JPH0783548B2 - Inverter abnormality external detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applied to a variable speed AC motor applied to a system in which the avoidance of stoppage of its operation is the most important, such as an AC motor for driving a pump in a tankless water supply system. The present invention relates to an abnormality detection circuit for a control inverter.

[Conventional technology]

As a conventional abnormality detection circuit of this type, it is configured by various state detection elements built into the inverter itself and a calculation element of the CPU, and further stops the operation of the inverter together with the occurrence of the target abnormality and further detects the abnormality. It is known to issue a signal to an external control circuit, and the external circuit switches the AC motor to the commercial alternative operation as described above.

[Problems to be Solved by the Invention]

However, in the inverter abnormality detection circuit according to the conventional method as described above, the accurate abnormality detection operation becomes impossible when the CPU malfunctions due to an accidental cause such as the peripheral noise of the inverter. Although the inverter has stopped its operation, the abnormality detection signal is not transmitted to the external control circuit, and there is a risk of system operation failure such that the AC motor cannot shift to the product replacement operation.

In view of the above, the present invention independently determines the occurrence of an inverter internal abnormality from the state signal of the inverter input / output specifications corresponding to the abnormality state, and reliably outputs the required commercial alternative operation command as described above and its arithmetic system. It is an object of the present invention to provide an inverter abnormality detection circuit which is configured independently of the control system of the inverter to ensure the abnormality detection function thereof.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, in the inverter abnormality external detection circuit of the present invention, an operation command for the inverter is applied and the output voltage of the output voltage of the inverter is normal although the power supply voltage and the output setting voltage are normal. An abnormal operating state caused by an internal abnormality of all circuits including the control circuit of the inverter is determined by a combined operation of various input / output state signals of the inverter, such as state detection when the abnormality continues for a specified time or more, and the determination is made. Based on the result of (1), it functions to output a command signal for performing a commercial alternative operation in which the AC motor is directly driven by a commercial AC power source, and its arithmetic system is configured independently of the control system of the inverter.

[Action]

The present invention determines an abnormal operating state caused by an internal abnormality of all circuits including a control circuit of an inverter by a combination calculation of various input / output state signals of the inverter, and based on the result of the determination, the AC motor is commercial AC power supply. The function of outputting a command signal for a commercial alternative operation to be directly driven by an inverter abnormality detection circuit whose operation system is configured independently of the control system of the inverter is separately provided. This makes it possible to reliably detect an abnormality and output the required control signal accordingly, regardless of the stability of the system against noise or other disturbances.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are a flow chart and a time chart corresponding to FIG. 1, respectively.

In FIG. 1, _Tr is a transformer, REC ₁ and REC ₂ are full-wave rectification stacks, CP _{1 to} CP ₃ are voltage comparators, NAND _{1 to} NAND ₄ are NAND gates, and PC ₁ and PC ₂ are photocouplers. , TD ₁ and TD ₂ are timers, and RY is a relay. Also, V _p , V _s, and V _o are the power supply voltage, the set voltage, and the output voltage of the inverter, respectively.
The _ps V _ss and the V _os a reference setting voltage for the each of the voltages V _p and V _s and V _o a determination is made whether or not there in the normal state, respectively, further S _i is the inverter operation command signal, S _c is a commercial alternative command signal for changing the AC motor power supply.
Hereinafter, when each of the voltages V _p , V _s , and V _o is a reference value or more, the voltage is “present”, and when it is less than the reference value, the voltage is “absent”.

The operation of FIG. 1 will be described below. The operating state of the inverter is the power supply voltage V _p , its output set voltage V _s , its output voltage
The four points of V _o and its operation command signal S _i are constantly monitored externally, and if none of the signals of the four points are input, a power failure or an operation stop regardless of the presence or absence of the inverter output voltage V _o As a state, the commercial substitute command signal S _c is not output.

Moreover, the power supply voltage V _p , the inverter set voltage V _s , and the inverter operation command signal S _i are all input, and the inverter output voltage
If V _o is not, the power supply voltage V _p is the transformer T _r rectified voltage comparator CP at further is transformed full-wave rectified Sutakkun REC ₁ by
Signal of the voltage comparator CP ₁ output by the comparison at ₁ and the reference voltage V _ps V _p ≧ V _ps is input to logic element NAND _1.
Further, the inverter set voltage V _s is compared with the reference voltage V _ss by the voltage comparator CP ₂ to recognize the presence or absence thereof, and the output of the CP ₂ is input to the NAND ₁ . The output of the element NAND ₁ is a logic element
Input to NAND ₂ . The inverter output voltage V _o is full-wave rectified by the rectification stack REC ₂ and converted to an isolated signal voltage by the photocoupler PC ₁ and then compared with the reference voltage V _{os by the} voltage comparator CP ₃ to confirm its presence. The output of the CP ₃ is connected to the NAND ₂
To enter. The element NAND ₂ has both the power supply voltage V _p and the inverter setting voltage V _p and the inverter output voltage
It operates only when V _o is in a non-conducting state and inputs its output to timer TD ₁ and logic element NAND ₃ . In the element NAND ₃ , it is monitored whether the inverter output voltage V _o has been restored within the set time of the timer TD ₁ , and if it is restored, it is reset to the initial state, and if it is not restored, the output of the NAND ₃ is output. It creates a pulsed signal at neglect TD ₂ for receiving the logical element NAND ₄
The pulse signal from the timer TD ₂ and the inverter operation signal S _i are confirmed by the element NAND ₄ and the pulse signal from the timer TD ₂ is stopped if the signal S _i is not input, and the inverter since the operation signal S _i is in inverter operation if it is input, the input pulses from the timer TD ₂ to the photocoupler PC ₂ is intended to output a commercial alternative signal activates the relay RY.

The flow chart of FIG. 2 is developed according to the operation contents of FIG. 1, and FIG. 3 is a time chart showing operation waveforms of various parts of the circuit of FIG.

〔The invention's effect〕

According to the present invention, the abnormality detection of the inverter in the variable speed control system of the AC electric motor is performed independently of the inverter, and the abnormality detection is performed separately by the combination calculation of various input / output state signals of the inverter. By using a circuit, erroneous detection of an abnormal state due to accidental disturbance due to noise or the like can be avoided, and the reliability of the command to switch the AC motor to the commercial AC power supply at the time of occurrence of an abnormality can be increased to make the variable speed control system useless. Can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 and FIG.
The figures are a flow chart and a time chart corresponding to FIG. 1, respectively. CP _{1 to} CP ₃ …… Voltage comparator, NAND _{1 to} NAND ₄ …… NAND element, PC ₁ , PC ₂ …… Photo coupler, REC ₁ , REC ₂ …… Full wave rectifying stack, TD ₁ , TD ₂ ...... Timer.

Claims (1)

[Claims] 1. An abnormality detection circuit for an inverter in a variable speed control system for an AC motor, wherein the output voltage of the inverter is applied even if a motion command is applied to the inverter and the power supply voltage and the output set voltage are normal. The abnormal operation state caused by the internal abnormality of all the circuits including the control circuit of the inverter is determined by a combination calculation of various input / output state signals of the inverter, such as the state detection when the abnormality continues for a specified time or more. A function of outputting a command signal for performing a commercial alternative operation in which the AC motor is directly driven by a commercial AC power source based on the result of the determination, and the arithmetic system thereof is configured independently of the control system of the inverter. External detection circuit for inverter malfunction.