JPH0136144Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" A phase detector detects whether the direction of phase rotation of multiphase alternating current is positive or reverse, and is necessary when installing or repairing electrical equipment wiring. It is.

"Prior Art" This invention relates to a phase detector for three-phase alternating current, and relates to an improvement in its detection method.

The method of connecting one impedance and two impedances with different properties in a Y-connection, and determining the phase order from the magnitude of the voltage drop of the impedance caused by the unbalance of the impedance, is based on the 50-19500 Utility Model Act and the 50-1950 Utility Model Act. -24219 is also applied and is widely known.

"Problems to be Solved by the Invention" The method described above has the disadvantage that it is not possible to determine an open phase state in which no voltage is applied to any one phase, and misjudgment of the phase order due to an open phase can lead to serious accidents. It's scary and dangerous.

This proposal adds a simple circuit to the basic circuit of the phase detector, and attempts to know the phase order, open phase, and approximate voltage of the power source to be measured.

This will be explained below using figures.

Figure 1 shows an example of a conventional phase detector, in which resistor R ₁ capacitor C ₁ and C ₂ are Y-connected, and the connection point
The sides opposite to O' are connected to terminals A, B, and C, respectively. Further, a series circuit consisting of a resistor R ₂ and a neon lamp L ₁ is connected in parallel to the capacitor C ₁ , and a series circuit consisting of a resistor R ₃ and a neon lamp L ₂ is similarly connected in parallel to the capacitor C ₂ .

The impedance of this capacitor C ₁ and C ₂ is X _c1 and
X _c2 is selected to have approximately the same value as resistor R ₁ .
Va, Vb, and Vc are the respective voltages between terminals A, B, and C and connection point O'. In addition, E ₃ 〓 is a three-phase AC power supply (hereinafter referred to as
(simply referred to as a three-phase power supply), and the voltages of each phase are Ea, Eb,
Ec, the neutral point is O, and the phase order is Ea, Eb, Ec.

In such a configuration, terminals A, B, and C of the phase detector
The three-phase power supply E ₃ φ lines a, b, and c are a-b-c.
When connected in the order of a-c-b (positive phase), the voltage Vc between terminals C and O' becomes higher than the voltage Vb between terminals B and O', and when connected in the order of a-c-b (negative phase) Conversely, voltage Vb becomes higher than voltage Vc.

Therefore, it is known that the brightness of lighting of the neon lamps L ₁ and L ₂ differs depending on the phase order, and when the neon lamp L ₂ is bright, the phase is positive, and when the neon lamp L ₁ is bright, the phase is reversed.

However, in a circuit with such a configuration, in the case of an open phase, for example, when the b phase is open, a voltage of √3/2 or more of the phase voltage Ea of the three-phase power supply E ₃ φ will be present between the terminals C and O'. In addition, there was a drawback that the neon lamp L ₂ would light up regardless of the phase order.

"Means and Embodiments for Solving the Problem" FIG. 2 shows a circuit of a phase detector according to the present invention. Since it is basically the same as the conventional example shown in FIG. 1, the same reference numerals are used for the same components as in FIG. 1, and the explanation thereof will be omitted.

In FIG. 2, a series circuit consisting of a resistor R ₆ , a diode D ₁ and a resistor R ₄ is connected in parallel with a capacitor C ₁ between terminals B and O'. Also, between the connection point of resistor R ₆ and diode D ₁ and terminal C,
A series circuit of diode D ₂ and resistor R ₅ is connected. The diodes D ₁ and D ₂ preferably have the same characteristics and high reverse withstand voltage, and both have the resistor R ₆ side as the anode side.

Resistor _R6 may be omitted and made into a shot shape.
There may be two approximately equal value resistors, each connected to the anodes of two diodes.

P ₁ is the connection point of diode D ₁ and resistor R ₄ , and the (-) terminal of indicator M is the connection point of diode D 1 and resistor R 4. R ₂ is diode D ₂ and resistor R ₅
The (+) terminals of the indicator M are connected at the connection points. The indicator M is a DC voltmeter of the average value indicating type, with the median value being O and suitable for indicating both + and - sides.

