In industrial battery chargers for rectifying the charging current and change its value sometimes used triacs COG. It should be noted here that the direct voltage included the triacs with a large charging current can reach 1.5 V. because Of this, they are extremely hot, and the passport case temperature of the SCR must not exceed +85°C. In such devices it is necessary to take measures to limit and temperature stabilization of the charging current, which leads to further complexity and cost.
Described below is relatively simple charger has a wide range of regulation of the charging current is practically zero to 10 A and can be used to charge a variety of starter batteries battery voltage of 12 V.
The basis of the device (see diagram) on the triac regulator, published in [2], with additionally introduced a low-power diode bridge VD1 - VD4 and resistors R3 and R5.
After you connect the device to the network at zero its halftime (plus on upper circuit on the wire) begins to charge the capacitor C2 through the resistor R3, diode VD1 and the series-connected resistors R1 and R2. When negative half cycle the capacitor is charged through the resistors R2 and R1, diode VD2 and a resistor R5. In both cases, the capacitor is charged to the same voltage, it only changes the polarity of the charge.
As the voltage on the capacitor reaches the threshold of ignition of the neon lamp HL1, it ignites and the capacitor is quickly discharged through the lamp and the control electrode of the triac VS1. In this case the triac opens. At the end of the half cycle, the triac is closed. The described process is repeated in each half-cycle of the network.
It is well known, for example from [1] that the administration of the thyristor by means of a short pulse has the disadvantage that when inductive or high-resistance resistive load anode current of the device may not be able to reach the value of the holding current for the duration of a control pulse. One of the measures for elimination of this disadvantage is the inclusion in parallel with the load resistor.
In the described charging device after turning on of the triac VS1 his main current flows not only through the primary winding of the transformer T1, and through one of the resistors R3 or R5, which, depending on the polarity of the half cycle of the mains voltage are alternately connected in parallel with the primary winding of the transformer, diodes and VD4 VD3, respectively.
The same purpose is powerful and resistor R6, which is the load of the rectifier VD5, VD6. Resistor R6, chrome, generates pulses of discharge current, which, according to [3], extends the battery life.
The main unit of the device is the transformer T1. It can be made on the basis of laboratory transformer Latr-2M, isolating the coil (it will be primary) three layers of lacocca and winding secondary winding consisting of 80 turns of insulated copper wire not less than 3 mm2, with a branch of the middle. The transformer and rectifier can be derived also from the power source, published in [4]. At independent manufacture of the transformer, you can use the calculation method presented in [5]; in this case set by the voltage on the secondary winding 20 V at a current of 10 A.
Capacitors C1 and C2 - MBM or other, for a voltage not less than 400 and 160, respectively. Resistors R1 and R2-SP 1-1 and SDR-45 respectively. Diodes VD1-VD4-D226, DB or KD105B. Neon lamp HL1 - INS-3, INS -; very desirable to use a lamp with the same design and dimensions of the electrodes - this will ensure the symmetry of the current pulses through the primary winding of the transformer.
Diodes KDA can be replaced by any of this series, and D, DA or other middle premim tone of not less than 5 A. the Diode is placed on the exposed dural plate with a useful surface area. scattering is not less than 120 cm2. The triac should also be strengthened on the heat sink plate is approximately twice smaller surface area. Resistor R6 - sew-10; it can be replaced with five parallel-connected resistors MLT-2 110 Ohm.
The device is assembled in a strong box made of insulating material (plywood, PCB, etc.). In its upper wall and at the bottom should be drilled ventilation holes. Placing items in the box is arbitrary. The resistor R1 ("Charging current") mounted on the front panel, attached to the handle of a small arrow, and scale. Chain bearing a load current, it is necessary to perform wire marks mgshv-section 2.5...3 mm2.
When creating a device, first install the required limit the charging current to a maximum of 10 (A) of the resistor R2. To exit the device through the ammeter 10 And connect the battery to the batteries in correct polarity. The engine of the resistor R1 translate V. extreme upper circuit position, the resistor R2 is in the lowermost, and include the device in the network. Moving the slider to the resistor R2, install the necessary value of the maximum charging current.
The final operation - calibration of the scale of the resistor R1 in amperes according to an exemplary ammeter.
In the process of charging current through the battery is changed, decreasing by the end of about 20%. Therefore, before you set the initial charging current of the battery in a few more of the nominal value (approximately 10%). The charging is finished and sent directly by the density of the electrolyte or a voltmeter to the power's off, the battery should be in the range of 13.8...14,2 V.
Instead of the resistor R6 is possible to set the filament voltage of 12 V power of about 10 watts, placing it outside of the case. She was interval would connect the charger to the battery and at the same time, would be covered workplace.
Literature
1. Power electronics. Reference book edited by V. A. Labuntsov - 1987. S. 280, 281, 426, 427.
2. Fomin V. Triac power regulator. Radio, 1981. No. 7, p. 63.
3. Zdrok A. G. Rectifying device for voltage regulation and battery charge - M.: Energoatomizdat, 1988.
4. Gwozdecky G. power Source of higher power. Radio, 1992. No. 4, p. 43-44..
5. Nikolaev, Y. Homemade power supply? No, nothing is easier. Radio, 1992, No. 4. C. to 53.54.
Authors: N. Talanov, V. Fomin, Nizhny Novgorod, Radio 7-94; Publication: N. Bolshakov, rf.atnn.ru