JP2015103388A - Load control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load control device capable of appropriately controlling an opening/closing state of an electromagnetic relay even in a situation that an operation switch is installed at a distant position.SOLUTION: A load control device 1 comprises: an electromagnetic relay 5 opening/closing an energization path to a motor 4; an operation switch 9 opening/closing an energization path to a coil 5b of the electromagnetic relay 5; a voltage detection circuit 12 detecting a power supply voltage (V1) of a bus 3 (a power line 3a) and a terminal voltage (V2) of the coil 5b; a capacitor switch circuit 14 in which a series circuit of a capacitor C and a switch SW is provided in parallel to the coil 5b; and a control circuit 10 (control means and determination means) determining whether or not a power supply voltage becomes lower than a reference voltage and whether or not the terminal voltage becomes lower than a release voltage of the coil 5b, and when the power supply voltage is lower than the reference voltage and the terminal voltage is not lower than the release voltage, performing control so as to turn on the capacitor switch circuit 14.

Description

  Embodiments described herein relate generally to a load control device having a function of supplying / cutting off power to a load.

  2. Description of the Related Art Conventionally, there is known a load control device including an electromagnetic relay that supplies and cuts off electric power to a load such as a motor. In such a load control device, a plurality of units are generally housed in a closed switchboard so as to be called a control center. On the other hand, as shown in Patent Document 1, for example, an operation operated by an operator The switch may be installed at a position away from the control center.

JP 2000-152488 A

However, if the operation switch is installed at a distant position, if the operation switch is a switch for controlling the open / close state of the electromagnetic relay, for example, due to the stray capacitance generated between the cables connecting between them, the switching operation is performed. Doing so may make it impossible to control the open / close state of the electromagnetic relay.
The problem to be solved by the present invention is to provide a load control device capable of appropriately controlling the open / close state of an electromagnetic relay even when the operation switch is installed at a separated position.

  According to the embodiment, the load control device is provided between the bus and the load, and switches between the electromagnetic relay that switches the energization path to the load to a closed state or an open state, and between the bus and the coil of the electromagnetic relay. An operation switch for switching an energization path to the coil to a closed state or an open state, a power supply voltage that is a voltage of the bus, and a terminal that is a voltage input to the coil at a subsequent stage of the operation switch A voltage detection means for detecting a voltage, a capacitor switch circuit provided in parallel with the coil, and having a series circuit composed of a capacitor and a switch connected in series to the capacitor, and a reference for which the power supply voltage is predetermined Determining means for determining whether or not the voltage has fallen below, and whether or not the terminal voltage has fallen below the release voltage of the coil; When the terminal voltage with the power voltage is determined to lower than the reference voltage it is determined to not lower than the released condition by the determining means, and a control means for performing control to turn on the capacitor switch circuit.

The figure which shows typically the electric constitution of the load control apparatus of one Embodiment. The figure which shows typically the flow of the control processing by the load control apparatus of one Embodiment.

Hereinafter, an embodiment will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, in the load control apparatus 1 of this embodiment, the unit main body 2 stored in a closed switchboard (not shown) used as a control center is connected to a bus 3 (for example, R, S, T in FIG. 1). (Three phases) is receiving power supply. The load control device 1 controls the supply, interruption, protection, monitoring, and the like of power to each load (motor 4). The load control device 1 is provided between the bus 3 and the motor 4 and energizes the motor 4. An electromagnetic relay 5 that switches the path to a closed state or an open state is provided. Further, a well-known circuit breaker 6 is provided between the bus 3 and the electromagnetic relay 5. Further, a known current detector 7 for detecting a current is provided between the electromagnetic relay 5 and the motor 4. In addition, although illustration is abbreviate | omitted, in order to make the load control apparatus 1 stop the start switch for starting a load between the bus-line 3 (more precisely, the secondary winding side mentioned later) and the coil 5b, and to stop. A stop switch or the like is provided.

