JP2001333525A - Overload preventing apparatus in commercial power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To learn know beforehand that a load connected to a commercial power source in a factory, etc., is overloading, and to prevent abrupt shutdown of a breaker. SOLUTION: This apparatus is composed of a load current detecting element 6 which detects current being consumed of a three-shape AC power source; a relay control unit 7 which turns an electromagnetic relay on or off according to the current value read from the detecting element 6; a timer control unit 8 which starts the counting of a timer, when the electromagnetic relay is turned on by the relay control unit and an operating signal is outputted, and outputs an operating signal when time set beforehand passes; and a reporting element 9 which issues an alarm, if the operating signal from the timer portion 8 is inputted. Overcurrent by the load 5 is monitored, by connecting the apparatus between a main breaker 3 and a switchboard 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting a three-phase AC commercial motive current distributed from a commercial power supply network between a main breaker (breaker) in a factory or the like and a load, and connecting the main breaker to the main breaker. The present invention relates to a device that issues an alarm before the current consumed by a load device reaches a maximum load current value.
In particular, when the equipment power contract is changed to a breaker contract for the purpose of cost saving and energy saving, the overload current continues due to the operation of various or many power machines installed in various factories etc. Therefore, before the main breaker shuts off, the power machine is efficiently or rationally changed by notifying it in advance,
Used to ensure continuity of work.

[0002]

2. Description of the Related Art Conventionally, there are various types of
Alternatively, regarding the operation of a large number of power machines, the low-voltage power contract between the business operator and the power company covers a load facility contract covering all installed machines and devices, and a breaker capacity. It is powered by one of the other breaker contracts.

[0003] In the case of a breaker contract,
Because it is a contract for breaker capacity, the number of machines and devices installed is irrelevant, and for companies that do not operate various machines and devices at full capacity, or for companies that consider adding mechanical equipment, A breaker contract has a greater merit in reducing power costs than a load equipment contract.

[0004] In particular, in the case of a breaker contract, it is advantageous that even if new mechanical equipment is added to the existing equipment, no special restrictions are imposed as long as the contracted capacity is not exceeded.

[0005] However, since the maximum current is restricted by the breaker, if the machine equipment is fully operated or the current is exceeded due to the operation of the additional machine, the breaker is shut off without any warning. There is an adverse effect.

[0006] For example, in the case of a low-voltage power, 50 ampere forward breaker contract, the breaker cutoff characteristics tend to be as shown in Fig. 5A and Fig. 5B. Among them, FIG. (A) shows the breaking operation time of the breaker with respect to the load current, and FIG. (B) shows the ratio with respect to the load current in%. At this time, although slightly fluctuating depending on the temperature around the machine and the operating machine, the time value of the maximum delay operation is represented by a curve X shown in FIG. It is represented as Y.

Therefore, in FIG. 1B, when the breaker contract capacity of 50 amps is 100% load value,
As shown in FIG. 7A, the minimum delay time is about 1 hour, and the maximum delay time is 4 hours or more. Therefore, as shown in FIG. 2B, the larger the load value Z indicating the percentage of the rated current, the shorter the time required for power interruption in inverse proportion to the load value Z, that is, the shorter the delay operation time. Therefore, the breaker shuts off while the equipment is operating,
The power supply is stopped.

For example, normally, the number of operating machines is four.
When the machine is operating at about 5 to 50 amps and another machine starts operating, and a current of 62.5 amps flows, the power is cut off after a minimum of about 6 minutes and a maximum of about 1 hour. Will be. Therefore, there is a need to prevent an unexpected situation by notifying the minimum delay operation time before reaching the minimum delay operation time and stopping the operation of unnecessary machines.

In this regard, conventionally, in order to avoid the above-mentioned unexpected situation, it is customary to carry out a contract procedure for increasing the contracted capacity of a breaker contract on the other side and an extension work of a main cable or the like.

