JP4607199B2 - Lifting magnet drive circuit - Google Patents

Description

  The present invention relates to a lifting magnet drive circuit that excites and demagnetizes a lifting magnet.

  Generally, a lifting magnet for lifting an iron piece in cargo handling work or construction work is known. As a lifting magnet, in addition to what is installed in a factory or the like, there are some that are mounted on a vehicle. When using a lifting magnet, the lifting magnet is energized and lifted by attracting iron pieces. Then, when releasing the iron piece, the lifting magnet is demagnetized.

  Patent Document 1 describes a lifting magnet drive circuit that excites and demagnetizes a lifting magnet. This lifting magnet drive circuit has four transistors and four diodes, and is connected in parallel to the H bridge circuit unit for controlling the excitation and demagnetization of the lifting magnet, and demagnetizes the lifting magnet. And an energy absorbing part for absorbing the energy stored in the lifting magnet.

This energy absorption part has a series circuit of a switch element and a resistance element, and absorbs the energy accumulated in the lifting magnet by the resistance element by conducting the switch element.
JP 2007-119160 A

  However, in the lifting magnet drive circuit described in Patent Document 1, since the energy absorbing unit is connected between the high potential side power source and the low potential side power source, if the switch element of the energy absorbing unit has an abnormal operation, There is a possibility that the resistance element generates heat, and there is a possibility that desired performance cannot be obtained.

  For example, if the switch element cannot be made conductive, the lifting magnet cannot be demagnetized, and the voltage across the lifting magnet continues to rise. Then, the switch element may be short-circuited due to overvoltage. As a result, since the energy absorbing portion is connected between the high potential side power source and the low potential side power source, there is a problem in that current always flows through the resistance element and heat generation increases.

  Therefore, an object of the present invention is to provide a lifting magnet drive circuit that can reduce the heat generation of the energy absorbing portion.

  The lifting magnet drive circuit of the present invention is a lifting magnet drive circuit that excites and demagnetizes a lifting magnet, and is connected in series between a high potential side power source and a low potential side power source in order. A third transistor having a node between the first and second transistors connected to one end of the lifting magnet and a high potential side power source and a low potential side power source electrically connected in series; And a fourth transistor, a node between which is connected to the other end of the lifting magnet, and the first to fourth transistors connected in parallel to the first to fourth transistors, respectively. An H bridge circuit unit that controls excitation and demagnetization of the lifting magnet, and a first transistor in the H bridge circuit unit. Between the terminal connected to the high potential side power source of the transistor and the terminal connected to the high potential side power source of the third transistor, and to the low potential side power source of the second transistor in the H bridge circuit section. A resistance element connected to one of the terminal and the terminal connected to the low-potential side power supply of the fourth transistor, and accumulated in the lifting magnet when demagnetizing the lifting magnet An energy absorbing part for absorbing energy.

  According to this lifting magnet drive circuit, for example, the resistance element in the energy absorption unit is connected to the terminal connected to the high potential side power source of the first transistor in the H bridge circuit unit and the high potential side power source of the third transistor. When connected between the two terminals of the lifting magnet, both ends of the lifting magnet are connected via the first and third transistors in the H-bridge circuit section, and between the high potential side power source and the low potential side power source. Are connected via the third and fourth transistors in the H-bridge circuit section. Therefore, even if the first and third transistors are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet, it is possible to prevent a constant current from flowing through the resistance element due to the fourth transistor. .

  On the other hand, for example, the resistance element in the energy absorption unit is between the terminal connected to the low potential side power source of the second transistor and the terminal connected to the low potential side power source of the fourth transistor in the H bridge circuit unit. When connected, both ends of the lifting magnet are connected via the second and fourth transistors in the H-bridge circuit section, and the high-voltage side power supply and the low-potential side power supply are connected in the H-bridge circuit section. The third and fourth transistors are connected. Therefore, even if the second and fourth transistors are short-circuited due to overvoltage due to the increase in the voltage across the lifting magnet, it is possible to prevent the third transistor from constantly flowing current through the resistance element. .

  The energy absorption unit described above may further include a capacitive element connected between the high potential side power source and the low potential side power source.

  According to this configuration, the demagnetization of the lifting magnet can be performed by the series circuit of the resistance element and the capacitance element in the energy absorption unit. At that time, resonance occurs due to the inductor component and the capacitive element of the lifting magnet, so that the discharge time of the voltage across the lifting magnet can be shortened. As a result, the demagnetization time of the lifting magnet can be shortened, and the iron piece can be released quickly.

  Here, the capacitive element acts to store energy from the lifting magnet. Since there are various sizes of the lifting magnet, if the capacitive element is selected in accordance with a large lifting magnet, the capacitive element becomes large. However, according to this configuration, since the demagnetization of the lifting magnet can be performed by the series circuit of the resistance element and the capacitance element, the demagnetization of the energy of the lifting magnet can be shared by the resistance element and the capacitance element. . As a result, energy stored in the capacitor can be reduced, and the capacitor can be made smaller.

  Furthermore, according to this configuration, a closed loop can be formed by the resistance element, the H bridge circuit, and the lifting magnet, and the voltage across the lifting magnet can be discharged without using the capacitive element. As a result, when demagnetizing a large lifting magnet, it is possible to demagnetize the lifting magnet by a series circuit of the resistance element and the capacitive element after reducing the holding energy of the lifting magnet only by the resistance element. Therefore, the capacitive element can be made smaller without depending on the size of the lifting magnet.

  Further, the energy absorption unit described above is connected in parallel to the resistance element and has a rectification function from the first transistor side to the third transistor side or from the fourth transistor side to the second transistor side. It may further have a rectifying element for use.

  The lifting magnet has residual magnetism due to hysteresis characteristics. In order to demagnetize the residual magnetism, it is necessary to pass a reverse current through the lifting magnet. According to this configuration, when a reverse current is passed through the lifting magnet, the absorbing portion rectifying element can be used, and thus the residual magnetism of the lifting magnet is efficiently demagnetized while suppressing loss due to the resistance element. be able to.

