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Common Mode and Differential Mode: Definition, Cause, and Elimination
Published in Richard Lee Ozenbaugh, Timothy M. Pullen, EMI Filter Design, 2017
Richard Lee Ozenbaugh, Timothy M. Pullen
Because common-mode noise is measured between both or all lines and ground, capacitors to ground are required to act as low-impedance shunts. In addition, common-mode chokes are used to present high impedance to common-mode current; these are discussed later. The reactive capacitor current to ground is also called leakage current. This ground current is the difference in current in the two ground capacitors from both sides of the lines. An isolation transformer eliminates the leakage current and greatly reduces the common-mode noise. Figure 3.7 shows two capacitors to ground for 220-V AC balanced lines. These capacitors could be feed-through type or leaded capacitors. If the voltage is equal and opposite (180 degrees out of phase) and the capacitors are equal, the ground current is zero at the line frequency. This works for capacitors with leads as well as for feed-through capacitors.
Transformers
Published in Muhammad H. Rashid, Ahmad Hemami, Electricity and Electronics for Renewable Energy Technology, 2017
Sometimes in electrical applications it is necessary that a device be isolated from the rest of the circuit feeding it. That is, the device receives a voltage while not directly in parallel with other devices. In such a case an isolation transformer is employed. The schematic of an isolation transformer is shown in Figure 10.12. In an isolation transformer the number of turns of the primary and secondary windings is the same. As a result, the secondary voltage is the same as the primary voltage. Nevertheless, if by a fault in the primary circuit the current suddenly jumps up, the device connected to the secondary side is not affected. The isolation transformer, thus, is used when a device must be protected from damage.
Mitigation Techniques
Published in L. Ashok Kumar, S. Albert Alexander, Computational Paradigm Techniques for Enhancing Electric Power Quality, 2018
L. Ashok Kumar, S. Albert Alexander
Isolation transformers can achieve the same harmonic attenuation as for line reactors, provided they are sized properly. De-rating a transformer or line reactor, results in lower effective percent impedance and thus higher harmonic current distortion. The advantage of an isolation transformer is that it can reduce both common mode (when an electrostatic shield is used) and normal mode disturbances as well as provide circuit isolation. Disadvantages are physical size, circuit losses, and cost. The typical cost of an isolation transformer for loads of 100 hp down to 20 hp can be $50 to $150 per horsepower.
Bi-directional DC/DC Converters Used in Interfacing ESSs for RESs and EVs: A Review
Published in IETE Technical Review, 2023
Om Prakash Jaga, Ritesh Gupta, Balaram Jena, Sumit GhatakChoudhuri
Figure 20(a) exhibits a CLLC three-level, half-bridge resonant DC/DC converter [77, 78]. The LV side consists of four active devices, S1–S4, two power diodes, D1–D2, four capacitors, CB1, CB2, C1 and C2 and an inductor, L1. HV side consists of four active devices, S5–S8, two power diodes, D3–D4, three capacitors, CDC1, CDC2 and C3, and an inductor, L2. A high-frequency galvanic isolation transformer, Tr isolates the HV and LV sides. ZVS is achieved for active devices by utilizing clamped diodes and capacitor units. The quasi-ZCS achieves to reduced switching losses. Synchronous rectifier realised on the secondary side to minimise conduction losses. It is applicable to high voltage and high power applications. Merits of such a topology include reduced voltage stresses of switching devices and minimisation of electromagnetic interference. This topology is designed for 1 kV input voltage and 3 kW output power. Such a converter achieved more than 96% efficiency under different loading conditions. Such a topology is suitable for EVs charging, plug-in hybrid EVs, RESs power generations as interfaced with BESS, etc.
Analysis, modelling and design of CLLC resonant converter for performance enhancement of fuel cell hybrid electric vehicle
Published in International Journal of Modelling and Simulation, 2022
Bandi Mallikarjuna Reddy, Paulson Samuel
A novel modulation technique is proposed for CLLC resonant converter. The flux linkage and frequency are modulated by using FLC modulation as well as with conventional techniques. In the conventional technique, the frequency is somewhat little constant but flux linkage remain decreased with increasing load. The utilization of isolation transformer is decreased at higher loads. Also, the power transfer characteristics of converter are nonlinear [37]. By using FLC method, the flux linkages became constant and frequency is decreased as load increased. The CLLC resonant converter has two merits with FLC technique that the power transfer characteristics are almost linear and converter losses would be decreased due to decreases in frequency. The design of controller is easier as the power transfer characteristics are linear unlike conventional techniques.
Real Time Implementation of Pollination Based Techniques for Radial Distribution Network Reconfiguration
Published in IETE Journal of Research, 2021
Mariaraja Paramasivam, Manigandan Thathan
As such, a scaled-down multi-phase RDS workstation [41] with 13 buses, 12 branches and several types of loads is built to facilitate physical experiments and real-time research work. The system has a base voltage of 0.11 kV and 0.1 MVA rating. The workstation is integrated with (i) a power station modeled with a 3-phase 440/110 V, 4A, isolation transformer with one 1:1 autotransformer, (ii) four Pi-section panels each of 2 km length, (iii) load control panels with the resistive, inductive, capacitive and motor loads, (iv) numerical overcurrent relay with a current rating of 1A/5A and storage capability of the last 20 events, (v) graphical user interface with data acquisition, (vi) smart meters for remote monitoring where each of which is provided with RS485 communication port, (vi) fault simulator panel to perform different types of power system faults and (vii) transmission line simulator MICRO-II software package.