Anglicky v odborných předmětech "Support of teaching technical subjects in English“

1. Anglicky v odborných předmětech"Support of teaching technical subjects in English“ Tutorial: Mechanic - electrician Topic: Technicaltraining II. class Passivecomponents – transformers Prepared by: Melichařík Lubomír Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

2. PASSIVE COMPONENTS - TRANSFORMERS Transformer Is a non-rotating electric machine -allows you to transfer electrical energy from one circuit to another through mutual electromagnetic induction -used mostly to convert AC voltage (e.g. from low voltage to high), or for galvanic isolation circuits.

3. TRANSFORMER Electrotechnical schematic symbols • Schematic symbol for a transformer with an air core • Schematic symbol for a transformer with a magnetic core • Schematic symbol for a transformer with a ferrite core • Schematic symbol for a transformer with a tap

4. TRANSFORMER • Electrotechnical schematic symbols • Schematic symbol for a transformer with multiple windings • Schematic symbol for a single-phase transformer

5. BASIC PRINCIPLE OF A TRANSFORMER • The transformer is an AC converter • -it consists of three main parts: the coil, the magnetic circuit, the insulation system. • -primary winding is used to convert electrical energy into magnetic. Passing a current creates a magnetic flux Φ [Fí]. • -this flux is guided in the magnetic circuit (core) to the secondary coil. • -in the secondary coil according to the principle of Faraday’s law of induction a voltage is induced • -therefore, the transformer works only on alternating or pulsating current because the DC does not change the magnetic flux (i.e. constant flux derivative is zero) and the secondary winding no longer has a voltage.

6. PRINCIPLE OF A TRANSFORMER AND WINDING • -winding of small transformers are made of painted (enameled) wires of various diameters • -the coil is wound onto the coil body (skeleton) thread after thread • -single-layer winding is interspersed with insulation. The surface of the coil is insulated with cardboard or linen. It impregnates the vacuum pressure impregnation • -voltage control taps on the second winding

7. AUTOTRANSFORMER • Autotransformers • -are transformers, whose primary and secondary winding use the same coil • -from a mechanical point of view, the coil is on an iron core, with taps for the primary and secondary voltages • -a disadvantage is, that when we come to construct a galvanic isolation of primary and secondary voltages • -a secondary winding tap can be realised by moving the slider • -used in electrical laboratories and in traction drive rail vehicles

8. Activities for students – mandatory slideTask, test, questions … . • Draw the schematic symbol for a transformer. • Draw and explain the principle of an autotransformer

9. Activities for students – mandatory slideTask, test, questions … . Two slides are better. • Divide the transformers • According to the number of phases • - • - • - • According to the design of the magnetic circuit • - • - • - • According to the uses • - • - • - • According to the number of windings • - • - • -

10. Bibliography • Václav Malina Poznáváme elektroniku I. • Adrian Schommers Elektronika tajemství zbavená. ISBN 3-92608-32-5