JPH0686449A - Motor controller - Google Patents

Abstract

PURPOSE:To set a reference value for deciding abnormality optimum for the conditions of protection automatically. CONSTITUTION:A logical operation circuit 14 compares detecting signals from current converters 5, 6 with a reference value for deciding abnormality, decides the presence of abnormality and outputs the open command of an electromagnetic contactor 4 at the time of abnormality. The reference value for deciding the abnormality is arithmetically operated on the basis of a time at the time of the (n)-times currents of the start current value of a motor 2 and rated currents from the detecting signals of the current converters 5, 6 by the logical operation circuit 14, and the result of the arithmetic operation is stored and set to an automatic setting circuit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling the opening and closing of a motor and protecting it using a switch such as an electromagnetic contactor, and more particularly to automatically determining a reference value for judgment for carrying out a protection operation. The present invention relates to a motor control device that can be set.

[0002]

2. Description of the Related Art Recently, in a control center unit or the like, by applying a microcomputer, an electric motor control device having a large number of functions such as operation / stop control, protection and monitoring of an induction motor is housed. Is provided. The protective function of this type of motor control device constantly monitors the main circuit current of the induction motor to compare it with the reference value for abnormality determination, and connects to the main circuit when an abnormality such as overload, phase loss or ground fault is detected. By opening the electromagnetic contactor, the induction motor is protected and the cause of the abnormality is displayed outside.

[0003]

By the way, in such a control center, the reference value for abnormality determination is set by actually measuring the starting current, the starting time and the steady-state current of the electric motor at the installation site and referring to the measured value. I decide the value and set it. However, in this case, if the set current is larger than the steady value, overload protection cannot be performed, and if the set time is short, malfunction occurs at start-up, and conversely, if the set current is too long, there is a problem that the withstand capacity of the electric motor is exceeded and protection cannot be performed. Therefore, an object of the present invention is to provide an electric motor control device capable of automatically setting a reference value for abnormality determination that is optimum for a protection condition.

[0004]

An electric motor controller according to the present invention includes an electromagnetic contactor for opening and closing a main circuit between a power bus and an electric motor, a current converter for detecting a main circuit current, and an opening and closing of the electromagnetic contactor. Input circuit for inputting the start and stop operation signals to determine the presence or absence of abnormality by comparing the detection signal from the current converter with the reference value for abnormality determination, and outputs the opening command of the electromagnetic contactor at the time of abnormality One of the logical operation circuits has a function of calculating the protection characteristic from the detection signal of the current converter based on the starting current value of the electric motor and the time when the current is n times the rated current. , And has a function of setting the calculation result in the automatic setting circuit.

[0005]

The starting current value I of the electric motor and the time t when the current is n times the rated current are automatically measured in the first operation such as the test operation of the electric motor, and based on the data, for example, I ² The protection characteristic is calculated by the logical operation circuit from the equation of t, and this can be set as the abnormality determination reference value in the automatic setting circuit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is an induction motor 2 which is a load.
This is a three-phase main circuit that supplies power to
The circuit breaker 3 for wiring, the electromagnetic contactor 4, the current converter or current transformer 5 for detecting the main circuit current, and the zero-phase current transformer 6 for detecting the zero-phase current of the main circuit are interposed as main circuit devices. ing. A primary winding 7a of an operating transformer 7 is connected between two phases of the main circuit 1 between the load side of the wiring breaker 3 and the power source side of the electromagnetic contactor 4. The output voltage of the secondary winding 7b of the operating transformer 7 is applied to the bus bar 8 as a power source for the operating circuit. The busbar 8 is provided with a coil 4a of the electromagnetic contactor 4 connected at one end so that the busbar 8 is used as one power supply line, an auxiliary contact 4b, a start operation switch 9, and a stop operation switch 10. The other end is connected to the operation signal output terminal 11a and the operation signal input terminal 11b of the control circuit 11. As a result, the control circuit 11 receives the start signal from the start operation switch 9 and the stop signal from the stop operation switch 10 to turn off the coil 4a,
A function of opening and closing the electromagnetic contactor 4 and inputting current signals from the current transformer 5 and the zero-phase current transformer 6 to perform protection operations such as overload protection, open-phase protection and ground fault protection of the induction motor. have. The power supply of the control circuit 11 is to prevent intrusion of switching noise generated by the coil 4a of the electromagnetic contactor 4, etc.
It is supplied from a tertiary winding 7c which is insulated from the secondary side of the operating transformer 7.

