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Some properties of the coil-capacitor
Unusual properties of an inductor can be obtained if it is assembled in a not quite classical way, by making a capacitor coil (CPC) out of it. Such an unusual element, in addition to non-standard circuitry, will show completely unexpected results of its work, for example, connecting a load to it will have almost no effect on the power consumption of the circuit. We will compare these data with the classics and draw conclusions about the advisability of using the CPC. How to get such effects, how to make such a coil design, what results can be obtained in this case, and will be described in this note.
First, let's try to assemble a classic converter circuit according to Figure 1a. It consists of an alternating high voltage source U1, a diode rectifier bridge VD1, assembled on a UF4007, smoothing capacitor C1, active resistance Rn and voltmeter V1.
Fig.1. Schematic diagram of the experiment: a - without a coil, b - with a coil-capacitor L1
Further, we will simply make measurements in order to compare the results obtained with the data on the CPC scheme in the future.
The circuit is investigated according to Figure 1a. In this case, there is no coil and the signal source voltage is applied directly to the rectifier bridge. There is a classic dependence of the power consumption (W) of the voltage source on the load resistance (Rn). In this case, the power consumption is fixed by measurements in the generator power supply U1 (not shown in the diagram). Also, hereinafter, we will carry out experiments at two generator frequencies: 21 kHz and 43 kHz. They will be discussed below.
f = 21 kHz f = 43 kHz
Rn, kOmh V1, V W, W Rn, kOmh V1, V W, W
10 74 1 10 73 1
3 67 1.6 3 64 1.6
1 51 3.8 1 44 3.3
As you can see from the top table, we got the classic results of the dependence of the power consumption of the circuit on the size of the load. Small deviations can be associated with internal resistances of the generator and the rest of the circuit, which are not taken into account here.
Its design can be completely different, here we will describe only one of its options. On a plastic frame with a diameter of 40 mm and a length of 250 mm, construction aluminum foil is wound along its entire length so that so that there is no contact between the turns (with a small step). The number of turns does not matter and can be 2-5. At the beginning of the winding, a contact is connected in a wire, which we will further connect to the circuit. Kevlar (high-voltage) electrical tape is wound on top in 2-3 layers.
A classic coil is wound over the electrical tape with a 0.3 mm copper wire, along the entire length of the frame, and is fixed at its ends so, so that between them and the foil leads, there is a gap of at least 1 cm. Alternatively, you can insulate the leads with Kevlar so that the high voltage does not break through this gap. A set of ferrite rings with a diameter of 28-32 mm is inserted inside the frame. According to the authors, such a coil had the following parameters: the inductance was about 6 mH, and the capacitance between any of the winding leads and the foil was about 3 nF (CL according to the scheme). In this diagram, the CPC is shown as L1, where, conventionally, the foil is drawn in orange.
If we calculate the resonant frequency of such a system, then it will be approximately 21 kHz, and we will tune the generator U1 to it in our experiment.
Next, we assemble the circuit according to Figure 1b and make measurements (further in the table). As you can see, changing the load Rn practically does not affect the power consumption of the generator (W). This is especially evident at a resonant frequency of 21 kHz. There was also a small maximum at 43 kHz, which we will explore in the table on the right. As it turned out, in this case, with a decrease in the load resistance, the power consumption significantly decreased.
f = 21 kHz f = 43 kHz
Rn, kOmh V1, V W, W Rn, kOmh V1, V W, W
10 60 1 10 65 1
3 34 1 3 28 0.9
1 15 0.9 1 14 0.7
It would seem that if you connect a high voltage to the other end of the foil (its lower output according to scheme 1b), then the transfer characteristic should be sharply worse than the previous one. However, in this case, we observe the same effect, and even with some improvements (see the bottom table).
f = 21 kHz f = 43 kHz
Rn, kOmh V1, V W, W Rn, kOmh V1, V W, W
10 65 1 10 70 1
3 40 1 3 33 0.7
1 18 0.8 1 15 0.5
Some conclusions
Despite the not entirely logical design, the CPC still has its own transfer characteristic and can transmit electrical power from the foil plate to the secondary winding - the inductor.
The transfer characteristic of the CPC differs from the classical one in that with a decrease in the load resistance, the power consumption of the circuit does not increase, and in some cases even decreases. Such an open-loop system can be used as a source of charges, as one of the elements of free energy devices.
The CPC can be used both in direct connection (according to Fig. 1b), and in reverse, in which a high voltage is applied to the opposite end of the foil.
In the CPC circuit, the voltage V1 decreases approximately in proportion to the square root of the load resistance Rn, or: V1~(Rn)0.5.
The maximum transmission efficiency in a circuit with a CPC is achieved when the load resistance is equal to the characteristic impedance of the circuit, or when: Rn=(L1/CL)0.5.
The CPC has its own resonant frequency, which is determined by the Thompson formula based on the known data: inductance L1 and capacitance CL.
The capacitance CL increases by 10-20% if a ferromagnetic core is inserted inside the coil.