[0010] However, in many establishments, the rate of increase in the operating rate of the equipment varies, and depending on the establishment, the frequency of the breaker can be as high as one to two or more at most several times per month. In most cases, the contract capacity exceeds the contract capacity.

By the way, in the case of the conventional device, in the shut-off method using the main power breaker at low voltage power, the circuit breaker for wiring itself has an overload or short-circuit protection function, or the motor or the like is continuously overloaded. In most cases, there is no technical idea that focuses on the notification of the maximum load current value of the power supply breaker, and further focuses on it by using it as an external device. Therefore, if the maximum current value during the operation of the equipment machine is known in advance, it is possible to stop some of the operating machines in advance,
Alternatively, if the load during operation can be reduced, this is an effective prevention measure against power interruption.

Therefore, conventionally, the current consumed by the load is constantly monitored, an alarm is issued before the main power supply breaker shuts down, or the load is automatically switched so as not to exceed the maximum load current of the power supply breaker. Products such as overcurrent protection devices have been commercialized and used in large-scale plant factories, general hospitals, and information-related companies that operate a large number of computers.

[0013]

However, these conventional devices are not only expensive but also large in size because the current meter relay is incorporated in the main breaker, and are mainly used for large-scale business establishments. It has become. In addition, since the control system is adapted to the contracted capacity of each breaker, a CT coil and a current-fixed relay
In addition to having to be incorporated in a breaker for each capacity, it has to be inspected by expensive inspection equipment.

Therefore, in the present invention, instead of using the expensive current meter relay in the conventional device, instead of using a current relay of about 0 to 5 amps,
By incorporating a control circuit with a setting (contrast) of about 5 amps for various types of breakers, a small and inexpensive overload alarm device for small businesses was invented.

[0015]

In order to solve the above-mentioned problems, the present invention provides a load current detecting section for detecting a load current and a load current detecting section for detecting the load current. Compares the read current value with a specified current value, and when it is determined that the detected current has reached the specified current, a relay control unit that activates the current relay, and when an operation current is output from the relay control unit, time counting is performed. A timer control unit that outputs an operation signal when it starts and reaches a specified time, and a notification unit that reads and notifies the operation signal output by the timer control unit, and an overload prevention device in a commercial power supply including: It was offered.

In this case, in the second aspect, a CT coil is used as a current transformer element of the load current detector, and a diode element R is provided between the current input circuit and the operation power supply circuit in the relay controller.
An overload prevention device in a commercial power supply according to claim 1, further comprising a switching circuit configured by an L element / transistor element. Accordingly, the above-described problem can be favorably achieved, and the device functions as a device independent of the main breaker, which facilitates retrofitting to the existing main breaker.

According to a third aspect of the present invention, there is provided an overload protection device for a commercial power supply according to the first aspect, wherein the time measured by the timer of the timer control unit can be changed from the outside. As a result, the above-described problem can be suitably achieved, and the operating point of the overload detection can be changed according to the capacity of the load connected to the main breaker.

According to a fourth aspect of the present invention, there is provided an overload prevention device for a commercial power supply according to the first aspect, wherein the notification unit is notified to the outside by a notification buzzer and a notification indicator lamp. As a result, the above-described problem can be suitably achieved, and the warning can be made by both the alarm sound and the display.

According to a fifth aspect of the present invention, the switching circuit of the relay control section includes a variable resistor on the side of the current input circuit so that the operating point of the current relay can be arbitrarily changed. According to a first aspect of the present invention, there is provided an overload prevention device for a commercial power supply. Accordingly, the above-described problem can be suitably achieved, and the operating point of the current relay can be adjusted.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an overload prevention device (hereinafter simply referred to as an overload prevention device) in a commercial power supply according to the present invention will be described below with reference to the drawings. FIG. 1 is a system block diagram in which the overload prevention device 1 of the present embodiment is incorporated in a commercial power supply three-phase AC supply network. Generally, as shown in FIG. 1, a three-phase AC commercial power is supplied to a main breaker 3 of a factory or the like through a service line from a distribution transformer 2 (a pole transformer or the like) distributed from a transmission line. . The three-phase AC supplied to the main breaker 3 is supplied to a plurality of loads 5 (power motors,
Air conditioning system, machine tools, etc.). The overcurrent prevention device 1 of the present embodiment is designed to be attached to this three-phase AC power supply unit.