The control circuit 11 also receives a detection current corresponding to the magnitude of the main circuit current output from the current transformer 5 and the zero-phase current transformer 6, and outputs from the current detection circuit 12. Of the main circuit current and the cause of abnormality of the main circuit current value and the logical operation circuit 14 that outputs a command to the drive circuit 13 that opens and closes the electromagnetic contactor 4 by calculating the detection signal of It comprises a display circuit 15 for displaying and an external output circuit 16 for outputting the content of abnormality to the outside. The logical operation circuit 14 is further provided with the functions and circuits described below for the purpose of the present invention.

That is, the logical operation circuit 14 detects the actual current of the electric motor 2 from the main circuit 1 by the current detection circuit 12, and the detection signal outputs the start current I _M shown in FIG. 2 and n times the rated current. Based on the time T _N , the formula I _M ² A reference value for abnormality determination is calculated from T _N. The reference value for abnormality determination is automatically set in the automatic setting circuit 18, and such automatic setting is performed only when the setting switch 19 is manually turned on. . The automatic setting circuit 18 has a storage unit, which not only stores the above-described reference value for abnormality determination, but also protects against overcurrent, open phase, undercurrent, ground fault, etc., and restarts instantaneous power failures and timed restarts. A control program for executing control operations such as the above and function data for determining protection operations are stored.

Therefore, first, the reference value for abnormality determination is automatically set.
To set the electric motor with the setting switch 19 turned on,
2 first run under actual load, ie test run for example
It Then, through the current transformer 5 and the zero-phase current transformer 6,
The actual motor that has flown into the main circuit 1 by the current detection circuit 12.
Starting current I corresponding to current_MAnd n times the rated current
Time T_NIs measured and based on this, a logical operation circuit
14 is the above formula I_M ² T_NTo reference value I for abnormality determination_I
Is calculated. This abnormality determination reference value I_IIs the setting switch
Since 19 is on, the automatic setting circuit 18 automatically
Is set, and thereafter this reference value for abnormality determination I_IFor abnormality determination
Will be used.

[0010] In FIG. 2, I _MCCB operation characteristic curve of the circuit breaker, I _M is the motor current, I _I overload protection characteristics, I _n is n times the current I _100, I ₁₀₀ is an electric motor actual The load current, T _S, indicates the overload protection characteristic setting time.

In a normal operating condition, the detected current of the main circuit 1 output from the current transformer 5 and the zero-phase current transformer 6 is converted into a predetermined signal by the current detection circuit 12, and this is converted into a logical operation circuit 14. On the basis of the control program stored in the storage unit of the automatic setting circuit 18 to perform a logical operation for comparing various functional data and the reference value for abnormality determination to check whether there is an abnormality such as an overload, a phase loss, or a ground fault. Always monitor. When an abnormality occurs, the logical operation circuit 14 outputs an opening operation command of the electromagnetic contactor 4 and a display command of the content of the abnormality to the drive circuit 13 and the display circuit 15. In the above-mentioned embodiment, the I ² Although the calculation formula of t is used, other calculation formulas can be used. An example is shown below. ( _N times the rated current I _N ) ² × (time T _N when the current is n times the rated current) + I _x ² t _x where I _x ² t _x is a value obtained by an experimental value or the like.

[0012]

According to the present invention, the reference value for abnormality determination can be automatically calculated and arbitrarily set from the starting characteristic of the electric motor obtained by the operation of the electric motor, so that the optimum reference value is always set. In addition, since this can be done automatically, an excellent effect such as extremely easy setting work can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a motor current characteristic and a current characteristic which is a protection condition.

[Explanation of symbols]

1 is a main circuit, 4 is an electromagnetic contactor, 5 is a current transformer (current converter), 6 is a zero-phase current transformer, 11 is a control circuit, 12 is a current detection circuit, 14 is a logic operation circuit, and 18 is automatic. Setting circuit, 1
Reference numeral 9 indicates a setting switch.

Claims (1)

[Claims] 1. An electromagnetic contactor for opening and closing a main circuit between a power bus and an electric motor, and a current converter for detecting a main circuit current.
An input circuit for inputting start and stop operation signals for opening and closing the electromagnetic contactor and a detection signal from the current converter are compared with a reference value for abnormality determination to determine the presence or absence of abnormality, and the electromagnetic contact In a motor control device including a logical operation circuit that outputs an opening command of the electric motor, the logical operation circuit is based on a starting current value of the electric motor from the detection signal of the current converter and a time when the current is n times the rated current. An electric motor control device having a function of calculating a protection characteristic by using the automatic setting circuit and a function of setting the calculation result in an automatic setting circuit.