JPH02146990A - Controller for motor - Google Patents

Abstract

PURPOSE:To increase a load current in a low frequency range by invalidating the operation of stroke preventing means when the output frequency of an inverter is a predetermined frequency or less. CONSTITUTION:Power from an AC power source is supplied to an induction motor IM through a converter/inverter to control rotation. The control of the inverter is conducted by a CPU 3. Since accelerating/decelerating time is not matched to load inertia at the time of accelerating/decelerating so that a load voltage might rise, a stroke preventing function is operated to wait the follow-up of the load. This function is not operated when the present frequency is lower than a predetermined value. Thus, a compensating current can flow to obtain a predetermined torque in a low frequency operating range.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device for an electric motor.

[Prior Art] Conventionally, a device that drives an electric motor using an inverter circuit reduces the load current or It was equipped with a stall prevention means that detects this state based on the load voltage and changes the acceleration and deceleration times to prevent operation stoppage due to overcurrent. Furthermore, since the stall prevention means operates even when the vehicle is not accelerating or decelerating, the stall prevention means is provided with a function to disable the operation of the stall prevention means when the load is inconvenient if the stall prevention means operates.

[Problem M to be solved by the invention] However, in the conventional example, the stall occurs over the entire output frequency range.
In order to select whether to enable or disable the prevention means, it was not possible to make it effective in a necessary frequency range and disabled in an unnecessary frequency range. In addition, if the stroll prevention means is activated by detecting a change in the load current or load voltage due to other factors when not accelerating or decelerating, the accelerating acid from there is activated during deceleration, and the desired accelerating acid is applied during deceleration. There was a problem that the electric motor could not be operated. Particularly in the low frequency operation range, even if it is necessary to compensate by increasing the load current in order to obtain a constant torque, the roll prevention function will be activated and eventually the operation will stop. there were.

The present invention has been made in view of the above-mentioned problems, and its purpose is to disable the operation of the anti-stroll means when not accelerating or decelerating, so that the operation of the electric motor is inadvertently stopped. The purpose of this invention is to provide a motor control device that prevents the

C Means for Solving the Problems The present invention consists of an inverter circuit that drives an electric motor and a control circuit that controls the inverter circuit. In a motor control device in which the control circuit is equipped with a stall prevention means that reduces the rate of increase or decrease in the frequency of the inverter circuit when the current or load voltage reaches a stall prevention level, the current frequency of the inverter circuit output is a predetermined frequency. The control circuit is equipped with a means for disabling the operation of the stall prevention means if the stall prevention means is below. If the current frequency of the circuit output is below a predetermined frequency, the operation of the anti-stroll means is disabled, so that the load current can be increased in the low frequency range where it is necessary to compensate for the load current.

[Embodiment] FIG. 1 shows a circuit of an actual M example of the M valve device for an electric motor according to the present invention. In this embodiment device, an inverter circuit 1 is used as driving means for the electric motor. The induction motor IM is controlled by controlling the switching of the switching elements Q1 to Qa with on/off commands from the control circuit 2.
It controls the rotation of. The control circuit 2 is managed by a one-chip microcomputer (hereinafter abbreviated as CPU) 3, which receives signals from the operation switches SW and (SW4') and uses frequency setting data stored in the built-in RAMBa in advance or an external device such as a sequencer. Control device and variable resistor VR
On/off command signals tJ, V;W are output based on frequency setting data from a reference input source such as. In addition, the control circuit 2 includes switches SW1 to SW y
The control conditions, that is, the control program, are set by the signal, and these setting conditions are displayed on the display sections L'E D + and L E
D2 and writes to EEPROM 5. Furthermore, in the event of an abnormality, the abnormality cause signal from the protection circuit 6 is determined, or the abnormality is displayed on the display unit LED, LED2 based on the abnormality judgment of the CPU itself. At the same time, the contents of the abnormality are written in the EEPROM 5, and at the same time, an abnormality signal ST is outputted to cause the disconnection relay 7, which trips the main contact S of the main circuit, to perform a disconnection operation.

Next, the basic operation of the electric motor control device will be explained with reference to the flowchart shown in FIG.

First, when the three-phase AC power supply AC of the device is turned on and the DC power supply Vec is supplied from the power supply circuit (not shown) to the control circuit 2,
The CPU 3 starts operating according to a built-in program, and first clears the stored contents of the built-in RAM 3a for initialization. After this initialization, the data stored in the EEPROM 5, such as the previous operating conditions and the final abnormality contents, are read and the built-in R
Write to AM3a, that is, read initial data.

