Chapter 10. Losses - 10. LOSSES Summary Transformer losses...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
369 10. LOSSES Summary Transformer losses comprise a small percentage of the power throughput in a transformer. Yet these losses can produce localized heating which can compromise its operation. It is important to be able to calculate these losses at the design stage so that adequate cooling can be provided. In addition, such calculations and their parameter dependencies can suggest ways of reducing these losses should that be necessary based on cost considerations or design feasibility. There are two main categories of losses, no-load and load losses. Noload losses are basically core losses associated with energizing the transformer and driving flux through the core. Load losses are further subdivided into I 2 R losses and stray losses. The I 2 R losses are resistive losses in the windings and leads caused by the main current flow. The stray losses are the result of the stray flux from the windings or leads impinging on metal parts such as the tank walls, the clamps, and even the windings themselves, resulting in induced eddy currents. We present formulas or methods for obtaining these losses in this report. 10.1 INTRODUCTION Transformer losses are broadly classified as no-load and load losses. Noload losses occur when the transformer is energized with its rated voltage at one set of terminals but the other sets of terminals are open circuited so that no through or load current flows. In this case, full flux is present in the core and only the necessary exciting current flows in the windings. The losses are predominately core losses due to hysteresis and eddy currents produced by the time varying flux in the core steel. Load losses occur when the output is connected to a load so that current flows through the transformer from input to output terminals. Although core losses also occur in this case, they are not considered part of the load losses. When measuring load losses, the output terminals are shorted to ground and only a small impedance related voltage is necessary to produce the desired full load current. In this case, the core losses are small because of the small core flux and do not significantly add to the measured losses. © 2002 by CRC Press
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
LOSSES 370 Load losses are in turn broadly classified as I 2 R losses due to Joule heating produced by current flow in the coils and as stray losses due to the stray flux as it encounters metal objects such as tank walls, clamps or bracing structures, and the coils themselves. Because the coil conductors are often stranded and transposed, the I 2 R losses are usually determined by the d.c. resistance of the windings. The stray losses depend on the conductivity, permeability, and shape of the metal object encountered. These losses are primarily due to induced eddy currents in these objects.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/19/2010 for the course ENGINEERIN ELEC121 taught by Professor Tang during the Spring '10 term at University of Liverpool.

Page1 / 60

Chapter 10. Losses - 10. LOSSES Summary Transformer losses...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online