JP2004129477A - Load limiting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a load limiting device that can easily achieve necessary and sufficient reliability in operation despite the simplest circuit structure, by detecting a load current at the side of first load terminals to which a higher priority load is connected, among the first and second load terminals, and by controlling the switching of the switching element at the side of the second load terminals. <P>SOLUTION: This load limiting device is provided with a current detector CT1 that detects a load current I1 at the side of first load terminals U1, W1, a switching element SS that is inserted into the side of the second load terminals U2, W2, and a control circuit 20. This control circuit 20 interrupts the switching element SS when the high-priority load at the side of the first load terminals U1, W1 is used so that the use of a low-priority load at the side of the second load terminals U2, W2 is prohibited forcibly. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a load limiting device that can automatically cut off low-priority loads when loads having different priorities are used simultaneously in electrical wiring in a general home or the like.
[0002]
[Prior art]
Priorities are set for appliances connected to the electrical wiring of ordinary households, and when high-priority loads are used, low-priority loads are automatically cut off, the contract current with the power company is reduced, and the basic power rate Has been proposed (Japanese Patent Application Laid-Open No. 11-341707).
[0003]
In this device, a load is connected to each outlet of the electric wiring via a parent device or a child device, and when the parent device detects a load current of a specified value or more, it sends a signal to the child device via the electric wiring, The control relay built into the slave unit is opened to automatically cut off low priority loads. The parent device and the child device can arbitrarily determine a paired combination by setting a specific address code.
[0004]
[Problems to be solved by the invention]
According to such a conventional technique, the parent device and the child device need to communicate with each other via a signal to be superimposed on the electric wiring by using a preset address code, and the circuit configuration becomes complicated and expensive. In addition, there is an unavoidable problem that a signal to be superimposed on the electric wiring leaks to the outside and there is a possibility that the slave unit may malfunction unexpectedly due to, for example, a signal from the parent unit of the neighbor.
[0005]
Therefore, an object of the present invention is to solve the above-described problem of the prior art, and to detect a load current on a first load terminal side of a first load terminal to which a high-priority load is connected. It is an object of the present invention to provide a load limiting device capable of easily realizing necessary and sufficient operation reliability while having the simplest circuit configuration by controlling switching of the switching element on the load terminal side.
[0006]
[Means for Solving the Problems]
In order to achieve this object, the configuration of the present invention comprises a first and a second load terminals branched from a common power supply input terminal, a current detector for detecting a load current on the first load terminal side, And a control circuit for shutting off the switching element when the load current on the first load terminal side is greater than a specified value. The first and second load terminals include: The gist is to connect high-priority and low-priority loads, respectively.
[0007]
In addition, a current detector for detecting a load current on the second load terminal side is provided, and the control circuit shuts off the switching element on condition that the load current on the second load terminal side is larger than a specified value. Can be.
[0008]
Further, the control circuit can make the switching element conductive when the load current on the first load terminal side is equal to or less than a specified value, and can control opening and closing of the switching element via a time delay element.
[0009]
Further, a manual switch for inhibiting conduction of the switching element may be added to the control circuit.
[0010]
[Action]
According to the configuration of the present invention, the high-priority load and the low-priority load are connected to the first and second load terminals, respectively. Therefore, the current detector detects the load current on the first load terminal side, that is, the load current of the high priority load, and when the current is larger than the specified value, the control circuit determines that the switching on the second load terminal side. The low priority load can be automatically stopped by shutting down the element. The high-priority load and the low-priority load connected to the first and second load terminals are respectively the former, for example, an induction heating cooker, and the latter, for example, a regenerative electric heater or an electric water heater. Is preferred. Both are high-power-consumption appliances, the former being much shorter in use time than the latter, and the latter being temporarily suspended due to the former's use. This is because there is no possibility of causing any particular trouble.