  Another lifting magnet drive circuit according to the present invention is a lifting magnet drive circuit that excites and demagnetizes the lifting magnet, and is connected in series between a high potential side power source and a low potential side power source in order. And a second transistor having a node between the first and second transistors connected to one end of the lifting magnet, and a high potential side power source and a low potential side power source connected in series in order. 3 and 4 transistors, a node between which is connected to the other end of the lifting magnet, and 3rd and 4th transistors, and 1st to 1st transistors connected in parallel to the 1st to 4th transistors, respectively. Between the high-potential side power source and the low-potential side power source, and an H bridge circuit unit that controls the excitation and demagnetization of the lifting magnet. It is continued, and a resistive element and a capacitive element connected in series to each other, and an energy absorbing portion for absorbing the energy stored in the lifting magnet during degaussing of the lifting magnet.

  According to the lifting magnet driving circuit, the energy absorption unit has the capacitive element connected in series with the resistance element, so that no current always flows through the resistance element, and the switch is connected in series with the resistance element. There is no need to provide an element.

  Further, according to the lifting magnet driving circuit, the lifting magnet can be demagnetized by the series circuit of the resistance element and the capacitance element in the energy absorbing portion. At that time, resonance occurs due to the inductor component and the capacitive element of the lifting magnet, so that the discharge time of the voltage across the lifting magnet can be shortened. As a result, the demagnetization time of the lifting magnet 2 can be shortened, and the iron piece can be released quickly.

  Further, according to this lifting magnet drive circuit, since the energy absorption unit is a series circuit of a resistance element and a capacitance element, demagnetization of the energy of the lifting magnet can be shared by the resistance element and the capacitance element. As a result, energy stored in the capacitor can be reduced, and the capacitor can be made smaller.

  The energy absorption unit described above may further include an absorption unit rectifier element connected in parallel to the resistance element and having a rectification function from the low potential side power source to the high potential side power source.

  According to this configuration, as described above, in order to demagnetize the remanent magnetism of the lifting magnet, the rectifying element for the absorber can be used when a reverse current is passed through the lifting magnet. It is possible to efficiently demagnetize the residual magnetism of the lifting magnet while suppressing loss.

  Further, another lifting magnet driving circuit of the present invention is a lifting magnet driving circuit that excites and demagnetizes the lifting magnet, and is connected in series between a high potential power source and a low potential power source. 1 and 2 transistors, and a node between them is connected in series between the first and second transistors connected to one end of the lifting magnet, and the high potential side power source and the low potential side power source in order. Third and fourth transistors, a node between which is connected to the other end of the lifting magnet, the third and fourth transistors, and the first to fourth transistors connected in parallel to the first to fourth transistors, respectively. A fourth rectifying element, and an H bridge circuit unit that controls excitation and demagnetization of the lifting magnet; The fourth transistor in series with the current element and in parallel with the third transistor together with the third rectifier element or in series with the fourth rectifier element in the H-bridge circuit section and with the fourth rectifier element And an energy absorption unit that absorbs energy accumulated in the lifting magnet when the lifting magnet is demagnetized.

  According to this lifting magnet drive circuit, for example, the resistance element in the energy absorption unit is connected in series to the third rectifying element in the H-bridge circuit unit and is connected in parallel to the third transistor together with the third rectifying element. In this case, both ends of the lifting magnet are connected via the first transistor and the third rectifier element in the H bridge circuit unit, and the high voltage side power source and the low potential side power source are connected in the H bridge circuit unit. The third rectifying element and the fourth transistor are connected. Therefore, even if the first transistor and the third rectifier element are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet, the fourth transistor prevents a constant current from flowing through the resistance element. be able to.

  On the other hand, for example, when the resistance element in the energy absorption unit is connected in series to the fourth rectifying element in the H bridge circuit unit in the H bridge circuit unit and connected in parallel to the fourth transistor together with the fourth rectifying element. The both ends of the lifting magnet are connected via the second transistor and the fourth rectifying element in the H bridge circuit unit, and the third in the H bridge circuit unit is connected between the high potential side power source and the low potential side power source. And the fourth rectifier element. Therefore, even if the second transistor and the fourth rectifying element are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet, the third transistor prevents a current from constantly flowing through the resistance element. be able to.

  The energy absorption unit described above may further include a capacitive element connected between the high potential side power source and the low potential side power source.

  According to this configuration, the demagnetization of the lifting magnet can be performed by the series circuit of the resistance element and the capacitance element in the energy absorption unit. At that time, resonance occurs due to the inductor component and the capacitive element of the lifting magnet, so that the discharge time of the voltage across the lifting magnet can be shortened. As a result, the demagnetization time of the lifting magnet can be shortened, and the iron piece can be released quickly.

  According to the present invention, in the lifting magnet driving circuit, the heat generation of the energy absorbing unit can be reduced.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.
[First Embodiment]

  FIG. 1 is a circuit diagram showing a lifting magnet drive circuit according to the first embodiment of the present invention. A lifting magnet drive circuit 1 shown in FIG. 1 is a circuit that performs excitation and demagnetization of the lifting magnet 2, and includes a DC conversion unit 3, an H bridge circuit unit 4, and an energy absorption unit 5.

The DC converter 3 converts the AC voltages V _{AC1 to} V _AC3 supplied from the three-phase AC power supply ACG into a DC voltage V _DC . The DC converter 3 has a positive output terminal 3a and a negative output terminal 3b, and provides the generated DC power supply voltage _VDC between the positive output terminal 3a and the negative output terminal 3b. In the present embodiment, the positive output terminal 3a functions as a high potential power source, and the negative output terminal 3b functions as a low potential power source. The DC conversion unit 3 may be configured to convert an AC voltage from a single-phase AC power source into a DC voltage. Further, the direct current converter 3 is not necessarily provided. In this case, a DC voltage is supplied between the positive output terminal 3a and the negative output terminal 3b from a battery, a DC generator, or the like.

  The DC conversion unit 3 of the present embodiment is configured by a bridge circuit including six diodes 31a to 31f, and performs three-phase full-wave rectification. Specifically, among the diodes 31a to 31f, the diodes 31a and 31b are connected in series, the diodes 31c and 31d are connected in series, and the diodes 31e and 31f are connected in series. In addition, the group consisting of the diodes 31a and 31b, the group consisting of the diodes 31c and 31d, and the group consisting of the diodes 31e and 31f are connected in parallel to each other. One end on the cathode side of the set of these diodes is electrically connected to the positive output end 3a, and the other end on the anode side is electrically connected to the negative output end 3b.