"Operation" In the circuit configured as above, terminals A, B, and C _are connected to lines a, b,
When connected to terminal C, voltages Vb and Vc of different magnitudes are generated between terminals B-O' and C-O' depending on the phase order. This is as explained in the conventional example shown in FIG.

Now, in the present invention, these two voltages Vb and Vc are rectified by diodes D ₁ and D ₂ , respectively, and a pulsating current (DC) potential is applied to the connection points P ₁ and P ₂ . Naturally, the average value of this potential is higher when the voltages Vb and Vc are larger.

Therefore, when the phase order is a-b-c and is a positive phase, the voltage
Vc is large, and the connection point _P2 is higher than _P1 , and the indicator M swings to the (+) side. In the case of reverse phase, the connection point _P1 is high and the indicator M swings to the (-) side, allowing the phase order to be known.

By the way, since the potential difference between the connection points P ₁ and P ₂ is proportional to the phase voltage E of the three-phase power supply E ₃ φ when the phase order is the same, the swing of the indicator M also swings significantly in proportion.

Therefore, according to the present invention, it is possible to know the voltage of the power supply to be measured at the same time as the phase order.

In addition, terminal B is connected to indicator M through resistors R ₄ and R ₅ .
An alternating current flows due to the voltage between -C, but since the indicator M is a DC voltmeter of the average value indicating type, there is no operation due to the current and it is no problem for phase detection.

Next, let's examine the case of open phase using the same figure 2. In the case of an open phase, the phase detector is in the same state as if a single-phase AC voltage was applied to any two of terminals A, B, and C.

<When the open phase is phase a> This is a state in which a single-phase AC voltage is applied between terminals B and C. In this case, as can be seen from Figure 2, the circuit is symmetrical with respect to the indicator M, so the average potentials at the connection points P ₁ and P ₂ are the same value, and the average value indicator M
doesn't work.

<When the open phase is phase b> A single-phase AC voltage is applied between terminals A and C.

Consider the case when terminal C has a (+) potential with respect to A. In this case, the diodes D ₁ and D ₂ are reverse biased, so the current flowing through them to the indicator M is O.

Next, when terminal A is (+) with respect to C, diodes D ₁ and D ₂ are forward biased and conductive, and their resistances are significantly reduced. If the resistance of the indicator M is set sufficiently large compared to that resistance, the resistance
Most of the current through R ₆ flows to the diode D ₂ side,
The current flowing through the diode _D1 to the indicator M is extremely small, and the indicator M hardly swings.

In addition, resistor R ₁ capacitor C ₁ resistor R ₄ , indicator M,
In the circuit of resistor _R5 , current flows due to the voltage applied between terminals A and C, but the DC component is blocked by capacitor _C1 , and only the AC component flows, regardless of the direction of the voltage between terminals A and C. It only flows. Therefore, the indicator M will not operate in this case as well.

<When the open phase is the C phase> In this case, since the circuit is symmetrical, the same concept as when the B phase is open, and as a result, the indicator M does not operate.

As explained in the three cases, the indicator M will not operate even if any of the phases a, b, and c becomes open, and you should notice an abnormality in the circuit, including in the case of a power outage.

``Effects'' As is clear from the above explanation, despite the simple circuit configuration of the present invention, it is possible to check three types of elements in one measurement: phase order, open phase, and approximate voltage value. I was able to make a convenient phase detector.

Note that there is no problem in using a digital DC voltmeter that can display polarity in place of the indicator M.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram illustrating a conventional phase detector. Second
The figure shows an example of the phase detector of the present invention. _R1 , _R4 , _R5 , _R6 : Resistor, _C1 , _C2 : Capacitor, _D1 , _D2 : Diode, M: Indicator.

Claims (1)

[Scope of utility model registration request] One resistor and two capacitors with almost the same impedance are connected in a Y connection, and the connection point is
In a phase detector configured to connect three independent terminals on the opposite side from O' to the three-phase AC power supply to be measured, rectification is performed in parallel with the two capacitors with almost the same configuration and in the same direction. A series circuit of two sets of diodes and a resistor is connected so that each anode side of the diode is on the connection point O' side, and two sets of series circuits of the two sets of diodes and a resistor are connected. A phase detector characterized by having an average value type DC voltmeter connected between the points.