Next, the CPU 3 makes a mode determination, but in this case, since it is the initial state, it determines the mode to be "00°".

At this time, the display LED is displaying 00'''.

When the mode is determined to be "°00", the display LED will indicate "
000" is driven and displayed through a driver (not shown). Here, the modes include increasing rotation speed (acceleration control),
Descending (deceleration control? 8) -, constant speed M control, PWM control V/
There is a program setting mode to set the F ratio, brake time, maximum frequency, etc., and there is a mode switch S for mode setting.
By operating Wl, switching settings can be made sequentially.

The illustrated mode determination is only the determination of the program setting mode (1, but of course routines for determining other modes are provided.

Now, the above initial display state <mode number is °゛00'°
), the induction motor IM can be started.

That is, unless the X constant conditions are changed, the inverter circuit 1 can be controlled to drive the induction motor IM according to the previously set conditions. Here, based on the operation of the mode switch SW, add "1j" to the current mode number, proceed to the mode, read the current setting data corresponding to this mode from the built-in RAM 3a, and display 3 on the display L E D 2.
The mode number is displayed in digits and the mode number is displayed on the display section LED. Current display area L E D
To change the setting conditions displayed in 2, all you have to do is operate the data switch SW2 for data setting. The contents are read from the display section and displayed using E D 2.

If the displayed contents meet the desired setting conditions, the user only has to operate the memory switch SW3.

This memory switch SW is a switch for determining the conditions, and when the switch SW3 is turned on, the CPU 3 writes the data of the setting conditions of the predetermined mode read for the above change into the built-in RAM 3a and EEPROM 5. Rewrite the data for the mode in question. When this rewriting is completed, a mode determination state is entered. In other words, the program setting is to be completed for each condition setting, and when setting or correcting each condition, it is sufficient to repeat the following steps.

If the setting conditions displayed by operating the data switch SW are not the desired conditions, the memory switch SW,
Simply operate the data switch SWz repeatedly until the desired setting condition is reached without operating the .If you wish to stop changing the conditions, do not operate the memory switch SW3 and operate the mode switch SW1 to proceed to the next setting. All you have to do is move to the mode display. If you only want to check the setting conditions of a predetermined mode, it is best to repeat the operation of setting switch SW 1. In this case, the mode will change sequentially and the display L
The display mode number of E D and the display LED2
The data of the setting conditions is j! I? ! iS switching is displayed. If you want to return the setting data to the initial state, you can turn on the reset switch SW.

When the changing (or checking) of each set condition is completed in sequence, the operation switch SW 4 can be activated at the time of completion. Now mode "00°'
If the operation switch SW or the operation switch SW a' connected to the remote control terminal is turned on in a state where the operation can be started, the CPU 3 detects this turning on and changes the setting conditions written in the built-in RAM 3a. Alternatively, on/off command signals U, V, and W are output based on the frequency setting signal from the variable resistor VR (or an external control device). In other words, the control operation shifts to acceleration control, constant speed control, and deceleration control based on the program settings.

Of course, the selection between the reference input source and the data in the built-in RAM 3a is determined by the setting of the operation mode.

Now, the above command signals U, V, W are sent to the switching elements Q, ~Qs via the pace driver 4 of the inverter circuit 10.
is switched to drive the three-layer induction electric fi1M.

The operating frequency during this drive is displayed by the display section LED2 under the control of the CPU3.

Next, if an abnormal condition such as overload occurs in the induction motor IM, the additional current increases. This increase causes the voltage across the detection resistor R to rise, and when this rise is detected by the protection circuit 6, the protection circuit 6 outputs an abnormality detection signal and provides an abnormality interrupt signal to the CPU 3. This interrupt causes CPLJ to
Step 3 skips the operation mode to the abnormal interrupt routine and moves to abnormal handling operation.

In other words, CPU3 that jumps to the abnormal interrupt routine is turned on/
The output of the off command signals U, V, and W is stopped, and the induction motor I
At the same time, an abnormal signal ST is generated, and the abnormal signal ST turns off the contact S of the cut-off relay 7 inserted into the power supply circuit, and the induction motor IM is stopped.
Stop the power supply to. Meanwhile, during this time, the CP of control circuit 2
U3 writes the abnormal data that has been written in the built-in RAM 3a from the protection circuit 6 to the abnormal data writing address of the EEPROM 5, and also displays the abnormal content on E D 2 based on the abnormal data, and resets this display. This is maintained until the switch SW5 is operated. Furthermore, if the power supply to the control circuit 2 is also completely stopped, the operation of the entire device will be completely stopped.