  More specifically, the electromagnetic relay 5 is a main circuit contact 5a that physically interrupts the energization path, a coil 5b for driving the main circuit contact 5a, and a self-holding normally open type (NO type). Normally open) auxiliary contact 5c and the like. In the electromagnetic relay 5, when the start switch is turned on and the voltage between the terminals of the coil 5b becomes equal to or higher than a specified value, the main circuit contact 5a is closed and the power supply to the motor 4 is started. On the other hand, in the electromagnetic relay 5, the stop switch is operated and the voltage between the terminals of the coil 5b is a prescribed release voltage corresponding to the coil 5b (voltage when the solenoid valve of the main circuit contact 5a is changed from the excited state to the non-excited state). Is less than, the main circuit contact 5a is opened and the power supply to the motor 4 is stopped. The auxiliary contact 5c closes to form a self-holding circuit when the start switch is turned on, and power is continuously supplied from the bus 3 to the motor 42 even when the start switch is returned to the off state. The electromagnetic relay 5 is further provided with a contact indicating that the coil 5b has been driven, and outputs an answerback signal indicating the open / closed state of the main circuit contact 5a to the unit body 2. .

  The primary winding of the transformer 8 is connected between any two phases on the load side of the circuit breaker 6 for wiring, and the secondary winding side of the transformer 8 (hereinafter, the secondary winding side is referred to for convenience). The coil 5b is connected to the power line 3a) via the operation switch 9. The operation switch 9 includes a normally open type on switch 9a and a normally closed (NC type: normally closed) off switch 9b. The on switch 9a is operated. Thus, the coil 5b is energized, while the turn-off switch 9b is operated to interrupt the energization of the coil 5b. Therefore, by using the operation switch 9 in place of the start switch and stop switch described above, the start operation of the motor 4 can be performed by operating the on / off switch 9a, and the motor 4 can be stopped by operating the off switch 9b. The operation can be performed.

  Specifically, when the on switch 9a is turned on, a voltage is applied to the MC (coil 5b). Accordingly, the main circuit contact 5a is turned on and the auxiliary contact 5c is turned on, whereby a self-holding circuit is formed and the ON state is maintained. On the other hand, when the turn-off switch 9b is turned on, the coil 5b is turned off, the excitation of the coil 5b is lost, and the auxiliary contact 5c is turned off. Thereby, it will be in an OFF state. Since the operation switch 9 is installed at a place where the operator can operate, the operation switch 9 is installed at a position away from the control center where the unit main body 2 is installed. Therefore, the operation switch 9 may be installed in a place where the length of the cable connecting the unit main body 2 is, for example, about several hundred meters.

The secondary winding side of the transformer 8 is also connected to the unit main body 2, and power is supplied to the unit main body 2. The unit body 2 includes a control circuit 10, a storage circuit 11, a voltage detection circuit 12, a drive circuit 13, a capacitor switch circuit 14, a notification circuit 15 and the like in relation to the present embodiment. Although not shown in the figure, a power supply circuit is also provided which generates various DC voltages used in the control circuit 10 and the like by converting the AC power supply from the power supply line 3a into a DC power supply.
The control circuit 10 (control means, determination means) is composed of a microcomputer having a CPU, a ROM, a RAM, and the like (not shown). For example, the entire load control device 1 is based on a computer program stored in the ROM or the like. To control. In the present embodiment, as will be described later, the determination unit and the control unit are realized by software by a computer program executed by the control circuit 10.

The storage circuit 11 is configured by a storage element such as a flash memory, for example, and stores various information for controlling the load control device 1 and information on operating conditions and faults (error occurrence, etc.).
The voltage detection circuit 12 detects a power supply voltage (V1) that is a voltage of the power supply line 3a and a terminal voltage (V2) that is a voltage input to the coil 5b in the subsequent stage of the operation switch 9. The detected voltage value is input to the control circuit 10 as an electrical signal. Since the power supply voltage (V1) and the terminal voltage (V2) are alternating current, the voltage detection circuit 12 can also detect the alternating voltage, and in this embodiment, the effective value of the alternating current power supply is used as each voltage value.

