JP2005341705A - Device for monitoring duration of interruption - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that, when controlling a motor by an inverter, the duration of the interruption of a commercial power supply or the duration of a voltage lowered to a prescribed voltage or below is monitored, but the capacity of a backup capacitor becomes large at the monitoring. <P>SOLUTION: A back-flow preventing diode is installed to a DC power supply, and a control operation unit and an input and output circuit that allows the transmission and the reception of a signal with the control operation unit are connected among the diode, a cathode and the DC power supply. The start and the stop of counting are conducted on the basis of a signal from the control operation unit at interruption and the recovery of the interruption. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power failure time monitoring device applied to an operation control device for an electric motor.

In an apparatus that drives an electric motor by an inverter device, the operation before the power failure is continued when the power is restored after a relatively short power failure. Therefore, a control device as shown in FIG. 4 is provided. In the figure, reference numeral 1 denotes a control calculation unit, which is provided with control calculation means, program storage means, data storage means, input / output means and the like. Reference numeral 2 denotes a backup capacitor, which is normally charged to a predetermined voltage from a power source via a diode D. Reference numeral 3 denotes an input / output circuit that outputs the occurrence of a power failure to the control arithmetic unit, monitors the charging state of the backup capacitor 2, and converts the analog charging voltage value that changes from time to time into a digital signal when the power failure occurs. Output to 1. The control arithmetic unit 1 executes a system program and a motor control program based on the input signal, and controls the controlled unit through the input / output means.
As such a control method for an electric motor or the like at the time of a power failure, for example, Patent Document 1 and Patent Document 2 are known.
In Patent Document 1, when the power failure is recovered during the regenerative operation of the motor, the rate of change in output is increased until the target speed is approached, compared to when the stopped motor is started. Patent Document 2 discloses a nonvolatile memory means for measuring the power failure time by applying the discharge characteristics of the CR circuit and increasing the measurement time accuracy when deciding whether or not to continue the operation before the power failure. The switch circuit is provided, and the actual allowable limit voltage is compared with the terminal voltage of the CR circuit immediately after recovery from the power failure to determine whether or not the operation can be continued.
JP-A-6-335288 JP-A-8-205384

Although the backup capacitor 2 gradually decreases in accordance with its discharge characteristics, the control calculation unit 1 changes the control method for the electric motor according to the voltage value.
The power failure continuation time is monitored by counting with a timer owned internally on the condition that a power failure occurrence signal is input to the control calculation unit 1 and confirming the power failure time at the power recovery timing. The power failure time is monitored up to the allowable limit voltage of the backup capacitor, that is, the allowable limit time. To monitor the power failure time as long as possible, it is necessary to increase the capacity of the capacitor.
In the conventional apparatus shown in FIG. 4, the output of the backup capacitor 2 is configured to be supplied also to the control arithmetic unit 1 and the input / output circuit 3, so that the backup capacitor needs to have a large capacity. The device itself is getting bigger.

  Accordingly, an object of the present invention is to provide a power failure time monitoring device capable of reducing the capacity of a backup capacitor.

In the first aspect of the present invention, the electric motor is controlled via the inverter, and the power failure time of the commercial power source or the time for the decrease of the predetermined voltage or less is monitored.
A direct current power source is provided with a diode for preventing a backflow, and a power source between the cathode of the diode and the direct current power source is connected to a control arithmetic unit and an input / output circuit capable of transferring signals between the control arithmetic unit, and the diode A backup capacitor is connected to the anode side of this, and a counter circuit having a clock generation unit is connected to the terminal of this backup capacitor, so that counting is started and stopped based on a signal from the control calculation unit at the time of power failure and power recovery It is characterized by comprising.

  According to a second aspect of the present invention, a reset circuit is connected to the terminal of the backup capacitor, and the counter circuit is reset when the backup capacitor voltage becomes a predetermined value or less.

In the third aspect of the present invention, the electric motor is controlled via an inverter, and the power failure time of the commercial power supply or the time of decrease below a predetermined voltage is monitored.
A direct current power supply diode is provided in the direct current power supply, and a power supply between the cathode of the diode and the direct current power supply includes a control arithmetic unit having a nonvolatile memory and an input / output circuit capable of transmitting / receiving signals to / from the control arithmetic unit. A backup capacitor is connected to the anode side of the diode, a real-time clock unit is provided at the terminal of the backup capacitor, and this clock signal is output to the control calculation unit.

As described above, according to the first aspect of the present invention, since the output of the backup capacitor is supplied only to the counter circuit, the capacity of the backup capacitor can be reduced, and the system can be miniaturized.
According to the second aspect of the present invention, malfunction can be prevented in addition to the first aspect of the invention. Further, according to the third aspect of the present invention, since the power failure time can be known without adding hardware, the capacity of the backup capacitor can be further reduced.

