Search Results for – "TRANSFORMERS"
TRANSFORMERS
TRANSFORMERS: Approximate Equivalent Circuit Transformer Audio Frequency Transformer Definition Auto Transformer Back to Back Test on Three phase Transformers Choice between Star Delta Connection Choice of Transformer Connections Construction of Transformer Efficiency and Voltage Regulation Excitation Phenomenon in Transformers Forced Cooling Transformer How does a Transformer Work Ideal Transformer Phasor Diagram Name Plate Rating Natural […]
Resonant Transformers
Resonant Transformers: The equivalent circuit of a high voltage testing Resonant Transformers consists of the leakage reactance of the windings, the winding resistances, the magnetizing reactance, and the shunt capacitance across the output terminal due to the bushing of the high voltage terminal and also that of the test object. This is shown in Fig. […]
Applications of Power Transformers
Applications of Power Transformers: Transformers are the first to encounter lightning and other high voltage surges. The transformer insulation has to withstand very high impulse voltages many times the power frequency operating voltages. The Applications of Power Transformers insulation is broadly divided into Conductor or turn-to-turn insulation, Coil-to-coil insulation, Low voltage coil-to-earth insulation, High voltage […]
Protection of Transformers
Protection of Transformers: Transformers are static devices, totally enclosed and generally oil immersed. Therefore, chances of faults occurring on them are very rare. However, the consequences of even a rare fault may be very serious unless the transformer is quickly disconnected from the system. This necessitates to provide adequate automatic Protection of Transformers against possible […]
Tap Changing Transformers
Tap Changing Transformers: The excitation control method is satisfactory only for relatively short lines. However, it is not suitable for long lines as the voltage at the alternator terminals will have to be varied too much in order that the voltage at the far end of the line may be constant. Under such situations, the […]
Sequence Impedance and Networks of Transformers
Sequence Impedance and Networks of Transformers: Sequence Impedance and Networks of Transformers – It is well known that almost all present day installations have three-phase transformers since they entail lower initial cost, have smaller space requirements and higher efficiency. The positive sequence series impedance of a transformer equals its leakage impedance. Since a transformer is […]
Phase Shift in Star Delta Transformers
Phase Shift in Star Delta Transformers: Phase Shift in Star Delta Transformers – Positive and negative sequence voltages and currents undergo a phase shift in passing through a star-delta transformer which depends upon the labelling of terminals. Before considering this phase shift, we need to discuss the standard polarity marking of a single-phase transformer as […]
Voltage and Current Transformers
Voltage and Current Transformers Voltage and Current Transformers – These transformers are designed to meet the specific need of measurement and instrumentation systems, which accept voltages in the range of 0-120 V and currents upto 5 A. Power system voltages can be as high as 750 kV and currents upto several tens of kA. Their […]
Three Winding Transformers
Three Winding Transformers Three Winding Transformers may be built with a third winding, called the tertiary, in addition to the primary and secondary. Various purposes which dictate the use of a tertiary winding are enumerated below: To supply the substation auxiliaries at a voltage different from those of the primary and secondary windings. Static capacitors […]
Parallel Operation of Transformers
Parallel Operation of Transformers When the load outgrows the capacity of an existing transformer, it may be economical to install another one in parallel with it rather than replacing it with a single larger unit. Also, sometimes in a new installation, two units in parallel, though more expensive, may be preferred over a single unit […]
Back to Back Test on Three phase Transformers
Back to Back Test on Three phase Transformers: Fig. 3.52(a) shows the connection arrangement for the Back to Back Test on two identical 3-phase transformers. The two secondaries must be connected in phase opposition and in proper phase sequence. The auxiliary transformer for circulating full-load current is included in the circuit of the two secondaries; it […]
Three phase Bank of Single phase Transformers
Three phase Bank of Single phase Transformers Delta/delta connection The supply voltage provides only sinusoidal magnetizing current so that core flux is flat-topped; but the third-harmonic emfs induced (cophasal) cause circulating currents in deltas restoring the flux to almost sinusoidal. The third-harmonic voltages are very small as the transformer offers low impedance to third-harmonic currents. […]
Excitation Phenomenon in Transformers
Excitation Phenomenon in Transformers It was stated in Sec. 3.3 that the no-load current in a transformer is nonsinusoidal. The basic cause for this phenomenon, which lies in hysteresis and saturation nonlinearities of the core material, will now be investigated; this can only be accomplished graphically. Assume that the voltage v1 applied to the transformer […]
Stripline and Microstrip Transmission Line
Stripline and Microstrip Transmission Line: Stripline and Microstrip Transmission Line are physically related to transmission lines but are covered here because they are microwave circuits used in conjunction with semiconductor microwave devices. As illustrated of Stripline and Microstrip Transmission Line shown in Figure 12-1, stripline consists of flat metallic ground planes, separated by a thickness […]
Rectangular Waveguides
Rectangular Waveguides: Rectangular Waveguides – As we know already that the term skin effect indicated that the majority of the current flow (at very high frequencies) will occur mostly along the surface of the conductor and very little at the center. This phenomenon has led to the development of hollow, conductors known as waveguides. To […]
Antenna Coupling
Antenna Coupling: Antenna Coupling : Low and medium frequency antennas are the ones least likely to be of resonant effective height and are therefore the least likely to have purely resistive input impedances. This precludes the connection of such an antenna directly, or via transmission line, to the output tank circuit of a transmitter. Some […]
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