|
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 Power consumer protection device. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network, uninterruptible power supplies The issue of protecting powered devices from unacceptable deviations of the mains voltage remains relevant. The device described in [1] is simple, but does not provide power supply after the disappearance of the emergency in the network. The device described in [2] does not have this drawback, however, the relay connected to control the triac requires a transformer to power the device. This makes it difficult to repeat the design in several instances, and the applied method of controlling the triac does not allow connecting, for example, sound-reproducing equipment, since a background with the mains frequency may appear. I offer a device that is made without electromagnetic relays and coil units. It provides load disconnection from the network when the supply voltage exceeds 220-240 V and when the voltage drops below the set 160-220 V. The device was developed to protect sufficiently powerful consumers (TV, refrigerator, power tool, etc.), with a power of up to 2 kW. The scheme of the device is shown in Fig.1.
The device is powered through the quenching circuit C1, C2, R1 from the rectifier VD1, VD2 and the stabilizer VD4, VD5. The power circuits of the control circuit and the control electrode (UE) of the VS1 triac are separated by a VD6 diode to reduce the influence of the latter on the control circuit. Since the device is powered through a quenching circuit, the voltage across the capacitor C3, when connected to the network, increases much more slowly than, for example, in a power source with a transformer input. This circumstance leads to the fact that the thyristor key mode with state fixation appears in the DD2 microcircuit [3, p.243, 244]. To eliminate this effect, the DD2 chip is powered through a current-limiting resistor R17. On the elements DD1.1, DD1.2 and DD1.3, DD1.4 Schmitt triggers (TSh) are assembled, on the elements DD2.3, DD2.4 - a pulse generator, on the elements DD2.1, DD2.2 a single vibrator that sets the delay for inclusion. Transistors VT1 and VT2 input amplifiers. The cascade on VT1 and TSh DD1.1, DD1.2 form a channel for monitoring the minimum voltage limit, VT2 and TSh DD1.3, DD1.4, VT3 - a channel for monitoring the maximum voltage limit. Through the diode VD3 and resistors R2-R5, negative half-cycles of the mains voltage are fed to the inputs of the voltage control channels. They are amplified by cascades on VT1 and VT2. In the cascade on VT1, the amplified voltage is smoothed out by capacitor C6. With a normal mains voltage, the value of which is between the lower and upper limits set, the voltage at the collector VT1 is higher than the threshold of the TSh DD1.1, DD1.2, so there is a high level at pin 3 DD1.2 and does not affect the operation of the single vibrator. At pins 8,9 DD2.1 and pin 11 DD2.2 - high levels. The level of the log. "1" on pin 2 DD2.3 allows the operation of the generator DD2.3, DD2.4. The generator generates short pulses with a frequency of 10 kHz, which are fed through an amplifier on VT4 to the UE of the triac VS1. In this case, current flows through the triac to the load. The use of an external generator to control the triac made it possible to reduce the level of interference that occurs when the latter is opened. Depending on the magnitude of the mains voltage, positive half-waves are present on the collector VT2 (or absent). If their amplitude is insufficient to trigger the TS DD1.3, DD1.4, the output 4 DD1.4 will be log. "0", the transistor VT3 is closed and does not affect the operation of the single vibrator. When the mains voltage exceeds the set threshold, the level of pulses on the collector VT2 reaches the threshold of operation TSh DD1.3, DD1.4. From the half-waves, positive impulses are formed, which through VT3 act on the one-shot. Each pulse restarts the single vibrator. During the one-shot DD2.1, DD2.2 turn-on delay, which depends on the capacitance of the capacitor C10, there is a log "11" at pin 2.2 DD0 and disables the operation of the generator, no pulses are received at the RE VS1, and the load is disconnected from networks. When the voltage fluctuates in the network near the maximum limit, the amplitude of the pulses on the VT2 collector may be unstable, therefore, at the output of the TS DD1.3, DD1.4, the pulse frequency is also unstable, even single pulses are possible. In this case, the load remains disconnected from the network, since even a single impulse that appears during the turn-on delay time set by the one-shot restarts the one-shot, and the delay is formed again. When the mains voltage decreases below the minimum limit, the voltage level at the collector VT1 becomes below the threshold of operation of the TS DD1.1, DD1.2, and a log "3" level appears at pin 1.2 DD0, which starts the single vibrator, the generator stops working, and the load is disconnected from the network. Since the single vibrator is not affected by pulses, but by a constant level (log "0"), the formation of the delay time begins after the network voltage exceeds the minimum limit threshold. Then TSh DD1.2, DD1.3 switches to the state of the log. "1", and the formation of the turn-on delay time begins, after which the load