# Tag Info

23

Ohmls Law states V = IR. That means when we increase voltage we must also increase the current (I). That is true when feeding a resistor. But transformer increases the current while decreasing the voltage or decreasing the current while increasing the voltage. A transformer is not a resistor so you can't use Ohm's law on it. How does it happen? A ...

8

"when we increase voltage we must also increase the current(I)" while R is constant. You should look at the transformer from a power perspective: P=I*V and Power In = Power Out, Now, if you have 10V in and 1 A then that is 10W, so then power out is 10W If you have 10 times the number of turns on the output compared to the input side then you will get ...

7

The "left" side of the transformer (the side the voltage is applied to) obeys Ohm's law (technically a generalised form that describes impedance instead of just resistance). The currents and voltages that don't seem to obey Ohm's law happen on the other side of the transformer, in an electrically isolated circuit. Ohm's law doesn't describe how two circuits ...

4

There are (at least) five ways to measure the earth fault current (zero sequence current) on a system. Residual or "Holmgreen" connection of the A, B, and C phase CT's. This physically implements the calculation IN = IA + IB + IC using the CT wiring. Advantage: Cheap. No additional CT's are required. Disadvantages: The phase CT's are subject to ...

3

Since you said that it didn't need to be isolated, maybe something like this would work: Output looks like this: If you are on 120Vac, then change the 2.2k to ~1.1k. Again, beware that the left hand side is not isolated from the mains. Source: https://circuitdigest.com/electronic-circuits/zero-crossing-detector-circuit-diagram

3

What you have drawn is a rough picture of a "pot core". The direction of the flux lines will be through the center and then out around the outside shell as shown in the cross section below.

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The transformer uses the shared-flux of the core as a negative feedback mechanism. The primary and secondary fluxes ALMOST perfectly cancel, with the residual called the "Magnetizing flux". If the magnetizing-flux becomes too small, then more energy is taken from the primary (the energy source) and the core flux is again adequate to produce what the ...

2

There are two types of transformer 1) High (ideally infinite) permeability, used as power transformers 2) Low permeability, used as flyback transformers, where $I_{sat}$ is a key specification The difference is that a power transformer is not intended to store energy in the core, that's minimised in the design. While it does have a net current that will ...

2

FCAN and FCBN designate voltage adjustment taps at Full Capacity Above Normal voltage and Full Capacity Below Normal voltage. That indicates that the voltage can be adjusted by a designated percentage above and below the normal primary or secondary voltage. The transformer can be operated at its full capacity with any tap setting. For the example ...

2

Why do I observe an increase in output voltage when I add more iron cores to my transformer? How do I explain this using the laws of physics? Think about it it must be better than air, why would this happen? One is because there is less leakage of magnetic fields. The other is that magnetic fields flow better through iron than air. Is there a ...

1

If you have two transformers, with their primaries in parallel, it's just fine to connect their secondaries in series. Their output voltages will add algebraically, which means if you have (for instance) a 35v and 40v secondary, you'll get either 75v or 5v, depending on the phasing of the two transformers. You should limit the current that you draw to the ...

1

All the energy is stored in the gaps between the magnetic core particles or gap in this case. As the gap size increases, flux will start to 'spray' into the area of the windings in proximity to the gap. This will generate high levels of eddy current losses in the wire. To avoid this problem you can wind on a few turns of insulating tape around the middle of ...

1

Arduino + Current Transformer sensor The CT is a conventional transformer in all ways, it only works for AC currents. simulate this circuit – Schematic created using CircuitLab If the input current is sinusoidal, then the output voltage will be sinusoidal. The CT will work for non-sinusoidal wave shapes, but then to maintain accuracy you must ...

1

The voltage on the primary side shouldn't ideally be zero as you claim. If you short the secondary winding of a transformer then all the power you put into the primary winding will be dissipated in the internal resistance of the secondary winding. Lets take the following example: We have a 1:1 transformer with an internal resistance in the secondary ...

1

There are four options: A three-phase VT wound on a three-limb core. A three-phase VT wound on a five-limb core. Three separate single-phase VT's. A voltage measuring device that measures your 600VAC directly without a VT. (Where I come from, direct voltage meaurement, without a VT, is used up to at least 440 VAC.) Of these, I would recommend that you ...

1

Amp Meter: TL;DR Just put the meter in series with the HV on the high side or low side. Don't plan on holding it in any configuration. I'm not sure how you expect you meter to measure anything in the setup given... Beyond that, your Amp meter seems like an over engineered setup. you should not need crazy resistors for it since the shunt voltage should be ...

1

does this mean that the magnetic field increases? Yes because Inductance increases with permeability the one with more iron cores will increase the current in the primary coils. No because primary current depends on I=V/Zin and Zin increases with inductance But it means you can use shorter lower resistance wire to create a no-load inductance < 10% or ...

1

So with the help from this community, I understand that more iron cores means a greater magnetic permeability and less magnetic leakage. But does this mean that the magnetic field increases? No, permeability is a material constant and is unrelated to the size or amount of the material just like the density of (say) water is 1000 $kg/m^3$ irrespective ...

1

Without a diagram, I can only assume that 'adding cores' to a transformer means increasing the effective area of iron within it. This interpretation is also consistent with the behaviour you describe. Let's assume it's some form of teaching transformer like this (image from betterequipped.co.uk) where you alter the iron area core you introduce into the ...

1

One way that I can think of would be to connect the LCR meter to the shield and to one of the primary or secondary terminals with all other ports on primary and secondary open. One thing that may get in the way of a capacitance measurement like this is inductance, so try and minimize wire length to the transformer. This would give a rough idea of what the ...

1

With the information given, method 2 is the proper sizing. For standard transformer sizing you need to select the closest larger standard transformer. Since you have KVAs, you don't need to consider power factor. If the altitude or ambient temperature exceed standard, that requires derating. If you do not apply a demand factor, you may have some capacitor ...

1

An ideal transformer has this realtion: $$\frac{V_P}{V_S}=\frac{N_P}{N_S}$$ Which for your transformer is not the case due to large leakage inductance. When you increase the core size makes this transformer more better in terms of coupling factor between primary and secondary coil (less leakage). Real transformer $X_P$ is the primary coil leakage ...

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