Resonance as such

MrCU204

Resonance as such [Copy link]

 

The resonance point is the center frequency of the passband.

The resonance referred to in the classic concept is the LC tank circuit.

The drivers of resonance are not limited to voltage sources.

Current sources or electromagnetic fields are also acceptable, and when the tank circuit is in resonance, the reactive topology is the same.

MrCU204

LC resonance, what fools people is the tank impedance! !

Isn't it said that the overall impedance of an ideal tank circuit is zero for series resonance and infinite for parallel resonance ? !

But in fact, X and X are the same as when measured separately. This is the core that must be grasped for intuitive cognition! !

Once the component is made, its own parameters are solidified, and once the settings are done, the operating parameters will not change, regardless of whether it is used alone or in combination.

MrCU204

To add or subtract fractions, first find the common denominator.

The meaning of "通" is unity and equality.

R, X, X, when measured separately at a given frequency, the proportional relationship between current and electromotive force (or voltage drop) is constant.

When a number of components are combined, their volt-ampere ratio remains the same. By unifying a certain parameter, the actual working condition of the entire circuit (and its parts) can be obtained. In this figure, the unified parameter is I.

MrCU204

Resonance, the "strange phenomenon" we see is that the voltage division (or current) of the reactance far exceeds the power supply.

The unification of a certain parameter is immediate and effective as soon as the power is turned on, but the steady state cannot be achieved overnight.

Instead, as the power source reciprocates, V and V alternately add an EMF every half cycle, superimposing back and forth.

This is the principle of resonant "growth". If a constant voltage source is connected in series to this tank circuit, when V rises to the same level as the EMF, the superposition will be unsustainable and this working condition will become the steady state of the tank circuit.

振动试验仪器

The resonance in the circuit and the mechanical structure also have resonance, which is called the resonant frequency. The formula is the same, which is proportional to √K/m. K is the stiffness and M is the mass.

MrCU204

Vibration Test Instrument Published on 2024-9-8 10:55 The resonance in the circuit and the mechanical structure also have resonance, which is called the resonance frequency. The formula is the same, which is proportional to √K/ ...

In terms of selectivity, there are passband and stopband in electrical terms, but in terms of mechanics, there seems to be no stopband (or if there is, it is not significant).

MrCU204

In reality, the load is generally inductive, so when a capacitor is connected in parallel, the power factor goes up, haha.

But what kind of power factor is this? It belongs to the power grid, not the load itself. The power factor of the load itself cannot be changed. The relationship between reactive current and power source electromotive force is always - calculus,

The volt-ampere characteristic of an ideal resistor is linear. When in resonance, the state presented by the slot circuit is equivalent to that of a pure resistor. So, how can the calculus relationship be reconciled with the linearity? Perhaps there are few people in this world who are curious about this.

MrCU204

On a practical level, parasitic vibration is a problem that professionals will face and solve.

Can a series resistor like the one in the picture suppress the parasitic oscillation caused by the parasitic or distributed parameters of the components? !

MrCU204

MrCU204 posted on 2024-9-9 09:19 On a practical level, parasitic oscillation is a problem that professionals will face and solve. Parasitic oscillation caused by the parasitic or distributed parameters of components, ...

The series resistor reduces the Q value of the slot circuit. The inter-turn capacitance of the inductor and the capacitance to ground, as well as the plate and lead inductance of the capacitor, can form a parasitic oscillation center with a high Q value.

Ordinary good conductors have resistance, so inductors and capacitors will have ESR, which is a good thing for non-oscillation applications. Sometimes the ESR is deliberately made larger. Otherwise, a resistor is connected in parallel with the inductor. Note that it is parallel. Parallel resistance is not conducive to the process of reactive power stacking, thereby hindering the generation of parasitic oscillations.

MrCU204

The initial conception of this diagram was not like this, but when I drew it like this, it suddenly occurred to me that
to cut off the connection between components or to isolate a certain area from the system, open circuit is not the only way, short circuit is also possible.
Also, why adding parallel resistance to the LC tank circuit can curb parasitic oscillations, I finally understood a little bit. If the middle wire has neither resistance nor EMF (or its EMF is a DC constant voltage source), then L and C cannot interact with each other.

qwqwqw2088

MrCU204 posted on 2024-9-19 00:29 The initial idea of this picture was not like this, but when I drew it like this, I suddenly thought of cutting off the connection between components, or separating a certain area...

It's strange, this picture of a closed LCR circuit passive circuit can make the OP feel infinitely emotional

The circuit diagram can also be imagined as the beauty of painting, which is also intoxicating

MrCU204

Who has ever tinkered with a crystal radio?

Take a 10kΩ or smaller resistor and connect it in parallel to the slot. Will the earphone still ring? Yes, but can you hear it? !

What is hanging around in the slot is reactive power, which is real energy. Resistance consumes energy, and if resistance is connected in parallel to the slot, it will "lose energy" and have no spare energy to drive the headphones.

MrCU204

In electronic circuits, especially single-tube circuits, parallel resonant tank circuits are often used.

The parallel resonance is often used in the form of partial access. Is there such a thing as partial access for series resonance? !

I don't think so, because if you want partial access, you have to set a tap point on the inductor or capacitor, which will create a branch circuit on the inductor or capacitor, which is not in line with the principle of series connection.

maychang

MrCU204 posted on 2024-9-22 01:23 Anyone tinkered with a crystal radio? If you connect a 10kΩ or smaller resistor in parallel to the slot, will the earphone still ring? Yes, but can you hear it? ! ...

[Who has tinkered with the crystal radio?]

I tinkered with it when I was a kid.

[Put a 10kΩ or smaller resistor in parallel with the slot. Will the earphone still ring? Yes, but can you hear it? ! ]

I can tell you: you can still hear it, just a little bit quieter. Even if you connect 1kΩ in parallel, you can still hear it, just a little quieter.

MrCU204

In a series resonant tank, if L or C (please note, it is or) is split into N series, there will be [N!+1] resonance points. The existence of LLC is based on this natural law.

Attenuation oscillation, there is a way to play it that is simpler than what is described in the book. First, connect the LC in series, and then snap it directly to the battery. What will happen in the slot is the attenuation oscillation with an amplitude exceeding the battery EMF.

Then, everything returns to calm, and electrostatic potential energy equal to EMF is stored in C. In this state, the tank circuit receives radio waves normally. For radio waves, the operating condition of the LC tank circuit is field-induced resonance, and the battery does not exist at all.