JPH0468762B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a lifting electromagnet device for attracting and transporting iron products such as steel materials using an electromagnet, and in particular a lifting electromagnet that can demagnetize iron products such as steel materials. Regarding equipment. (Prior Art) Lifting electromagnetic devices that attract and transport iron products such as steel materials have been known. When a steel material is attracted and transported using this lifting electromagnet device, residual magnetism is generated in the steel material, so it is necessary to remove this residual magnetism. In other words, it is necessary to demagnetize it. Here, a conventional lifting electromagnet device will be explained with reference to FIG. When demagnetizing steel materials, control circuit (command circuit) 1
0 to the current coincidence detection circuit 8 and the phase control circuit 9, and at the same time, a designation signal designating the thyristor rectifier to be operated is sent to the phase control circuit 9. (It is assumed that a designation signal designating the thyristor rectifier 2 is sent.) Based on the first current command signal and the designated signal, the phase control circuit 9 sends a gate signal to the thyristor rectifier 2. As a result, the thyristor rectifier 2 is turned on, and current flows through the excitation coil 4 of the suspension electromagnet in the direction shown by the solid arrow. At this time, the current flowing through the excitation coil 4 gradually increases depending on the output voltage of the thyristor rectifier and the time constant of the hoisting electromagnet (section '-' shown in FIG. 6). On the other hand, the current flowing through the excitation coil 4 is detected by a current detector 7 and input to a current coincidence detection circuit 8. The current coincidence detection circuit 8 compares the first current setting value set by the first current command signal and the current detection value, and as a result, if the first current setting value and the current detection value match, A current coincidence signal is sent from the current coincidence detection circuit 8 to the control circuit 10 (point '' in FIG. 6). Upon receiving this current coincidence detection signal, the control circuit 10 resets the first current command signal. When the first current command signal is reset, the phase control circuit 9 controls the thyristor rectifier 2 (gives a gate signal) using the phase control angle as the power regeneration operation range. As a result, the thyristor rectifier 2 performs a regenerative operation. At this time, the current flowing through the excitation coil 4 rapidly decreases (as shown in Fig. 6).
'point). A circuit current is detected by a current detector 5 and a detection signal is sent to a zero current detection circuit 6. When the circuit current becomes zero, the zero current detection circuit 6 activates the time limit circuit 11.
Sends a zero detection signal to When the timer circuit 11 receives the zero detection signal, it measures a predetermined time, and
A time-up signal is sent to the control circuit 10. When the control circuit 10 receives this time-up signal, it sends out a second current command signal (first current command value>second current command value) to the current matching circuit 8 and phase control circuit 9, and also sends a second current command signal (first current command value>second current command value) to the current matching circuit 8 and phase control circuit 9. A designation signal designating the thyristor rectifier 3 is sent to the thyristor rectifier 9. As a result, the phase control circuit 9 sends a gate signal to the thyristor rectifier 3. As a result, the thyristor rectifier 3 is turned on, and current flows through the excitation coil 4 in the direction indicated by the dashed arrow (point '' in FIG. 6). Thereafter, the current flowing through the exciting coil 4 is controlled in the same manner. As described above, the thyristor rectifier 2 and the thyristor rectifier 3 are controlled alternately to gradually reduce the current flowing through the excitation coil 4 to zero as shown in FIG. 6, thereby eliminating residual magnetism in the steel material. . (Problems to be Solved by the Invention) By the way, when demagnetizing a steel material using a conventional lifting electromagnet device, if the thyristor rectifiers 2 and 3 are turned on at the same time even momentarily, a short circuit will occur in the power supply. Therefore, as mentioned above, the thyristor rectifier 2
When switching the thyristor rectifier 3, the thyristor rectifier 2 or 3 is operated after the timer circuit 11 measures a predetermined time after detecting zero current. That is, it is necessary to provide a predetermined prohibition time after zero current detection, and this prohibition time needs to be longer as the inductance of the lifting electromagnet is larger. Therefore, it is necessary to consider the above-mentioned prohibition time when determining the demagnetization time. Normally, the transportation cycle using a lifting electromagnet device is
It takes about 30 seconds to 2 minutes. On the other hand, conventionally, a demagnetization time of at least 20 seconds is required. Since this demagnetization time is added to the above-mentioned transportation cycle time, the conventional lifting electromagnet device has a problem in that cargo handling efficiency is significantly reduced. An object of the present invention is to provide a lifting electromagnet device with good cargo handling efficiency. (Means for Solving the Problems) The lifting electromagnet device of the present invention includes an electromagnet including first and second excitation coils respectively connected to first and second rectifiers connected to an AC power supply. ,
A detection means for detecting the current flowing in the first and second exciting coils, and a first and second rectifier are controlled based on the current values detected by the detection means, and the first and second rectifiers are controlled at predetermined timing. and a control means for controlling the current flowing through the second excitation coil, and furthermore, the electromagnet control method described above is characterized in that the current flowing through one of the first and second excitation coils is set in advance. When the set value is reached, the current flowing through one excitation coil is attenuated and the current is passed through the other excitation coil. It is characterized by what it did. (Example) The present invention will be described below with reference to Examples. First, referring to FIG. 3, the lifting electromagnet used in the present invention includes an iron core (yoke) 12, a first excitation coil 4a wound around the yoke 12, and a second excitation coil 4a wound around the yoke 12.
