JPS6231392A - Controlling method for motor-driven rotary chemical machine - Google Patents

Abstract

PURPOSE:To prevent a motor from burning or shortening its life without an extreme overload state by electrically detecting the variation of an operating weight, and controlling the rotating speed in response to the variation. CONSTITUTION:A current (i) and a voltage V of a motor 4 are continuously detected by a current transformer 9 and a power transformer 10 during the operation of a rotary drying machine 1. A phase controller 7 obtains the optimum rotating speed by the current (i), the voltage V and a speed detection signal N to generate the primary frequency and the primary voltage of the motor 4 in response to the optimum speed, thereby driving a power transistor in the main circuit 6 of an inverter to generate a PWM wave. Thus, the voltage and the frequency applied to the primary side of the motor 4 are varied.

Description

[Detailed Description of the Invention] This invention provides a ball mill, a centrifugal separator, a rotary dryer,
The present invention relates to a method of controlling various electric rotary chemical machines such as dehydrators, rotary filtration machines, and the like.

Conventionally, electric rotary chemical machines such as those described above are generally equipped with cage-type induction motors or synchronous motors that are not capable of stepless variable speed operation. Therefore, it is necessary to always adjust the amount of the processed material supplied to the chemical machine within a certain range.

However, since it is practically impossible to always keep the amount of processed material supplied to the chemical machine within a certain range, the chemical machine is often used with overload or underload, which results in energy efficiency. In addition to high losses in terms of loss, in the case of an overload, the life of the motor is shortened due to the overload on the motor, and there are problems such as burnout.

In order to alleviate such problems, dewatering machines that use a hydraulic motor as the driving engine have been proposed (for example, see Japanese Patent Application Laid-Open No. 59-50058), but when using a hydraulic motor as the driving engine, Not only is the drive device, including the hydraulic pump and piping system, extremely large, but it is also highly dangerous from a disaster prevention perspective because it requires the use of flammable oil as the working fluid. There was a drawback.

An object of the present invention is to provide a control method that allows a variable speed electric rotary chemical machine that does not use a hydraulic motor to be operated at optimum efficiency at all times in accordance with the operating weight of the machine.

In the method of the present invention, the instantaneous power consumption of the driving electric motor of the chemical machine is detected, the instantaneous rotational speed is detected, the corrected power value at the instantaneous rotational speed is determined from the power consumption value and the instantaneous rotational speed, and the corrected power value is determined at the instantaneous rotational speed. From the electric power value and the instantaneous rotation speed,
The present invention is characterized in that the drive torque is determined, the weight of the object to be processed in the chemical machine is determined from the instantaneous drive torque, and the drive electric motor is further controlled based on the optimum rotation speed corresponding to the weight of the object to be processed.

The method of the present invention is a method applied to a rotary chemical machine equipped with a steplessly variable speed electric motor, and the electric motor may be a DC shunt type electric motor, an electric induction motor controlled by an inverter, or an electric type induction motor also controlled by an inverter. Rotary chemical machines (e.g. grinders, mixers, decanters, rotary filters, It is applied to chemical machines with rotating parts such as centrifuges, rotary dehydration dryers, Shirafuna, kneader granulators, dispersers, etc.

In the method of the present invention, fluctuations in the operating weight of equipment in a rotary chemical machine are electrically detected and the rotating parts of the chemical machine are rotated at the optimum rotation speed corresponding to the operating weight, which may lead to an extreme overload condition. This prevents the motor from burning out and shortening its lifespan, and unlike the hydraulic drive type, there is no risk of fire or the like. Moreover, since it is based on an electronic control device, it can be realized as a small 6D rotary chemical machine with a small installation floor space.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. In the embodiment shown in the accompanying drawings, the rotary chemical machine to which the method of the present invention is applied is a VVVF (Variable Frequent
A rotary dryer equipped with a three-phase AC induction motor equipped with a variable voltage
(rotary dryer with indirect heating tube). However, the variable speed control device may be an inverter that changes only the primary voltage of the three-phase induction motor;
When employing an F inverter, the motor may be a periodic motor, or a cycloconverter may be used instead of the inverter. Furthermore, a DC shunt motor may be used (in this case, a converter is used as the DC power source). FIG. 1 is a schematic diagram of a drive device for a rotary chemical machine to which the method of the present invention is applied. . 1 is a rotary dryer with an indirect heating tube, 2 is its rotating shaft, 3 is a reducer connected to the rotating shaft 2, 4 is an electric three-phase induction motor connected to the input shaft 5 of the reducer 3, 6 is a main circuit section of a vvvp transistor inverter that changes the primary frequency and primary voltage of the motor 4,
7 is a phase control device for controlling the power transistors etc. in the main circuit section 6; 8 is a speed generator attached to the shaft of the motor 4 and feeding back a detection signal N corresponding to the rotational speed of the motor 4 to the control device 7; 9 is a current transformer for detecting the current 1 supplied from the main circuit section 6 to the motor 4;
10 is a power transformer for detecting the □voltage v applied to the electric motor 4.