  An AC power supply line 11a extending from a one-phase power supply terminal in the three-phase AC power supply ACG is electrically connected between the diode 31a and the diode 31b. An AC power supply line 11b extending from another one-phase power supply terminal in the three-phase AC power supply ACG is electrically connected between the diode 31c and the diode 31d. Between the diode 31e and the diode 31f, an AC power supply line 11c extending from another one-phase power supply terminal in the three-phase AC power supply ACG is electrically connected. In addition, the DC conversion unit may be configured by, for example, a pure bridge circuit using a thyristor or a mixed bridge circuit using a diode and a thyristor. In the case where the DC conversion unit is configured by a pure bridge circuit or a mixed bridge circuit, the thyristor is phase-controlled at a predetermined control angle by a phase control circuit (not shown).

  The H bridge circuit unit 4 controls excitation and demagnetization of the lifting magnet 2. The H bridge circuit unit 4 includes first to fourth n-type transistors 41a to 41d and first to fourth transistors electrically connected between drains and sources of the first to fourth transistors 41a to 41d. And H diode circuits (first to fourth rectifying elements) 42a to 42d.

  Specifically, the drain of the first transistor 41a is connected to the positive output terminal 3a of the DC converter 3, and the source of the first transistor 41a is connected to the drain of the second transistor 41b. The source of the second transistor 41 b is connected to the negative output terminal 3 b of the DC converter 3. On the other hand, the drain of the third transistor 41c is connected to the positive output terminal 3a of the DC converter 3 via the energy absorber 5, and the source of the third transistor 41c is the drain of the fourth transistor 41d. It is connected to the. The source of the fourth transistor 41 d is connected to the negative output terminal 3 b of the DC converter 3. The anodes of the first to fourth diodes 42a to 42d are connected to the sources of the first to fourth transistors 41a to 41d, respectively. The cathodes of the first to fourth diodes 42a to 42d are respectively The drains of the first to fourth transistors 41a to 41d are connected. The source of the first transistor 41 a and the drain of the second transistor 41 b are connected to one end of the lifting magnet 2, and the source of the third transistor 41 c and the drain of the fourth transistor 41 d are other than the lifting magnet 2. Connected to the end.

  The gates of the first to fourth transistors 41a to 41d are connected to a control circuit (not shown), and the conduction state between the drain and source in each of the first to fourth transistors 41a to 41d is provided from the control circuit. Controlled by a control current (or control voltage).

  The energy absorbing unit 5 is a circuit part for absorbing energy stored in the lifting magnet 2 when the lifting magnet 2 is demagnetized. The energy absorption unit 5 is between the positive output terminal 3 a of the DC conversion unit 3 and the drain of the third transistor 41 c in the H bridge circuit unit 4, and the drain of the first transistor 41 a in the H bridge circuit unit 4. And the drain of the third transistor 41c. The energy absorption unit 5 includes a resistance element 51 and a diode (absorption unit rectifying element) 52.

  The resistance element 51 and the diode 52 are connected in parallel, and these parallel circuits are connected between the drain of the first transistor 41a and the drain of the third transistor 41c in the H-bridge circuit unit 4. . Specifically, the anode of the diode 52 is connected to the drain of the first transistor 41a, and the cathode of the diode 52 is connected to the drain of the third transistor 41c. The diode 52 is arranged as necessary and can be omitted.

Next, the operation of the lifting magnet drive circuit 1 according to the first embodiment will be described with reference to FIGS. 2 to 5 are diagrams showing current flows in the respective operation modes in the lifting magnet drive circuit shown in FIG.
(Excitation mode of lifting magnet)

  The first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are turned on. As a result, as shown in FIG. 2, the exciting current is applied to the positive output terminal 3a of the DC converter 3, the first transistor 41a, the lifting magnet 2, the fourth transistor 42d, and the negative output terminal 3b of the DC converter 3. I1 flows.

  Next, the first transistor 41a is turned off. As a result, as shown in FIG. 3, a return current I2 flows through the lifting magnet 2, the fourth transistor 41d, and the second diode 42b. Thereafter, the first transistor 41a is turned on again. As a result, the excitation current I1 flows as shown in FIG.

In this way, by switching the first transistor 41a, the lifting magnet 2 is excited and can attract and lift an iron piece or the like. The voltage applied to the lifting magnet 2 can be adjusted by adjusting the switching ratio of the first transistor 41a, and the energy accumulated in the lifting magnet 2 can be adjusted. Thereby, for example, the strength of the iron piece adsorption can be adjusted.
(Demagnetization mode of lifting magnet)

  The first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are made non-conductive, and the voltage across the lifting magnet 2 is inverted. Thereafter, the first transistor 41a is turned on. As a result, as shown in FIG. 4, the return current, that is, the demagnetizing current I3 flows through the lifting magnet 2, the third diode 42 c, the resistance element 51 in the energy absorption unit 5, and the first transistor 41 a, and the resistance element 51 lifts the current. The energy stored in the magnet 2 is consumed.

As a result, the lifting magnet 2 is demagnetized, and the attracted iron pieces and the like can be released.
(Demagnetization mode of remanence of lifting magnet)

  Here, the lifting magnet 2 has residual magnetism due to hysteresis characteristics. Therefore, the first transistor 41a in the H-bridge circuit unit 4 is turned off, and the second transistor 41b and the third transistor 41c are turned on. Accordingly, as shown in FIG. 5, the positive side output terminal 3 a of the DC conversion unit 3, the diode 52 in the energy absorption unit 5, the third transistor 41 c, the lifting magnet 2, the second transistor 41 b, and the DC conversion unit 3. A demagnetizing current I4 of residual magnetism flows through the negative output terminal 3b. That is, a residual magnetism demagnetizing current I4 flows in the lifting magnet 2 in a direction opposite to the demagnetizing current I3.

