JPH03150025A - Load controller - Google Patents

Abstract

PURPOSE:To detect chattering in an electromagnetic contactor accurately by producing an alarm signal from a logical operation circuit when a detected time variation rate of main circuit current exceeds a reference current variation rate stored in a memory means. CONSTITUTION:Upon occurrence of chattering in an electromagnetic contact section 5, main circuit current fluctuates considerably at chattering parts thus producing a sawtooth waveform. Consequently, variation rate signal Svf to be outputted from a differentiating circuit 20 increases at the chattering parts. When a reference current variation rate to be stored in a memory circuit 18 is set higher than the variation rate signal Svf at the time of chattering in the electromagnetic contactor 5, a logical operation circuit 11 outputs an alarm signal Sa through an output circuit 21 it a relation, i.e., variation rate signal Svf > reference voltage variation rate, is satisfied upon occurrence of chattering.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides a main circuit in which a main circuit device such as a molded circuit breaker or a magnetic contactor is interposed in the main circuit between a power supply bus and a load. The present invention relates to a load control device comprising:

(Prior Art) As an example of this type of load control device, a control center having a function of controlling and protecting a load such as an electric motor is known. In other words, in the control center, molded circuit breakers and electromagnetic contactors are used.

A display operation panel that stores multiple units in which main circuit devices such as current converters are grouped into unit circuits in multiple stages, and is equipped with a start/stop indicator lamp, a start operation switch, a stop operation switch, etc. for each unit. It is constructed by providing the following. In addition, in recent years, in order to easily deal with changes in unit specifications, by adopting electronic applied technology, configurations have been developed that allow necessary functions to be set, added, and changed among multiple control and protection functions as appropriate. An example of this is shown in FIG. 4.

That is, this figure 4 shows the outline of the circuit configuration for one unit of the control center, and the main circuit 3 between the three-phase power supply bus 1 and the electric motor 2, which is the load, is equipped with main circuit equipment. A molded circuit breaker 4° Magnetic contactor 5. Current converter 6 for main circuit current detection and zero-phase current transformer 7 for ground fault current detection
is provided. The load side of the molded circuit breaker 4 is connected to the primary side of an operating transformer 8, and the secondary side of this transformer 8 is connected to control buses 9a and 9b.

The control unit 10, which is supplied with power from the control buses 9g and 9b via a DC power supply circuit (not shown), is mainly composed of a logic operation circuit 11 composed of a microcomputer. This logic operation circuit 11 includes starting operation switches 12 . It receives each ON signal from the stop operation switch 13 and the normally open auxiliary contact 5a of the electromagnetic contactor 5 via the input circuit 14, and receives each signal from the current converter 6 and zero-phase current transformer 7. The power is received through the A-D conversion circuits 15 and 16, respectively, and the operating coil 5b of the electromagnetic contactor 5 is controlled to be energized or disconnected through the output circuit 17. The storage circuit 18 stores control programs and functional data for executing protective operations such as overcurrent, phase loss, undercurrent, and ground fault, as well as control operations such as instantaneous power failure restart and timed restart. The logic control circuit 11 is
A protection operation and a control operation are executed based on the control program, function data, and input signal. Setting section 19
is comprised of a large number of selection switches (not shown) so that the above functional data stored in the memory circuit 18 can be set and selected as desired at the installation site of the control center.

(Problem to be solved by the invention) By the way, in the above-mentioned control center,
If a chattering phenomenon occurs in the electromagnetic contactor 5, the entire unit including the electromagnetic contactor 5 may malfunction due to welding of the contacts, falling off of the contacts, etc. Therefore, in order to prevent such a malfunction and improve the reliability of the control center, it is necessary to detect the chattering phenomenon of the electromagnetic contactor at an early stage. However, conventionally, there is no device that can detect the chattering phenomenon of an electromagnetic contactor with high reliability, and this point has been an unresolved problem.

The present invention addresses the above-mentioned circumstances and the fact that recent load control devices are provided with a logic operation circuit that controls main circuit devices based on a pre-stored control program in accordance with the human input signal from the operating device and the magnitude of the main circuit current. The purpose of this design is to provide a load control system that can accurately detect the chattering phenomenon occurring in electromagnetic contactors using the logic control circuit and generate an alarm signal. We are in the process of providing equipment.

[Structure of the Invention] (Means for Solving Problems) In order to achieve the above object, the present invention provides main circuit equipment such as a molded circuit breaker and an S magnetic contactor in the main circuit between the power bus and the load. A load control device provided with a logic operation circuit that controls the main circuit device according to the magnitude of the main circuit current and a human signal by the operating device for operating the load, based on a control program stored in advance. , a change rate detection means for detecting a time change rate of the main circuit current;
A storage means storing a reference current change rate is provided, and the logical operation circuit is configured to detect a time change rate of the main circuit current detected by the change rate detection means as a reference current change rate stored in the storage means. The structure is such that an alarm signal is output when the limit is exceeded.

(Function) When chattering occurs in the electromagnetic contactor, the main circuit current begins to fluctuate greatly, and the time change rate of the main circuit current detected by the change rate detection means increases accordingly. In this case, when the time rate of change of the main circuit current detected as described above exceeds the reference current rate of change stored in the storage means, the logic operation circuit generates an alarm signal, and this alarm signal You can know that chattering has occurred in the electromagnetic contactor.