When the internal structure of the overcurrent prevention device 1 of the present embodiment is systematically divided, the load current detection unit 6 and the load current detection unit 6 detect the consumption current of the three-phase AC flowing from the main breaker 3 to the switchboard. The relay control unit 7 turns on or off the electromagnetic relay according to the current value read from the control unit. When the relay control unit turns on the electromagnetic relay and outputs an operation signal, the timer starts counting, and the timer is set in advance. A timer control unit 8 outputs an operation signal when a certain time elapses, and a notification unit 9 that issues an alarm when an operation signal from the timer control unit 8 is input. In addition,
In addition, a power supply unit for supplying power to each unit and a control panel for sending various commands to each unit are provided. However, since these are generally well-known, their illustration is omitted.

A specific internal structure of the overcurrent prevention device 1 of the present embodiment will be described with reference to the drawings. In the overcurrent prevention device 1 of the present embodiment, as shown in FIG. 2, three power cables 10, 11, and 12 of three-phase AC are wired from a main breaker 3 to a switchboard 4 to which a load 5 is connected. . Among them, the current transformer coil 13 is provided in the power cable 10,
A current transformer coil 14 is attached to the power cable 12. The output of the current transformer coil 13 is connected to an overcurrent relay board 16 having a current relay 15, and the output of the current transformer coil 14 is connected to an overcurrent relay board 18 having a current relay 17. I have.

The outputs of the overcurrent relay boards 16 and 18 are connected to a notification timer 19, respectively, and start timing when the current relays 15 and 17 are turned on. The notification timer 19 has an external setting function, and is capable of arbitrarily adjusting the length of time elapsed from the start of timing to the stop of timing. A timer switch 20 is connected to the notification timer 19, and is turned on when the counting of a preset time is completed. The timer switch 20 has a notification buzzer 2
1 is connected, and an alarm is issued when the timer switch 20 is turned on.

On the other hand, a notification buzzer 21 and a notification indicator lamp 22 are connected to the timer switch 20, and when the timer switch 20 is turned on, the notification buzzer 21 and the notification indicator lamp 22 are operated. In addition, the notification buzzer 21 and the notification indicator lamp 22 are provided with a test switch 23 so that an operation test can be performed. Further, the notification buzzer 21 is provided with a buzzer stop switch 24 and a relay 25 for stopping the alarm of the notification buzzer 21. 26 is a master switch.

The circuit configuration of the overcurrent relay boards 16 and 18 of the overcurrent prevention device 1 of the present embodiment will be described with reference to the drawings. As shown in FIG. 3, the electronic circuits of the overcurrent relay boards 16 and 18 of the present embodiment include terminals K and L to which the output of the current transformer coil 13 (or 14) is connected, a choke transformer CT, and a choke transformer CT. Bridge diode BD1, bridge diode BD1 connected to secondary side
Voltage drop resistor R connected to the output side (DC current) of
1. The current flowing through the resistor R1 is constant (5 in this embodiment).
A), a fixed resistor VR1 for controlling current, a semi-fixed resistor VR2 for adjusting current, a transistor Q1 and a Zener diode ZD.
Control circuit, transistors Q2 and Q3
, A two-stage grounded amplifier circuit, a relay circuit including a switching transistor Q4 and a current relay RY1, a power transformer TR, a bridge diode BD2, a collector resistor R11 for supplying + VCC voltage to the transistor, a rectifying capacitor C6, and an output contact RY of a current relay RY1.
2, bypass capacitors C1, C2, C3, C4, base resistors R3, R4, bypass resistors R5, R6, R7,
R13, collector resistors R8, R9, R12, and diodes D1, D2, D3. Among them, the semi-fixed resistor VR2 for current adjustment is provided to stop the notification at 5% of the maximum current value.