  The drive circuit 13 is a circuit that drives the capacitor switch circuit 14 and controls each switch of the capacitor switch circuit 14. The capacitor switch circuit 14 includes a plurality of capacitors C1 to Cn and a plurality of switches SW1 to SWn connected in series to the capacitors C1 to Cn. More specifically, the switch SW is connected to the power supply line side and the capacitor C is connected to the subsequent stage side. When the switch SW is turned off, the capacitor C does not affect the power supply line. ing. Each capacitor C1 to Cn and each switch SW1 to SWn form a series circuit, and each series circuit is connected in parallel to the coil 5b. For this reason, when the capacitor switch circuit 14 is turned on, that is, when any one of the switches is turned on, the capacitor is connected in parallel to the coil 5b. In this embodiment, the capacitor switch circuit 14 is provided with a plurality of n series circuits, and capacitors of the same capacity are used in each series circuit. In addition, the drive circuit 13 can selectively turn on a plurality of switches, simultaneously turn on, and turn on sequentially. Hereinafter, the number of series circuits is referred to as the number of series circuits (see step S6 in FIG. 2 described later).

  The notification circuit 15 is a circuit that drives notification means for performing some kind of notification to the operator or the like (in the present embodiment, notification of an error). A speaker 17 (notifying means, which may be a buzzer) is connected via a terminal block 18. The notification circuit 15 may be configured to output a drive signal that directly drives the lamp 16 or the speaker 17, but may be configured to output a contact signal, and the user can arbitrarily set the notification means to be connected. Alternatively, the notification circuit 15 itself may be used as a notification means by connecting to another device.

Next, the operation of the load control device 1 will be described.
As described above, when the operation switch 9 is installed at a position away from the unit main body 2, a stray capacitance Cp (see FIG. 1) is generated according to the length of the cable to the operation switch 9. For this reason, even if the off switch 9b of the operation switch 9 is operated, there is a possibility that the terminal voltage of the coil 5b will not fall below the release voltage (or the time until it drops) will be longer due to the stray capacitance Cp. At this time, the allowable amount of stray capacitance Cp varies depending on the voltage and frequency, and also depends on the contact configuration of the electromagnetic relay 5, the release voltage (standard value) of the coil 5b, the impedance of the coil 5b, and the like. It depends heavily.

  Although a general control center is provided with a plurality of load control devices 1, the operation switches 9 are installed in various places, and the cable length to the operation switches 9 in all the load control devices 1 is different. It was extremely rare to be exactly the same. Moreover, since the specifications (for example, the release voltage of the coil 5b) of the electromagnetic relay 5 are different if the load is different, different countermeasures are required for each load control device 1. Therefore, conventionally, when there is a possibility that the stray capacitance Cp may become a problem, individual measures are taken by so-called actual matching.

Therefore, in the load control device 1 having the above-described configuration, the stray capacitance Cp can be automatically handled as follows regardless of the cable length, the specifications of the electromagnetic relay 5, and the like.
The control circuit 10 of the load control device 1 executes the control process shown in FIG. This control process is substantially started after the start switch is operated and the above answerback signal is input (that is, after the motor 4 is started).

  When starting the processing, the load control device 1 first detects and stores the power supply voltage (V1) that is the voltage value of the power supply line 3a, and initializes the variable N to 1 (S1). This variable N is a variable for counting the turn-on order when there are a plurality of series circuits in the capacitor switch circuit 14 as described above. Subsequently, the load control device 1 detects a terminal voltage (V2) that is a voltage value on the input side of the coil 5b (S2), and determines whether or not the terminal voltage is lower than the reference voltage (S3). The reference voltage is a reference value for determining whether the operation switch 9 is turned off. In the present embodiment, it is essential that the voltage fluctuation in the power supply line 3a (bus 3) may be about 15%, and that it is equal to or greater than the release voltage value (varies depending on the specifications of the coil 5b). The reference voltage is set to about 70% of the power supply voltage (V1) corresponding to the voltage of the power supply line 3a. The reference voltage is set at the time when the power supply voltage (V1) is detected in step S1 (that is, the time immediately after the start operation and when it can be determined that the turning operation has not yet been performed).

