Inductors and Inductance

1. Inductors and Inductance CCTC: Industrial Technology Electrical Systems

2. Magnetic Field Around a Coiled Wire There exists a strong connection between Magnetic fields andElectrical current flow. As current flows through the a coiled conductor, a strong Magnetic field is expanding around the conductor. The greater the number of windings and current flow, the stronger the Magnetic Field. Michael Faraday

3. Inductor An inductor is as simple as an electronic component can get – its just a coil of wire. An inductor resists a change in the flow of electrons.

4. Inductance Inductance (L) is the ability of an electric circuit or component to oppose any change in current flow. Inductance is present ONLY when the current changes. The amount of inductance in a coil is measured in Henrys (H)

5. The Capacity of an Inductor The capacity of an inductor is controlled by: • The number of coils in the inductor • The material the coils are wrapped around (core) • Iron cores creates more inductance (magnetic) • The cross-sectional area of the coil • More area more inductance • The length of the coil • Short overlapping coils – more inductance

6. How an Inductor Works • As current flows through the coils of an inductor, a strong magnetic field begins to expand around the conductor. • Energy is stored inside this magnetic field.

7. How an Inductor Works • If current flow slows or stops, the magnetic field collapses and as this happens, it induces more current flow in the wire. • Energy is released in the form of current flow • Thus current flow doesn’t “change”

8. Water Wheel Analogy • When you start the water flowing down a narrow channel towards a heavy water wheel, the paddle wheel will prevent the water from flowing until the wheel has come up to speed with the water. • If you stop the flow of water in the channel, the water wheel will try to keep the water moving until the speed of the rotation slows back down to the speed of the water.

9. Inductor Circuit As the switch is closed and circuit is complete, the inductor sucks up most of the current as it expands the magnetic field around it. The light bulb begins to burn with a dim glow and burns brightly as the magnetic field is fully expanded.

10. Inductor Circuit As the switch and circuit is opened, the magnetic field collapses and current flow is induced into the circuit from the inductor. The light bulb burns brightly for a brief time. When the magnetic field is fully collapsed and current flow stops, the bulb flickers out.

11. No Inductive Reactance In a DC circuit, the current only changes twice: • When the circuit is closed to start current flow • When the circuit is opened to stop current flow Steady DC Voltage produces no change in current, thus no varying magnetic field on the inductor. There is no counter voltage; so the lamp burns brightly.

12. Inductive Reactance In an AC circuit, the current is continually changing each time the voltage alternates There’s a constant opposition offered by the inductor to the ac current therefore the lamp is much dimmer even though the voltage potential is the same (12 volts).

13. Inductive Reactance Inductance Reactance: the constant opposition to current flow offered by an inductor to the AC current • Inductive Reactance is measured in Ohms and is represented by the symbol: XL

14. Inductive Reactance Formula Inductive Reactance equals two Pi times the frequency times the inductance

15. Example of the Formula Remember the prefix milli means 10 to the power of negative 3 . So move the decimal point three places to the left