  Thereby, the lifting magnet 2 is completely demagnetized, and the adhering iron pieces and the like can be released.

  Thus, according to the lifting magnet drive circuit 1 of the first embodiment, for example, both ends of the lifting magnet 2 are connected via the first and third transistors 41a and 41c in the H-bridge circuit unit 4. The third and fourth transistors 41c and 41d in the H-bridge circuit unit 4 are provided between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3. It will be connected via. Accordingly, even if the first and third transistors 41a and 41c are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet 2, a current always flows through the resistance element 51 by the fourth transistor 41d. Can be prevented. Therefore, according to the lifting magnet drive circuit 1 of the first embodiment, it is possible to reduce the heat generation of the energy absorbing unit 5 during abnormal operation.

Further, according to the lifting magnet driving circuit 1 of the first embodiment, the energy absorbing unit 5 includes the diode (absorbing unit rectifying element) 52 connected in parallel to the resistance element 51. When the demagnetization of the residual magnetism is performed, the demagnetization current I4 of the residual magnetism flows through the diode 52, and the demagnetization of the residual magnetism of the lifting magnet 2 can be efficiently performed while suppressing the loss caused by the resistance element 51.
[Second Embodiment]

  FIG. 6 is a circuit diagram showing a lifting magnet drive circuit according to the second embodiment of the present invention. A lifting magnet drive circuit 1A shown in FIG. 6 is different from the first embodiment in that the lifting magnet drive circuit 1 includes an energy absorption unit 5A instead of the energy absorption unit 5.

  The energy absorption unit 5 </ b> A is different from the energy absorption unit 5 in that the energy absorption unit 5 further includes a capacitive element 53. The capacitive element 53 is connected between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3.

Next, the operation of the lifting magnet drive circuit 1A of the second embodiment will be described with reference to FIGS. 7 to 11 are diagrams showing current flows in the respective operation modes in the lifting magnet drive circuit shown in FIG.
(Excitation mode of lifting magnet)

  Similar to the lifting magnet drive circuit 1A of the first embodiment, the first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are made conductive. As a result, as shown in FIG. 7, the exciting current is applied to the positive output terminal 3 a of the DC converter 3, the first transistor 41 a, the lifting magnet 2, the fourth transistor 42 d, and the negative output terminal 3 b of the DC converter 3. I1 flows.

  Next, the first transistor 41a is turned off. As a result, as shown in FIG. 8, a return current I2 flows through the lifting magnet 2, the fourth transistor 41d, and the second diode 42b. Thereafter, the first transistor 41a is turned on again. As a result, the excitation current I1 flows as shown in FIG.

In this way, by switching the first transistor 41a, the lifting magnet 2 is excited and can attract and lift an iron piece or the like. The voltage applied to the lifting magnet 2 can be adjusted by adjusting the switching ratio of the first transistor 41a, and the energy accumulated in the lifting magnet 2 can be adjusted. Thereby, for example, the strength of the iron piece adsorption can be adjusted.
(First demagnetization mode of lifting magnet)

  Similar to the lifting magnet drive circuit 1A of the first embodiment, the first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are made non-conductive, and the voltage across the lifting magnet 2 is inverted. Thereafter, the first transistor 41a is turned on. As a result, as shown in FIG. 9, a return current, that is, a demagnetizing current I3a flows through the lifting magnet 2, the third diode 42c, the resistance element 51 in the energy absorption unit 5A, and the first transistor 41a. The energy stored in the magnet 2 is consumed.

As a result, the lifting magnet 2 is demagnetized, and the voltage across the lifting magnet 2 can be reduced.
(Second demagnetization mode of lifting magnet)

  Next, the first transistor 41a is turned off. As a result, as shown in FIG. 10, a return current, that is, a demagnetizing current I3b flows through the lifting magnet 2, the third diode 42c, the resistive element 51, the capacitive element 53, and the second diode 42b in the energy absorbing unit 5, and the resistance A part of the energy stored in the lifting magnet 2 is consumed by the element 51 and other energy is stored in the capacitive element 53.

  At this time, resonance is generated by the inductor component of the lifting magnet 2 and the capacitive element 53, and the discharge of the voltage across the lifting magnet 2 is accelerated.

As a result, the lifting magnet 2 is demagnetized, and the attracted iron pieces and the like can be released.
(Demagnetization mode of remanence of lifting magnet)

  Here, as described above, the lifting magnet 2 has residual magnetism due to hysteresis characteristics. Therefore, the second transistor 41b and the third transistor 41c in the H-bridge circuit unit 4 are turned on. As a result, as shown in FIG. 11, a demagnetizing current I4 of residual magnetism flows through the capacitive element 53, the diode 52, the third transistor 41c, the lifting magnet 2, and the second transistor 41b in the energy absorbing unit 5A. That is, the demagnetizing current I4 of the remanent magnetism flowing in the direction opposite to the demagnetizing currents I3a and I3b flows in the lifting magnet 2 due to the electric charge accumulated in the capacitive element 53.

  Thereby, the lifting magnet 2 is completely demagnetized, and the adhering iron pieces and the like can be released.

  Thus, also in the lifting magnet drive circuit 1A of the second embodiment, for example, both ends of the lifting magnet 2 are connected via the first and third transistors 41a and 41c in the H-bridge circuit unit 4 and are connected to the direct current. Between the positive side output terminal (high potential side power source) 3a and the negative side output terminal (low potential side power source) 3b of the conversion unit 3, the third and fourth transistors 41c and 41d in the H bridge circuit unit 4 are interposed. Will be connected. Accordingly, even if the first and third transistors 41a and 41c are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet 2, a current always flows through the resistance element 51 by the fourth transistor 41d. Can be prevented. Therefore, according to the lifting magnet drive circuit 1A of the second embodiment, it is possible to reduce the heat generation of the energy absorbing unit 5A during abnormal operation.

  Also in the lifting magnet drive circuit 1A of the second embodiment, the energy absorbing portion 5A has the diode (absorbing portion rectifying element) 52 connected in parallel to the resistance element 51, so that the lifting magnet 2 remains. When demagnetizing the magnetism, the demagnetizing current I4 of the residual magnetism flows through the diode 52, and the residual magnetism of the lifting magnet 2 can be efficiently demagnetized while suppressing the loss caused by the resistance element 51.