When the cutting operation is performed, the terminal voltage decreases because the coil 5b is disconnected from the power supply line 3a. That is, in step S3, it is determined whether or not the cutting operation has been performed based on whether or not the terminal voltage <the reference voltage. Therefore, when the terminal voltage <the reference voltage is not satisfied (S3: NO), the load control device 1 proceeds to step S2 and continues to monitor the terminal voltage.
On the other hand, when the terminal voltage is less than the reference voltage (S3: YES), that is, when it is determined that the turning operation has been performed, the load control device 1 determines whether the terminal voltage has fallen below the release voltage. Determine (S4). Note that immediately after the determination in step S3: YES in the control circuit 10, although it depends on the processing speed of the CPU, it may be determined that the terminal voltage is less than the release voltage. A response waiting time of an acceptable level (for example, several tens to several hundreds of milliseconds) may be set.

When the terminal voltage is less than the release voltage (S4: YES), the load control device 1 determines that the main circuit contact 5a has been opened, and if necessary as in the case of step S4: NO described later, the predetermined time is required. Later, the capacitor switch circuit 14 is turned off (S5), and the process is terminated.
On the other hand, when the terminal voltage <the release voltage is not satisfied (S4: NO), the load control device 1 determines that the variable N (N = 1 in the first stage) is the number of series circuits (n in this embodiment). It is determined whether or not a plurality of pieces are exceeded (S6). In step S6, it is determined whether there is a series circuit that can be turned on.

  Since the load control device 1 currently has N = 1, that is, since N> the number of series circuits is not satisfied (S6: NO), the Nth switch of the capacitor switch circuit 14 (this time switch SW1) is turned on. (S8) After incrementing N (S9), the process proceeds to step S4. In this case as well, depending on the processing speed of the CPU, step S4: NO may be determined immediately. Therefore, a predetermined waiting time is provided, or a time that can be determined that the turned on switch is completely turned on ( For example, processing such as waiting for a time until chattering is settled may be performed.

  When the process proceeds to step S4, the load control device 1 determines again whether the terminal voltage is less than the release voltage. If the terminal voltage is not yet less than the release voltage (S4: NO), N> the number of series circuits. It is determined whether or not there is (S6). Since N is equal to 2 this time and N> the number of series circuits is not satisfied (S6: NO), the Nth switch (SW2 this time) is turned on (S8). , N is incremented (S9), and the process proceeds to step S4.

  As described above, when the load control device 1 sequentially turns on the switches of the capacitor switch circuit 14 until the terminal voltage is less than the release voltage and determines that the terminal voltage is less than the release voltage (S4: YES), a predetermined time later The capacitor switch circuit 14 is turned off (S5), and the process ends. As a result, the terminal voltage of the coil 5b can be made lower than the release voltage, and the main circuit contact 5a can be reliably opened (the power supply to the motor 4 is cut off) when the cutting operation is performed. it can.

  By the way, even if all the switches SW constituting the capacitor switch circuit 14 are turned on, there is a possibility that the terminal voltage is not less than the release voltage. Therefore, when the terminal voltage <the release voltage is not satisfied even when all the switches SW are turned on (S4: NO and S6: YES), the load control device 1 is in spite of the turning operation being performed. If the terminal voltage does not fall below the release voltage, an error is reported (S7). At this time, the load control device 1 notifies the error by turning on the lamp 16 or issuing a warning sound or a voice message from the speaker 17. Thereafter, the load control device 1 proceeds to error processing (for example, a processing routine such as emergency stop) if necessary. Instead of directly shifting from the control process shown in FIG. 2 to the error process, the control process may be terminated and the error process may be left to another process routine.

As described above, according to the load control device 1 according to the present embodiment, the following effects can be obtained.
The load control device 1 is a capacitor switch circuit having a series circuit including a voltage detection means for detecting a power supply voltage terminal voltage, a capacitor C, and a switch SW connected in series to the capacitor C in parallel with the coil 5b. 14, whether or not the power supply voltage has fallen below a predetermined reference voltage, and whether or not the terminal voltage has fallen below the release voltage, and the terminal voltage is determined in a state where the power supply voltage has fallen below the reference voltage. A control circuit 10 (determination means, control means) that performs control to turn on the capacitor switch circuit 14 (more precisely, the switch SW provided in each series circuit) when it is determined that the release state is not lower than I have. As a result, even if the operation switch 9 is installed far away, stray capacitance Cp is generated in the cable connecting between them, and the size of the stray capacitance Cp is different in each load control device 1, The open / close state of the electromagnetic relay 5 can be appropriately controlled, such as being able to perform an appropriate cutting operation.