The steel material 13 is demagnetized as described later. Here, referring also to FIG. 1, when demagnetizing the steel material, first, a first current command signal is sent from the control circuit (command circuit) 10 to the phase control circuit 9b and the current coincidence detection circuit 8b. The phase control circuit 9b is the first
Based on the current command signal of thyristor rectifier 3
Sends a gate signal to. As a result, the thyristor rectifier 3 is turned on, and current I ₂ flows through the exciting coil 4b. At this time, the current I ₂ flowing through the exciting coil 4b
gradually increases depending on the output voltage of the thyristor rectifier and the time constant of the lifting electromagnet (section ~ shown in FIG. 2b). On the other hand, the current I ₂ flowing through the exciting coil 4b is detected by the current detector 7b, and the current matching detection circuit 8b
is input. The current coincidence detection circuit 8b compares the first current setting value set by the first current command signal and the current detection value, and as a result, if the first current setting value and the current detection value match, A current coincidence signal is sent from the current coincidence detection circuit 8b to the control circuit 10 (shown in FIG. 2b). When the control circuit 10 receives this current matching signal, it resets the first current command signal and sends a second current command signal to the phase control circuit 9a and the current matching detection circuit 8a. By resetting the first current command signal, the phase control circuit 9b controls the thyristor rectifier 3 (gives a gate signal) by setting the phase control angle to the power regeneration operation range. As a result, the thyristor rectifier 3 performs a regenerative operation, and the current flowing through the exciting coil 4b is
It decreases rapidly (~points shown in Figure 2b). When the current flowing through the excitation coil 4b becomes equal to or less than the holding current, the thyristor rectifier 3 is turned off (point shown in FIG. 2b). On the other hand, the phase control circuit 9a sends a gate signal to the thyristor rectifier 2 based on the second current command signal. As a result, the thyristor rectifier 2 is turned on, and current I ₁ flows through the exciting coil 4a. On this occasion,
This current _I1 gradually increases (section ~ shown in FIG. 2a). The current I ₁ flowing through the exciting coil 4a is detected by the current detector 7a and input to the current coincidence detection circuit 8a. The current coincidence detection circuit 8a compares the second current setting value set by the second current command signal (second current setting value < first current setting value) and the current detection value, and as a result, When the second current setting value and the detected current value match, a current matching signal is sent from the current matching detection circuit 8a to the control circuit 10 (point shown in FIG. 2a). When the control circuit 10 receives this current coincidence signal, it resets the second current signal and sends out a third current command signal to the phase control circuit 9b and the current coincidence detection circuit 8b. Thereafter, thyristor rectifiers 2 and 3 are controlled at predetermined timing in the same manner. Referring to FIGS. 2a to 2c, when the current _I2 flowing through the exciting coil 4b reaches a point, the current
I ₂ decreases rapidly. On the other hand, when the current I ₂ reaches the point, the current I ₁ begins to flow through the exciting coil 4a.