  Furthermore, according to the lifting magnet drive circuit 1A of the second embodiment, the following advantages can be obtained.

  The lifting magnet 2 can be demagnetized by the series circuit of the resistive element 51 and the capacitive element 53 in the energy absorbing portion 5A. At that time, resonance occurs due to the inductor component of the lifting magnet 2 and the capacitive element 53, so that the discharge time of the voltage across the lifting magnet 2 can be shortened. As a result, the demagnetization time of the lifting magnet 2 can be shortened, and the iron piece can be released quickly.

  Here, the capacitive element acts to store energy from the lifting magnet 2. Since there are various sizes of the lifting magnet, if the capacitive element is selected in accordance with a large lifting magnet, the capacitive element becomes large. However, according to the lifting magnet drive circuit 1A of the second embodiment, the demagnetization of the lifting magnet 2 can be performed by the series circuit of the resistance element 51 and the capacitance element 53. Therefore, the resistance element 51 and the capacitance element 53 The energy demagnetization of the lifting magnet 2 can be shared. As a result, the energy stored in the capacitive element 53 can be reduced, and the capacitive element 53 can be reduced.

  Furthermore, according to the lifting magnet drive circuit 1A of the second embodiment, the resistance element 51, the H bridge circuit 4, and the lifting magnet 2 can form a closed loop, and the lifting magnet can be used without using the capacitive element 53. 2 can be discharged. As a result, when demagnetizing the large lifting magnet 2, the holding energy of the lifting magnet 2 is reduced only by the resistance element 51, and then the demagnetization of the lifting magnet is performed by the series circuit of the resistance element 51 and the capacitive element 53. Can do. Therefore, the capacitive element 53 can be made smaller without depending on the size of the lifting magnet 2.

  Below, it verifies about the discharge time of the both-ends voltage of the lifting magnet 2 by the energy absorption part 5A of the lifting magnet drive circuit 1A.

  In an energy absorption part having only a resistive element, such as the energy absorption part described in Patent Document 1 and the energy absorption part 5 of the first embodiment, the time constant is large, and the discharge time of the voltage across the lifting magnet 2 is long. It is obvious that it is long. Moreover, even in an energy absorption part having only a capacitive element, as in another energy absorption part described in Patent Document 1, the time constant is large, and the discharge time of the voltage across the lifting magnet 2 becomes long.

  FIG. 12 is a diagram illustrating the discharge time of the voltage across the lifting magnet by the energy absorbing unit having only the capacitive element. FIG. 12 (a) shows a simulation result of the discharge time of the voltage across the lifting magnet 2 by the energy absorbing part 5X having only the capacitive element, and FIG. 12 (b) shows the simulation result of FIG. 12 (a). A simulation circuit diagram is shown. In FIG. 12B, the size of the lifting magnet 2 is 1500 / nominal 17 kW, rated current 75A, and coil inductance 4H. The energy absorbing unit 5X has ten 18000 μF capacitive elements in parallel.

  FIG. 12A shows that the time until the discharge current of the lifting magnet 2 becomes approximately 0 A, that is, the discharge time of the voltage across the lifting magnet 2 is about 650 ms.

  On the other hand, FIG. 13 is a diagram illustrating the discharge time of the voltage across the lifting magnet by the energy absorbing unit of the second embodiment. FIG. 13A shows a simulation result of the discharge time of the voltage across the lifting magnet 2 by the energy absorbing portion 5A of the second embodiment. FIG. 13B shows the simulation result of FIG. A simulation circuit diagram is shown. In FIG. 13B, the size of the lifting magnet 2 is the same as the simulation in FIG. In addition, the energy absorption unit 5A includes a resistance element 51 in which two 10Ω resistance elements are connected in parallel, a diode 52, and two capacitance elements of 18000 μF are connected in series, and two series circuits are connected in parallel. Capacitance element 53 is provided.

According to FIG. 13A, the time until the discharge current of the lifting magnet 2 becomes approximately 0 A, that is, the discharge time of the voltage across the lifting magnet 2 is about 450 ms, and the energy having only the capacitive element shown in FIG. It can be seen that the length is shorter than that of the absorbing portion 5X. This is because resonance is generated by the inductor component of the lifting magnet 2 and the capacitive element 53.
[Third Embodiment]

  FIG. 14 is a circuit diagram showing a lifting magnet drive circuit according to the third embodiment of the present invention. A lifting magnet drive circuit 1B shown in FIG. 14 is different from the first embodiment in that the lifting magnet drive circuit 1 includes an energy absorption unit 5B instead of the energy absorption unit 5.

  The energy absorbing unit 5B is connected between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3. The energy absorption unit 5 </ b> B includes a resistance element 51, a diode 52, and a capacitance element 53.

  The resistive element 51 and the capacitive element 53 are connected in series between the positive output terminal 3 a and the negative output terminal 3 b of the DC converter 3, and the diode 52 is connected in parallel to the resistive element 51. . In the present embodiment, the anode of the diode 52 is connected to the positive output end 3 a of the DC converter 3, and the cathode of the diode 52 is connected to the capacitive element 53. The diode 52 is arranged as necessary and can be omitted.

Next, the operation of the lifting magnet drive circuit 1B of the third embodiment will be described with reference to FIGS. 15 to 18 are diagrams showing current flows in the respective operation modes in the lifting magnet drive circuit shown in FIG.
(Excitation mode of lifting magnet)

  The first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are turned on. As a result, as shown in FIG. 15, the exciting current is applied to the positive output terminal 3a of the DC converter 3, the first transistor 41a, the lifting magnet 2, the fourth transistor 42d, and the negative output terminal 3b of the DC converter 3. I1 flows.

  Next, the fourth transistor 41d is turned off. As a result, as shown in FIG. 16, a return current I2 flows through the lifting magnet 2, the third diode 42c, and the first transistor 41a. Thereafter, the fourth transistor 41d is turned on again. As a result, the excitation current I1 flows as shown in FIG.

