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

1. Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“ Tutorial: Mechanik - elektrotechnik Topic: Basicsofelectricalengineering the2nd. year Measuringinductance Prepared by: Ing. Jiří Smílek Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

2. Measuring Inductance • Inductanceis the ratio of the coupled induction flux to the current which passes through the coil. • Coupled magnetic flux to the current that flows through the coil • The basic unit - 1 H (henry) • L- inductance coil • M - magnetic flux coupled coils • I – current passing through the coil • N – number of turns in the coils • The mutual inductance M of two close coils is the ratio of the induced emf in the first coil caused by a current in the second coil or vice versa - M1 = M2 • Definition:

3. Measuring inductance Deviation method – inductance is measured by an A-metre and V-metre to determine the value of the measured resistance deviation or determine the numeric value. Connection for the measurement of smaller inductance/ coils Connection for the measurement of larger inductance/coils • The used method:

4. Measuring inductance Self inductance can be determined from the definition of impedance: Apparent power coils: Coil impedance: Coil resistance • Calculation:

5. Measuring induction • To measure inductance using the indirect method we must know the voltage and the current – calculate RX and ZLX ⇒calculate LX • To measure the resistance a DC current must flow in the circuit • To measure the inductance an AC current must flow in the circuit • ⇒ • ⇒ • Method suitable for measuring air coils in operation • The measurement procedure:

6. Measuring inductance with an iron core Deviation method – inductance is measured by an A-metre, V-metre and aW-metre - Inductance coils with an iron core are not constant because they depend on the magnetic flux, that is the current passing through the coil ResistanceRregadjusted current for example of 0.25 A andread currentI, voltageU and powerP (losses in the turns and the iron). From the measured values we calculate the coils impedance: • The used method: • The measurement procedure:

7. Measuring inductance with an iron core • From the measured values we calculate: • Coil impedance: • Active resistance: • Inductance: • Inductance can also be calculated from the relationship: • Of which • Calculations:

8. Measurement of inductance bridges Bridge method– inductance with a Maxwell-Wien bridge The condition of the bridge balance: After treatment and separation of real and imaginary members: • The used method:

9. Activities for students - questions • Describe how induction is defined • Describe how mutual inductance is defined • Write how you know the types of coils • Write what methods can measure inductance • direct – • indirect –

10. Activities for students – questions • Explain why an inductance coil with an iron core is not constant • Write a procedure to measure inductance with an iron core • Write the procedure to calculate the inductance from the measured values

11. Bibliography • Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7. • Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013. • Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-konkurenceschopnost • Učebnice Elektrická měření – Ing. Pavel Vylegala, SŠE Ostrava, 2006 • Učebnice Elektrické měření – SNTL, 1981 • Elektrotechnika - Laboratorní cvičení pro bakalářské studium - Doc. Ing. Miloš Hammer, CSc.