Editor’s choice
between current and voltage without needing to derive any values for the magnetic field itself. When the current through the coil stops changing and is held constant, the induced voltage therefore drops to zero. The magnetic field still stores potential energy.
The unit of inductance is the henry (H), and induction values in commonly used components range from 1µH to 10H and beyond. An actual inductor will not, of course, exactly follow this theoretical behaviour of an ideal inductor. Other factors to consider include the resistance of the wire and parasitic capacitance between the turns of wire in the coil.
INDUCTOR USE CASES
Figure 2: Abracon ASPI-F4030 and ASPI-F6060 molded SMD power inductors. (Source: Mouser Electronics)
Figure 3: Bourns SRN3010C semi-shielded power inductors. (Source: Mouser Electronics)
Inductors find a wide range of use cases across many different industries. One of the most important general uses is filtering in power supplies to remove high-frequency noise and ripple. The inductor, or choke, acts as a low- pass filter, allowing the DC current to pass while blocking higher frequencies. A specific use case is blocking noise in differential pairs of power or data cables, where common-mode chokes remove the common-mode noise that is induced in the cables.
This high-frequency filtering is important to reduce electromagnetic interference (EMI) and to meet the standards for electromagnetic compatibility (EMC); without this filtering, products cannot legally be sold.
In automotive applications, the challenge of EMI is increasing due to the increasing number of electronic modules and systems within vehicles. This means there are more switching power supplies and, therefore, more EMI that must be mitigated.
Figure 4: Murata Power Solutions 3000D surface- mount power inductors. (Source: Mouser Electronics)
Another use for inductors is to combine them with capacitors to create an LC circuit or LC filter, also known as a resonant or tuned circuit. The simplest LC filter uses one inductor (L) and one capacitor (C). Adding more components can improve performance in blocking unwanted frequencies. An LC circuit can also be used as a bandpass filter, which allows only signals in a specific frequency range to pass. Inductors’ ability to store energy for short periods of time means they can be useful in DC/DC convertors; combining multiple inductors with a shared magnetic field is the basis of creating transformers. Inductors are also used in relays and switchgear, where the magnetic field causes movement of contacts which close an electronic switch, allowing current to flow to the load. Another application, induction motors, use an alternating current to generate a magnetic field in the inductor, which then causes a motor spindle to rotate. Previously, we described how a ferromagnetic core can greatly change the inductance value of an inductor. This property is how inductive sensors work: When a metallic object comes close to the coil of an inductor, the change in current in the coil can be detected. Inductive sensors are widely used in automation and industrial processes, partly because they require no physical contact, so
Instrumentation Monthly May 2024
Continued on page 14... 13
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84
