Phase sequence determinant. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Electric installation work

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When connecting a load to a three-phase network, it is often necessary to observe a certain phase sequence. If an erroneous connection, for example, of an electric motor, its shaft will rotate in the wrong direction. Other troubles are also possible. The author offers his own version of the device for quickly determining the phase sequence, which, in his opinion, is more convenient in operation compared to well-known industrial and amateur developments.

The device, which will be discussed, allows you to quickly determine the phase sequence in a three-phase network with a linear voltage of 380 V. In contrast, for example, from the one described in the article by N. Safonkin "Simple phase indicator" ("Radio", 2002, No. 9, p. 40 ), it does not need to be connected to the "neutral" wire.

The appearance of the device is shown in Fig. 1, and the diagram is in fig. 2.

After connecting the terminals ХР1-ХРЗ to the network, a three-phase bridge rectifier based on diodes VD1, VD3, VD4, VD6, VD7, VD9 starts working. The rectified voltage is limited by the VD10 zener diode to 15 V, which is necessary to power the microcircuits and transistors of the device. Excess voltage is quenched by resistors R7-R10 connected in parallel. The power dissipated by them is close to the maximum allowable, so it is not recommended to keep the device connected to the network for a long time. Capacitor C1 - smoothing. LEDs HL1-HL3, connected in series with diodes VD1, VD4, VD7, indicate the presence of voltage in each of the phases.

The voltage of each of the three phases is supplied to the inputs of the elements DD1.1-DD1.3 through the diodes VD2, VD5, VD8 and voltage dividers on resistors R1-R6. The resistor values ​​are chosen in such a way that the amplitude value of the voltage at the input of the logic element slightly exceeds its switching threshold.

On fig. 3 shows the timing diagrams of signals at various points in the circuit: on the left - for the "direct" (A-B-C), on the right - for the "reverse" (A-C-B) phase order. For phase A, any of the three phases of the network is conditionally taken.

While the SB1 button is not pressed, the device is in its initial state. A high logic level from the output of the anti-bounce protection node of the button on the element DD1.4 is fed to the input S of the trigger DD2.1. Although the input R of this trigger receives pulses from the output of the element DD1.2, it remains in a high state at the output (pin 2), since the input S has priority.

A high logic level applied from the output of the trigger DD2.1 to the inputs S of the triggers DD2.2 and DD2.3, in turn, keeps the latter in a high state at the outputs. Transistors VT1 and VT2 are closed, LEDs HL4 and HL5 are off.

When you press the SB1 button, the high logic level at the output of the element DD1.4 and the input S of the trigger DD2.1 connected to it is replaced by a low one. As a result, the first pulse from the output of the element DD1.2 will change the state of the trigger DD2.1, which will enable the operation of triggers DD2.2 and DD2.3. What happens next depends on the order of the phases.

If the first after unlocking the triggers will be the pulse at the output of the element DD1.1, the state of the trigger DD2.2 will change. The transistor VT1 will be open, and the LED HL4 "A-B" will be turned on. Pulses from the output of the element DD1.3 to the input R of the trigger DD2.3 will not come due to the diode VD2.2 that opens at a low logic level at the output of the trigger DD12. Therefore, the trigger DD2.3 will retain the state corresponding to the extinguished LED HL5 "A-C". This position will remain unchanged until the SB1 button is released, after which the device will return to its original state.

If after pressing the button and switching the trigger DD2.1 the first pulse will follow at the output of the element DD1.3, the state of the trigger DD2.3 will change, and the trigger DD2.2 will remain the same. Accordingly, the HL5 LED will be on, but HL4 will not.

During the manufacture of the device, the following replacements are permissible: chip K561LP2 - KR1561LP14; quad trigger K561TMZ - for two dual triggers K561TM2 switched on accordingly; transistors KT3107A - for any of the series KT3107, KT361; Zener diode KS515A - for KS215Zh, KS515G, KS511A, KS528G. Diodes VD1-VD9 should be selected with a permissible reverse voltage of at least 600 V. Suitable, for example, KD105V, KD105G, KD209B, KD209V, KD243D-KD243Zh, 1 N4005-1 N4007. LEDs - any domestic or imported corresponding glow color.

Resistors R7-R10 - MLT-2. They can be replaced by an assembly of any number of identical resistors connected in parallel or in series. When calculating the rating and power of the resistors, proceed from the fact that with a voltage drop across the entire assembly of 500 V, the current flowing through it should be within 10 ... 15 mA.

All parts of the determinant are mounted on a board placed in a housing made of insulating material, for example, polystyrene or fiberglass. Instead of contact pins ХР1-ХРЗ, the device can be equipped with connecting wires 0,5 ... 1 m long with crocodile clips, necessarily insulated.

When you first connect a newly manufactured phase sequencer to the network, it is enough to make sure that when you repeatedly press the SB1 button, the same LED from the pair HL4, HL5 lights up. If failures are observed, slightly (by 200 ... 500 Ohms) reduce the resistance of resistors R2, R4, R6. Each of them can be made up of two connected in series. However, in all three copies of the device made by the author, it was not necessary to select resistors.

Author: I.Potachin, Fokino, Bryansk region

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