Prezentace na téma: "Tutorial: Mechanik - elektrotechnik Topic: Basics of electrical engineering the 2nd. year Measuring inductance Prepared by: Ing. Jiří Smílek Projekt Anglicky."— Transkript prezentace:
Tutorial: Mechanik - elektrotechnik Topic: Basics of electrical engineering the 2nd. year Measuring inductance 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.
Definition: Inductance is 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 - M 1 = M 2
The used method: 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. a)Connection for the measurement of smaller inductance/ coils b)Connection for the measurement of larger inductance/coils
Calculation: Self inductance can be determined from the definition of impedance: Apparent power coils: Coil impedance: Coil resistance
The measurement procedure: To measure inductance using the indirect method we must know the voltage and the current – calculate R X and Z LX ⇒calculate L X 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 used method: Deviation method – inductance is measured by an A-metre, V- metre and a W-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 Resistance R reg adjusted current for example of 0.25 A and read current I, voltage U and power P (losses in the turns and the iron). From the measured values we calculate the coils impedance: The measurement procedure:
Calculations: From the measured values we calculate: Coil impedance: Active resistance: Inductance: Inductance can also be calculated from the relationship: Of which
The used method: Bridge method– inductance with a Maxwell-Wien bridge The condition of the bridge balance: After treatment and separation of real and imaginary members:
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 –
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 ◦
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- konkurenceschopnosthttp://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.