At this time, since it is determined whether or not the switching operation has been performed based on whether or not the terminal voltage has fallen below the reference voltage, another cable or the like is connected between the operation switch 9 and the like in order to notify the switching operation. There is no need to provide additional parts such as.
The capacitor switch circuit 14 is provided with a plurality of series circuits, and the control circuit 10 automatically controls the number of times the series circuit is turned on according to the determination result by the determination means, so one capacitor C is connected to the coil 5b. If the voltage does not drop to the release voltage even when added in parallel, the next capacitor C can be further added in parallel. Thereby, even when the stray capacitances Cp are different, the open / close state of the electromagnetic relay 5 can be controlled.

  If the terminal voltage does not fall below the release voltage even when the capacitor switch circuit 14 is turned on, the notification is made by the notification means such as the lamp 16 and the speaker 17, so that the operator does not open the electromagnetic relay 5. (That is, energization of the motor 4 continues).

(Other embodiments)
The load control device 1 illustrated in the embodiment can be modified or expanded as follows, for example.

Of course, the capacitor switch circuit 14 may have a single series circuit.
When the capacitor switch circuit 14 is configured by a plurality of series circuits, the capacitance of the capacitor C may be different in each series circuit. In one embodiment, since the capacitor C has the same capacity, the switch SW is sequentially turned on. However, when a plurality of capacitors having different capacities are provided, the capacitors C are turned on in order from the largest. Or it is good also as a process which turns on in an order from the thing with a small capacity | capacitance. That is, the order of turning on the series circuit may be automatically controlled. In this case, the switch SW may be turned on at the same time according to the change in the terminal voltage before and after the terminal voltage capacitor C is turned on, and the approximate length of the cable to the operation switch 9 may be set / set in advance. It may be registered and the switch SW of the capacitor C corresponding to the length of the cable may be turned on first.

The capacitor C of the capacitor switch circuit 14 (or each series circuit of the capacitor C and the switch SW) may be detachable, that is, exchangeable.
When the capacitor switch circuit 14 is automatically turned off as in the embodiment, if the terminal voltage does not fall below the release voltage unless a plurality of switches SW are turned on in the capacitor switch circuit 14, the state of each switch SW is changed. Data may be stored in the storage circuit 11 or the like, and the next time the switch is turned on, a plurality of switches SW may be turned on from the beginning based on the data. Thereby, the period until the terminal voltage falls below the release voltage can be further shortened. In this case, it is preferable that the operator can select whether or not the capacitor switch circuit 14 is automatically turned off when the voltage is lower than the release voltage. Alternatively, the capacitor switch circuit 14 may be turned off when the power of the unit body 2 is turned off.

  In one embodiment, the capacitor switch circuit 14 is automatically turned off when the voltage is equal to or lower than the release voltage. However, the capacitor switch circuit 14 may be configured not to be turned off. In actual work sites where the load control device 1 is used, since the cable length and the like are not changed frequently, it is expected that the terminal voltage will not fall below the release voltage in the next time as well. The Therefore, by maintaining the ON state of the capacitor switch circuit 14, it is possible to further shorten the period until the terminal voltage falls below the release voltage when the next switching operation is performed.

  In this case, if the capacitor switch circuit 14 is turned on at the time of starting, since the capacitor C is added in parallel to the coil 5b, the time until the release voltage is exceeded when the start switch is operated may be increased. is there. Therefore, in the control processing, when the voltage is lower than the release voltage, the capacitor switch circuit 14 is turned off, and at the time after the start switch is operated next (for example, when the above answerback signal is received). The capacitor switch circuit 14 may be turned on to prepare for the operation of the off switch 9b. At this time, when there are a plurality of series circuits, the state of the capacitor switch circuit 14 (the ON / OFF state of each switch SW) at the time when the release voltage falls below is stored, and the start switch is operated. Alternatively, the capacitor switch circuit 14 may be turned on so that the state is reached at a later time.