[0011]
If a current detector for detecting a load current on the second load terminal side is provided, the control circuit may provide the first load terminal side with a condition that the load current on the second load terminal side is larger than a specified value. When the load current of the second load terminal is lower than the specified value, the switching element can be cut off. For example, when the low-priority load on the second load terminal side is an electric water heater, a more rational load limiting operation is realized. be able to. That is, when the heater for water heater of the electric water heater is not energized and only a small load current consumed by the control device for standby is flowing to the second load terminal side, the first load terminal side This is because it is not always necessary to stop the electric water heater on the second load terminal side just because the load current has become larger than the specified value.
[0012]
When the load current on the first load terminal side is equal to or less than a specified value, the control circuit automatically turns on the switching element, thereby automatically stopping the low-priority load using the high-priority load. Can be automatically restored by stopping the high-priority load, and does not require any special manual return operation for reuse. In addition, the control circuit controls the switching element via the time delay element, thereby preventing malfunction due to noise or the like and improving operation reliability. In addition, the time limit of the time delay element should be about 0.1 second or more and several seconds or less, taking into account the operating time of the main breaker that regulates the contract current with the power company and the branch breaker in each distribution board. It is preferable to set.
[0013]
The control circuit can set the use of the low-priority load to be prohibited by adding a manual switch. When a seasonally limited appliance such as an electric heater is a low-priority load, useless conduction operation of the switching element can be avoided, so that the magnet contactor mechanically operates as the switching element. This is particularly effective when adopting such a method.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
[0015]
The load limiting device 10 includes a first load terminal U1, W1, a second load terminal U2, W2 branched from a common power supply input terminal R, T, and a current detector on the first load terminal U1, W1 side ( Current transformer) CT1, a switching element SS inserted on the side of the second load terminals U2, W2, and a control circuit 20 (FIG. 1). The load limiting device 10 is provided with ground terminals E and ET.
[0016]
The output of the current detector CT1 is guided to the control circuit 20, and is terminated in the control circuit 20 via a grounded resistor R1. The non-ground side of the resistor R1 is input to the comparator 21 as a DC voltage V1 via a rectifying diode D and a resistor R2, and the resistor R3 having one end grounded and the capacitor C connected to the comparator 21 side of the resistor R2. , A zener diode ZD are connected in parallel. The resistors R2 and R3 are voltage-dividing resistors, and the capacitor C and the Zener diode ZD are for smoothing and limiting the DC voltage V1, respectively. However, a series of circuits from the resistor R1 to the Zener diode ZD forms the current detection circuit 23. Further, the specified voltage Vo1 with respect to the DC voltage V1 is also input to the comparator 21.
[0017]
The output of the comparator 21 is connected to the base of a common emitter Q transistor for output via a time delay element 22 using, for example, an integrating circuit. The collector of the transistor Q is connected to the gate of the switching element SS, and the switching element SS is supplied with a gate control voltage Vc.
[0018]
A power supply circuit 31 for the control circuit 20 is incorporated in the load limiting device 10. The power supply circuit 31 can input an AC voltage branched from the power supply input terminals R and T, and supply the control voltage Vc for the control circuit 20 and the gate of the switching element SS.
[0019]
The current detector CT1 is mounted on one of the first load terminals U1 and W1. The switching element SS is inserted in series with one of the second load terminals U2 and W2.
[0020]
The load limiting device 10 connects the power input terminals R and T to the secondary sides of breakers Bn (n = 1, 2,... N) for arbitrary branches in the distribution board DB for each house (FIG. 2). The first load terminals U1 and W1 are connected to a high-priority load L1 and the second load terminals U2 and W2 are connected to a low-priority load L2. Each of the distribution boards DB includes a main breaker BK that regulates a contract current with a power company, and a plurality of branch breakers B1, B2,... Bn that branch the secondary side of the main breaker BK into a plurality of wiring systems. And a single-phase three-wire 200V power supply from an external distribution line is supplied to the primary side of the main breaker BK. However, in FIG. 2, the system of the breakers B1 and B2 is a single-phase 100V system, and the system of the breakers B3 and Bn is a single-phase 200V system. The housings (not shown) of the loads L1 and L2 are grounded via the ground terminals E and ET of the load limiting device 10, respectively.
