Experiment 9

1. Experiment 9 Part A: Simulation of a Transformer Part B: Making an Inductor Part C: Measurement of Inductance Part D: Making a Transformer

2. Inductors & Transformers • How do transformers work? • How to make an inductor? • How to measure inductance? • How to make a transformer? ? Electronic Instrumentation

3. Some Interesting Inductors • Induction Heating Electronic Instrumentation

4. Some Interesting Inductors • Induction Heating in Aerospace Electronic Instrumentation

5. Some Interesting Inductors • Induction Forming Electronic Instrumentation

6. Primary Coil Secondary Coil Some Interesting Inductors • Coin Flipper Electronic Instrumentation

7. Some Interesting Inductors • GE Genura Light Electronic Instrumentation

8. Some Interesting Transformers • A huge range in sizes Electronic Instrumentation

9. Wall Warts Electronic Instrumentation

10. Some Interesting Transformers • High Temperature Superconducting Transformer Electronic Instrumentation

11. Household Power • 7200V transformed to 240V for household use Electronic Instrumentation

12. Inductors-Review • General form of I-V relationship • For steady-state sine wave excitation Electronic Instrumentation

13. Inductors-Review • Simple R-L Filter • High Pass Filter • Corner Frequency Electronic Instrumentation

14. Inductors-Review Electronic Instrumentation

15. Making an Inductor • For a simple cylindrical inductor (called a solenoid), we wind N turns of wire around a cylindrical form. The inductance is ideally given by where this expression only holds when the length d is very much greater than the diameter 2rc Electronic Instrumentation

16. Making an Inductor • Note that the constant o = 4 x 10-7 H/m is required to have inductance in Henries (named after Joseph Henry of Albany) • For magnetic materials, we use  instead, which can typically be 105 times larger for materials like iron •  is called the permeability Electronic Instrumentation

17. Some Typical Permeabilities • Air 1.257x10-6 H/m • Ferrite U M33 9.42x10-4 H/m • Nickel 7.54x10-4 H/m • Iron 6.28x10-3 H/m • Ferrite T38 1.26x10-2 H/m • Silicon GO steel 5.03x10-2 H/m • supermalloy 1.26 H/m Electronic Instrumentation

18. Making an Inductor • If the coil length is much small than the diameter (rwis the wire radius) Such a coil is used in the metal detector at the right Electronic Instrumentation

19. Making an Inductor • All wires have some finite resistance. Much of the time, this resistance is negligible when compared with other circuit components. • Resistance of a wire is given by l is the wire length A is the wire cross sectional area (prw2) s is the wire conductivity Electronic Instrumentation

20. Some Typical Conductivities • Silver 6.17x107 Siemens/m • Copper 5.8x107 S/m • Aluminum 3.72x107 S/m • Iron 1x107 S/m • Sea Water 5 S/m • Fresh Water 25x10-6 S/m • Teflon 1x10-20 S/m Electronic Instrumentation

21. Wire Resistance • Using the Megaconverter at http://www.megaconverter.com/Mega2/ (see course website) Electronic Instrumentation

22. Transformers • Note that for a transformer, the symbol shows two inductors. One is the primary (source end) and one is the secondary (load end): LS& LL • The inductors work as expected, but they also couple to one another through their mutual inductance: M2=k2 LS LL Symbol for transformer Electronic Instrumentation

23. Transformers IS IL Note Current Direction • Let the current through the primary be • Let the current through the secondary be • The voltage across the primary inductor is • The voltage across the secondary inductor is Electronic Instrumentation

24. Transformers • Sum of primary voltages must equal the source • Sum of secondary voltages must equal zero Electronic Instrumentation

25. Transformers • Note the following simplifying information for cylindrical or toroidal inductors • For Electronic Instrumentation

26. Transformers • Cylinders (solenoids) • Toroids Electronic Instrumentation

27. Electronic Instrumentation

28. Transformers • Transformers are designed so that the inductive impedances are much larger than any resistance in the circuit. Then, from the second loop equation Electronic Instrumentation

29. Transformers • The voltages across the primary and secondary terminals of the transformer are related by Note that the coil with more turns has the larger voltage Electronic Instrumentation

30. Transformers • The input impedance of the primary winding reflects the load impedance. It can be determined from the loop equations Electronic Instrumentation

31. Transformer Rectifier • Adding a full wave rectifier to the transformer makes a low voltage DC power supply, like the wall warts used on most of the electronics we buy these days. Electronic Instrumentation

32. Transformer Rectifier Filtered Unfiltered Electronic Instrumentation

33. Determining Inductance • Calculate it from dimensions and material properties • Measure using commercial bridge (expensive device) • Infer inductance from response of a circuit. This latter approach is the cheapest and usually the simplest to apply. Most of the time, we can determine circuit parameters from circuit performance. Electronic Instrumentation

34. Determining Inductance • For this circuit, a resonance should occur for the parallel combination of the unknown inductor and the known capacitor. If we find this frequency, we can find the inductance. Electronic Instrumentation

35. Determining Inductance • Reminder—The parallel combination of L and C goes to infinity at resonance. Electronic Instrumentation

36. Electronic Instrumentation

37. Even 1 ohm of resistance in the coil can spoil this response somewhat Electronic Instrumentation

38. Project 3: Beakman’s Motor • The coil in this motor can be characterized in the same way Electronic Instrumentation

39. Optional Project: Paperclip Launcher • A small disposable flash camera can be used to build a magnetic paperclip launcher Electronic Instrumentation