JPH0116118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter failure diagnosis device using a microcomputer (hereinafter abbreviated as μCPU).

Conventionally, multiple synchronous motors are operated at the same speed using a PWM control inverter device using power transistors. If a short-circuit accident occurs in one motor during this operation, the short-circuit current is detected and the base drive current of the inverter transistor is cut off, disconnecting the load side and the inverter, and all motors are stopped. Was. However, only the motor that caused the short-circuit accident can be repaired by blowing the fuse or
In many cases, it is desired to disconnect the MCB by tripping and allow other healthy motors to continue operating.

To deal with this problem, analog control cannot determine the cause of a failure, for example, whether it is a short circuit or an element is destroyed. Even if it could be determined, it would be impossible to continue operating the healthy motor for reasons such as the inability to detect and calculate the rotational speed and induced voltage of the healthy motor for re-synchronization.

Furthermore, in recent years, there has been a demand for more sophisticated inverter devices, and of course there has also been an increase in the demand for a self-diagnosis function in the event of a failure.

The present invention has been made in view of the above circumstances, and its purpose is to provide a failure diagnosis control device that enables determination of the cause of failure, which has not been possible in the past, and enables continuous operation of a healthy electric motor. It is.

Hereinafter, the present invention will be explained in detail based on FIGS. 1 to 4.

In FIG. 1, a transistor inverter 1 surrounded by a dotted line is composed of transistors U to Z and feedback diodes _D1 to _D6 . This inverter 1 is connected to an electrolytic capacitor C and a fuse F, and is also connected to each of the synchronous motors _M1 to _M3 .

Now, if each transistor U, X of transistor inverter 1 is destroyed, electrolytic capacitor C
As shown in the figure, as the electric discharge flows,
As shown in the figure, the output current flows through L due to the induced voltage on the inverter load side. The relationship between the discharge current of the electrolytic capacitor C and the output current of the inverter 1 at this time is shown in FIG. In the figure, A indicates the discharge current of the electrolytic capacitor C, and B indicates the output current. As shown in Figure B, the output current is
Since it flows through the L portion on the load side, the current rises later than the discharge current of the capacitor C shown in A.

Therefore, if the output current is within the rated value when the discharge current of the capacitor C deviates from the gate cutoff current setting value A, it can be seen that the transistor element of the inverter 1 has been destroyed.

Furthermore, in FIG. 1, if the load side is short-circuited, for example, the synchronous motor _M2 is short-circuited, the current flows as shown in FIG. Electrolytic capacitor C at this time
Figure 3 shows the relationship between the discharge current and the output current.
In the figure, C indicates the discharge current of the electrolytic capacitor C, and D indicates the output current, respectively. As shown in the figure, when the load side is short-circuited, the discharge current of the electrolytic capacitor C and the output current rise with approximately the same time constant. Furthermore, in the load short-circuit state, no output voltage is generated because the output of the inverter 1 is short-circuited.

Therefore, when the discharge current of the electrolytic capacitor C is equal to or higher than the gate break current setting value A, the output current deviates from the gate break current setting value A, and furthermore, the output voltage becomes 20 % or less, it can be seen that there is a short circuit on the load side. At this time, the discharge current of the electrolytic capacitor C is gated and the cut-off current setting value A
If the output current deviates from the set value and the output voltage is 20% or less of the operating voltage, a short circuit can be established on the load side.

Further, when the discharge current is equal to or higher than the set value A, and the output current is equal to or higher than the set value A, and the output voltage is equal to or higher than 20%, an output overcurrent occurs.

FIG. 4 shows an embodiment of the present invention. In the same figure, transistor inverter 1
is connected to converter 2 via fuse F on one side, and to converter 2 on the other side. An electrolytic capacitor C is connected in parallel between inverter 1 and converter 2. Further, each of the synchronous motors M 1 _{to M o} is connected to the transistor inverter 1 via each fuse (or MCB) F ₁ to F _o . 3 is a current detector for detecting the discharge current of electrolytic capacitor C, 4 is a transformer, and transistor inverter 1
A so-called voltage detector that inputs the output voltage of and outputs it to the rectifier 5. 6 is a current detector for detecting the output current of the transistor inverter 1, and 7 is an I/O port, into which current values and voltage values are input from the current detectors 3 and 6 and the rectifier 5, respectively. 8 is a μCPU, 9 is a memory, and 10 is a programmable timer.

Next, the operation of the device configured as described above will be explained.

Now, it is assumed that the memory 9 stores in advance a gate cutoff current setting value A, and each of the synchronous motors M ₁ to M _o is operated normally by the inverter 1 . Then, the μCPU 8 transfers the normal output voltage B output from the inverter 1 to the transformer 4, rectifier 5, I/O
Input via port 7 and bus 11, memory 9
Remember it.