[0021]
The current detector CT1 detects the load current I1 of the load L1 on the first load terminals U1 and W1 side. Then, the comparator 21 of the control circuit 20 inputs the DC voltage V1 corresponding to the load current I1, and cuts off the switching element SS via the time delay element 22 and the transistor Q when DC voltage V1> Vo1. Further, the comparator 21 turns on the switching element SS when the DC voltage V1 ≦ Vo1. Note that the specified voltage Vo1> 0 is appropriately set in advance in order to detect the load current I1 due to the use of the load L1.
[0022]
Therefore, when the load L1 on the first load terminals U1 and W1 side is not used, the control circuit 20 continuously conducts the switching element SS. At this time, the load on the second load terminals U2 and W2 side is used. L2 can be used arbitrarily and stopped. That is, the low-priority load L2 can be used arbitrarily, provided that the high-priority load L1 is not used.
[0023]
On the other hand, when the load L1 is used, the control circuit 20 detects the DC voltage V1> Vo1 and shuts off the switching element SS. That is, when the load L1 having the higher priority is used, the control circuit 20 detects that the load current I1 is larger than the specified value Io1 corresponding to the specified voltage Vo1, and the time corresponding to the time limit of the time delay element 22 elapses. Later, the switching element SS can be shut off, and the use of the low-priority load L2 can be forcibly prohibited.
[0024]
When the use of the high-priority load L1 is stopped, the load current becomes I1 = 0. Therefore, the comparator 21 detects the DC voltage V1 = 0 <Vol, turns on the switching element SS, and automatically returns to normal. Enable low priority load L2. That is, the control circuit 20 can control the opening and closing of the switching element SS via the time delay element 22 based on the presence or absence of the load current I1 detected by the current detector CT.
[0025]
Therefore, assuming that the load currents I1 and I2 of the loads L1 and L2 and the rated current Ibn of the breaker Bn are, the breaker Bn has a load L1 such that I1 + I2> Ibn as long as I1 <Ibn and I2 <Ibn. , L2 are commonly connected to the secondary side, there is no risk of tripping due to overcurrent. Similarly, even if I1 + I2> Ibk with respect to the rated current Ibk of the main breaker BK, if I1 <Ibk and I2 <Ibk, there is no possibility that the main breaker BK will trip due to an overcurrent. That is, the load limiting device 10 can use the loads L1 and L2 of the load current I1 + I2> Ibk exceeding the contract current with the power company defined by the rated current Ibk of the main breaker BK without any trouble. However, the time limit of the time delay element 22 in the control circuit 20 is set so as not to exceed the operation time of the breaker Bn and the main breaker BK at the load current I1 + I2.
[0026]
The switching element SS may be a semiconductor switching element such as a thyristor or a GTO, or a mechanical switch such as a magnet contactor. In addition, the switching element SS may open and close both lines of the second load terminals U2 and W2 at the same time.
[0027]
[Other embodiments]
A current detector (current transformer) CT2 for detecting the load current I2 on the second load terminals U2 and W2 may be added (FIG. 3). In FIG. 3, the power supply circuit 31 and the ground terminals ET, ET are not shown.
[0028]
At this time, the control circuit 20 includes current detectors 23, 23 corresponding to the first load terminals U1, W1 side current detector CT1, the second load terminals U2, W2 side current detector CT2, a comparator, respectively. The outputs of the respective comparators 21 having the reference voltages Vo1 and Vo2 are connected to the time delay element 22 via the gate circuit 24. A control voltage Vc is supplied to the collector of the output transistor Q via a manual switch SW and an auxiliary relay X. On the other hand, a magnet contactor RY is connected between the power input terminals R and T via a fuse F and a normally open contact Xa of the auxiliary relay X, and the switching element SS is connected to the second load terminals U2 and W2. It is a contact point of the magnet contactor RY that intermits both lines.
