How does inductor work?  - Page 1
Forum section: electronics / beginners

author: NASK
author_rank: Contributor
timestamp: September 14, 2021, 06:11:00 pm
content: Generally inductor or capacitor use as filters in AC to DC conversion for smoothing process. When use inductor after half wave rectified voltage, what is the behavior of the inductor , voltage current wave form in inductor and the load . Help me to understand the concept

author: harerod
author_rank: Frequent Contributor
timestamp: September 14, 2021, 07:37:12 pm
content: As a simple model: An inductor "wants" to maintain its current, while a capacitor "wants" to maintain its voltage. The (ideal) diode "wants" current to only flow in one direction.Looking at your schematic, things depend a bit on the voltage source frequency and the L/R time constant.Suggestion: After mulling this over in your mind, fire up the free LTspice and simulate the schematic.

author: bob91343
author_rank: Super Contributor
timestamp: September 15, 2021, 12:25:00 am
content: If you provide a path for the inductor current to flow during the off time of the rectifier (say a diode to ground or across the inductor) that should work well.

author: xavier60
author_rank: Super Contributor
timestamp: September 15, 2021, 12:27:37 am
content: A diode between the left side of the inductor and ground will prevent the inductor from trying to pass its stored energy back into the AC supply during the negative half-cycles.

author: Cerebus
author_rank: Super Contributor
timestamp: September 15, 2021, 02:27:43 am
content: "How does an inductor work?" really calls for a textbook reply. As in, it would really take copying out a large chunk of a text book to explain it. There really is quite a lot to understand before you'll know how an inductor works. Moreover, it really does help to actually know this stuff rather than to just know a few effects of indictors, which is what a lot of people get by on but which isn't really enough to fully understand what's going on.So, the trite answer would be "read the appropriate chapters of a good textbook". But that's not particularly helpful. So instead I would suggest watching a set of lectures from Walter Lewin on YouTube he gave for the Physics 8.02 course on Electricity and Magnetism at MIT. They are here:https://www.youtube.com/playlist?list=PLyQSN7X0ro2314mKyUiOILaOC2hk6Pc3jThe whole course is a bit much if you just want to learn how inductors work, but I'd recommend persevering with it if you can. If you do, you will be one of the few people who understandwhya current flows in a wire - worth the price of admission by itself. If you must, you can just watch lectures 11, 14, 15, 16 and 20, and I think you will have collected enough background to understand lecture 20 which covers inductanceper se. The fact that there's a minimum of five lectures to watch to get to "how does an inductor work" is a pretty strong indicator of why I'm not going to post an explanation of "how inductors work" here or why you can't really expect a full proper answer from anyone here.

author: bob91343
author_rank: Super Contributor
timestamp: September 15, 2021, 04:04:24 am
content: Good post, Cerebus. It's human nature to seek short cuts and this is but one example. It's not a bad thing but when it comes to technical topics, it's not good. If one truly wants to understand, one needs to respect the many scientists who built the foundation of physics, and try to comprehend their efforts. Coulomb and Henry and Kirchoff and Ohm and so many others were not flashes in the pan. They devoted their lives to advancing the technology, to attempt to understand nature. We can't dismiss their efforts with a quick explanation.

author: amyk
author_rank: Super Contributor
timestamp: September 15, 2021, 04:20:06 am
content: Quote from: bob91343 on September 15, 2021, 12:25:00 am...otherwise, you also get to learn about reverse breakdown voltage

author: Cerebus
author_rank: Super Contributor
timestamp: September 15, 2021, 11:39:14 am
content: Quote from: amyk on September 15, 2021, 04:20:06 amOr even insulation breakdown voltage! One thing that surprisedmewhen I learned it is that an inductor can create anunlimitedvoltage in the process of doing its thing of behaving like an inductor. This is counterintuitive as most things we experience in life and physics aren't unbounded like that.

author: silverback
author_rank: Contributor
timestamp: September 15, 2021, 11:49:32 am
content: Quote from: bob91343 on September 15, 2021, 04:04:24 amDon't forget Faraday!!!!

author: harerod
author_rank: Frequent Contributor
timestamp: September 15, 2021, 01:04:27 pm
content: Quote from: Cerebus on September 15, 2021, 11:39:14 amLooking at an ideal inductor, the voltage is the derivative of the current. An infinitely fast change in current will result in an infinitely high voltage. In the real world, the boundaries are the breakdown voltages in the insulation.An ideal capacitor is the same, with the roles of voltage and current reversed. In the real world, the most obvious limitation will be the various impedances of the plates an leads.Compare this to the simple worded model that I gave in my first post and you see nothing wrong. We just added the mathematical operation "derivative".If we decide to look into the proportionality factors to fit real world measurements, we are pretty much done with building a mathematical model of ideal inductors/capacitors.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 15, 2021, 11:40:18 pm
content: The basic idea is that it is a store of energy. A finite bottle of magnetic flux. Just as capcitor is a finite bottle of electric flux. You fill it with current (poterntial), when no more enegy can be stored the inductor is said to be saturated. The magnetic field can get any larger A capacitor can only hold so much flux before it is said to be fully charged.Sometimes you need to drink that energy, sometimes you're refilling. This temprary store is at the theart of swich mode power supplies. Inductor energy storage is efficient so you can charge at one rate and discharge at another. This lets you transorm you stored joules in your input I.V to a preferred I.V format. This is key to SMPS functionReally though, indcutors (and capacitors) constrain and concentrate the EM fields that permiate spacetime in all directions.We are not gerating magetism with our coils, we are just gathering togetherThe FieldAs positied by Mr Faraday back in the day- Yes, he read did say that well before Maxwell!Note that the critcal calculations to design these components refer to three dimensions, stacking and constants Uo and Eo. Some special materials like iron (or plastics in capacitors) increase EM field densities in useful ways. sqrt/(1/Uo.Eo)= C. If that aint spooky, I dont know what is.

author: Shock
author_rank: Super Contributor
timestamp: September 16, 2021, 03:07:25 am
content: Inductors store charge as a magnetic field as current flows, a capacitor in an electrical field. If you disconnect the voltage (and therefore current) to an inductor it will briefly continue to provide current to an attached circuit until it's field is completely collapsed.After the AC rectification to DC we essentially have a fluctuating DC voltage source. If an inductor (an appropriate value and type) is utilized as a series filter it will stay in a semi consistent state of charge (unregulated). The attached circuit/load sees less voltage change.

author: amyk
author_rank: Super Contributor
timestamp: September 16, 2021, 04:09:45 am
content: Quote from: Cerebus on September 15, 2021, 11:39:14 amIn ideal physics, two completely inelastic objects colliding can also exert an infinite amount of force on each other. In practice, just like the ideal inductor that can generate an infinite "pressure" when the circuit it's in is suddenly broken, such a thing doesn't exist; if no breakdown occurs, the voltage simply rises as far as the parasitic capacitance of the circuit allows, and then it oscillates like an RLC circuit, also emitting EM radiation.

author: Zero999
author_rank: Super Contributor
timestamp: September 16, 2021, 10:11:00 am
content: The back-EMF generated by the inductor, depends on how quickly the switch turns off. If it's really slow, there won't be a very high voltage generated.An inductor opposes changes in current, because magnetism and electric current are linked. I'm sure most people are aware of the old experiment where a magnet is placed inside a coil, moved back and forth and generates a changing voltage, or applying a voltage, causes a force to be exerted on the magnet, causing it to move. In the case of an inductor, the change in magnetic field around the coil, when the current through it is change, always opposes the change in current. The energy is stored in the magnetic fielt.