JPS6056377B2 - Multifunctional automatic current limiter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides for, in a premises power distribution circuit under a contract with an electric power company, when electrical equipment is operated exceeding the contracted current, the power distribution circuit is not completely disconnected; Provides a new current limiting device related to a multifunctional current limiting device that automatically shuts off electrical equipment with large thermal inertia, such as electric motors, while allowing other electrical equipment to continue operating. It is intended to.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
In Figure 1, 10 is a feeder line shown in a single line diagram, 1
1 is the main/breaker, such as an air shield or disconnector, 12~
16 is a branch breaker for branching and distributing power to each load; 20
is a first or ordinal first automatic current limiting circuit; 30 is a second or ordinal second automatic current limiting circuit;

The first automatic current limiting circuit 20 includes a current transformer 21 inserted into the bus of the power supply line 10, and rectifies the secondary output of this current transformer to convert it into a DC voltage, as indicated by a dotted line frame. After the conversion, a setting section 22 for setting the voltage corresponding to the contract current using the variable resistor 22-1 to set the limit current detection value of the first automatic current limit circuit 20; A comparison unit 23 compares the current (contract current) and the load current of the electrical equipment, and compares the load current and the return current, and a comparison unit 23 that compares the electrical equipment with the load current (contract current) and the return current, and a comparison unit that stops the electrical equipment due to overload operation, that is, the load current is larger than the contract current. A return current setting section 24 sets the magnitude of the return current at which operation should be resumed after the operation is stopped based on the comparison result of the comparison section 23, and a return current setting section 24 starts measuring the fixed saw time based on the comparison result of the comparison section 23. a timer unit 25 that prevents a device that has stopped due to overload operation from restarting for a certain period of time by retaining the comparison result of the unit 23;
An output section 26 that amplifies the comparison result of the comparison section 23, an electromagnetic contactor 27 having a normally closed contact 27'' that is driven to open and close by the output section 26, and a comparison section 33 of the second automatic current limiting circuit 30. It also includes a simultaneous return prevention circuit 28 that controls the operation of the comparator 23 based on the comparison result.

Similarly, the second automatic current limiting circuit 30 includes a current transformer 31;
A setting section 32 having a variable resistor 32-1 and a comparison section 33
, a return current setting section 34, a timer section 35, an output section 36, and an electromagnetic contactor 37 having a normally closed contact 37'',
It is composed of a simultaneous return prevention circuit 38.

Note that the comparison section 33 (comparison section for other automatic current limit circuits other than the first automatic current limit circuit) is the comparison section 23 (comparison section for automatic current limit circuits with smaller ordinal numbers among the automatic current limit circuits with previous or subsequent ordinal numbers). ) is the contract current and the comparison result is that the load current 1T is larger than the contract current (IT>Ip), the comparison operation becomes possible. The present invention thus constructed operates temporally as shown in FIG.

That is, in FIG. 3, first of all, the load current of the electrical equipment,
In other words, if the load current 1, as seen from the power company side, is smaller than the contract current 1p, the comparator 23 determines whether the load current 1T is the trigger!
Since it is determined that the current is less than approximately 1 p, the timer section 25
does not start the timing operation, and the output section 26 does not start the timing operation, and the output section 26
The normally closed contact 27'' of No. 7 is kept closed. Second, to explain the case where the load current 1T becomes larger than the contract current 1p, the comparator 23 detects that the load current 1, is larger than the contract current h. Since the determination is made, the timer section 25 starts timing, and the output section 26 turns off the electromagnetic contactor 27.

Furthermore, the comparator 33 of the second automatic current limiting circuit 30 is in a state where it can perform a comparison operation between the load current 1T and the contract current 1p. When the timer unit 25 starts measuring time, the load current is 1T until the timer unit 25 finishes measuring the predetermined time.
The comparison result of the comparator 23 that is larger than the contract current 1p is held. In addition, the normally open contact 27 of the electromagnetic contactor 27
'' opens, power supply to the load 1 is stopped, and the load current 1T becomes smaller than the contract current 1p.

After the timer unit 25 completes one time measurement, the comparison unit 23 compares the load current 1T and the recovery current 1R1 set by the recovery current setting unit 24, and when the load current 1T is smaller than the recovery current 1R1, it is reset and reset again. Compare the load current of 1T and the contract current. By resetting the comparator 23, the electromagnetic contactor 27 is closed, and power supply to the load 1 is restarted. Thirdly, in the second case, the case where the load current 1T increases due to an increase in the usage load and becomes larger than the contract current 1p will be explained.

In this case, the comparison section 33 of the second automatic current limiting circuit 30 determines that the load current IT is larger than the contract current 1p, so the timer section 35 starts timing, and the output section 36 outputs the normally closed signal of the magnetic contactor 37. Open contact 37″. Said normally closed contact 2
The load current 1T becomes smaller than the contract current 1p due to the stoppage of power supply to the load 11 due to the opening of the contact 7'' and the stoppage of power supply to the load 2 due to the opening of the normally closed contact 37''.

At this time, even when the timer section 25 finishes counting, the comparison result of the comparison section 33 that the load current 1T is larger than the contract current is held, and based on the comparison result, the simultaneous return prevention circuit 28 (Nth The comparison section 33 (comparison section of the automatic current limiting circuit with the larger ordinal number among the automatic current limiting circuits with the preceding ordinal numbers) is loaded more than the contract current 1p. Since the comparison result shows that the current ■T is large (IT>■p), the comparing operation of the load current 1 and the recovery current 1R1 of the comparator 23 is stopped. When the timer section 35 starts counting when the load current 1T becomes larger than the contract current, the comparator section 33 compares the load current 1T with the set current 1R2 of the recovery current setting section 34, and calculates the load current IT.
When the current is smaller than the return current R2, it is reset, and the load current 1T and the contract current 1p are compared again.