FIG. 1 is a block diagram showing an embodiment of the present invention. Reference numeral 10 denotes a control arithmetic unit connected to a power source. This control arithmetic unit functions to control an electric motor (not shown) via the input / output circuit 11, that is, a control arithmetic unit, a program storage unit, a data storage unit, etc. It has. In general, the power source has a predetermined voltage of, for example, 5 V from the inverter side through the DC / DC converter. Reference numeral 11 denotes an input / output circuit which introduces analog motor information such as a terminal voltage of the motor, converts the information into a digital signal, and outputs the digital signal to the control calculation unit 10. The calculation output signal of the control calculation unit 10 is also input to the input / output circuit 11. Is output as an inverter control signal. D is a backflow prevention diode, which has a cathode connected to the power source on the control arithmetic unit 10 and the input / output circuit 11 side, and a backup capacitor 12 connected to the anode side.
Reference numeral 13 denotes a counter circuit connected to the backup capacitor 12, and this counter circuit 13 has a clock generation unit and a count unit for counting the clock. Reference numeral 14 denotes a power failure detection unit, which detects a commercial power failure or a voltage lower than a predetermined value and notifies the control calculation unit 10 of the detected power failure.

In the present invention configured as described above, when the power supply is normal, the control calculation unit 10 executes the motor information input from the input / output circuit 11, the system program stored in the program storage means, and the motor control program, The output is controlled via the input / output circuit 11 to the electric motor as the controlled device. The backup capacitor 12 is charged via a power supply and a diode D.
When a power failure occurs or a voltage drop below a predetermined value occurs in the commercial power supply, the power failure detection unit 14 detects this and notifies the control arithmetic unit 10 of the occurrence of the power failure. On the condition of this signal, the control arithmetic unit 10 gives a start command to the counter circuit 13 to start up. The counter circuit 13 uses the backup capacitor 12 as an operating power supply and starts counting the clock generated in the clock generation unit. This count continues until power is restored, but when power is restored, the power failure detection unit 14 detects this, and a count stop command is output to the counter circuit 13 via the control calculation unit 10. The control calculation unit 10 reads the count value from the start of the count to the stop of the count to know the power failure time, determines whether or not the inverter returns to the operation before the power failure according to the power failure time, and can continue the operation. In the case of, the continuous control is resumed.
According to this embodiment, only the counter circuit may be used as the power source for the backup capacitor 12, so that the capacitance of the capacitor can be reduced as compared with the conventional case, and the system can be downsized.

FIG. 2 shows another embodiment. The difference from FIG. 1 is that a reset circuit 15 is provided. The terminal voltage of the backup capacitor 12 gradually decreases in accordance with the discharge characteristics, but the reset circuit 15 resets the counter circuit 11 to make the count value zero when the voltage of the backup capacitor 12 falls below a predetermined value. It is. When the control operation unit 10 recovers power and reads the count value of the counter circuit 11, if the count value is zero, the voltage of the backup capacitor 12 becomes a predetermined value or less, and the power failure continues for a certain time or more. Judgment is made and the continuous control is canceled.
If the backup capacitor voltage falls below the count operating voltage, the count value may not be read correctly. According to this embodiment, it is possible to further prevent malfunctions in addition to the effects of FIG.

FIG. 3 shows another embodiment. The difference from FIG. 1 is that a real-time clock unit 16 is provided in place of the counter circuit 13. The real-time clock unit 16 operates using a capacitor as a backup. In this case, a non-volatile memory is provided in the control calculation unit 10 and time is stored in the non-volatile memory when a power failure occurs. The time of the real-time clock is read when the power is restored, and the power failure time is determined based on the difference from the time stored in the memory.
According to this embodiment, by using the normally well-known real-time clock unit, the power failure time can be known without adding extra hardware, and the capacity of the backup capacitor can be further reduced.

The block diagram which shows embodiment of this invention. The block diagram which shows the other Example of this invention. The block diagram which shows the other Example of this invention. The block diagram of the conventional power failure time monitoring apparatus.

Explanation of symbols

1, 10 ... control calculation section
2, 12 ... Backup capacitors
3, 11 ... I / O circuit
13 ... Counter circuit 14 ... Power failure detection unit
15 ... Reset circuit
16 ... Real time clock

Claims (3)

For controlling an electric motor through an inverter and monitoring a power failure time of a commercial power source or a decrease time below a predetermined voltage,
A direct current power source is provided with a diode for preventing a backflow, and a power source between the cathode of the diode and the direct current power source is connected to a control arithmetic unit and an input / output circuit capable of transferring signals between the control arithmetic unit, and the diode A backup capacitor is connected to the anode side of this, and a counter circuit having a clock generation unit is connected to the terminal of this backup capacitor, so that counting is started and stopped based on a signal from the control calculation unit at the time of power failure and power recovery A power failure time monitoring device that is configured. 2. The power failure time monitoring apparatus according to claim 1, wherein a reset circuit is connected to a terminal of the backup capacitor, and the counter circuit is reset when a backup capacitor voltage becomes a predetermined value or less. For controlling an electric motor through an inverter and monitoring a power failure time of a commercial power source or a decrease time below a predetermined voltage,
A direct current power supply diode is provided in the direct current power supply, and a power supply between the cathode of the diode and the direct current power supply includes a control arithmetic unit having a nonvolatile memory and an input / output circuit capable of transmitting / receiving signals to / from the control arithmetic unit. A power failure time monitoring device comprising: a backup capacitor connected to the anode side of the diode; a real-time clock unit provided at a terminal of the backup capacitor; and the clock signal output to the control calculation unit. .

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