  In this way, by switching the fourth transistor 41d, the lifting magnet 2 is excited and can attract and lift an iron piece or the like. The voltage applied to the lifting magnet 2 can be adjusted by adjusting the switching ratio of the fourth transistor 41d, and the energy accumulated in the lifting magnet 2 can be adjusted. Thereby, for example, the strength of the iron piece adsorption can be adjusted.

In the present embodiment, the fourth transistor 41d is switched, but the first transistor 41a may be switched instead of the fourth transistor 41d as in the first and second embodiments.
(Demagnetization mode of lifting magnet)

  The first transistor 41a and the fourth transistor 41d in the H-bridge circuit unit 4 are made non-conductive, and the voltage across the lifting magnet 2 is inverted. As a result, as shown in FIG. 17, a return current, that is, a demagnetizing current I3 flows through the lifting magnet 2, the third diode 42c, the resistive element 51, the capacitive element 53, and the second diode 42b in the energy absorbing section 5B, and the resistance A part of the energy stored in the lifting magnet 2 is consumed by the element 51 and other energy is stored in the capacitive element 53.

  At this time, resonance is generated by the inductor component of the lifting magnet 2 and the capacitive element 53, and the discharge of the voltage across the lifting magnet 2 is accelerated.

As a result, the lifting magnet 2 is demagnetized, and the attracted iron pieces and the like can be released.
(Excitation mode of lifting magnet's residual magnetism)

  Here, as described above, the lifting magnet 2 has residual magnetism due to hysteresis characteristics. Therefore, the second transistor 41b and the third transistor 41c in the H-bridge circuit unit 4 are turned on. As a result, as shown in FIG. 18, a demagnetizing current I4 of residual magnetism flows through the capacitive element 53, the diode 52, the third transistor 41c, the lifting magnet 2, and the second transistor 41b in the energy absorbing unit 5B. That is, due to the electric charge accumulated in the capacitive element 53, a demagnetizing current I4 of remanence that flows in the opposite direction to the demagnetizing current I3 flows in the lifting magnet 2.

  Thereby, the lifting magnet 2 is completely demagnetized, and the adhering iron pieces and the like can be released.

  As described above, according to the lifting magnet drive circuit 1B of the third embodiment, the energy absorbing unit 5B includes the capacitive element 53 connected in series to the resistive element 51. Does not flow, and there is no need to provide a switch element in series with the resistance element 51. Therefore, according to the lifting magnet drive circuit 1B of the third embodiment, it is possible to reduce the heat generation of the energy absorbing unit 5B.

  Moreover, according to the lifting magnet drive circuit 1B of the third embodiment, the lifting magnet 2 can be demagnetized by the series circuit of the resistance element 51 and the capacitance element 53 in the energy absorbing unit 5B. At that time, resonance occurs due to the inductor component of the lifting magnet 2 and the capacitive element 53, so that the discharge time of the voltage across the lifting magnet 2 can be shortened. As a result, the demagnetization time of the lifting magnet 2 can be shortened, and the iron piece can be released quickly.

  In addition, according to the lifting magnet drive circuit 1B of the third embodiment, the energy absorbing unit 5B is a series circuit of the resistance element 51 and the capacitance element 53. Energy demagnetization can be shared. As a result, the energy stored in the capacitive element 53 can be reduced, and the capacitive element 53 can be reduced.

Further, according to the lifting magnet drive circuit 1B of the third embodiment, the energy absorbing unit 5A has the diode (absorbing unit rectifying element) 52 connected in parallel to the resistance element 51. Therefore, the lifting magnet 2 When the demagnetization of the residual magnetism is performed, the demagnetization current I4 of the residual magnetism flows through the diode 52, and the demagnetization of the residual magnetism of the lifting magnet 2 can be efficiently performed while suppressing the loss caused by the resistance element 51.
[Fourth Embodiment]

  FIG. 19 is a circuit diagram showing a lifting magnet drive circuit according to the fourth embodiment of the present invention. A lifting magnet drive circuit 1C shown in FIG. 19 is different from the first embodiment in that the lifting magnet drive circuit 1 includes an energy absorption unit 5C instead of the energy absorption unit 5. The other configuration of the lifting magnet drive circuit 1C is the same as that of the lifting magnet drive circuit 1.

  The energy absorbing unit 5C is different from the energy absorbing unit 5 in that the energy absorbing unit 5 does not include the diode 52 but includes only the resistance element 51. The resistance element 51 is connected in series to the third rectifying element 42c in the H-bridge circuit unit 4, and is connected in parallel to the third transistor 41c together with the third rectifying element 42c.

  In the lifting magnet drive circuit 1C, as in the lifting magnet drive circuit 1, when the lifting magnet 2 is excited, demagnetized, and residual magnetism is demagnetized, the above-described exciting operation mode, demagnetizing operation mode, and residual magnetism of the lifting magnet 2 are used. The demagnetization operation mode is operated (see FIGS. 2 to 5). Here, in the demagnetization operation mode of the residual magnetism of the lifting magnet 2 by the lifting magnet drive circuit 1C, the positive side output terminal 3a of the DC converter 3, the third transistor 41c in the energy absorber 5C, the lifting magnet 2, the second This is different from the demagnetization operation mode of the residual magnetism of the lifting magnet 2 by the lifting magnet driving circuit 1 shown in FIG. As a result, when the residual magnetism of the lifting magnet 2 is demagnetized, the residual magnetism demagnetizing current I4 flows through the third transistor 41c, and the residual magnetism of the lifting magnet 2 is suppressed while suppressing the loss caused by the resistance element 51. Demagnetization can be performed efficiently.

  Thus, according to the lifting magnet drive circuit 1C of the fourth embodiment, the same advantages as those of the lifting magnet drive circuit 1 of the first embodiment can be obtained without providing the diode 52 in the energy absorber 5. it can.

