JPH0561501A - Digital setting device - Google Patents

Abstract

PURPOSE:To surely prevent the abnormal operations of an equipment even if the equipment which receives e set signal is misset to possibly cause the abnormality by inhibiting the output of the misset signal to the equipment. CONSTITUTION:A digital setting device 21 is provided with a setting circuit 21A which contains a logical, switch for the bit numbers end produces the digital signal Of a BCD code in correspondence with the designated numerical. value among 0-9, a bias setting circuit 2C which produces the digital signal of the BCD code corresponding to the prescribed numerical value, end the circuits 30 end 32 which select the circuit 21C in place of the circuit 21A when the logical switch has a specific open/close pattern corresponding to the specific numerical value. These specific numerical values are different from each other. In such a constitution, an equipment never has the abnormality even if such specific value that may possibly cause the abnormality is misset to the equipment because a set signal is applied to the equipment from the circuit 21C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital setter.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a low-frequency power source for an electromagnetic stirrer provided in an aluminium melting furnace. In the figure, 1 is an input terminal connected to a commercial power source, CB is a circuit breaker, 2 is a switch equipped with an initial charging circuit 3, 4 is a converter, 5 is a smoothing reactor, 6 is a smoothing capacitor, 7 Is a PWM-controlled transistor type inverter, 8 is an output terminal, 9 is a feeder, 1
0 is an electromagnetic stirring coil, DCCT is a direct current detector, CT
Is an alternating current detector.

Reference numeral 11 denotes a terminal for inputting a forward / reverse setting signal, 1
Reference numeral 2 is a terminal for inputting the current setting signal I, and 13 is a digital frequency setting device for outputting the frequency setting signal ω. 1
Reference numeral 4 is a frequency conversion circuit, and based on the current setting signal I and the frequency setting signal ω, a current command I ^* = Isin θ
Is calculated and sent to the current control circuit 15. The current control circuit 15 calculates the deviation between the current feedback signal I _F and the current command I ^* from CT which detects the inverter output current, and inputs the deviation to the PWM circuit 16. PW
The M circuit 16 compares this input with the carrier wave and controls the transistor of the inverter 7 via the base amplifier 17 so that the deviation becomes zero. Reference numeral 18 is a failure detection circuit.

The digital frequency setting device 13 has a 0.1
A digital switch DS of 4 bits for each digit for setting a frequency in the range of Hz to 9.9 Hz. As shown in FIG. 3, as many logical switches X ₁ as the number of bits,
A built-in X _2, X4 ₄ X _8, on the surface, to be externally operated, for example, are arranged in a matrix, it has a button denoted by numbers 0 through 9, one of the button, for example, numbers When the button 9 is pressed once, the logical contacts having the weights of 2 and 4 are closed, and the digital signal having the BCD code "00001001" is output.

[0005]

Now, if the operator mistakenly presses the button with the numerical value 0 twice, the frequency will be 0.0 Hz.
Since the frequency has been set, that is, the direct current has been set, only the transistor of the arm of the specific phase among the six transistors of the inverter 7 is turned on. Therefore, the switching loss increases to about 3 times that of normal operation,
If the transistor is selected with the rated output current, it causes thermal destruction, and in order to prevent this, the capacity of the transistor must be increased, which is uneconomical.

Further, since a direct current flows through the electromagnetic stirring coil 10, the function of stirring the molten metal is lost.

The present invention has been made to solve this problem, and prevents the output of an erroneous setting signal to a device even if an erroneous setting that may cause an abnormality in the device receiving the setting signal is performed. An object of the present invention is to provide a digital setting device that can reliably prevent abnormal operation of the device.

[0008]

In order to achieve the above object, the present invention has a setting which has a logical switch for the number of bits and which generates a digital signal of a BCD code corresponding to a designated numerical value of 0-9. In a digital setting device provided with a circuit, a bias setting circuit for generating a digital signal of a BCD code corresponding to a predetermined numerical value, and the above setting circuit when the opening / closing pattern of the logic switch is a specific pattern corresponding to a specific numerical value. And a circuit for selecting the bias setting circuit, and the predetermined numerical value and the specific numerical value are different from each other.

According to another aspect of the present invention, the converter has a converter and a three-phase inverter controlled by current feedback, generates a current command based on the current setting signal and the frequency setting signal, and supplies a three-phase alternating current to the electromagnetic stirring coil at a low frequency. Used to provide the frequency setting signal in the power supply.

According to a third aspect, in the second aspect, the specific numerical value is 0 frequency.

