JPH0336994A - Treating method for malfunction of inverter - Google Patents

Abstract

PURPOSE:To abruptly reset a motor decelerated to a predetermined low speed to one before a malfunction by interrupting an inverter output by the malfunction detection of the inverter, coasting a motor, and DC-braking it to avoid the voltage rise of the inverter. CONSTITUTION:If a malfunction is detected by a malfunction detector 11 during operation of a motor 3, the output of an inverter 2 is interrupted, and the motor 3 is coasted. The value of a frequency command 7 of a malfunction detection point t0 is stored. After predetermined time is elapsed, a DC current is supplied to the motor 3 to DC-brake the motor 3 to abruptly decelerate it. The command 7 is checked at a time point t3 when the motor 3 becomes a set speed or less, and if the command 7 is applied, it is recovered to the rotating speed N at the time t0 of the malfunction detection, while if the command is reversely not applied, it can be stopped as it is. The motor can be recovered from a low speed state to that before the malfunction at an abrupt speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an abnormality handling method in an inverter having a function of cutting off output when an abnormality is detected.

[Conventional technology]

In the conventional means, if an abnormality occurs while driving the motor with an inverter, the output is generally cut off in a relatively short period of time.

By the way, such conventional means have a problem in that when an abnormality is detected, the operation is stopped and the operation cannot be restarted unless it is restored by some method.

For example, when the compressor drive motor of a freezer is driven by an inverter, if the motor is stopped due to an abnormality, the functionality of the freezer will be completely lost and the products inside will be damaged, causing a great deal of damage.

When a transient abnormality such as overcurrent or overvoltage occurs, if the motor is restarted after the abnormality is cleared without stopping for a long time,
Damage can be minimized.

As a countermeasure to these problems, methods have been adopted that cut off the output only while an abnormality is occurring, or that cut off the output when an abnormality is detected and release the output cutoff after a certain period of time. Ta.

For example, JP-A-61-102171 [hereinafter referred to as JP-A-61-102171].

Below, this is referred to as the "first conventional example"], when a fault is detected, the output of the inverter is cut off, and the
After , sec, the cut-off is canceled, and 50 Il is reached after the cut-off is canceled.
A proposed method is to continue operation if no abnormality is detected within 50 m, sec, and to stop the above-mentioned re-try operation and stop the motor if an abnormality is detected within 50 m, sec. has been done.

However, in this first conventional method, if an abnormality occurs during high-speed operation, when the inverter output is cut off, if the phase of the inverter output and the motor residual voltage are different, However, there remains the problem that abnormalities such as overcurrent and overvoltage are likely to occur after the interruption is released.

In addition, as a second conventional example, Japanese Patent Application Laid-open No. 64-81689 can be seen, which states that if an abnormality occurs for a long time, such as low voltage or overload, retry is stopped and
This is a solution to the drawback of previous devices, which requires stopping the motor drive system.

This second conventional method synchronizes the output frequency of the inverter at the beginning of a retry in order to eliminate the problem that abnormalities such as overcurrent and overvoltage are likely to occur after the interruption is released. After the cutoff is released, the generation of overcurrent and overvoltage is suppressed during the process of increasing the output frequency to the level at which the abnormality occurred.

[Problem to be solved by the invention]

However, even in the method described in the second conventional example, in order to synchronize the output frequency of the inverter and the rotational speed of the motor, it is necessary to detect the motor current or the motor induced voltage. The problem was that the cost was high.

Furthermore, in order to increase the rotation speed to the level before the abnormality occurs, regardless of the status of the drive system other than the inverter device after frequency synchronization, the cause of the abnormality occurs outside the inverter.
If the abnormality is not resolved by the time the inverter starts its recovery operation, there is a risk of equipment destruction.

Here, the present invention overcomes all the problems of the conventional method by cutting off the output by detecting an abnormality.
Let it coast ~ When abnormal recovery is detected ~ Apply DC braking ~
The purpose is to provide a method for handling an abnormality through the process of decelerating to a constant low speed and rapidly returning to the speed before starting the vehicle.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an inverter that cuts off the output when an abnormality occurs.When an abnormality is detected, the inverter output is cut off and the motor connected to the inverter is temporarily put in a coasting state. After the release, the inverter's output frequency is reduced to zero and the motor is decelerated by DC braking, and after the motor rotation speed reaches the set speed or less, the inverter's output frequency is reduced within the allowable range to the output frequency at the time the error occurred. This is an inverter abnormality processing method characterized by causing a steep linear rise, and the inverter abnormality processing described in the previous section, in which whether or not to recover from the abnormality is determined based on the presence or absence of an inverter speed command. Furthermore, the present invention is an inverter abnormality handling method described in the preceding paragraph in which the application time of DC braking to the motor is determined from the braking current and the motor and load inertia.