[0029]
The comparator 21 on the side of the current detector CT1 generates an output when the DC voltage V1> Vo1, that is, when the load current I1> Io1 on the first load terminals U1 and W1, and the comparator 21 on the side of the current detector CT2. The unit 21 generates an output when the DC voltage V2> Vo2, that is, when the load current I2> Io2 on the second load terminals U2 and W2 side. Here, V1 and V2 are DC voltages from the current detection circuits 23 and 23 on the current detectors CT1 and CT2 side, respectively, and Io1 and Io2 are specified values of the load currents I1 and I2, respectively.
[0030]
On the other hand, the gate circuit 24 uses the respective outputs of the comparators 21 and 21 to turn on and turn off the transistor Q via the time delay element 22 according to the logic table of FIG. When the transistor Q is turned on, the auxiliary relay X operates and the magnet contactor RY is turned on as long as the manual switch SW is turned on. That is, the control circuit 20 cuts off the switching element SS when the first load terminals U1 and the load current I1 on the W1 side are greater than Io1, provided that the second load terminals U2 and W2 have a load current I2> Io2. Can be. However, even if the switching element SS is cut off and I2 ≦ Io2, the switching element SS is assumed to maintain the cutoff state unless I1 ≦ Io1 (ON (OFF) display in FIG. 4). The specified value Io2 of the load current I2 is set to an appropriate value sufficiently smaller than the rated current of the low-priority load L2 connected to the second load terminals U2 and W2. Further, by opening the manual switch SW, the operation of the auxiliary relay X and the magnet contactor RY can be prohibited, and the conduction of the switching element SS can be prohibited regardless of the output of the gate circuit 24.
[0031]
In the above description, each of the control circuits 20 in FIGS. 1 and 3 may realize the operations of the comparator 21, the gate circuit 24, and the time delay element 22 by software in a microcomputer.
[0032]
【The invention's effect】
As described above, according to the present invention, when the load current on the first load terminal side detected by the current detector is larger than a specified value, the control circuit that shuts off the switching element on the second load terminal side is provided. The control circuit thereby inhibits the use of the low-priority load on the second load terminal side by using the high-priority load on the first load terminal side without superimposing a signal on the electric wiring. Therefore, there is an excellent effect that the intended purpose can be achieved even with the simplest circuit configuration, and necessary and sufficient operation reliability can be easily realized.
[Brief description of the drawings]
FIG. 1 is an overall configuration block diagram. FIG. 2 is a diagram illustrating a use state. FIG. 3 is a diagram corresponding to FIG. 1 showing another embodiment. FIG. 4 is an operation logic table of a gate circuit.
R, T: power input terminals U1, W1: first load terminals U2, W2: second load terminals CT1, CT2: current detector SS: switching elements L1, L2: loads I1, I2: load currents Io1, Io2 ... Specified value 10 ... Load limiter 20 ... Control circuit 22 ... Time delay element

Claims (5)

First and second load terminals branched from a common power supply input terminal, a current detector for detecting a load current on the first load terminal side, and a switching element inserted on the second load terminal side; A control circuit for shutting off the switching element when the load current on the first load terminal side is greater than a specified value, wherein the first and second load terminals have a high priority and a low priority, respectively. A load limiting device for connecting a load. A current detector for detecting a load current on the second load terminal side, wherein the control circuit cuts off the switching element on condition that the load current on the second load terminal side is larger than a specified value. The load limiting device according to claim 1, wherein: 3. The load limiting device according to claim 1, wherein the control circuit turns on the switching element when a load current on the first load terminal side is equal to or less than a specified value. 4. The load limiting device according to any one of claims 1 to 3, wherein the control circuit controls opening and closing of the switching element via a time delay element. 5. The load limiting device according to claim 1, wherein a manual switch for inhibiting conduction of the switching element is added to the control circuit.

Images