JPH0678593A - Monitor for motor - Google Patents

Abstract

PURPOSE:To easily grasp an operating state of a motor group connected with many motors and to simply discover a motor route in which a trouble occurs. CONSTITUTION:A motor monitor 3 is branched to a connecting line for connecting a plurality of motors 1 connected in parallel to an inverter 2 through a current transformer CT. The monitor 3 has a detector 4 connected to the transformer CT, an arithmetic processor CPU, and a monitoring unit 8. The detector 4 has a current detector 5 for detecting a sum of currents flowing to the motor, and a slope detector 6 for detecting a slope of a starting current of the motor. The processor CPU compares a previously stored current and its varied reference value with actually detected one to calculate number of connected motors. The unit 8 indicates calculated number, detected current value, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for monitoring the operating state of a motor in a motor control system using a multi-type inverter unit for controlling a plurality of motors.

[0002]

2. Description of the Related Art In a conventional motor control system, as shown in FIG. 3, one inverter circuit 2 is connected to a plurality of motors 1 connected in parallel to control the speed of the motor 1. The motor 1 is activated by first operating the inverter circuit 2 and sequentially turning on the electromagnetic contactors MC. If a ground fault or the like occurs in the path during startup, the electromagnetic contactor MC is sequence-controlled so as to cut off the power supply.

[0003]

In the above-mentioned conventional motor control system, for example, an electromagnetic contactor MC or a thermal device is attached to the secondary side of the motor alone to take measures against overload. When a failure occurs in the motor or its connection path, all the electromagnetic contactors MC operate simultaneously, so there is a problem that it is difficult to find the failure when the number of motors is large.

Therefore, it is an object of the present invention to provide a monitoring device capable of easily grasping the operating states of a large number of connected motor groups and easily finding a failed motor path.

[0005]

In order to solve the above problems, in the present invention, a motor control system for controlling the operation of a plurality of motors 1 by one inverter unit 2 detects the current of the motor 1 and its change. Detection circuit 4, an arithmetic control unit CPU that calculates the number of connected motors 1 by comparing the detected current and its change with a reference value stored in advance, and a monitor device that displays the calculated number of connected motors and the detected value. A motor monitoring device 3 consisting of 8 and 8 was provided.

[0006]

In the motor monitoring device 3 of the present invention, when the plurality of motors 1 are controlled by the inverter unit 2, the detection circuit 4 detects the current of the motor 1 and its change, and the arithmetic and control unit CPU detects it. The number of connected motors 1 is calculated by comparing the generated current and its change with a reference value stored in advance. The calculated number of connected motors 1 and the detected current are displayed by the monitor device 8. Therefore, the operator can operate the motor while looking at the monitor device 8 and monitoring the operating condition of the motor. If a motor or the like fails, the number of connected units at this time can be confirmed.

[0007]

Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, a motor monitoring device 3 is branched and connected via a current transformer CT on a connection line connecting a plurality of motors 1 and an inverter circuit 2 which are connected in parallel.
Detection circuit 4 in the motor monitoring device 3 connected to the current transformer CT
Is composed of a current detection circuit 5 for detecting the sum of currents flowing into the motor and a slope detection circuit 6 for detecting the slope of the starting current of the motor, which are connected in parallel. The slope detection circuit 6 detects the differential value of the continuously changing current and the synchronous pull-in time from the closing to the steady state.

The current detection circuit 5 and the inclination detection circuit 6 are connected to the arithmetic processing unit CPU, respectively. The arithmetic processing unit CPU is located in the inverter unit and compares the respective reference values of the differential value of the current, the synchronous pull-in time and the steady current, which are previously input and stored by the input device 7, with the actually detected values. , Calculate the number of connected motors. Generally, when the motor 1 is started at full voltage, a transient overcurrent flows during the synchronous pull-in time, as shown in FIG. Therefore, the current change per unit is grasped from the differential value of the increase / decrease change, the synchronous pull-in time and the steady current, and the total is made to correspond to the connected number.

The arithmetic processing unit CPU is connected to a monitor unit 8 capable of displaying the calculated number of units or detected current value and monitoring the operating state.

In the motor control system of the above embodiment, when the motor 1 is controlled by the single inverter circuit 2, the detection circuit 4 of the monitoring device 3 detects the current change of the motor 1 and the arithmetic and control unit CPU Compares this with a pre-stored reference value to calculate the number of connected motors 1. The calculated number of connected motors, the detected current value, etc. are monitored by the monitor device 8.
Displayed by. Therefore, the operator can operate the motor while looking at the monitor device 8 and can monitor the number of connected motors. That is, when a ground fault or the like occurs on the connection path of the motor 1 at the time of starting, the number of connected units at that time can be confirmed by the monitor device 8 and the number of the motor that has failed is specified. be able to. Further, the operating state can be grasped by the load current of the motor 1.

[0012]

As described above, according to the present invention, in the motor control system for controlling the operation of the plurality of motors 1 by the single inverter unit 2, the detection circuit 4 for detecting the current of the motor 1 and its change, and the detection circuit 4. Monitoring of the motor including an arithmetic and control unit CPU that calculates the number of connected motors 1 by comparing the generated current and its change with a reference value stored in advance, and a monitor device 8 that displays the calculated number of connected motors and the detected value. Since the device 3 is provided, the operator can operate the motor by looking at the monitor device 8, the number of connected devices and the operating state can be easily monitored, and the failure of the motor 1 can be easily found. It has the effect that it can be dealt with promptly.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a motor control system having a faulty motor detection device according to the present invention.

FIG. 2 is a graph showing a change in current with time.

FIG. 3 is a circuit diagram of a conventional motor control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Inverter unit 3 ... Monitoring device 4 ... Detection circuit 8 ... Monitoring device CPU ... Arithmetic control device

Claims (1)

[Claims] 1. In a motor control system for controlling the operation of a plurality of motors by a single inverter unit, a detection circuit for detecting the current of the motor and its change, and the detected current and its change are compared with a reference value stored in advance. 2. A motor monitoring device, comprising: an arithmetic and control unit for calculating the number of connected motors and a monitor device for displaying the calculated number of connected motors and detected values.