[0011]

According to the present invention, the setting signal from the bias setting circuit is given to the device even if a specific numerical value that may cause an abnormality of the device receiving the setting signal is erroneously set. Even if the device is operated, no abnormality occurs in the device, and if a wrong setting is noticed and the setting is performed again, the set value for the device is automatically changed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 20 denotes a drive power source for the digital frequency setting device 21. In addition to the setting circuit 21A for setting the low-order digit and the setting circuit 21B for setting the high-order digit, the digital frequency setting device 21 includes the bias setting circuit 2
It is equipped with 1C. The bias setting circuit 21C is connected to the drive power supply 20 via the relay contact 31a of the switching circuit 30, the setting circuits 21A and 21B are connected to the drive power supply 20 via the relay contact 31b of the switching circuit 30, and the bias setting circuit 21C. And the output side of the setting circuit 21A are interconnected via butt diodes D1 and D2. Reference numeral 32 denotes a switching operation circuit, which is a relay coil 31.
The relay coil 31 is inserted between the positive and negative electrodes of the control power supply 33 via the AND circuit 34. This AND circuit 34 has logical contacts X ₁ , X ₂ of the setting circuit 21A,
X _4, logical contacts X ₁ of X ₈ and setting circuit 21B, X _2, X
₄ and X ₈ are connected in series, and logical contacts X ₁ , X ₂ ,
When X _4, X ₈ all become "closed", it biased exciting coil 31 becomes contact 31a is closed, the contact 31b is opened. In this embodiment, the bias setting circuit 21C has, for example, 0.1
Set Hz. Other configurations are the same as those of the conventional one.

In this configuration, if the operator mistakenly sets a frequency of 0.0 Hz, the logic switches X ₁ , X ₂ , X ₄ , X _{8 of} the setting circuit 21A and the logic switches of the setting circuit 21B are set. since _{X 1, X 2, X 4} , X 8 and are all set to "closed", the relay coil 31 is energized, the relay contact 31a is closed, relay contact 31b is opened, the setting circuit 21A from the driving power source 1 Since the bias setting circuit 21C is disconnected and connected to the driving power source 1, the bias setting circuit 21C outputs the code signal "00001000". Therefore, even if the operator ignores the fact that the frequency is set to 0.0 and starts the operation of the electromagnetic stirrer, the frequency setting signal of 0.1 Hz remains in the frequency conversion circuit 1.
4, the inverter 7 is not operated by direct current, and the stirring function is not lost.

When the operator notices that the 0 frequency is set and resets the operating frequency to a value other than 0 frequency,
Since the bias of the relay coil 31 is released, the setting circuit 21
Since A and 21B are connected to the drive power source 1 and the bias setting circuit 21C is disconnected from the drive power source 1, the frequency conversion circuit 14 is supplied with the frequency setting signal of the above operating frequency.

In the above embodiment, the digital setter is used as the frequency setter, but the setter 20 may be used for setting other physical quantities such as the current value.

[0017]

As described above, the present invention provides a setting signal from the bias setting circuit to the above-mentioned device even if a specific numerical value that may cause an abnormality in the device receiving the setting signal is set erroneously. Even if the above equipment is operated with the settings set,
It will not cause any abnormalities in the equipment, and if you make a mistake and set it again, the setting values for the above equipment will be automatically changed, reducing the burden on the operator and increasing the reliability. Can be increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a low frequency power supply including a digital frequency setting device.

FIG. 3 is a diagram for explaining the operation of the digital setting device.

[Explanation of symbols]

20 drive power source 21 digital frequency setting device 21A, 21B setting circuit 21C bias setting circuit 30 the switching circuit 31 a relay coil 31a, 31b relay contact 32 switching operation circuit 33 controls the power supply 34 and circuit X ₁ to X ₈ logical switch

Claims (3)

[Claims] 1. A logical switch having a number of bits is provided, and 0 to 9 is provided.
In a digital setter provided with a setting circuit for generating a BCD code digital signal corresponding to a designated numerical value, a bias setting circuit for generating a BCD code digital signal corresponding to a predetermined numerical value and the logical contact When the opening / closing pattern is a specific pattern corresponding to a specific numerical value, it has a switching circuit that selects the bias setting circuit instead of the setting circuit, and the predetermined numerical value and the specific numerical value are different from each other. Characteristic digital setting device. 2. A low frequency power supply having a converter and a three-phase inverter controlled by current feedback, which generates a current command based on a current setting signal and a frequency setting signal and supplies a three-phase alternating current to an electromagnetic stirring coil. 2. The digital setter according to claim 1, wherein a frequency setting signal is provided. 3. The digital setter according to claim 2, wherein the specific numerical value is zero.