is connected to the network. Capacitor C6 somewhat reduces the device's response to a decrease in voltage, but reducing the voltage for the load is less dangerous than increasing it. When the device is connected to the network, the load is connected with a delay set by a single vibrator. The initial start of the single vibrator is provided by both control channels. At a voltage close to the minimum, but exceeding it, the start of the single vibrator is provided by capacitors C6 and C8. At the same time, at pin 3 DD1.2, initially there is a log level. "0" and delays the countdown of the pause with a single vibrator. When the voltage on C6 and C8 reaches the threshold of operation of the TS DD1.1, DD1.2, the latter switches to the state of the log. "1", and the formation of the turn-on delay time by the single vibrator begins. At a higher voltage, capacitor C6 charges quickly, since VT2 is already operating in saturation mode, so capacitor C8 is used to keep TS DD1.1, DD1.2 in the zero state until the supply voltage rises (at C3). When the mains voltage is close to the minimum, the time to connect the load to the network increases slightly due to the slower discharge of the capacitor C6. At a higher mains voltage, pulses already appear on the VT2 collector. At the moment when the supply voltage of the device (at C3) has not yet reached the nominal value, the switching threshold of the TS is lower than in the steady state, therefore, TS pulses DD2 and DD1.3 are formed from the pulses on the VT1.4 collector, and the single vibrator is started in parallel with the TS DD1.1, DD1.2. With an increase in the supply voltage, after the device is connected to the network, even before the start of the single-vibrator operation, the generator DD2.3, DD2.4 can generate several pulses, their amplitude is lower than in the steady state, but sufficient for the operation of the VT4 pulse amplifier and triac control. To eliminate the influence of these pulses when turned on, the turn-on threshold of the cascade on VT4 is increased due to the use of the VD9 zener diode. These solutions made it possible to exclude even a short-term appearance of voltage on the load when connected to the network before the expiration of the delay time for switching on in the range from the minimum to the maximum set voltage limits of the network. The hysteresis for both control channels is 2-3 V. In the minimum limit channel at a voltage of 160-170 V, the hysteresis increases to 4-5 V. The minimum limit channel is necessary mainly for installations containing an electric motor, since electronic devices contain, if necessary for trouble-free operation, nodes that turn off the device or part of it when the mains voltage drops below the set value, for example, a TV power supply module. In installations containing an electric motor, it is necessary to determine the minimum voltage limit using LATR, at which a reliable start of the engine is still ensured and it does not stop at maximum load on the shaft. If this is not possible, then the minimum voltage limit is set from the passport data for the installation. The specified channel can be used with other devices. If shutdown at minimum voltage is not required, then the elements R2, R4, R7, R8, R11, C6, VT1 can be omitted, and the left terminal R13 according to the diagram can be connected to the connection point of the emitter VT1. Since the triac is controlled by pulses with a high frequency, installations with a collector motor, for example, an electric drill, etc., can be connected to the device. The parameters of the power supply circuits of the device are designed so that a voltage of up to 380 V is allowed to be supplied to the input of the device. Therefore, replacing the zener diodes VD4, VD5 with one is not desirable, and they must be in metal cases. The operating voltage of capacitors C1, C2, C11 is at least 630 V. The DD1 chip can be replaced with K561 LA7. Capacitors C8, C10 type K53 or similar. The Zener diode VD9 can be with a stabilization voltage of 6,8-8,2 V. Triac VS1 with a voltage class of at least 6. The resistance of the resistor R14 must be within 510 kOhm - 1 MΩ. At the same time, there is no noticeable effect on the maximum limit on the on-off threshold of the channel. Resistors R6, R7 type SP-5. The cascade on VT4 provides control of a triac, in which the resistance between the RE and pin 1 is more than 40 ohms. When using a triac with a lower resistance (which means with a large control current), you need to reduce the resistance of the resistor R24 to 150-160 ohms. It is also possible to use other triacs, in which the resistance of the output 1-UE is more than 40 ohms. But when using triacs with a resistance close to 40 ohms, one should also take into account the ambient temperature at which the device will operate, since with decreasing temperature the control current increases and a later opening of the triac (relative to the beginning of the half-cycle) is possible, and for different half-waves of the voltage this the process is not the same. The triac is installed on a radiator with an area S=0,12Rn cm2, where Рн is the load power, W. This provides a heatsink temperature of 69°C at an ambient temperature of 20-25°C. The layout of the printed circuit board is shown in Fig. 2, the location of the elements in Fig. 3.