In this state, if an element in the transistor inverter 1 is destroyed, the μCPU 8 inputs the discharge current of the electrolytic capacitor C from the current detector 3 via the I/O port 7, and this discharge flow is transferred to the memory. 9
When the gate current is higher than the set value A stored in
If this output current is within the rated value, it can be determined that the elements of inverter 1 are faulty under the AND condition that the discharge current is above the set value A and the output current is within the rated value. . Then, the device will stop due to fuse F blowing out, or if only one element is destroyed, the device will stop due to gate rupture. Also, if one of the synchronous motors M ₁ to _{M o} is short-circuited, μCPU 8
means that the discharge current of the electrolytic capacitor C input from the current detector 3 is equal to or higher than the set value A, and the current detector 6
When the output current inputted through the transformer 4 and the rectifier 5 is equal to or higher than the set value A, and when the output voltage inputted through the transformer 4 and the rectifier 5 is less than 20% of the output voltage B input during normal operation and stored in the memory 9, that is, A short circuit on the load side is determined under the AND conditions that the discharge current is above the set value A, the output current is above the set value A, and the output voltage is 20% or less of normal. In addition, even if electrolytic capacitor C does not operate, the output current will exceed the set value A,
Under the AND condition that the output voltage is 20% or more of normal, the load side is short-circuited.

In the case of a short circuit on the load side, it is desired that the other healthy synchronous motors except the faulty synchronous motor M _n continue to operate as they are, so by cutting off the gate of the transistor of inverter 1 due to overcurrent, 1 and the load side are disconnected from each other, but a short-circuit current flows from the synchronous motor connected to the same output side to the faulty synchronous motor _Mn due to its induced voltage. As a result, the fuse F _n of the faulty synchronous motor M _n blows, and the synchronous motor M _n
completely separate. When the faulty synchronous motor M _n is separated in this way, the load short-circuit phenomenon has been eliminated, so that the induced voltage of a healthy synchronous motor appears on the inverter output side.

After diagnosing the load short circuit, the programmable timer 10 inputs this induced voltage to the μCPU 8 through the transformer 4, current flow device 5, and I/O port 7 after a certain period of time for checking. Then, it is determined whether the failed synchronous motor M _n has been separated. If the faulty synchronous motor M _n is separated, the voltage coefficient of inverter 1 is calculated from the induced voltage value of the synchronous motor, the frequency is calculated from the synchronization of the output voltage, and the synchronous pull-in operation (pickup process) of inverter 1 is performed. By entering, the healthy synchronous motor operation can be continued.

Although the present invention has been described with respect to a synchronous motor using an inverter, it is needless to say that the invention is not limited to a synchronous motor and may be any general motor.

As described above, the present invention uses a μCPU for fault diagnosis in the event of a load short circuit in a constant speed operation system of a transistor inverter-driven synchronous motor. It became. In addition, the discharge current of electrolytic capacitor C and the output current of the inverter are
By checking the value of the inverter output voltage in addition to the AND condition, it is possible to easily diagnose whether it is a load short circuit, a DC side overcurrent (element destruction), or an output side overcurrent. Furthermore, in the case of a load short circuit failure, whether the failed motor has been isolated can be easily determined by checking the induced voltage, and by using the μCPU timer, the time from the load short circuit to the induced voltage check can be controlled. It has excellent advantages such as being able to

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an inverter device for explaining the present invention, FIGS. 2 and 3 are time chart diagrams for explaining the present invention, and FIG. 4 is a configuration showing an embodiment of the present invention. It is a diagram. 1 is a transistor inverter, 2 is a converter, 3 and 6 are current detectors, 4 is a transformer, 5 is a rectifier, 7 is an I/O port, 8 is a μCPU, 9 is a memory, 10 is a programmable timer, C is an electrolytic capacitor, M ₁ to M _o are synchronous motors.

Claims (1)

[Scope of Claims] 1. In a device that controls a plurality of electric motors using an inverter, there is provided a discharge current detection means for detecting a discharge current of a capacitor provided on the DC input side of the inverter, and a discharge current detection means for detecting an output current of the inverter. output current detection means, output voltage detection means for detecting the output voltage of the inverter, and failure determination means for inputting the detection signals of the respective detection means and comparing them with preset values to determine the location of the failure. In addition, when the discharge current or the output current reaches a gating cutoff setting value, it is compared with a preset setting value, and the failure location is determined by the failure determination means under the following conditions. Inverter failure diagnosis device. (a) Determination of inverter element destruction When the capacitor discharge current is greater than the gate cutoff current setting value and the output current is within the inverter's rated value. (b) Determination of load short circuit When the capacitor discharge current is greater than the gate cutoff current setting value, or the output current is greater than the gate cutoff setting value and the output voltage is less than the voltage drop setting value.