That is, according to the lifting magnet drive circuit 1C of the fourth embodiment, for example, the resistance element 51 in the energy absorbing unit 5C is connected between the first transistor 41a and the second transistor 41 in the H bridge circuit unit 4 between both ends of the lifting magnet 2. 3 between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3 in the H bridge circuit unit 4. The third rectifying element 42c and the fourth transistor 41d are connected. Therefore, even if the first transistor 41a and the third rectifier element 42c are short-circuited due to an overvoltage due to the rise in the voltage across the lifting magnet 2, a constant current is always supplied to the resistance element 51 by the fourth transistor 41d. It can be prevented from flowing. Therefore, according to the lifting magnet drive circuit 1C of the fourth embodiment, it is possible to reduce the heat generation of the energy absorbing unit 5C during abnormal operation.
[Fifth Embodiment]

  FIG. 20 is a circuit diagram showing a lifting magnet drive circuit according to the fifth embodiment of the present invention. A lifting magnet driving circuit 1D shown in FIG. 20 is different from the fourth embodiment in that the lifting magnet driving circuit 1C includes an energy absorbing unit 5D instead of the energy absorbing unit 5C. The other configuration of the lifting magnet driving circuit 1D is the same as that of the lifting magnet driving circuit 1C.

  The energy absorption unit 5D is different from the energy absorption unit 5C in that the energy absorption unit 5C further includes a capacitive element 53 in the energy absorption unit 5C. The capacitive element 53 is connected between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3.

  In the lifting magnet driving circuit 1D, similarly to the lifting magnet driving circuit 1A, when the lifting magnet 2 is excited, demagnetized, and residual magnetism is demagnetized, the above-described exciting operation mode of the lifting magnet 2, first and second It operates in a demagnetization operation mode and a demagnetization operation mode of residual magnetism (see FIGS. 7 to 11). Here, in the demagnetization operation mode of the residual magnetism of the lifting magnet 2 by the lifting magnet drive circuit 1D, the demagnetization of the residual magnetism in the capacitive element 53, the third transistor 41c, the lifting magnet 2, and the second transistor 41b in the energy absorbing unit 5D. It differs from the demagnetization operation mode of the residual magnetism of the lifting magnet 2 by the lifting magnet drive circuit 1A shown in FIG. 11 in that the current I4 flows. As a result, when the residual magnetism of the lifting magnet 2 is demagnetized, the residual magnetism demagnetizing current I4 flows through the third transistor 41c, and the residual magnetism of the lifting magnet 2 is suppressed while suppressing the loss caused by the resistance element 51. Demagnetization can be performed efficiently.

  Thus, according to the lifting magnet drive circuit 1D of the fifth embodiment, the same advantages as the lifting magnet drive circuit 1A of the second embodiment can be obtained without providing the diode 52 in the energy absorbing unit 5A. it can.

  That is, according to the lifting magnet drive circuit 1D of the fifth embodiment, for example, the resistance element 51 in the energy absorption unit 5D is connected between the first transistor 41a and the second transistor 41 in the H bridge circuit unit 4 between both ends of the lifting magnet 2. 3 between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3 in the H bridge circuit unit 4. The third rectifying element 42c and the fourth transistor 41d are connected. Therefore, even if the first transistor 41a and the third rectifier element 42c are short-circuited due to an overvoltage due to the rise in the voltage across the lifting magnet 2, a constant current is always supplied to the resistance element 51 by the fourth transistor 41d. It can be prevented from flowing. Therefore, according to the lifting magnet drive circuit 1C of the fourth embodiment, it is possible to reduce the heat generation of the energy absorbing unit 5C during abnormal operation.

  Further, the lifting magnet 2 can be demagnetized by a series circuit of the resistive element 51 and the capacitive element 53 in the energy absorbing unit 5D. At that time, resonance occurs due to the inductor component of the lifting magnet 2 and the capacitive element 53, so that the discharge time of the voltage across the lifting magnet 2 can be shortened. As a result, the demagnetization time of the lifting magnet 2 can be shortened, and the iron piece can be released quickly.

  Further, according to the lifting magnet drive circuit 1D of the fifth embodiment, the lifting magnet 2 can be demagnetized by the series circuit of the resistance element 51 and the capacitance element 53. Therefore, the resistance element 51 and the capacitance element 53 The energy demagnetization of the lifting magnet 2 can be shared. As a result, the energy stored in the capacitive element 53 can be reduced, and the capacitive element 53 can be reduced.

  Further, according to the lifting magnet drive circuit 1D of the fifth embodiment, a closed loop can be formed by the resistance element 51, the H-bridge circuit 4, and the lifting magnet 2, and the lifting magnet can be used without using the capacitive element 53. 2 can be discharged. As a result, when demagnetizing the large lifting magnet 2, the holding energy of the lifting magnet 2 is reduced only by the resistance element 51, and then the demagnetization of the lifting magnet is performed by the series circuit of the resistance element 51 and the capacitive element 53. Can do. Therefore, the capacitive element 53 can be made smaller without depending on the size of the lifting magnet 2.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the first to fourth transistors 41a to 41d in the H-bridge circuit unit 4 may be bipolar transistors instead of field effect transistors, and may be replaced with elements other than transistors as long as they have a switching function. It is. Further, the diodes 31a to 31f in the DC conversion unit 3, the first to fourth diodes 42a to 42d in the H-bridge circuit unit 4, and the diode 52 in the energy absorption units 5, 5A and 5B have a rectifying function in one direction. An element other than a diode can be substituted if provided.

  In the first and second embodiments, the parallel circuit of the resistance element 51 and the diode 52 in the energy absorption units 5 and 5A is connected to the positive output terminal 3a side of the DC conversion unit 3 in the H bridge circuit unit 4. Although provided, the DC conversion unit 3 may be provided on the negative output end 3b side.

  Specifically, the parallel circuit of the resistance element 51 and the diode 52 in the energy absorption units 5 and 5A is connected to the negative output terminal 3b of the DC conversion unit 3 and the source of the fourth transistor 41d in the H bridge circuit unit 4. It may be connected between the source of the second transistor 41b and the source of the fourth transistor 41d in the H-bridge circuit section 4. In this case, the anode of the diode 52 is connected to the source of the fourth transistor 41d, and the cathode of the diode 52 is connected to the source of the second transistor 41b.

