Transformer | Electrical and Instrumentation Engineering
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Short questions with answers and important five mark questions.
Transformer
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate (termed the fundamental frequency; usually 50 or 60 Hz).
Equivalent Circuit, Working Principle, Uses, Advantages, Disadvantages
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Auto transformer is a transformer with one winding, in which part of winding is common to both primary and secondary. Primary and secondary are not electrically isolated from each other as in case with a 2 winding transformer.
Working Principle, Construction, Connection Types, Phasor diagram, Advantages, Disadvantages, Applications, Solved Example Problems
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Three Phase Transformer Connections are 1. Star-Star (Y-Y) Connection 2. Delta-Delta (A-A) Connection 3. Star-Delta (Y-A) Connection 4. Delta-Star (A-Y) Connection 5. Open-Delta (or) V - V Connection 6. Scott Connection (or) T - T Connection.
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
The performance of such transformers is judged on the basis of energy consumption during the whole day (i.e., 24 hours). This is known as all day efficiency.
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
The voltage regulation of a transformer is the arithmetic difference between the no load secondary voltage and voltage at load condition. Voltage in a transformer on load varies mainly due to its leakage reactance.
with Solved Example Problems
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
The circuit constants, efficiency and Voltage regulation of a transformer can be determined by open circuit and short circuit tests. These tests are very convenient as they provide the required information without actually loading the transformer. The Tests are i)Open Circuit or No load test ii)Short Circuit or Impedance test iii)Polarity test iv)Sumpner (or) Back to Back Test
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Equivalent circuit of transformer is resolved into an equivalent circuit in which the resistance and leakage reactance of the transformer are imagined to be external to the winding which transform the voltage.
Equivalent Circuit, Solved Example Problems
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Transformer windings has resistance R1 and R2 in primary and secondary of the transformer. Both resistance and reactance of the windings can be shifted any one side of the two windings using the factor k2. It makes the calculations easy by doing it one side only.
Equivalent Circuit
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Two winding transformer has primary and secondary winding. Therefore the p.u impedance deserves particular attention. (a) The approximate equivalent circuit of a two winding transformer with impedance referred to low voltage (primary) side. (b) The approximate equivalent circuit with impedance referred to high voltage (secondary) side.
Transformer On Load and No Load with Solved Example Problems
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
We will consider two cases: (i) when a transformer is on no load, (ii) when it is loaded.
Solved Example Problems
Subject and UNIT: Electrical and Instrumentation Engineering: Unit I: Transformer
Keeping supply frequency constant, if primary voltage is increased by 10%, magnetizing current will increase by much more than 10%. However, due to saturation, flux density will increase only marginally and so will the eddy current and hysteresis losses.