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The real design of the heater with savings of up to 30%
Non-classical distribution of the magnetic field (MP) in the coil with slow magnetic waves causes the same uneven distribution of current along its length. This means that if the coil has resistance, then the heating along its length is also uneven. This leads to excess heat generation due to the redistribution of energy. This fact is confirmed by research. But the savings of electrical energy is only about 20% that is not effective enough.
Enhance this effect allows the design described below, in which the heating element is mounted on aluminum heatsink, and the winding of the coil is copper wire. This sandwich gives rise to another effect — magnitostriktsionnye when the aluminium vibrates with the frequency of the coil. This allows the use of parametric properties of electrical circuits, which in this case increase the initial impact and allow you to achieve 30% energy savings. In addition to the positive impact of magnetostriction, unfortunately, is a disadvantage of this device is the radiator a beeping sound frequency. However, it can be compensated by putting the radiator in the box with small diameter holes. Throughout the rest of the scheme showed a good side: simple and does not require expensive parts, works steadily and reliably, and its configuration is simple.
The scheme of device is shown in the following figure. DA1 the generator produces rectangular pulses, which are applied to the input of driver DA2. The latter brings them into line with the level of signal required for proper operation of the key on mosfet-transistor VT1. Chain VD1, R4, ZD1 protects the driver from possible overloads, and R5, R6, ZD2 is used to supply the circuits DA1 and DA2 and limits the total circuit voltage to the level of 12V. Key VT1, together with a resonant capacitor C6, forms a powerful impulse to the coil L1. C7 eliminates possible spurious excitation scheme.
Принципиальная схема нагревателя с экономией до 30%
The two most costly element in this design is the copper wire for winding coil L1 and aluminum radiator. The wire you need to take with a diameter of 0.63 mm in the varnish insulation, and the heat sink be chosen such that it was two plane for winding with one and other. These planes should be located opposite each other so that they can be wound wire, and the whole winding must occupy 60% or more of the total length of the radiator (see photo).
Алюминиевый радиатор с намотанным медным проводом (1). Нагреватель с 30% экономией Алюминиевый радиатор с намотанным медным проводом (2). Нагреватель с 30% экономией Алюминиевый радиатор с намотанным медным проводом (3). Нагреватель с 30% экономией Алюминиевый радиатор с намотанным медным проводом (4). Нагреватель с 30% экономией
The coils are wound maximally filling the potential space. The total inductance L1 should be of the order of 2-2.5 mH, and active resistance of 5-6 Ohms. Between the wire and the radiator is better to lay a thin layer of construction paper.
All capacitors in the circuit — not electrolytic; this is important because they should not dry out over time from the heat. Pay attention to C3 — this capacitor should have a low temperature coefficient, because it sets the frequency of operation of the circuit. C6 and C7 must be rated for a voltage below 1000V, as well as having good frequency characteristics. Well capacitors MKP10 or similar — from induction cookers.
Resistors R5 and R6 — dvuhmestnye, all the rest can be any capacity. The deviation of each resistor of the nominal value should not exceed 15%.
The power scheme may be exercised as from power units of its own design and standard. For example, for powering multiple radiators it is possible to apply S-350-70, and for most of them — even more powerful S-720-72.
Other elements of the scheme are:
Features of installation
According to the specifications for the hardware key driver, DA2, its findings 1-4 and 8-5 are needed to connect two capacitors (C4 and C5 according to the scheme, respectively) in the vicinity of the housing chip. This should be considered when designing the PCB. The whole scheme and power supply should be placed in the lower part of the structure, where it will have the lowest temperature. Although the transistor VT1 is not heated, it will still need to install a small radiator.
Adjusting the trimming resistance R1 and selecting capacitor C6, the drain VT1, the oscilloscope, you need to get a clear pulse of one half cycle of a sine wave amplitude of the order of 550V. On the photo they are shown in yellow. If additional visible band with a sharp front, then the circuit is oscillating and it is necessary to increase the capacitance value of C7; it is usually 330-1200пФ and, if possible, should be minimal. The green graph in this figure shows the electric field around the bottom (under the scheme) of the coil, which can be fixed by placing next to the probe of the oscilloscope. This can be another sign of correct operation of the device. The total current consumed by the circuit should be in the range of 1.4-1.6 amperes.
I must say that the possibilities of this scheme implemented is not yet at 100%. By increasing the supply voltage and selection frequency, capacitance and resonant capacitance C6, you can achieve the best performance. It will also have to pick up and more high voltage VT1 is key.