JPS6111960Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an abnormality detection device for a three-phase circuit that has the function of preventing reverse rotation of a three-phase motor, etc. and also protecting against phase loss.In particular, the device has a function of determining reverse phase order and phase loss abnormality. It has great practical value because it is excellent, has a simple structure, has few failures, and can be made at low cost. Various types of detection devices have been proposed in the past as this type of detection device, among which one as shown in FIG. 1 is known. That is, in Figure 1,
A three-phase motor M is connected to each phase U, V, and W of the three-phase power supply via main contacts P ₁ , P ₂ , and P ₃ of the abnormality detection device 1 . Main contacts P ₁ , P ₂ and P ₃ of abnormality detection device 1
is a so-called electromagnetic switch that closes when the electromagnetic coil Lc is energized and opens when it is deenergized. The electromagnetic coil Lc is connected between the U phase and the W phase via a manually operated switch Sw and a contact Pr of a relay for determining the phase order. The relay contacts Pr are driven by a coil Lr, and are closed when the coil Lr is energized by a predetermined voltage and open when the coil Lr is not energized. A capacitor C is connected to the U phase of the three-phase circuit, a coil Lr is connected to the V phase, and a discrimination resistor R is connected to the W phase. The circuit including the protective resistor Rp and the normally closed contact Pp connected in series with the V-phase coil Lr will be ignored until described later. The capacitor C, the coil Lr, and the discrimination resistor R are connected in a star shape. To determine the three elements connected in this star shape, for example, first select an appropriate relay, and then select the capacitance of capacitor C that has the same impedance as the impedance of the relay coil Lr, and check paper. The value of the resistor R is slightly adjusted to select the following appropriate value. That is, when the phase rotation order of the three-phase power supply is in a positive phase state such as U-V-W, a voltage of a predetermined value or higher is applied to the relay coil Lr for determining the phase order, and the contact Pr is closed. When the phase order of the phase power supply is reversed, such as U-W-V, a voltage higher than a predetermined value is not applied to the relay coil Lr, and the contact Pr remains open. Furthermore, the fluctuation of the power supply voltage should be taken into account about ±10% of the rated value, and the frequency should be 50Hz and 50Hz.
Even in the case of 60Hz, it is necessary to adjust the values of capacitor C and discrimination resistor R so that the normal phase state and negative phase state can be discriminated reliably. ) is attracted or released to close or open contact Pr, so the reactance of coil Lr varies depending on the position of the movable iron piece, and this is applied to each element connected in a star shape. This poses the difficulty of having to take this into account when setting conditions in order to change the voltage vector. Therefore, if we determine appropriate values for the elements connected in a star shape on the assumption that the voltage applied to coil Lr after contact attraction will be higher than before contact attraction, the voltage applied to relay coil Lr will be There are cases where the temperature rise of the coil exceeds the limit due to exceeding the rated value. To prevent this, an auxiliary circuit is required, such as inserting a protective resistor Rp in series with the relay coil Lr after attracting it. Since the normally open contact Pp opens its circuit when attracted by the coil Lr, the above purpose can be achieved by connecting it in parallel to the protective resistor Rp. In the conventional circuit configured in this way, when the phase order of the three-phase circuit is U-V-W, which is a positive phase state, a voltage higher than a predetermined value is applied to the relay coil Lr. Contact Pr is attracted and enters a closed circuit state. (Also, since the contact Pp is attracted and opens, as mentioned above, the coil Lr after the movable iron piece is attracted)
The excessive voltage applied to the terminal can be prevented by dividing the voltage by the protection resistor Rp. ) Therefore, manually operated switch Sw
When the switch is operated and closed, the U-W phase voltage is applied to the coil Lc of the electromagnetic switch via the contact Pr, so the electromagnetic switch is energized and its contacts P ₁ , P ₂ and P ₃
is closed and power is supplied to motor M. When the phase order of a three-phase circuit is reversed, such as U-W-V, only 1/3 of the specified voltage is applied to the relay coil Lr, so the contact Pr is not attracted and is therefore in an open state, and cannot be operated. Even if the switch Sw is closed, the coil Lc of the electromagnetic switch remains deenergized and the contact is closed.
Since P ₁ , P ₂ and P ₃ are not closed, no power is supplied to the motor M, so there is no fear that it will be driven in the opposite direction. In addition, if the V phase of the three-phase circuit is open, the relay coil Lr will not be energized, and the electromagnetic coil Lc cannot be energized if the U or W phase is open. Even if a phase is missing, the abnormality of single-phase operation can be avoided. In contrast to the conventional three-phase circuit abnormality detection device described above, the abnormality detection device of the present invention is different from the symbol 11 in FIG.
As shown in Figure 2, a three-terminal bidirectional thyristor is used to facilitate and reduce the cost of setting the conditions for each element of the phase order determination circuit. In FIG. 2, the same symbols as in FIG. 1 indicate the same or equivalent effects. A resistor R connected to the V phase of a three-phase power supply, a resistor _R2 connected to the W phase, and a capacitor C connected to the U phase are connected in a star shape. Furthermore, the resistor connected to the V phase
R ₁ has a tap in the middle, and for convenience, the resistance between the taps is indicated by the symbols R ₁₁ and R ₁₂ , respectively. A series circuit of the main poles T ₁ , T ₂ and the electromagnetic coil Lc of the three-terminal bidirectional thyristor is connected to the V and W phases in parallel with the resistors R ₁ and R ₂ . The gate G of the three-terminal bidirectional thyristor is connected to a suitable point of the voltage division value of the resistor _R1 . To give specific numerical examples of each element used in the example, the three-terminal bidirectional thyristor is a small one with an effective on-current of 2A class, and the electromagnetic switch has a small operating current of its electromagnetic coil Lc. It does not matter what value the impedance of the coil Lc is as long as it is within the range of the effective on-current. The capacitance of capacitor C is 0.05μF, and the _R11 part of resistor _R1 is
22.2K made up of 7.2KΩ and _R12 part is 15KΩ
Ω, and the resistance R ₂ was 56KΩ. In the case of this configuration, the voltage distribution applied to each element when a balanced three-phase voltage is applied, and other matters are as follows. Note that the phase-to-phase voltage is 200 volts (V).