[For production]

The present invention is a method for handling an inverter abnormality as described above, so when an abnormality is detected, the output is cut off to reduce the motor residual voltage, and when the abnormality is cleared, the inverter output frequency is set to zero and DC braking is applied, and regeneration is performed by regenerative braking. Avoiding the increase in the voltage at both the positive and negative terminals of the inverter due to energy, the motor residual voltage is reduced to a small rotation speed and the speed is suddenly decelerated, so there is no need for synchronization and there is no need to check the direction (phase) of the motor residual voltage. Also, there is no need for a current transformer as a current detection means, the loss time between power outages can be shortened, and it is possible to return to the state before the abnormality by rapid acceleration from a low speed state.

〔Example〕

FIG. 1 shows a block diagram showing the overall circuit configuration of an inverter load (motor) drive circuit in an embodiment of the present invention.

FIG. 2 shows a time chart when an abnormality occurs, and FIG. 3 shows a flowchart of abnormality processing in the inverter.

The AC voltage from the commercial power supply 10 is converted into a DC voltage in the forward conversion unit 1, and converted into a smooth DC voltage by the voltage smoothing unit (capacitor) 12.
) Add to 2. The inverter 2 converts the DC voltage into a required AC voltage to drive the motor 3.

When the frequency command 7 of the AC voltage to the motor 3 is given to the V/f [converts input terminal into frequency and motor applied voltage] converter 4, it is compared with the value set by the V/f setting device 6. A predetermined voltage signal is converted into PWM (Pulse World).
Modulation) is output to the control circuit 5.

This frequency command 7 is an output signal of a main controller (not shown) of the motor 3 drive system, and is a command for the same rotation speed of the motor 3 according to a request of the motor 3 drive system.

PWM control circuit 5 outputs a PWM signal to inverter 2.

Note that the abnormality detection circuit 11 has a resistance (impedance) 1
3, and an inverter low voltage detection signal 9 from the voltage across the capacitor 12 (although overvoltage is processed in the same way).
are introduced to detect inverter overcurrent and inverter undervoltage, respectively, and are controlled to appropriate values by the PWM control circuit 5.

That is, the abnormal signal of the inverter 2 is the inverter overcurrent detection signal 8 and the inverter low voltage (overvoltage) detection signal 9.
Detected by For example, if the motor 3 loses synchronization for some reason or is overloaded, an abnormal signal will be generated indicating overcurrent detection, and if the deceleration time is too fast, an excessive voltage will be generated, and if there is a power outage, an abnormal signal will be generated such as low voltage.

Here, the processing of the present invention when these abnormalities occur will be specifically explained based on the time chart shown in FIG.

When the abnormality detection circuit 11 detects an abnormality while the motor 3 is operating, [the abnormality has stopped at time to, and has recovered to normal at time tl], the output of the inverter 2 is cut off [at time to]
, the motor 3 is coasted [from time tO to t2].

Further, the value of the frequency command 7 at the abnormality detection time point to is stored.

After a certain period of time has elapsed, for example, at time t2 when the residual voltage of the motor 3 has decreased (approximately 50 m, sec in this example), a DC current is applied to the motor 3 to perform DC braking,
suddenly decelerate.

Here, the present invention employs DC braking, because in regenerative braking, the positive/quick opening DC voltage of the inverter 2 increases due to regenerative energy, causing a problem. In addition, by applying DC braking, the residual voltage of the motor 3 is reduced to a small rotation speed, so there is no need to synchronize when reaccelerating, and there is no need to check the direction (phase) of the residual voltage. .

At time t3 when the motor 3 becomes lower than the set speed [in the figure, it is zero, that is, the motor 3 is stopped], the frequency command 7 is checked, and if the frequency command 7 is applied, the host controller has returned to normal. If the frequency command 7 is not applied, the rotation speed returns to the rotation speed N at the abnormality detection time point to, and if the frequency command 7 is not applied, the rotation speed is stopped.