As shown in FIG. 2, the phase control device 7 is provided with a pace drive circuit 71 for driving the power transistor in the main circuit section 6, and also generates a phase control pulse in the base drive circuit 71. A PWM control circuit 72 is provided for this purpose.

The PWM control circuit 72 is a circuit for performing pulse width calculation to generate a PWM wave (pulse width modulated wave) in the main circuit section 6 of the inverter, and has an A/D converter 73 at its input terminal. A V/F converter 74 is connected. A/D
The converter 73 converts a reference voltage signal inputted from a control circuit 75, which will be described later, into a digital signal and applies it to the PWM control circuit 72.
A signal is generated that changes the reference frequency signal input from the converter according to a predetermined voltage ratio V/F.

The input signal V to the A/D f converter 73 (!: The input signal f to the V/F converter 74 is generated in a control circuit 75. This control circuit 75 is, for example, shown in FIG. It has the configuration shown in .

In FIG. 3, 75a is a power detector that determines the stain force based on the detection signals of the power transformer 10 and current transformer 9 (that is, voltage in the former and current in the latter), and 75b is the speed from the speed generator 8. Detection signal N and power detector 75a
The corrected power value P expressed by the power detection value P from
75c is a speed detection signal N and a corrected power value PM calculator, 75d is a torque-weight converter for determining the operating weight of the rotary dryer main body from the instantaneous driving torque, and 75e is an operation unit for calculating Mk. Rotary dryer body 1 relative to weight
75f is an acceleration/deceleration control circuit which generates a frequency signal K representing the optimum rotation speed Ns as an output signal.

Next, a control method of the present invention executed in the above configuration will be explained.

During operation of the rotary dryer 1, the current 1 and voltage V in the motor 4 are continuously detected via the current transformer 9 and the power transformer 10, and based on these values, the power detector 75a calculates the instantaneous power consumption P. is detected. Next, the corrected power value calculator 75
After the corrected power value pM corrected by the speed detection signal N generated from the speed generator 8 is calculated in step b, the instantaneous drive torque calculator 75c calculates the corrected power value PM as a ratio of the corrected power value PM and the speed detection value N. Instantaneous drive torque T is calculated.

Then, in the next torque-weight converter 75d, the operating weight within the rotary dryer 1 corresponding to this torque T is determined.

Furthermore, in the next optimum rotation speed setting device 75e, the above operation! The optimum rotational speed Ns corresponding to the amount is determined. The output of the optimum rotation speed setter 75e is applied to the acceleration/deceleration control circuit 75f, and the acceleration/deceleration control circuit 75f selects the electric motor 4 corresponding to the rotation speed Ns.
Signals V, f representing the primary frequency and -order voltage of are generated and applied to the A7D converter 73 and the V/F converter 74.

Therefore, the PWM control circuit 72 to which the output signal of the A/D converter 73 and the output signal of the V/F converter 74 are applied performs pulse width calculation for Norms width modulation (PWM), and the output is used to calculate the pulse width. Controls the drive circuit 71. The base drive circuit 71 drives the power transistor in the main circuit section 6 of the inverter to generate a PWM wave and change the voltage and frequency applied to the primary side of the motor 4. the result,
Since the rotary dryer 1 is driven at an appropriate rotational speed corresponding to its operating weight, there is no risk of burnout due to overload of the motor.

As described above, according to the method of the present invention, the electric motor can be driven at the optimal rotation speed for the operating weight of the device, which varies depending on the chemical machine, so there is no risk of overloading or burning out the electric motor.
Moreover, compared to chemical machines with variable speed control that use hydraulic motors, etc., the machine occupies a much smaller installation area.
In terms of disaster prevention, benefits such as much higher safety can be obtained.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams of an embodiment of a control system for carrying out the method of the present invention.

Claims (1)

[Claims] A control method for an electric rotary chemical machine that performs various unit operations such as crushing, mixing, stirring, filtration, separation, dehydration, and drying, the method comprising: detecting the instantaneous current and instantaneous voltage of a drive motor of the chemical machine; After calculating the instantaneous power consumption value from the value, calculate the corrected power value at the instantaneous rotation speed from the instantaneous rotation speed detection value and the instantaneous rotation speed detection value, and calculate the instantaneous power consumption value from the corrected power value and the instantaneous rotation speed detection value. Find the driving torque, and further,
A method for controlling an electric rotary chemical machine, characterized in that the operating weight of the chemical machine device is calculated from the instantaneous driving torque, and the electric motor is controlled based on an optimum rotation speed corresponding to the operating weight.