Setting up the device is reduced to setting the required thresholds for turning off the load and the turn-on delay time. The initial state of the resistor R6 is the minimum resistance, R7 is the maximum. For the time of adjustment, the capacitance of the capacitor C10 is chosen in the range of 10-22 microfarads, and instead of the load, an incandescent lamp is turned on. When setting up, it must be taken into account that the device is galvanically connected to the network. To select the shutdown threshold in the minimum limit channel, you need to set the minimum voltage (for the load used) using the LATR at the output of the device and by adjusting R7 to disconnect the load from the network. You need to rotate R7 slowly, because due to the presence of capacitances C6 and C8, when you rotate R7 quickly, you can get an overestimated response threshold. When adjusting the maximum limit channel, the required maximum input voltage is set and by adjusting R6, the load is disconnected. Then check the operation of the device when the input voltage changes. If necessary, the cut-off thresholds in the channels are adjusted. With an increase in the resistance of resistors R6 and R7, the load is disconnected at lower input voltages. By changing the capacitance C10, the required turn-on delay time is selected. Approximate delay time (s) t = R18С10, where R18 is the resistance (in ohms); C10 - capacity (in F). With R18=270 kOhm, C10=220 uF, the delay time is approximately 1 min. When using collector motors as a load, the stability of the device is checked under the conditions of interference generated by the motor. If there is a disconnection from interference (at normal mains voltage), then it is necessary to increase C7 by 200-1000 pF (determined empirically). Do not excessively increase the capacitance of the capacitor C7, as this will affect the turn-off time with a sharp increase in the voltage in the network. In the absence of LATR, voltage can be applied to the input of the device from the regulator (Fig. 4). In this case, the load is not connected to the XS1 socket, and the control during setup is carried out with a voltmeter or oscilloscope at pin 11 DD2. Level "0" corresponds to disconnection, and level "1" - connection of the load to the network. When using an oscilloscope, control can also be carried out by the presence of control pulses on the VT4 collector. The setup procedure does not differ from that described above.
In the circuit in Fig. 4, any transformer T1 for 220 V with a secondary winding for voltage UII=30+ΔUI, where UII is the voltage of the secondary winding T1; ΔUI - minimum voltage drop on the primary winding T2 at R=0. Transformer T1 must have several secondary windings, then when adjusting the device, you can more accurately set the voltage, including the required number of windings, and this will require a resistor R with a smaller range of resistance changes. Transformer T2 can be 220 V, but it is better to have a network winding with a tap for 110-127 V. The voltage on the secondary winding is 20-30 V. Resistor R - wire with a power of 25-50 W with a resistance of 20-50 Ohms. Lamp VL1 with a power of 25-40 watts. At high lamp powers, a large power of the resistor R is also required. The specific parameters of the circuit elements are specified experimentally, depending on those available. The presence of the transformer T4 provides galvanic isolation from the network of the resistor R and safety during adjustment. With the load connected to the device and the triac closed, the load remains connected to the network through the C11R21 circuit. This is especially undesirable when connecting a low-power transformer, since the winding inductance and the C11R21 circuit form a series circuit. This, under certain conditions (with a minimum load of the transformer or when an increased voltage from the network enters the input of the device), can lead to an excess of the operating voltage of the transformer's mains winding. Therefore, it is necessary to determine experimentally the possibility of connecting a low-power load to the device. To do this, a low-power load is connected to the network through a 0,1 μF capacitor and the voltage across it is measured. Multiply the measured value by 1,7. If the resulting voltage is not dangerous, and the reduced voltage (when powered through a capacitor) does not create undesirable modes for the load, then such a load can be connected to the device. If the load contains a power transformer, then it is connected to the network in turn through a capacitor with a capacity of 0,01; 0,05; 0,1 µF, so that due to resonance the voltage on the transformer winding does not exceed the maximum allowable voltage at a network voltage of 220 V. If this does not happen, then the capability of the device for protection is determined further, as described above. The described device was tested when working together with a refrigerator, a stationary TV and a sound reproducing complex. The TV has a switching power supply (does not have a standby transformer) and was tested in normal and standby modes; in the sound reproducing complex, any of the sources was switched on together with the amplifier. No changes were detected in the operation of protected devices. References:
Author: A.N. Karakurchi
Machine for thinning flowers in gardens
02.05.2024 Advanced Infrared Microscope
02.05.2024 Air trap for insects
01.05.2024
▪ Helmet-wearing cyclist takes more risks ▪ The use of graphene will become even more efficient ▪ Anti-crisis LED drivers FDL-65 from Mean Well ▪ Across the English Channel on a jet hoverboard
▪ section of the website Audiotechnics. Article selection ▪ Aurora article. Popular expression ▪ article How did the South American Indians make rubber shoes? Detailed answer ▪ article Brunfelsia latifolia. Legends, cultivation, methods of application ▪ article Camera with a hole. physical experiment
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