This FIG. 2 shows the case where the frequency command 7 is applied.

FIG. 3 shows a flowchart of the above-mentioned procedure.

Calculation is started in step 301, and in step 302 it is determined whether or not an abnormality has occurred. If no (NO), the process proceeds to step 311 and normality is restored, but if an abnormality has occurred (YES) , the process proceeds to step 303, the output is cut off, and the process proceeds to step 304, where the frequency command 7 number [
No. corresponding to each numerical value of the frequency command 7 is memorized, and at the same time, in step 305, a timer (not shown) is set to a time tO.
~t2 is set, and when the time point t2 is reached, the process proceeds to step 306, where it is determined whether the abnormality has been removed [in this example, the abnormality has already been removed at time tl], and if not, the process continues until the abnormality is removed. Repeat this process, and if the abnormality is resolved (YES), proceed to step 307 and perform DC braking [from time t2]. At the same time, in step 308, a timer (not shown) is set to indicate time t2.
~t3 is reached, DC braking is stopped at time t3, and the process proceeds to step 309, where the number of frequency command 7 is set at time t3.
Determine whether it exists or not, and if it does not exist (no) step 31
Go to Step 2 and stop the motor 3, and if the number of frequency command 7 is at t3 at this time (Yes), proceed to step 310 and run at the speed within the allowable range up to the number of frequency command 7 (motor 3 rotation speed N). It accelerates, proceeds to step 311, and returns to normal at specialty t4.

[Effects of the Invention] As explained above, in the present invention, when an abnormality is detected, the output of the inverter is cut off, the residual voltage of the motor is waited for to decrease, and after confirming that the abnormality has been removed, By reducing the output frequency of the inverter to zero and rapidly decelerating the motor using DC braking, the motor is temporarily brought into a low speed state. Thereafter, it is determined whether a frequency command is being applied, and the rotation speed is returned to the speed before the occurrence of the foreign item.

As a result, it is possible to quickly return to normal from an abnormality without using a special current detector such as a current transformer, so that a low-cost inverter device can be constructed.

Furthermore, since whether or not to restart the inverter is determined based on the presence or absence of a frequency command, it is also possible to confirm that the controller system has returned to normal from an abnormality as described above, making it possible to create a safe drive system. .

In addition, when the abnormality is cleared, DC braking is applied with the inverter output frequency set to zero, avoiding the rise in the voltage at both the positive and negative terminals of the inverter due to regenerative energy in so-called regenerative braking, and the motor is rapidly decelerated to a rotational speed with a small residual voltage. , there is no need for synchronization, there is no need to check the direction (phase) of the motor's residual voltage, there is no need for a current transformer as a current detection means, and loss time in the event of a power outage can be shortened. It is possible to return to the state before the abnormality by rapid acceleration.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an inverter load drive circuit according to an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the embodiment of the present invention when an abnormality occurs, and FIG. 3 is a diagram showing the operation of the embodiment of the present invention. It is a flowchart of inverter abnormality processing of one example. 1... Forward conversion unit 2... Inverse conversion unit (inverter) 3... Motor 4... V/f converter 5... PWM control circuit 6... V/f setting device 7... - Frequency command 8... Inverter overcurrent detection signal 9... Low (over) voltage detection signal 10... Commercial power supply 11... Abnormality detection circuit 12... Voltage smoothing section (capacitor) 13... Resistance (impedance).

Claims (1)

[Claims] 1. In an inverter that cuts off output when an abnormality occurs, the inverter output is cut off when an abnormality is detected, the motor connected to this inverter is temporarily put in a coasting state, and after the abnormality is cleared. , The inverter's output frequency is reduced to zero, the motor is decelerated by DC braking, and after the motor rotation speed reaches the set speed or less, the inverter's output frequency is moved in a steep straight line within the allowable range, until the motor rotation speed reaches the set speed or less. An inverter abnormality processing method characterized by causing an increase in temperature. 2. The inverter abnormality processing method according to claim 1, wherein whether or not to recover from the abnormality is determined based on the presence or absence of a speed command for the inverter. 3. The inverter abnormality processing method according to claim 1, wherein the application time of the DC braking applied to the motor is determined based on the braking current and the motor and load inertia.