(Example) Hereinafter, an example in which the present invention is applied to a control center will be described with reference to FIGS. 1 to 3. However, in FIG. 1, the parts designated by the same reference numerals as those in FIG. 4 have the same structure and function, and therefore the description thereof will be omitted.

That is, in FIG. 1 showing the circuit configuration for one unit of the control center, from the current converter 5 to the A-D converter 1
5 is a voltage signal Vs indicating the main circuit current Is, and this voltage signal Vs is directly applied to the logic operation circuit 11 and also applied to the differentiating circuit 20 serving as a rate of change detection means. It will be done. The differentiating circuit 20 obtains a change rate signal Svf indicating the time change rate of the main circuit current Is by differentiating the manually inputted voltage signal Vs by digital calculation. given to 11.

The memory circuit 18, which is a memory means, has overcurrent and phase loss.

Protective actions such as undercurrent and earth rating, as well as instantaneous power outage restart,
In addition to a control program and functional data for executing control operations such as timed restart, a predetermined reference current change rate W is stored. Then, the logical operation circuit 11 compares the rate of change signal Svr and the reference current rate of change W, and when the rate of change signal Svf exceeds the reference current rate of change W, an alarm is sent to an external device (not shown) through the output circuit 21. Signal Sa
Output. Note that the logic operation circuit 11 is configured to perform the above comparison operation only for a certain period of time from the time when the ON signal from the auxiliary contact 5a is applied through the input circuit 14, that is, only when the main circuit 3 is powered on. The structure is as follows.

Therefore, in the above configuration, the voltage signal Vs from the A-D converter 15, that is, the waveform of the main circuit current Is becomes a sine wave as shown in FIG. 2(a) in a steady state. Therefore, in the steady state, the time rate of change of the change rate signal Svrs, or the main circuit current 1rh, output from the differentiating circuit 20 becomes a cosine wave as shown in FIG. 2(b). On the other hand, when chattering occurs in the electromagnetic contactor 5, the main circuit current Is is
As shown in Figure (a), it fluctuates greatly and becomes sawtooth-like. Therefore, the rate of change signal Svr output from the differentiating circuit 20
As shown in FIG. 3(b), becomes large in the part where chattering occurs.

Therefore, the reference current change rate W stored in the storage circuit 18 is
As shown in FIG. 3(b), if the change rate signal Svf is set to be larger than the change rate signal Svf when chattering occurs in the electromagnetic contactor 5, when the relationship Svf>W occurs due to chattering, the logical operation circuit 11 outputs an alarm signal Sa through the output circuit 21. As a result, it is possible to know from the above-mentioned alarm signal Sa that chattering has occurred in the electromagnetic contactor 5. This makes it possible to eliminate the cause of chattering at an early stage, and to prevent the occurrence of chattering in the electromagnetic contactor 5 as in the conventional It becomes possible to prevent the entire unit including the electromagnetic contactor 5 from falling into a malfunctioning state due to contact welding, contact falling out, or the like. Moreover, since the detection of the main circuit current Is is performed using the current converter 6, which is originally present for overcurrent protection operation, etc., it is possible to prevent the overall configuration from becoming complicated as much as possible.

In addition, in the above embodiment, the differential u by digital calculation
Although the circuit 20 is provided after the A-D conversion circuit 15, it is also possible to provide an analog differentiation circuit as a rate of change detection means before the A-D conversion circuit 15.

[Effects of the Invention] According to the load control device of the present invention, as is clear from the above explanation, by using a logic operation circuit provided to control a main circuit device such as an electromagnetic contactor,
This provides an excellent effect in that the chattering phenomenon occurring in the electromagnetic contactor can be detected with high accuracy and an alarm signal can be generated.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention, with Figure 1 being a schematic diagram of the electric circuit configuration, and Figures 2 and 3 showing the main circuit current waveforms for explaining the operation. It is a diagram. Also,
FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional example. In the figure, 1 is the power bus, 2 is the electric a (load), -3 is the main circuit, 4 is the circuit breaker (main circuit equipment), 5 is the electromagnetic contactor (main circuit equipment, specific equipment), 5a is Auxiliary contact, 5b is an operating coil, 6 is a current converter (main circuit device), 7 is a zero-phase current transformer (main circuit device), 10 is a control circuit, 11 is a logic operation circuit, 12 is a starting operation switch (operating device), 13
18 is a stop operation switch (operation device), and 18 is a memory circuit (
19 is a setting section, and 20 is a differentiation circuit (rate of change detection means). Applicant Toshiba Corporation Agent Patent Attorney Tsuyoshi Sato 4.5, 6.7 Main circuit equipment 1 12.13 Building construction equipment No.
1 Figure 11, - 11 Ken・ (1b) Figure 2 Current ↑1. - (a) @ZukeI rI. Figure 3

Claims (1)

[Claims] 1. A device comprising a main circuit device such as a molded circuit breaker or an electromagnetic contactor interposed in the main circuit between a power supply bus and a load, and an operating device for operating the load, the operating device Detecting the time rate of change of the main circuit current in a load control device equipped with a logic operation circuit that controls the main circuit appliance according to the input signal and the magnitude of the main circuit current based on a control program stored in advance. A change rate detection means for detecting a reference current change rate and a storage means for storing a reference current change rate are provided, and the logical operation circuit is configured such that the time change rate of the main circuit current detected by the change rate detection means is stored in the storage means. A load control device characterized in that it is configured to output an alarm signal when a stored reference current change rate is exceeded.