|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Protection device for inverter converter. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Voltage converters, rectifiers, inverters Recently, inverter converters from DC 12 V to AC 230 V with a three-level stepped approximation of half-waves of a sinusoidal voltage have become widespread. They are used mainly for backup power supply of household equipment, including those critical to the form of the supply voltage. Unfortunately, quite often, in order to reduce the cost of construction, a manufacturer uses circuit solutions that cause damage, if not to the connected equipment, then to the inverter itself. One of the frequently encountered and, most importantly, undocumented features of inverters is the impossibility of their long-term use in the mode of combined operation on the load and charging the battery. That is, it is understood that in the presence of mains voltage, the load must be disconnected from the inverter, and it can work as a charger, and in the absence of mains voltage, you must manually connect the load and disconnect the power cord from the mains to prevent switching to combined mode when the mains voltage is restored . In principle, such an implementation is normal for devices used in the field, where the possibility of combined mode is practically excluded. But if you intend to use the inverter as an automatic backup power source, this becomes risky. In practice, the author had to deal with a recurring typical malfunction of inverters of various capacities that arose for this reason. To prevent such failures, it is proposed to use a simple external device. It is designed to work with lead-acid automotive batteries and provides protection of the inverter from switching to combined mode and the necessary switching of power circuits, monitoring the voltage on the battery and controlling the inclusion of the inverter charger, as well as protecting the battery from deep discharge. Functionally, the device consists of two nodes: one of them (its diagram is shown in Fig. 1) serves to control the battery voltage, the second (Fig. 2) - to control the mains voltage and switching (element numbering through). Consider the principle of operation of the first node. Its basis is a comparator based on the K140UD1A OU, assembled according to the classical scheme. The source of exemplary voltage is the zener diode VD1. When the supply voltage drops to the threshold value set by the trimmer R2, the comparator switches to a high output level. After some time, determined by the time constant of the R10C3 circuit and the breakdown voltage of the zener diode VD3, the transistor VT1 opens and the relay K1 is activated. Its turn-on delay is recommended for safe mode switching and completion of all transients. The HL1 LED (red glow) indicates the state of the comparator (turns on when a high level appears at the output of the latter). The value of the switching hysteresis is set by changing the resistance of the tuning resistor R8.
When mains voltage is present, the node monitors the battery voltage and controls the inverter charger. The lower threshold for turning on the charger is 12,2 V when the battery load is off, the upper threshold for turning it off is 13,8 V [1-5]. In the absence of mains voltage, the node protects the battery from deep discharge and switches the inverter to the off state at a voltage of 11,3 V and operation under load [1, 3, 6, 7]. The necessary correction of the lower threshold is provided by changing the resistance of the lower arm of the divider R1-R3 using the elements VT2, R18 of the mains voltage control and switching unit. This node (Fig. 2) contains a step-down transformer T1, four electronic switches on transistors VT2-VT5 and three relays K2-K4. In the absence of mains voltage, relays K2, K3 are de-energized, their contacts are in the position shown in the diagram, the load is connected to the converter output U1. In this case, the transistor VT3 is closed, and VT5, on the contrary, is open (the bias voltage is supplied to its base from the battery), so the relay K4 is turned on, and its contacts K4.1, together with normally closed K1.2, turn on the converter. Transistor VT2 is also closed and does not affect the switching threshold of the comparator. If the battery voltage drops to 11,3 V, then in order to avoid deep discharge, the comparator will switch, the transistor VT1 will open, as a result of which the relay K1 will operate and its contacts K1.2 will open, turning off the inverter U1. Contacts K1.1 will close, but due to the lack of mains voltage, this will not cause any consequences. When the input voltage is restored and the battery voltage is normal, relays K2, K3 are activated and the load is switched to mains power. Transistors VT3, VT5 change their state to the opposite, relay K4 is de-energized and turns off the inverter. At the same time, transistor VT2 opens, resistor R18 is connected in parallel with R3 (see Fig. 1), which provides correction of the lower threshold to 12,2 V. If the battery voltage is higher than this value, nothing else will happen, and if it is