JPH0322898Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention consists of a current detector, in particular, three current transformers that detect each current value of the three-phase line under test, and one current transformer that detects the current of all three-phase lines under test. The present invention relates to a current detector having a current transformer.

When an overcurrent flows or a ground fault occurs in a three-phase load, such as a three-phase induction motor, it is necessary to immediately disconnect the motor from the power supply to prevent damage to the motor. For this reason, the electric motor is usually provided with an overcurrent protection relay and a ground fault protection relay, and in the event of an abnormality such as an overcurrent or a ground fault, the relay operation of these relays disconnects the motor from the power source. However, a large current normally flows through the power circuit of an electric motor, and it is not practical to directly operate a protective relay with this large current due to the capacity of the protective relay.

Therefore, current detectors are generally used that have a current transformer (CT) that transforms the large current flowing through the power circuit into a small current. Abnormalities such as ground faults are detected.

Conventionally, a circuit shown in FIG. 1 has been used as this type of protective relay circuit. In Fig. 1, the power circuit consists of a circuit configuration from a three-phase AC power source (not shown) to the electric motor 10, and this power circuit has wiring that performs a tripping operation when a load current exceeding the rated current flows. A circuit breaker 12 is provided,
The molded circuit breaker 12 has a tripping characteristic matched to that of the starting switch so that the starting current of the motor 10 will not cause an erroneous tripping operation. Further, the power circuit is provided with an electromagnetic switch 14, and when an abnormality such as overcurrent or ground fault occurs, the electromagnetic switch 14 is opened and the motor 10 is opened.
and the power supply can be separated.

A current detector is provided to transform and detect the large current flowing in the power circuit into a desired small current, and the current detector is connected to each of the three-phase test lines 15a to 1.
A circuit current detector 16 that detects the current flowing through 5c.
and a zero-sequence current detector 18 for detecting zero-sequence current.

The circuit configuration of the circuit current detector 16 is shown in FIG. -24, three first current transformers 26-30 are provided. Coils are wound around the iron cores (not shown) of the first current transformers 26 to 30 via insulators, one end of each coil is connected to each other, and the other end is connected to six diodes. A full-wave rectifier circuit 32 is connected, and a load resistor 36 for setting an output voltage is further connected to output terminals 34a and 34b of the rectifier circuit 32.

FIG. 3 shows the appearance of the circuit current detector 16, and in the figure, the storage case 38 has three through holes 40 to 44 communicating with the core openings 20 to 24 of the first current transformers 26 to 30. The three first current transformers 26 to 30 are housed in this storage case 38. Specifically, the cross-sectional structure is as shown in FIG. Each of the through holes 40 to 44 of the storage case 38 has three-phase test lines 15a to 15c.
are arranged through each line, and as a result, each tested line 1 is connected to the coil of each first current transformer 26 to 30.
A small three-phase current flows through the currents 5a to 15c, which are transformed. This three-phase current flows through the full-wave rectifier circuit 32
The test lines 15a to 1 are rectified by the output terminals 34a and 34b, which are both terminals of the load resistor 36.
A voltage is generated according to the current flowing through 5c.

Further, the zero-phase current detector 18 has one second current transformer 46 having one core opening (not shown), and all three-phase tested lines 15a to 15a are connected to the core opening.
15c is arranged through.

FIG. 4 shows the external appearance of the zero-phase current detector 18, and FIG. 9 shows the cross-sectional structure. In these figures, the storage case 48 is provided with one through hole 50 that communicates with the core opening of the second current transformer 46, and all three-phase test lines 15 are connected to the through hole 50.
a to 15c are arranged through. Therefore, a voltage corresponding to the zero-sequence current of the power circuit is induced at the output terminals 52a, 52b of the zero-sequence current detector 18.

Output terminals 34a, 34b, 52a of the circuit current detector 16 and zero-phase current detector 18,
52b are connected to an overcurrent protection relay 54 and a ground fault protection relay 56, respectively, and are further connected to the test line 15.
Between the two lines 15a and 15b of a to 15c, there is a normally closed contact 5 that performs on/off operation by the relay operation of a start switch 58, a stop switch 60, an electromagnetic switch coil 14a, and each of the protection relays 54 and 56.
4a and 56a are each connected in series.
The start switch 58 also has a normally open contact 14b.
are connected in parallel, and the normally open contact 14b remains closed until the stop switch or the normally closed contacts 54a, 56a open and separate after the start switch 58 is once closed.

The conventional current detector has the above configuration, and its operation will be explained below.

When the start switch 58 is turned on, an exciting current flows through the electromagnetic switch coil 14a, and the electromagnetic switch 1
4 is operated to close. Therefore, power is supplied from the power source to the electric motor 10 through the molded circuit breaker 12 and the electromagnetic switch 14, and the electric motor 10 is driven. At this time,
A load current flows through each of the three-phase tested lines 15a to 15c, and the circuit current and zero-sequence current of each tested line 15a to 15c are detected by the circuit current detector 16 and the zero-sequence current detector 18, Each detection current is an overcurrent protection relay 54 and a ground fault protection relay 5, respectively.
It flows to 6.