The operation of the overcurrent prevention device 1 according to the present embodiment having the above configuration will be described with reference to the drawings. FIG. 4 is a flowchart showing a process of the overcurrent monitoring process of the overcurrent prevention device 1. First, when the master switch 26 in FIG. 2 is turned on, the overcurrent prevention device starts a monitoring operation, and proceeds to step 100. In step 100, the current values detected from the current transformer coils 13 and 14 are read into the overcurrent relay boards 16 and 18, and the process proceeds to step 110. In step 110, as shown in FIG. 3, after the AC current read into the overcurrent relay boards 16 and 18 is stepped down by the choke transformer CT, the bridge diode BD
It is rectified to DC at 1. The value of the semi-fixed resistor VR2 is determined so that the DC current does not exceed 5 A while the current consumption of the load 5 is at the rated value. At this time, the base of the transistor Q2 has no signal. This allows
The current relay RY1 repeatedly determines whether or not the current value exceeds 5A while maintaining the OFF state. Here, when the current consumed by the load 5 exceeds the rated value, the transistors Q2, Q3, and Q4 are turned on, and it is determined that the detected current has exceeded 5A. In step 130, the current values of the current relays 15, 17 of the overcurrent relay boards 16, 18 are turned on, and the notification timer 19 starts counting time. When the counting of the predetermined time is completed, the process proceeds to step 140, and the timer switch 2
0 turns ON. When the timer switch 20 is turned on, the process proceeds to step 150, and at the same time as the notification buzzer 21 issues an alarm, the process proceeds to step 160 and the notification indicator light 2
2 is turned on. After the process proceeds to step 160, the process proceeds to step 170. At step 170, it is repeatedly determined whether or not the current values detected from the current transformer coils 13 and 14 have decreased by 5% from the maximum current value. The notification indicator lamp 22 is stopped, and this series of processing ends once. When the overcurrent monitoring process is stopped during execution, the buzzer stop switch 24 is pressed to interrupt the process.

As described above, the overcurrent prevention device 1 of the present embodiment can be installed between the main breaker 3 and the switchboard 4 without special modification or large-scale construction as shown in FIG. Thus, the overload of a plurality of loads 5 connected to the switchboard 4 can be monitored.
As a result, it is possible to prevent a sudden shutdown of the main breaker 3 during operation in a factory or the like. Further, the delay time from the overload to the shutdown of the load 5 can be adjusted by the timer control unit 8, so that various types of loads 5 can be operated efficiently. Further, when a value 5% lower than the maximum current value of the overload is detected, the notification is automatically stopped, so that it can be used in a maintenance-free manner especially in a summer where voltage fluctuation is large or in a situation where electric power is poor, which is extremely economically advantageous. .

The present invention is not limited to the above-described embodiments or the embodiments, but can be modified without departing from the technical idea of the present invention. Equivalents and the like are also included in the technical scope of the present invention.

[0029]

According to the present invention, as described in claim 1,
A main breaker that cuts off power distribution to the load when the total load current of the three-phase alternating current supplied from the transmission line of the commercial power supply via the distribution transformer exceeds a set current, and a load connected to the main breaker. A device connected between the load current detection unit for detecting the load current, the current value read by the load current detection unit is compared with a specified current value,
A relay control unit that activates a current relay when it is determined that the detected current has reached a specified current; and a timer that starts timing when an operation current is output from the relay control unit and outputs an operation signal when the specified time is reached. Since the control unit and the notification unit for reading and notifying the operation signal output by the timer control unit are provided, it can be easily attached to a general commercial power supply to easily monitor an overcurrent.