  According to such a configuration, for example, the resistance element 51 in the energy absorbing units 5 and 5A is connected between the both ends of the lifting magnet 2 via the second and fourth transistors 41b and 41d in the H bridge circuit unit 4. The third and fourth transistors 41c, 41c in the H-bridge circuit unit 4 are provided between the positive output terminal (high potential power source) 3a and the negative output terminal (low potential power source) 3b of the DC converter 3. It will be connected via 41d. Therefore, even if the second and fourth transistors 41b and 41d are short-circuited due to an overvoltage due to an increase in the voltage across the lifting magnet 2, a current constantly flows through the resistance element due to the third transistor 41c. Can be prevented. Therefore, it is possible to reduce the heat generation of the energy absorbing parts 5 and 5A during abnormal operation.

  In the fourth and fifth embodiments, the resistance element 51 in the energy absorption units 5C and 5D is connected in series to the third rectification element 42c in the H bridge circuit unit 4, and the third rectification element 42c. Are connected in parallel to the third transistor 41c, but are connected in series to the fourth rectifying element 42d in the H-bridge circuit unit 4, and are connected in parallel to the fourth transistor 41d together with the fourth rectifying element 42d. May be.

  According to such a configuration, for example, the resistance element 51 in the energy absorbing units 5C and 5D is interposed between the both ends of the lifting magnet 2 via the second transistor 41b and the fourth rectifying element 42d in the H bridge circuit unit 4. The third transistor 41c and the second transistor 41c in the H bridge circuit section 4 are connected between the positive output terminal (high potential power supply) 3a and the negative output terminal (low potential power supply) 3b of the DC converter 3. 4 rectifier elements 42d. Therefore, even if the second transistor 41b and the fourth rectifying element 42d are short-circuited due to an overvoltage due to the rise in the voltage across the lifting magnet 2, a current is always applied to the resistance element 51 by the third transistor 41c. It can be prevented from flowing. Therefore, it is possible to reduce the heat generation of the energy absorbing portions 5C and 5D during abnormal operation.

1 is a circuit diagram showing a lifting magnet drive circuit according to a first embodiment of the present invention. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the demagnetization operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of an electric current in the demagnetization operation mode of the residual magnetism in the lifting magnet drive circuit shown in FIG. It is a circuit diagram which shows the lifting magnet drive circuit based on the 2nd Embodiment of this invention. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the demagnetization operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the demagnetization operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of an electric current in the demagnetization operation mode of the residual magnetism in the lifting magnet drive circuit shown in FIG. It is a figure which shows the discharge time of the both-ends voltage of a lifting magnet by the energy absorption part which has only a capacitive element. It is a figure which shows the discharge time of the both-ends voltage of the lifting magnet by the energy absorption part of 2nd Embodiment. It is a circuit diagram which shows the lifting magnet drive circuit based on the 3rd Embodiment of this invention. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the excitation operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of the electric current in the demagnetization operation mode in the lifting magnet drive circuit shown in FIG. It is a figure which shows the flow of an electric current in each demagnetization operation mode of the residual magnetism in the lifting magnet drive circuit shown in FIG. It is a circuit diagram which shows the lifting magnet drive circuit based on the 4th Embodiment of this invention. It is a circuit diagram which shows the lifting magnet drive circuit based on the 5th Embodiment of this invention.

Explanation of symbols

1, 1A, 1B, 1C, 1D ... Lifting magnet drive circuit, 2 ... Lifting magnet, 3 ... DC converter, 3a ... Positive output terminal (high potential side power supply), 3b ... Negative output terminal (low potential side power supply) ), 31a to 31f... Diode, 4... Bridge circuit section, 41a to 41d... First to fourth transistors, 42a to 42d... First to fourth diodes (first to fourth rectifier elements), 5A, 5B, 5C, 5D ... energy absorbing part, 51 ... resistive element, 52 ... diode, 53 ... capacitive element.

Claims (5)

A lifting magnet drive circuit for exciting and demagnetizing a lifting magnet,
First and second transistors connected in series between a high-potential-side power supply and a low-potential-side power supply in order, and a node between them is connected to one end of the lifting magnet. A third transistor and a fourth transistor electrically connected in series between the transistor and the high-potential-side power supply and the low-potential-side power supply, and a node therebetween is connected to the other end of the lifting magnet The third and fourth transistors, and the first to fourth rectifier elements connected in parallel to the first to fourth transistors, respectively, to control excitation and demagnetization of the lifting magnet. An H-bridge circuit section;
Between the terminal connected to the high potential side power source of the first transistor and the terminal connected to the high potential side power source of the third transistor in the H bridge circuit unit, and the H bridge circuit unit A resistive element connected to any one of a terminal connected to the low potential side power source of the second transistor and a terminal connected to the low potential side power source of the fourth transistor An energy absorbing part that absorbs energy accumulated in the lifting magnet when demagnetizing the lifting magnet;
A lifting magnet drive circuit.   The lifting magnet drive circuit according to claim 1, wherein the energy absorption unit further includes a capacitive element connected between the high potential side power source and the low potential side power source.   The energy absorption unit is connected in parallel to the resistance element and has a rectifying function from the first transistor side to the third transistor side or from the fourth transistor side to the second transistor side. The lifting magnet drive circuit according to claim 1, further comprising a rectifier for the absorber. A lifting magnet drive circuit for exciting and demagnetizing a lifting magnet,
First and second transistors connected in series between a high-potential-side power supply and a low-potential-side power supply in order, and a node between them is connected to one end of the lifting magnet. A third transistor and a fourth transistor connected in series between a transistor and the high-potential-side power source and the low-potential-side power source, the node between them being connected to the other end of the lifting magnet An H-bridge circuit that includes third and fourth transistors and first to fourth rectifier elements connected in parallel to the first to fourth transistors, respectively, and controls excitation and demagnetization of the lifting magnet. And
In series with the third rectifier element in the H-bridge circuit section and in parallel with the third transistor together with the third rectifier element, or in series with the fourth rectifier element in the H-bridge circuit section And having a resistance element connected in parallel to the fourth transistor together with the fourth rectifying element, and absorbing energy stored in the lifting magnet when demagnetizing the lifting magnet An absorption part;
A lifting magnet drive circuit. 5. The lifting magnet drive circuit according to claim 4 , wherein the energy absorption unit further includes a capacitive element connected between the high potential side power source and the low potential side power source.

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