JPS5941144B2 - Current imbalance detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current unbalance detection device for detecting current unbalance or human appearance.

FIG. 1 is an electrical wiring diagram showing a conventional current imbalance detection device.

In FIG. 1, a load current flowing through a load line 1 is detected by a current transformer 2 and rectified by a rectifier circuit 3. In FIG. Now, if the load current flowing through the load line 1 is balanced, the current waveform appearing between the pair of output terminals 3a and 3b of the rectifier circuit 3 becomes almost direct current as shown in FIG. Therefore, the capacitors 13 and 14 are connected by a closed circuit of output terminal 3a → resistor 12 → capacitor 13 → output terminal 3 and a closed circuit of output terminal 3a → resistor 12 → capacitor 14 → resistor 15 → output terminal 3b. are the voltages V shown in FIG. After this charging, no current flows through the resistor 15. Therefore, the transistor 16 becomes conductive and does not produce an output at the output terminal 10. Next, when the load current flowing through the load line 1 is unbalanced or in phase, the pair of output terminals 3 of the rectifier circuit 3
The current waveform appearing between a and 3b has a peak value V1 and a ripple portion V as shown in FIG. It becomes a ripple waveform containing 1.

Therefore, the ripple component V. 1 by capacitor 13, 1
4 repeats charging and discharging, and a charging current flows through the resistor 15.

Therefore, the transistor 16 becomes non-conductive, producing an output at the output terminal 10, and operating a circuit (not shown) that disconnects the load line 1. However, in this conventional device, the level of unbalance detection is determined by the magnitude of ripple in the output of the rectifier circuit 3.

Therefore, the unbalance detection level differs depending on the magnitude of the load current flowing through the load line 1, and the device operates with a slight unbalance in a region of large load current. This invention was made to eliminate the drawbacks of the conventional ones as described above, and aims to provide a current unbalance detection device that always operates at a constant unbalance detection level regardless of the magnitude of the load current. As a purpose.

An embodiment of the present invention will be described below with reference to the drawings. Fourth
The figure is an electrical wiring diagram showing one embodiment of the current imbalance detection device according to the present invention.

In FIG. 4, the load line 1 carries the load current to be detected. The current transformer 2 detects the load current flowing through the load line 1. The rectifier circuit 3 rectifies the load current detected by the current transformer 2, and produces a rectified output at a pair of output terminals 3a and 3b. Capacitor 4 and diode 5 are connected in series between a pair of output terminals 3a and 3b. The first and second voltage dividing resistors 6 and □ are connected in series with each other and connected in parallel with the capacitor 4. One input terminal of the comparator circuit 3 is connected to the connection point of the first and second voltage dividing resistors 6 and 7 via a resistor 9, and the input terminal on the other side is connected to the output terminal 3b, which is the ground potential of the rectifier circuit 3. The two terminals are connected to each other, and when the input at one side input terminal becomes a negative potential, an output is generated at the output terminal 10. The DC power supply 11 is the power supply for the comparator circuit 8 . Next, this operation will be explained. A load current flowing through the load line 1 is detected by a current transformer 2 and rectified by a rectifier circuit 13. When the load current is balanced and the output waveform appearing between the pair of output terminals 3a and 3b of the rectifier circuit 3 is as shown in Fig. 2, a closed circuit of output terminal 3a → capacitor 4 → diode 5 → output terminal 3b is formed. Therefore, the voltage of the capacitor 4 is as shown in FIG. is charged to. this voltage. is divided by first and second voltage dividing resistors 6 and 7, and this divided voltage is applied to one side input terminal of comparator circuit 8 via resistor 9. Therefore, the one side input terminal has a positive potential, and no output is generated at the output terminal 10. On the other hand, when the load current is unbalanced or out of phase, the output waveform appearing between the pair of output terminals 3a and 3b of the rectifier circuit 3 has a peak value V1 and a ripple amount V as shown in FIG. It becomes a ripple waveform containing l. Therefore, when the peak value is 1 o'clock, the capacitor 4 is charged to the peak value 1 by the closed circuit of the output terminal 3a → capacitor 4 → diode 5 → output terminal 3b. Next, in the valley portion of the output waveform shown in FIG. 3, since the diode 5 is present, the ripple portion of the charging voltage V1 of the capacitor 4 is generated. The voltage corresponding to 1 is about to discharge through the first and second voltage dividing resistors 6 and 7 having high resistance.

The potential waveforms at points A, B, and C shown in FIG. 4 in this case are shown as A, b, and c in FIG. 5, respectively. That is, capacitor 4
When charged to a peak value of 1, the potential at point B becomes as shown in Figure 5, and the potential at point C becomes as shown in Figure 5c, which is the same as the potential shown in Figure 5a and Figure 5b. The potential shown is divided by the first and second voltage dividing resistors 6 and 7. As is clear from the potential waveform shown in FIG. Voltage 0CV shown in Figure 5
], the comparator circuit 8 operates and the output terminal 1
produces an output of 0. This output causes a shield breaker (not shown) to operate and disconnect the load line 1. This invention is configured as described above and detects the ripple component of the load current, but does not directly detect the magnitude of the ripple component.
Since the comparator circuit 8 is operated according to the ratio of the ripple component to the entire load current determined by the voltage division ratio of the first and second voltage dividing resistors 6 and 7, it does not depend on the magnitude of the load current. First, it can be operated at a constant unbalance detection level.

Next, an example of this will be explained with reference to FIGS. 6A and 6B.

FIG. 6a shows the input waveform of the one side input terminal of the comparator circuit 8 in FIG. 4. When the output waveform of the rectifier circuit 3 has a peak value of 1.5 and a ripple portion of 0.5V, point C shown in FIG. The case where the first and second voltage dividing resistors 6 and 7 are set so that the voltage becomes O is shown. In this case, when the ripple component exceeds 0.5V, the comparison circuit 8 produces an output at the output terminal 10. In other words, if ripple rate=ripple amount/peak value, then in this case the ripple rate will operate at 33%. In this way the first
, in the device in which the second voltage dividing resistors 6 and 7 are set, when the load current increases and the peak value reaches 15V, the comparator circuit 8
The waveform at the input terminal of is shown in FIG. 6b. In this case, when the ripple component exceeds 5V, the comparator circuit 8 produces an output at the output terminal 10. In this case, the ripple portion of 5 V means the ripple rate is 33%, and the comparator circuit 8 operates at a constant ripple rate regardless of the magnitude of the load current. In the above embodiment, a comparator is used as the comparison circuit 8, but a transistor, a voltage detection element, etc. can be used instead of the comparator to perform the same operation, and these are collectively referred to as the comparison circuit 8. Make it.

As described above, according to the present invention, the unbalance detection level can always be maintained regardless of the magnitude of the load current with a simple circuit configuration.
can be set.

[Brief explanation of drawings]

FIG. 1 is an electrical wiring diagram showing a conventional current imbalance detection device.

Claims (1)

[Claims] 1. A rectifier circuit that rectifies a load current, a capacitor and a diode connected in series between a pair of output terminals of the rectifier circuit, and a first voltage dividing resistor and a second voltage dividing resistor connected in parallel to the capacitor in series. A current circuit comprising: a comparator circuit that operates and produces an output at an output terminal when a potential at a connection point between the first voltage dividing resistor and the second voltage dividing resistor exceeds a predetermined value. Imbalance detection device.