By resetting the comparator 33, the simultaneous recovery prevention circuit 28 is reset after a certain period of time, so the comparator 23 releases the stop of the comparison operation and compares the load current 1T and the recovery current 1R1, and the load current 1 is recovered. When the current is smaller than 1R1, it is reset and the load current 1 and the contract current 1p are compared again. Incidentally, by increasing the number of automatic current limiting circuits 20 and 30 to two or more circuits, expanding and expanding each of these circuits from FIG. You can.

For example, if there are three automatic current limiting circuits, the simultaneous return prevention circuit 38 of the automatic current limiting circuit 30 will operate based on the comparison result of the comparison section of the third automatic current limiting circuit. Therefore, when the comparison section of the third automatic current limiting circuit outputs a comparison result that the load current 1T is larger than the contract current 1p (IT>), the simultaneous recovery prevention circuit 38 reduces the load current I
The comparator 33 is locked so as not to perform a comparison operation between T and the return current 1R2. That is, the operation of the simultaneous return prevention circuit 28 of the first automatic current limiting circuit 20 is controlled by the comparator 33 of the second automatic current limiting circuit 30, and the simultaneous return preventing circuit 38 of the second automatic current limiting circuit 30 is controlled. is operated by the comparison section of the third automatic current limiting circuit, and the first automatic current limiting circuit 20 and the second automatic current limiting circuit 30 are each controlled by the second automatic current limiting circuit 30. Unless the third automatic current limiting circuit and the third automatic current limiting circuit reconnect the power supply to the respective loads, the power supply to the corresponding loads will not be reconnected. Another embodiment of the invention is given in FIG.

Note that in FIG. 2, parts that perform the same functions as those in FIG. 1 are designated by the same reference numerals, and their explanations are omitted.
In this embodiment, the first automatic current limiting circuit 2 in FIG.
The current transformer 21 and the setting section 22 that partially constitute the second automatic current limiting circuit 30 are used in common, respectively. By connecting the wiring so that the voltage generated by the automatic current limiting circuit is applied to each comparator section of each automatic current limiting circuit interconnected in a cascade, the sequential starting operation similar to that described above is performed.

As described above, according to the present invention, when the load current of the power distribution circuit becomes equal to or higher than the contract current, one of the plurality of electric devices connected to this circuit, for example, one having a large thermal inertia is automatically selected as appropriate. After stopping the operation and after a certain period of time, the load current and the return current are compared, and if the load current is smaller than the return current, the load current is constantly maintained by guiding the stopped equipment to the operating state again. It is possible to monitor and control the current below the contracted current, and there is no need to operate the main switch or disconnector that is normally inserted at the lead-in side of the power distribution circuit, which has the effect of reducing power outage accidents in the power distribution circuit as a whole. .

In addition, by sequential operation of first entry and last cut for two or more loads, it is possible to stop only the operation of the minimum load.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, which is a block diagram of a multifunctional automatic current limiting device consisting of two automatic current limiting circuits;
The figure is a block diagram showing another embodiment of the present invention,
FIG. 3 shows an operation timing diagram of the operating state of the present invention, which is plotted using the current used by the power distribution circuit as a parameter. 21, 31 are current transformers, 22, 32 are setting parts, 23, 33
24 and 34 are comparison parts, 24 and 34 are return current setting parts, 25 and 35 are timer parts, 26 and 36 are output parts, 27 and 37 are electromagnetic contactors, and 28 and 37 are simultaneous/return prevention circuits.

Claims (1)

[Claims] 1 Comparison of the load current I_T of the power distribution circuit with a preset contract current I_P and the comparison of the load current I_T and the return current I
A comparison section that performs a comparison with R and a comparison result of the comparison section that the load current I_T is larger than the contract current I_P start measuring a predetermined time, and during the time measurement, the comparison result is held in the comparison section. an electromagnetic contactor whose normally closed contact opens according to the comparison result; and an electromagnetic contactor whose normally closed contact opens according to the comparison result;
comprising first to N-th (N is an integer of 2 or more) automatic current limiting circuits each configured of a return current setting section that sets R, and a simultaneous return prevention circuit that controls the comparison operation of the comparison section; The first to Nth automatic current limiting circuits each have a first to Nth automatic current limiting circuit that is supplied with power via the electromagnetic contactor.
loads of the automatic current limiting circuits other than the first automatic current limiting circuit are connected; The load current I_ from the contract current I_P
When the comparison result that T is large (I_T>I_P) is obtained, the comparison operation becomes possible; When the comparing section of the automatic current limiting circuit with a larger ordinal number among the automatic current limiting circuits outputs a comparison result that the load current I_T is larger than the contract current I_P (I_T>I_P), the simultaneous recovery prevention circuit performs a comparison operation. At the same time, the comparison unit of the automatic current limiting circuit with the larger ordinal number among the automatic current limiting circuits with the preceding ordinal numbers determines that the return current IR is larger than the load current I_T (IR>I_T ), the multifunctional automatic current limiting device is characterized in that the simultaneous return prevention circuit is wired so as to release the stoppage of the comparison operation of the comparison section that controls the comparison operation. .