In this regard, in claim 2, a CT coil is used as a current transformer element of the load current detecting section, and the relay control section includes:
Since a switching circuit composed of a diode element, an RL element, and a transistor element is employed between the current input circuit and the operation power supply circuit, an economical device having a simple structure is realized.

According to the third aspect of the present invention, it is possible to cope with various kinds of loads by making it possible to change the set time of the timer from outside.

According to the fourth aspect of the present invention, since the notification is made to the outside by the notification buzzer and the notification display lamp, the notification can be made by both sound and light.

According to a fifth aspect of the present invention, a variable resistor is provided on the current input circuit side of the switching circuit of the relay control section so that the operating point of the current relay can be arbitrarily changed, so that the overcurrent notification release point can be changed. Can now be changed arbitrarily.

[Brief description of the drawings]

FIG. 1 is a system block diagram in which an overload prevention device according to an embodiment of the present invention is incorporated into a commercial power supply three-phase AC supply network.

FIG. 2 is a system diagram showing the internal structure.

FIG. 3 is a circuit diagram showing a circuit configuration of the overcurrent relay board.

FIG. 4 is a flowchart showing an overcurrent monitoring process.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Overcurrent prevention device, 2 ... Distribution transformer, 3 ... Main breaker, 4 ... Distribution board 5 ... Load, 6 ... Load current detection part, 7 ... Relay control part, 8
... Timer control unit 9 ... Notification unit 9, 10, 11, 12 ... Power cable, 1
3, 14 ... current transformer coil 15, 17 ... current relay, 16, 18 ... overcurrent relay board, 19 ... notification timer 20 ... timer switch, 21 ... notification buzzer, 22 ... notification indicator light, 23 ... test switch, 24 ... Buzzer stop switch, 25 ... relay, 26 ... master switch K, L
... Terminal, CT ... Choke transformer, BD1, BD2 ... Bridge diode R1 ... Resistance, VR1 ... Fixed resistance, VR1 ... Semi-fixed resistance Q1, Q2, Q2, Q4 ... Transistor, ZD ... Zener diode RY1 ... Current relay, TR ... Power supply Transformer, R11: Collector resistance, C6: Rectifying capacitor, RY2: Output contact C1, C2, C3, C4: Bypass capacitor, R
3, R4: Base resistance R5, R6, R7, R13: Bypass resistance, R8, R
9, R12: collector resistance D1, D2, D3: diode, VR2: semi-fixed resistance

Claims (5)

[Claims] A main breaker for interrupting power distribution to a load when a full load current of three-phase alternating current supplied from a transmission line of a commercial power supply via a distribution transformer exceeds a set current;
A device connected between a load connected to the main breaker and a load current detection unit for detecting a load current, and comparing a current value read by the load current detection unit with a specified current value to detect the load current. A relay control unit that activates a current relay when it is determined that the current has reached a specified current; and a timer control that starts timekeeping when an operation current is output from the relay control unit and outputs an operation signal when the specified time is reached. An overload prevention device for a commercial power supply, comprising: a notification unit that reads an operation signal output by the timer control unit and notifies the read operation signal. 2. A switching circuit comprising a diode element, an RL element, and a transistor element between a current input circuit and an operation power supply circuit, wherein a CT coil is used as a current transformer element of a load current detector. The overload prevention device for a commercial power supply according to claim 1, further comprising a circuit. 3. The overload protection device for a commercial power supply according to claim 1, wherein the timer control unit is capable of externally changing the setting of the time measured by the timer. 4. The notification unit according to claim 1, wherein a notification buzzer and a notification indicator light notify the outside.
An overload prevention device for a commercial power supply according to the above. 5. The switching circuit of the relay control unit includes:
5. The overload protection device for a commercial power supply according to claim 1, wherein a variable resistor is provided on the current input circuit side so that the operating point of the current relay can be arbitrarily changed.