Timeline for Equivalent circuit of a transformer
Current License: CC BY-SA 4.0
17 events
| when toggle format | what | by | license | comment | |
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| Jan 30, 2020 at 12:57 | vote | accept | Aravindh Vasu | ||
| Jan 30, 2020 at 12:40 | comment | added | Andy aka | The current that flows in the primary of the ideal part of the "converter" is that current that is needed in the secondary circuit modified by the turns ratio. Think of the ideal transformer as a perfect (or ideal) impedance converter. You don't have to think of it as a transformer at all - think of it as a black box that sets the secondary voltage at a value dictated by N (the turns ratio) and the primary voltage. So, if there is an unloaded secondary, no current will flow into the primary. If the secondary is shorted then infinite current flows in the primary if it is fed with voltage. | |
| Jan 30, 2020 at 12:35 | comment | added | Aravindh Vasu | Thanks a lot for your patience, I've got one more doubt, if the magnetization current is what produces the magnetic flux and we have modeled it with Lm, what's happening in the remaining "ideal" transformer, what current flows in the primary? | |
| Jan 30, 2020 at 10:36 | comment | added | Andy aka | Regards the lagging leading thing, there is a minus sign (Lenz's law) involved in all of this that most times folk leave out and that converts things so that induced voltage (Faraday) in a secondary is in phase with applied primary voltage. | |
| Jan 30, 2020 at 10:32 | comment | added | Andy aka | You are over thinking the secondary inductance thing. Once you have two coils perfectly coupled (I'm ignoring leakages) then only the driven side primary magnetization inductance has any relevance. Think about this a little an think what happens in a perfect transformer with mag inductance on the primary - the secondary inductance is of no consequence to any loading, resonance or induction effects. | |
| Jan 30, 2020 at 10:30 | comment | added | Aravindh Vasu | "If I said that induced voltage lagged the flux by 90 degrees would you tend to feel this was a better explanation? " Yes, but that doesn't seem to be true :( Should we move this to chat? | |
| Jan 30, 2020 at 10:29 | comment | added | Aravindh Vasu | "Ls is NOT the secondary coils self inductance. The secondary self inductance includes leakage but, the rest couples 100% with Lm and is in series with Ls." Oh, so Lm includes the self inductance of secondary? | |
| Jan 30, 2020 at 10:29 | comment | added | Andy aka | If I said that induced voltage lagged the flux by 90 degrees would you tend to feel this was a better explanation? (thought experiment). | |
| Jan 30, 2020 at 10:26 | comment | added | Aravindh Vasu | The previous comment; When I have a coil of wire, an induced voltage is produced only when there's a flux across the cross sectional area because of the current I passed, right? Then how can the induced voltage lead the flux? | |
| Jan 30, 2020 at 10:24 | comment | added | Andy aka | Ls is NOT the secondary coils self inductance. The secondary self inductance includes leakage but, the rest couples 100% with Lm and is in series with Ls. | |
| Jan 30, 2020 at 10:23 | comment | added | Andy aka | It's 10 mH because impedances reflected from one side to the other are modified by turns ratio squared. For your previous comment I don't understand what you are trying to say. | |
| Jan 30, 2020 at 10:21 | comment | added | Aravindh Vasu | Please bare with me here, very sorry if you had already answered this question, how did you say that the secondary inductance would be 10mH. Ls is that inductance which induces a voltage due to the leakage flux only right? Is Ls the secondary coil's self-inductance? | |
| Jan 30, 2020 at 10:15 | comment | added | Aravindh Vasu | For the second question, sorry I don't understand it intuitively. The voltage across an inductor is proportional to the change in current because \$\epsilon= \dfrac{d\phi}{dt}\$ and \$\phi=Li\$. So doesn't it fundamentally depend on the change in flux and hence current? The current increases(changes) the maximum while starting in a sine wave, which means the flux changes the maximum so the voltage is at the maximum, but there flux had to be present before the induced voltage, doesn't it? | |
| Jan 30, 2020 at 10:15 | comment | added | Andy aka | Yes Lm is (apart from leakage) and, it 100% couples to the secondary coil but don't forget the leakage inductance Ls because that doesn't couple. So if Lm is 1 henry and turns ratio is 10:1, the equivalent secondary inductance (if it could be disentangled from the primary mag inductance) would be 10 mH. | |
| Jan 30, 2020 at 10:07 | comment | added | Aravindh Vasu | Thank you for answering, so is Lm the self-inductance of primary coil? then what about secondary coil's self-inductance? | |
| Jan 30, 2020 at 8:52 | history | edited | Andy aka | CC BY-SA 4.0 |
added 32 characters in body
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| Jan 30, 2020 at 8:27 | history | answered | Andy aka | CC BY-SA 4.0 |