-turns.
Basic Philosophy of Relaying
Published in Y. G. Paithankar, Transmission Network Protection, 2017
Current transformers have certain dot or polarity marks. If current enters the dot mark on the primary side, secondary current exits at the dot on the secondary mark side. This ensures that the primary and secondary ampere-turns are equal and of opposite polarity, necessary for any transformer to operate (i.e., the primary and secondary ampere-turns balance).
Short-Circuit Performance Analysis of a Distribution Transformer Using Coupled Field-Circuit Approach
Published in Electric Power Components and Systems, 2023
Table 2 presents the total radial and axial EFs exerted on the HV and LV windings at peak SC fault current with the different winding configurations of the LV windings. It can be recognized that the LV and HV winding experience a total radial force directed inwards (toward the core) and outwards (toward the tank or adjacent HV winding), respectively. On the other hand, the direction of the axial end thrust in both windings is upwards (toward the yoke upper part). It can be recognized that during normal operation, the forces are modest, as mentioned above. However, since the total axial force is not zero, the axial forces in the upper and lower parts of the windings do not have the exact same magnitude. If the windings are not placed at the same central line, this total axial force might increase the windings asymmetry [25]. These axial displacements result in the imbalance of ampere-turn distribution between the windings, which in turn can cause transformer failure. Thus, it is extremely important to place the HV and LV windings at the same magnetic center to avoid an increase in the end thrusts on the clamping structures [25]. In addition, it may be observed that the occurrence of radial and axial deformation in the LV winding is more likely than in the HV winding. This is because the LV winding faces higher EFs than the HV winding because it is closer to the limb, and the flux is concentrated there [25, 26].
Thermal Analysis of Power Transformer Using an Improved Dynamic Thermal Equivalent Circuit Model
Published in Electric Power Components and Systems, 2019
Morteza Mikhak-Beyranvand, Jawad Faiz, B. Rezaeealam
The windings consist of many disks with a uniform ampere-turn distribution, so the RI2 losses are the same for the disks and easily is calculated, but the eddy current losses vary depending on the location of disks. The local values of the axial and radial flux densities for each disk can be obtained from the electromagnetic analysis, whereupon the axial and radial components of the eddy losses are calculated for each strand using the following equation [32]: where d (in m) is the strand dimension perpendicular to the direction of the leakage flux density in m. The axial and radial flux density are assumed to be constant over all strands of a disk, so the average axial and radial flux density of disk are used to calculate the strand eddy loss [33].
A New Soft Switching qZSC Converter by Using Coupled Inductor
Published in Electric Power Components and Systems, 2018
Mojtaba Karimi, Mohammad Mahdavi, Amir Torki Harchegani
Mode 3 [t2 − t3] By reaching Cr voltage to zero, D2 begins to conduct under Zero Voltage Switching (ZVS) condition. A freewheeling current ILr(t3) circulate between Lr1 and Lr2. So the ampere turn of the Lr1 and Lr2 must remain constant. This mode is similar to the switches on time in qZSC. This mode continues until turning off the switch.