# Tag Info

6

This answer assumes that "no load current" refers to the magnetization current in the primary of the transformer and that is defined by the magnetization inductance. If the radius is halved then the inductance falls by 4 times because area is quartered. If the core is a regular shaped core with a decent value of permeability then you can assume ...

5

Your proposed balancer is similar to the one you posted in your own answer. Your understanding of its function seems to be correct - the charge current is distributed to the cells depending on the discharge state of each cell. A cell with lower voltage will get more current than a cell with higher voltage. In that sense it will work. The folks who wrote the ...

4

If you can wind some turns onto the transformer without interfering with the winding that are there, add as many as you can comfortably add. Apply 230 volts to the primary and measure the voltage produced by the added winding. Divide the number of added turns by the measured voltage. The result is the turns per volt for any winding. Multiply the calculated ...

4

That transformer is unsuitable for use at 25 Hz, as it says 150 kHz. It's a flyback transformer, and no flyback transformer is suitable for use at 25 Hz, as they are meant for frequencies far above the mains frequencies, like tens to few hundred kilohertz. The auxiliary winding is to power up the mains side switch mode chip that drives the primary coil. It ...

3

One interpretation is that rating is not there to give you any indication of how the transformer should be used in a flyback application, but only to tell you what peak voltages it was designed to work with. The likely reason for this is there are too may conditions, caveats, and gotchas with different flyback applications to give you a simple number rating. ...

3

I think you are confused about transformers in general and flyback transformers in particular. Transformers are not fed with DC typically. While you could use half-waved rectified "DC" (and it's not really DC) but full-wave rectified DC would do nothing but generate heat in the primary winding of the transformer. Without AC you get no changing ...

3

Can you use it? Yes you can. Raspberry pi uses a PoE transfromer but doesn't support POE (an additional circuit can be added to provide POE) I'm not aware of any major downsides.

3

A laminated iron transformer is designed to work with low frequencies, usually 50-60Hz and with some derating could go up to about 500Hz. Switching converters, on the other hand, work at usually more than 20kHz, so you saturate the core quite fast. It won't really work, unless probably with extreme derating just to say you made it working

3

A 150 kHz flyback transformer is totally unsuitable. Your best bet would be to use a transformer rated at mains frequency, and run it backwards. As voltage scales with frequency, your 12 V and 75 V windings would have to be rated at a minimum of 24 V and 150 V. A transformer rated for 120 V would probably not have sufficient headroom to over-run it to 150 V, ...

2

Is it normal for this size of core to get to those temperatures at those powers? If not - What is causing the excessive heating? That is a pretty reasonable temperature to run at. In fact I'd say it's probably running cool compared to most flyback designs. If you generally look at ferrite data sheets they state how much the temperature will rise under ...

2

Choose line-input AC-to-DC supplies that have isolated outputs. This kind of supply has an internal transformer between the primary and secondary that allows the output to float with respect to the line input, or to chassis ground. This will be the case for closed-frame switchers intended for IT and industrial use. Example: https://www.mouser.com/...

2

Is this correct? Yes, theoretically that is correct. As soon as the power supply starts to limit current, it's the end of the output voltage being constant. This is because induction stops i.e. the flux is no longer changing linearly with time because the current has abruptly halted at some value. Given that voltage induction into the secondary is ...

2

the main cause of high leakage inductance is too much separation between the primary and secondary windings. But please provide more details, such as a picture of the cross section, what's the core material, is it gapped, etc.

1

You can use two identical transformers with their primaries in series if you put their secondaries in parallel. This will guarrantee that they share the input voltage equally. Transformers core sizes are closely matched to the operating voltage. Little increase over the design voltage is needed to saturate a transformer, which will result in an orders of ...

1

If the only purpose of the transformer is to detect (in a binary fashion) the higher voltage (not to act as a power supply, for example), there may be other ways of accomplishing that task. If you put a capacitor in series with the primary that is rated for mains X service that has a low impedance relative to the magnetizing current it should limit the ...