[Table] Since the three-terminal bidirectional thyristor conducts when the voltage across the resistor _R1 corresponds to 65V, it can be seen from the above results that it can be determined sufficiently even if the power supply voltage fluctuates by about ±15%. Since the electromagnetic coil Lc cannot be energized in the case of an open phase in the V phase and the W phase, it can naturally be determined. As mentioned above, in the three-phase circuit abnormality detection device of the present invention, it is much easier and more reliable to set the conditions that enable detection of normal and abnormal conditions than with conventional devices, and in addition, the voltage applied to the relay is There is no inconvenience such as the contact point changing before and after suction, and therefore a protection circuit is not required, and the structure is simple and can be provided at low cost, which is of high practical value.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing an embodiment of a conventional abnormality detection device for a three-phase circuit, and FIG. 2 is an electrical circuit diagram showing an embodiment of the abnormality detection device according to the present invention. U, V, W...three-phase power supply, _R1 ...resistance, _R2 ...
...Resistor, C...Capacitor, _T1 , _T2 ...Main pole of three-terminal bidirectional thyristor, G...Gate of three-terminal bidirectional thyristor, Lc...Coil of electromagnetic relay.

Claims (1)

[Scope of utility model registration request] Two resistors and a capacitor are connected in a star shape to a three-phase power supply, and the main pole of a three-terminal bidirectional thyristor and an electromagnetic relay are connected so that the two resistors are connected in parallel to the two phases connected in series. A circuit is connected in series with a coil of the contacts of the electromagnetic relay are configured to supply power to the gate of the thyristor;
When the three-phase power supply has a reverse phase or an open phase, a voltage of less than a predetermined value or zero is applied to the coil of the electromagnetic relay,
An abnormality detection device for a three-phase circuit, characterized in that a voltage of a predetermined value or higher is applied when the three-phase power supply is in positive phase.