  In one embodiment, the storage circuit 11 is provided in the unit main body 2. However, the unit main body 2 and a higher-level management device (not shown) are connected so as to communicate with each other, and an appropriate capacitor switch is provided on the management device side. The state of the circuit 14 may be stored. At this time, if the unit main body 2 is stored in association with the management information (information such as the installation location), the length of the cable to the operation switch 9 can be obtained even when the unit main body 2 is replaced for repair or the like. If the state is not changed, an appropriate state of the capacitor switch circuit 14 can be read out. Further, the management device may store the length of the cable, or may store the length of the cable in association with the state of the standard capacitor switch circuit 14 corresponding thereto.

  The voltage value detected by the voltage detection circuit 12 may detect the maximum value of the AC power supply. In one embodiment, the reference voltage is about 70% of the power supply voltage. However, the reference voltage may be in a range not affected by the voltage fluctuation of the power supply line 3a. For example, the fluctuation of the power supply line 3a is suppressed to about 5%. If so, it may be set to 80%, for example. The reference voltage may be calculated each time based on the power supply voltage, or a value corresponding to the power supply voltage may be stored in the storage circuit 11 or the like, and the corresponding value may be read out. You may make it acquire from external apparatuses, such as a management apparatus. Of course, the reference voltage is set to be equal to or higher than the release voltage.

An example in which the power supply voltage is detected and stored at the start of the control process is shown. However, the power supply voltage is also monitored, the power supply voltage is not lower than the reference voltage, etc., and the terminal voltage is lower than the reference voltage. This may be a criterion for determining whether or not an operation has been performed. This is because when the power supply voltage itself is lowered, the terminal voltage may have been lowered due to a factor other than the turning-off operation (for example, shutting off the main power supply due to a power failure or the like).
The notification means may be provided on the operation panel of the unit main body 2, but may be installed at a position where the operator who operates the operation switch 9 such as the vicinity of the operation switch 9 (within the same field of view) can grasp the notification. Or you may provide in both the unit main body 2 and the position where an operator can grasp | ascertain alert | report.

Although the motor 4 is exemplified as the load, the load control device 1 of the embodiment may be applied to a load other than the motor 4.
Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

In the drawing,
1 is a load control device, 3 is a bus, 3a is a power supply line 3a, 4 is a motor (load), 5 is an electromagnetic relay, 5a is a main circuit contact, 9 is an operation switch, 10 is a control circuit (control means, determination means) , 12 is a voltage detection circuit (voltage detection means), 14 is a capacitor switch circuit, 15 is a notification circuit (notification means), 16 is a lamp (notification means), 17 is a speaker (notification means), C1 to Cn are capacitors, SW1 SWn is a switch, V1 is a power supply voltage, and V2 is a terminal voltage.

Claims (3)

An electromagnetic relay that is provided between the bus and the load, and switches an energization path to the load to a closed state or an open state;
An operation switch provided between the bus and the coil of the electromagnetic relay, and for switching the energization path to the coil to a closed state or an open state;
A voltage detection means for detecting a power supply voltage which is a voltage of the bus bar and a terminal voltage which is a voltage input to the coil in a subsequent stage of the operation switch;
A capacitor switch circuit provided in parallel with the coil and having a series circuit including a capacitor and a switch connected in series to the capacitor;
Determining means for determining whether or not the power supply voltage is lower than a predetermined reference voltage, and whether or not the terminal voltage is lower than a release voltage of the coil;
Control means for performing control to turn on the capacitor switch circuit when it is determined that the terminal voltage is not lower than the release state in a state where the power supply voltage is determined to be lower than a reference voltage by the determination means;
A load control device comprising: The capacitor switch circuit is provided with a plurality of the series circuits,
The control means automatically controls the number of series circuits to be turned on among the plurality of series circuits and / or the order in which the series circuits are turned on among the plurality of series circuits, according to the determination result by the determination means. The load control device according to claim 1.   3. The system according to claim 1, further comprising notification means for notifying that if the terminal voltage does not fall below the release voltage of the coil even when the capacitor switch circuit is turned on by the control means. Load control device.

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