1

my only concern is whether the 250 VAC (rms) primary rated transformer will survive high voltages (upto 400 VAC rms). Most commercial transformers will operate close to magnetic core saturation and so any significant increase in the AC supply voltage may result in fuses blowing or breakers tripping. Plus, the insulation rating between primary and secondary ...

1

Use the applied 11kV and rated current to find S, and then the pf.

1

A bit more detail: because of core saturation, the output signal will vary linearly with the input signals only for small signals. When saturation first appears the predominant nonlinearity will be cubic, so for sinusoidal input sin(x) (where x = 2 pi f) the output will have one term proportional to sin(x) and another one proportional to sin(x)^3. The cubed ...

1

could you explain what it is that causes harmonics in transformers? A transformer is only approximately linear, and that only within limits. The net current in a transformer (the magnetizing current) creates an "H" field proportional to the instantaneous current. The "H" field induces a "B" field, but the relationship between H ...

1

Put a linear 7812 regulator to make 12V for the fan. Running it directly from 18V can exceed fan ratings. However, otherwise the design makes thermally no sense. If the 5V regulator provides 1A charging current (5 watts), it needs to dissipate 12-13 watts as heat when doing so. If the junction temperature is allowed to go up to 125 °C, and the thermal ...

1

Transformer differential protection is not comparing corresponding phase currents on each side of the bank, it is a comparison between an intentional combination of phase currents. The figure below is from a set of my lecture notes on transformer protection. The currents shown in red are the primary phase currents, those in green are the secondary currents ...

1

Now, there is a fundamental issue in your methodology. There are two magnetic elements: the first one is a CM choke, which is used to remove HF noise; the second one is you balun transformer (could be 1:1 or other winding ratio) which does the effective conversion. That said, such a circuit is designed to work At a certain source impedance With a certain ...

1

The question really seems too long. Anyway ... about this excerpt: My question is why are those induced EMFs selected as the reference for those cases? Why not the voltages (V)? It might be for convenience or tradition, but I was wondering if there are other reasons besides those if those are one of the reasons. Using EMF as a reference facilitates the ...

1

I don't get why having a secondary current produces a antiphase secondary current at the same instant That is incorrect - it produces an antiphase primary current. If it didn't do this then the magnetic flux would have to either grow or fall (due to the secondary current flow) and the transformer output would rise to infinite volts or fall to zero volts ...

1

If the input voltage is constant amplitude sinusoid, then the core flux is also a constant amplitude cosinusoid, as the input voltage is balanced by the EMF generated by the changing core flux through the primary windings. This means a secondary voltage is generated. If the secondary is loaded, then a secondary current will flow. On no load, the core flux is ...

1

If you connected 240 V into a transformer winding rated 120 V, the core would have saturated and the winding drawn a very large current, which would have taken out any reasonable value fuse upstream. If you have a fuse upstream of it, congratulations, it's saved your transformer from any overheating damage. Replace the fuse with another fuse of the same ...

1

If the heater resistance increases by, say 15% with temperature and the transformer voltage drops by 15% under full load, and there is maybe 1V drop in the switching transistor and lead wires, we have: P = $\frac{(23.5V\cdot 0.85-1V)^2}{2.5\Omega\cdot 1.15)}\approx$ 125W Close enough for government work.

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It is similar to the proximity effect, but it is not the proximity since there is only one conductor (as you have stated in your long comment thread with Andy aka , but maybe that is too much insisting on semantics since it is basically same phenomena ). It comes down to Maxwell's equations, but this is the intuition: By placing a core with high permeability ...

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I believe that you will not find any commercially available (or free) software that has been written to do just that. Some manufacturers develop programs like this, but only for their own use. Often, for a number of reasons, the easiest way is to use the Finite Element Method. There are excellent paid programs, but also free. In this work here, we used FEMM ...

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