When the current I ₁ reaches the point, the current I ₂ starts flowing through the exciting coil 4b again. In other words, as shown in FIG. 2b, the excitation coil 4b has points, points, points,
A current flows through point C-1, point B-1, etc., and the maximum value of this current gradually decreases and finally reaches zero. On the other hand, as shown in Figure 2a, a current flows through the exciting coil 4a from point to point to point F-1, and the maximum value of this current gradually decreases until it finally reaches zero. Become. Here, as shown in Fig. 3, if the magnetic flux due to the current I ₁ is φ ₁ , the magnetic flux due to the current I ₂ is φ ₂ , and the composite magnetic flux of magnetic fluxes φ ₁ and φ ₂ is φ, the composite magnetic flux φ is as shown in Figure 2. As shown in c, it changes from point, point, point, point, point, point... Note that this composite magnetic flux φ is as shown in the following table depending on the current flowing through the exciting coils 4a and 4b.

【table】

[Table] By the way, as shown in FIG. 4, the sub-excitation coil 4a ₁ and the sub-excitation coil 4a ₂ are connected in series or in parallel (in series in the example shown) to form the first excitation coil 4a, and Connect the excitation coil 4b ₁ and sub-excitation coil 4b ₂ in series or in parallel (in series in the example shown)
Alternatively, the first and second excitation coils 4a and 4b may be connected to the thyristor rectifiers 2 and 3 to control the thyristor rectifiers 2 and 3 as described above. good. That is, the first and second exciting coils 4a and 4
b may be divided into a plurality of sub-excitation coils connected in series or in parallel, and the first and second excitation coils 4a and 4b may be connected to the thyristor rectifiers 2 and 3, respectively. (Effects of the Invention) As explained above, in the present invention, an electromagnet is provided with a first excitation coil and a second excitation coil, and these first and second excitation coils are connected to first and second thyristor rectifiers, respectively. Since the thyristor rectifier is connected to the alternating current power supply via the thyristor rectifier, even if the first and second thyristor rectifiers are turned on at the same time, a power supply short circuit will not occur. Therefore, current can be passed through the second excitation coil while current is flowing through the first excitation coil, and the prohibition time that was conventionally required becomes unnecessary. Furthermore, when the current flowing through the first exciting coil reaches the set value, a current in the opposite direction is caused to flow through the second exciting coil, so that the attenuation of the current can be accelerated. As described above, in the lifting electromagnet device according to the present invention, the demagnetization time can be significantly reduced compared to the conventional one, and as a result, cargo handling efficiency can be significantly improved. Furthermore, as mentioned above, even if the first and second thyristor rectifiers are turned on at the same time, there will be no power supply short circuit, so not only is there no need for the conventional timing circuit, but there is also the possibility of erroneous ignition due to noise, etc. Prevention measures are simple and therefore cost-effective and reliable.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the lifting electromagnet device according to the present invention, and Fig. 2 shows the current flowing in the first excitation coil, the current flowing in the second excitation coil, and the current generated in the lifting electromagnet. A diagram showing the composite magnetic flux, FIG. 3 is a diagram showing one embodiment of the lifting electromagnet used in the present invention, and FIG. 4 is a diagram showing another embodiment of the lifting electromagnet used in the present invention. FIG. 5 is a diagram showing a conventional lifting electromagnet device, and FIG. 6 is a diagram showing a current flowing through an excitation coil of the lifting electromagnet device shown in FIG. 1... AC power supply, 2, 3... Thyristor rectifier, 4a... First excitation coil, 4b... Second excitation coil, 7a, 7b... Current detector, 8a,
8b... Current coincidence detection circuit, 9a, 9b... Phase control circuit, 10... Command circuit (control circuit).

Claims (1)

[Claims] 1. An electromagnet comprising first and second excitation coils respectively connected to first and second rectifiers connected to an AC power source, and current flowing through the first and second excitation coils. and controlling the first and second rectifiers based on the current values detected by the detection means to control the current flowing through the first and second excitation coils at a predetermined timing. A lifting electromagnet device characterized by having a control means for controlling. 2. When the current flowing through one of the excitation coils of the electromagnet including the first and second excitation coils reaches a predetermined setting value, the current flowing through the one excitation coil is attenuated and the current is applied to the other excitation coil. 1. A method of controlling an electromagnetic device for lifting, comprising a step of allowing the flow to flow, and performing the step a plurality of times while sequentially reducing the set value.