lower, then switching the comparator will trigger relay K1 and switching on the battery charging mode by closing contacts K1.1. The closing of the transistor VT3 at the moment of loss of mains voltage is accompanied by a short-term opening of the transistor VT4 (during the charging of the capacitor C5 through its emitter junction and resistors R16, R19). An open transistor shunts the VD1 zener diode, the comparator goes into a low output voltage state regardless of the battery voltage, and the converter is forced to turn on. This is necessary, since at the time of mains voltage failure the device may be in charging mode, the battery voltage will be clearly above the comparator switching threshold and it will need to be reset to its original state. Further operation of the device depends on the level of battery charge in accordance with the described principle of operation. Diode VD8 serves to quickly discharge the capacitor C5 when the mains voltage is restored. LED HL2 (green glow) - an indicator of the presence of mains voltage. By the glow of the HL1 and HL2 LEDs, one can judge the operating mode of the device and the inverter. So, if HL1 is lit, this means that there is no mains voltage, the inverter is off, and the battery voltage is below 11,3 V. The HL2 LED is lit, indicating the presence of mains voltage and the battery is fully charged. Finally, the simultaneous glow of both indicators indicates that there is voltage in the network and the battery is being charged. The device uses small-sized fixed resistors of any type indicated on the power dissipation diagrams. Trimmer resistors - preferably multi-turn (with a worm drive engine). Polar capacitors - oxide K50-83, K50-16 of similar capacity or similar imported ones, C2 - any ceramic small-sized, for example, K10-73-1b, K10-17v. Instead of K140UD1A, other op amps of the K(R) 140UD1 series or any op amp with similar parameters, an allowable supply voltage of 12 V ± 5% and appropriate correction circuits can be used as a comparator. Transistors VT2-VT4 are interchangeable with any analogues with parameters no worse than those used by the author (for example, domestic KT3102 series or imported BC547 with any letter index). Instead of KT972A, you can install other transistors of this series or use composite transistors from conventional low-power and high-power transistors connected appropriately (for example, the KT315 and KT817 series). Zener diode VD1 - with a stabilization voltage of 5 ... 6 V at a stabilization current of 5 mA, VD2 - 11 V, with a possible lower minimum current and a maximum stabilization current of at least 12 mA, VD3 - 3 ... 3,6 V. Instead of KS211Zh (VD2) you can use KS211E or any of KS211G, KS211D (in the second case, R9 should be replaced with a 160 Ohm resistor and a dissipation power of 0,25 W). Relays K1 - K4 - OMRON G2RL112DC or similar for printed wiring with a rated voltage of 12 V windings, designed for switching voltage of 240 V at a current of at least 5 A (the maximum load power depends on the permissible current). Transformer T1 - step-down with a secondary winding 2x9 V at a current of 100 mA. LEDs HL1 and HL2 - respectively AL307BM and AL307VM, AL307GM or super-bright, for example, CREE C503-GC (HL1) and C503-RC (HL2). The device is assembled in an IP65 or IP67 plastic housing with internal dimensions of 110x110x82 mm. The location of boards and remote elements inside the case is shown in fig. 3. Relay contacts K1.2, K4.1 are connected to the wire break of the inverter power switch. When installing power circuits, electrical safety rules must be observed.
Establishment consists in setting the comparator switching thresholds using trimmers R2 and R8, as well as with the possible selection of resistor R18. During adjustment, the comparator assembly is recommended to be powered from an external regulated source. By connecting the terminals of the collector and emitter of the transistor VT2 with a jumper, first, using the resistor R2, set the lower threshold of 12,2 V, then with the help of R8 - the upper 13,8 V. Through successive approximations, a clear operation of the comparator is achieved at the specified voltage values. After that, removing the jumper from the VT2 terminals, check the lower threshold offset to the level of 11,3 V. If necessary, select the resistor R18, temporarily replacing it with a tuning resistor with a resistance of 6,8 ... 10 kOhm. On this, the adjustment can be considered complete. Literature
Author: D. Pankratiev
Machine for thinning flowers in gardens
02.05.2024 Advanced Infrared Microscope
02.05.2024 Air trap for insects
01.05.2024
▪ Classes in old gyms are more effective than in modern ones ▪ Solar storms will become more destructive ▪ B vitamins with omega-3 fatty acids slow brain aging ▪ The TV is preparing to force the computer out of the apartment
▪ section of the site Data transfer. Article selection ▪ article Zhivinka in action. Popular expression ▪ article When did you start collecting honey? Detailed answer ▪ article Kalmyk knot. Tourist tips ▪ article Clouds in the room. Focus Secret
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page