JP3075828B2 - Load control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load control device having an electromagnetic contactor and a current detector in a main circuit for controlling and protecting a load.

[0002]

2. Description of the Related Art As an example of this type of load control device, a control center having a function of controlling and protecting loads such as an electric motor is known. That is, in the control center, a plurality of units in which main circuit devices such as a circuit breaker, an electromagnetic contactor, and a current detector are integrated in each unit circuit are housed in multiple stages, and a start / stop indicator lamp is provided for each unit. It is configured by providing a display panel provided with a start operation switch, a stop operation switch, and the like.
In recent years, in order to easily cope with a change in the specification of a unit, a configuration in which necessary functions among a plurality of control and protection functions can be appropriately set, added, and changed by adopting electronic application technology. It is also performed.

[0003]

In such a control center, when a chattering phenomenon occurs in the electromagnetic contactor, the contact of the electromagnetic contactor is caused by the welding of the contact or the falling off of the contact. The entire unit, including the vessel, may fail.

[0004] Therefore, in order to prevent such a malfunction from occurring and to enhance the reliability of the control center, the cause of the chattering phenomenon of the electromagnetic contactor is discovered at an early stage, and the electromagnetic contactor is detected. It is necessary to prevent chattering from occurring. However, this has been an unsolved problem in conventional devices.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a load control device that does not cause a chattering phenomenon in an electromagnetic contactor.

[0005]

According to the present invention, there is provided a logic circuit comprising a main circuit including an electromagnetic contactor and a current detector interposed between a power supply bus and a load. In a configuration in which operation control and protection of the load are performed via the electromagnetic contactor based on a program stored in advance by an arithmetic circuit, the logical operation circuit includes an answerback signal of the electromagnetic contactor and the load of the load. When a plurality of pulses of a signal based on the operation and stop commands are present within a preset time, an output to the operation coil of the electromagnetic contactor is prevented and a comparison determination function is output to a display unit.

[0006]

The chattering of the electromagnetic contactor is caused by a voltage drop of the electromagnetic contactor or a failure of a relay provided in a higher-order operation system of a switch for outputting an operation / stop command of a load. Therefore, the answer back signal of the electromagnetic contactor is detected to detect the voltage drop of the electromagnetic contactor, and the output signal of the operation switch is detected to detect the failure of the relay of the higher operation system,
An abnormality is determined when the detection signal has a plurality of pulses within a preset time, and in this case, the output to the operating coil of the electromagnetic contactor is blocked and displayed on the display unit, so that the electromagnetic contactor is detected. Chattering can be prevented beforehand, and the reliability of the device can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a control center will be described below with reference to FIG. That is, FIG. 1 schematically shows a circuit configuration for one unit of a control center. In a main circuit 3 between a three-phase power bus 1 and a motor 2 as a load, a circuit breaker 4, an electromagnetic A contactor 5, a current detector 6 for detecting a main circuit current, and a zero-phase current transformer 7 for detecting a ground fault current are provided. A primary side of an operation transformer 8 is connected to a load side of the circuit breaker 4, and a control bus 9 is connected to a secondary side of the transformer 8.
a and 9b are connected.

The control unit 10 supplied with power from the control buses 9a and 9b via a DC power supply circuit (not shown) is mainly composed of a logical operation circuit 11 composed of a microcomputer. The logical operation circuit 11 includes a start operation switch 12 and a stop operation switch 1 which are operation devices.
3 and the answer back signal from the normally open auxiliary contact 5a of the electromagnetic contactor 5 via the input circuit 14, and receives the signals from the current detector 6 and the zero-phase current transformer 7 respectively. They are received via the A / D conversion circuit 15 and the power supply of the operating coil 5b of the electromagnetic contactor 5 is controlled via the output circuit 16 for power cutoff. In the storage circuit 17,
Control programs and functional data for executing control operations such as overcurrent, open phase, undercurrent, protection operations such as ground fault, instantaneous power failure restart, timed restart, and the like are stored.
The logical operation circuit 11 performs a protection operation and a control operation based on the control program, the function data, and the input signal. The setting circuit 18 includes a large number of selection switches (not shown) so that the function data stored in the storage circuit 17 can be set and selected as desired at the installation site of the control center.

The logic operation circuit 11 controls each device of the main circuit 3 based on the control program. For example, even if the specification of a unit is changed, the control program is executed. The change can be easily dealt with.

Here, the logical operation circuit 11 is connected to the input circuit 14
In addition to executing the protection operation and the control operation based on the input signal from the input circuit, the number of pulses of the input signal is counted, and when the counted number of pulses is two or more within a preset time, the output circuit 16 A control program for preventing output and outputting to the display unit 19 is executed. This control program is stored in the storage circuit 17 in the same manner as a control program for executing control operations such as overcurrent, phase loss, undercurrent, ground fault, etc. and instantaneous power failure restart, timed restart, etc. Thus, the set time T can be changed by the setting circuit 18. The set time T is set to, for example, a minimum of 30 ms for an electromagnetic contactor that energizes 20 A. This means that the time required to turn on the main contact in an electromagnetic contactor energizing 20 A is approximately 15
Since the main contact of the electromagnetic contactor is not turned on in 15 ms or less, and chattering occurs in the electromagnetic contactor due to repetition of two or more input signals, setting the set time T to at least 30 ms ,
It is obtained so as to detect an input signal of a plurality of pulses. Since the time required for closing the main contact differs depending on the capacity of the electromagnetic contactor, the set time T also needs to be different. Similarly, due to the voltage drop of the electromagnetic contactor 5,
Each ON signal from the normally open auxiliary contact 5a, that is, the answer
Pulse signal is generated and the number of pulses
Output circuit 16 when there are two or more within the set time.
Output to the display unit 19
It is something that has become.

Accordingly, the logical operation circuit 11 compares the set time T with the input signal as shown in FIG. 2, and if the input signal is shorter than the set time T and the input signal is input again, that is, a plurality of pulses are set within the set time T. When it is present, there is a possibility that chattering may occur in the electromagnetic contactor. In this case, the output to the output circuit 16 is prevented and the output is displayed on the display unit 19 for display. On the other hand, if the input signal
If it is less than the pulse, a signal is output to the output circuit 16 to turn on the operation coil 5b. Thereby, the electromagnetic contactor 5 operates without generating chattering, so that the reliability of the device is improved.

[0012]

According to the present invention, as will be apparent from the above description, the cause of chattering of the electromagnetic contactor is detected in advance to prevent the operation coil of the electromagnetic contactor from being turned on and displayed. As a result, the reliability of the entire apparatus can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic electric circuit configuration diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing a time chart of a signal.

[Explanation of symbols]

1 is a power bus (AC circuit), 2 is an electric motor, 3 is a main circuit,
4 is a circuit breaker, 5 is an electromagnetic contactor, 5b is an operating coil, 6 is a current detector , 7 is a zero-phase current transformer, 10 is a control circuit, 11 is a logic operation circuit, 14 is an input circuit, 16 is An output circuit, 17 is a storage circuit, 18 is a setting circuit, and 19 is a display unit.

Claims (1)

(57) [Claims] 1. A main circuit including an electromagnetic contactor and a current detector interposed between a power supply bus and a load, and the electromagnetic contactor is operated based on a program stored in advance by a logical operation circuit. In the apparatus for controlling and protecting the operation of the load through the logic operation circuit, the logical operation circuit may generate a plurality of pulses within a preset time period based on an answerback signal of the electromagnetic contactor and a signal based on the operation and stop commands of the load. A load control device having a comparison / determination function of preventing output to a working coil of the electromagnetic contactor when present, and outputting the result to a display unit.