If you turn on the reset switch SWS when the above abnormality is displayed, or turn on the power again after the device has stopped operating, the CPU
3 is set to the initial state and contains the control condition data and abnormal content data written in EEPROM5.
It is transferred to RAM3a. When restarted after this transfer, if the above-mentioned abnormality has not been resolved, the protection circuit 6 detects the abnormality, generates the above-mentioned interrupt, and jumps to the above-mentioned abnormality interrupt routine, but the mode judgment When the switch SWl is operated to set the abnormality display mode, the contents of the abnormality that occurred during the previous operation will be displayed on the display L E
D, is displayed. The user can reconfirm the cause of the abnormality based on the display on the display section LED2.

Now, in the process of acceleration control to increase the rotational speed of the induction motor IM, or deceleration control to decrease the rotational speed, the inverter circuit 1 controls the control circuit so that the frequency of the output signal of the inverter circuit 1 gradually increases or decreases. However, the value of the load current or load voltage may increase because the acceleration time or deceleration time and the load inertia do not match.

At this time, the control circuit 2 temporarily reduces the frequency change (rise rate or fall rate) and controls the inverter circuit 1 by activating a stroke prevention function that waits for the load to follow.

FIG. 3 shows, for example, an acceleration control routine that activates the anti-stroll function. When moving to this acceleration control, the CPU 3 of the control circuit 2 compares the current output frequency of the inverter circuit 2 with the target set frequency. When the set frequency reaches the current frequency, acceleration control is stopped and the process moves to the next control routine. Conversely, if the current frequency is lower than the set frequency, the Stroll prevention function is activated.For example, if the current frequency is lower than the Stroll frequency by comparing the low frequency - approximately 51 (z >) with the current frequency, the Stroll prevention function is activated. , disable the anti-stroll function and CPU
3 is determined and inverter times l! The output frequency of 81 is increased at the current rate of increase to increase the load current. In other words, it is possible to flow a compensation current to obtain constant torque in the low frequency operation region.

On the other hand, if the stroke frequency is higher than the current frequency, the CPU 3 determines that the stroke prevention function is valid, and the CPU 3 determines that the stroke prevention function is valid.
3 takes in the value of the load current detected by the resistor R through the protection circuit 6 and compares it with a preset stroll current value. In this comparison, if the load current value exceeds the stroke current value, the rate of increase in the output frequency of the inverter circuit 1 is lowered and the frequency is further increased.5Also, if the load current value is lower than the stroke current value, the frequency is increased. Increase the rate at the current rate.

Then, the CPU 3 repeatedly performs the above operation i- until the current frequency reaches the set frequency. During this operation process, if the load current value exceeds an abnormal current value (trip current value) that should cause the motor to stop, CF)
IJ3 is determined to be abnormal and jumps to the above-mentioned abnormality interrupt routine, where the operation of the induction motor MI is forcibly stopped.

Note that the stall frequency may be freely variable.

[Effects of the Invention] The present invention consists of an inverter circuit that drives an electric motor and a control circuit that controls the inverter circuit, and the load current or load voltage reaches a stall prevention level during acceleration or deceleration to increase or decrease the output frequency of the inverter circuit. In a motor control device, the control circuit is equipped with a stall prevention means that reduces the rate of rise or fall of the frequency of the inverter circuit if the current frequency of the inverter circuit output is below a predetermined frequency. Since the control circuit is equipped with a means for disabling the operation of the preventive means described in steps 1 to 1, the control circuit is equipped with a means for disabling the operation of the preventive means in steps 1 to 1. This has the effect of disabling the stroll prevention means and preventing the electric motor from being forced to stop inadvertently.

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, and FIGS. 2 and 3 are flowcharts for explaining the operation of the same.

IM is an induction motor, 1 is an inverter circuit, 2 is a control circuit, 3 is a CPU, and 3a is a built-in RAM.

Agent Patent Attorney Ishi 1) Choshichi

Claims (1)

[Claims] (1) Consisting of an inverter circuit that drives the motor and a control circuit that controls the inverter circuit, if the load current or load voltage reaches the stall prevention level during acceleration or deceleration to increase or decrease the output frequency of the inverter circuit, the inverter circuit In a motor control device, the control circuit is equipped with a stall prevention means that reduces the rate of increase or decrease in the frequency of the inverter, and if the current frequency of the inverter circuit output is below a predetermined frequency, the operation of the stall prevention means is disabled. 1. A control device for an electric motor, characterized in that a control circuit is provided with means for controlling the electric motor.