When an overcurrent flows in the power circuit, a detection current corresponding to the current flowing in the power circuit flows from the circuit current detector 16 to the overcurrent protection relay 54, and the overcurrent protection relay 54 performs a relay operation. As a result, the normally closed contact 54a is operated to open and separate, the excitation current flowing through the electromagnetic switch coil 14a is cut off, the electromagnetic switch 14 is operated to open, and the motor 10 and the power source are disconnected. Further, when a ground fault occurs in the motor 10, a ground fault detection current flows from the zero-phase current detector 18 to the ground fault protection relay 56,
performs relay operation. As a result, the normally closed contact 56a
is operated to open, the excitation current flowing through the electromagnetic switch coil 14a is cut off, and the electromagnetic switch 14 is operated to open, thereby disconnecting the motor 10 from the power source.

Note that if the stop switch 60 is not activated while the electric motor 10 is being driven,
When the electromagnetic switch coil 14 is opened, the electromagnetic switch coil 14
The excitation current flowing through a is cut off, and the electric motor 10 is disconnected from the power source.

However, in the conventional current detector, as is clear from FIGS. 3 and 4, the circuit current detector 16 and the zero-sequence current detector 18 are housed in separate storage cases 38 and 48. Wiring of the power circuit, which is the test lines 15a to 15c, must be done for each of the circuit current detector 16 and the zero-sequence current detector 18, which requires a large installation space and has the disadvantage of increasing wiring cost. It was hot.

The present invention has been devised in view of the above-mentioned conventional problems, and its purpose is to provide a current detector that is compact and allows easy wiring of the line to be tested.

In order to achieve the above object, the present invention includes a storage case having three through holes through which one three-phase test line passes through each line, and a case in which one different through hole passes through the core opening. comprising three first current transformers housed in a storage case and one second current transformer housed in the storage case so that three through holes pass through the core opening, Said 3
The present invention is characterized in that two first current transformers and one second current transformer are integrated and housed adjacently in one storage case.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 5 shows a preferred embodiment of the current detector according to the present invention, and in the figure, the same parts as those of the conventional example described above are given the same reference numerals and the explanation thereof will be omitted.

A characteristic feature of the present invention is that the circuit current detector 16 and the zero-sequence current detector 18 are housed in one storage case 62, and the through holes 64 to 68 through which each of the lines to be tested 15a to 15c pass are provided on both sides. Detector 16, 18
It was shared by

That is, the storage case 62 used in the current detector of the present invention includes the core openings 20 to 24 of each of the first current transformers 26 to 30 and the core opening of the second current transformer 46 (not shown). Through holes 64 to 68 communicating with
In this one storage case 62, three first current transformers 26 to 30 and one second current transformer 46 are stored adjacent to each other. FIG. 7 shows the external appearance of the current detector, and FIG. 10 shows its cross-sectional structure. As is clear from these figures, each output terminal 34a, 34 of the circuit current detector 16 and zero-phase current detector 18 is provided at the end of the storage case 62.
b, 52a, and 52b are arranged adjacent to each other.

In this way, in this embodiment, the circuit current detector 16 and the zero-sequence current detector 18 are housed in one storage case 62, so unlike the conventional device, two storage cases 38 and 48 are used. It can be made more compact than if they were installed separately.

In addition, the storage case 62 of this embodiment includes each first
The core openings 20 to 24 of the current transformers 26 to 30 and the second
Three through holes 64 to 68 are provided that communicate with the core opening of the current transformer 46, and these through holes 64 to 6
8 is shared by both detectors 16 and 18, so
Each test line 15a to 15c is inserted into each through hole 64 to 68.
It is only necessary to pass through the test lines 15a to 15c once.
Wiring can be done easily.

Furthermore, in this embodiment, the output terminals 34a and 34a of each detector 16 and 18 are provided at the end of the storage case 62, respectively.
Since 34b, 52a, and 52b are taken out separately, there is no need for a special protection relay, and the conventional protection relays 54 and 56 can be used as they are.

As explained above, according to the present invention, three first current transformers and one second current transformer are housed in one storage case, and the through-hole through which each test line passes is set as the first current transformer. By sharing the 1st current transformer and the 2nd current transformer,
It is compact and allows easy wiring of the line to be tested.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional current detector, Fig. 2 is a detailed circuit diagram of the circuit current detector shown in Fig. 1, and Fig. 3 is a circuit diagram of the circuit current detector shown in Fig. 1. Fig. 4 is an external view of a storage case containing the zero-sequence current detector shown in Fig. 1, and Fig. 5 shows a preferred embodiment of the current detector according to the present invention. Circuit configuration diagram shown, No. 6
The figure is a detailed circuit configuration diagram of the current detector shown in Figure 5, Figure 7 is an external view showing the storage case of the current detector according to the present invention, and Figure 8 is the circuit current detection circuit shown in Figure 3. 9 is a horizontal sectional view of the zero-phase current detector shown in FIG. 4, and FIG. 10 is a horizontal sectional view of the current detector according to the present invention shown in FIG. 7. In each figure, the same parts are denoted by the same reference numerals.
is a motor, 15a to 15c are test lines, 16 is a circuit current detector, 18 is a zero-phase current detector, 20 to 2
4 is the core opening, 26 to 30 are the first current transformers, 46
is a second current transformer, 62 is a storage case, and 64 to 68 are through holes.

Claims (1)

[Scope of Claim for Utility Model Registration] A storage case having three through holes through which three-phase expanded lines pass through, one through each, and a storage case in which one different through hole passes through the core opening. three first current transformers housed in the core opening; and one second current transformer housed in the storage case so that the three through holes pass through the core opening. A current detector characterized in that a first current transformer and a second current transformer are integrated and housed adjacently in one storage case.