JP5419388B2 - Three-phase motor with integrated control device - Google Patents

Description

  The present invention relates to a controller-integrated three-phase motor used for driving a cooling tower fan in which a reduction gear is incorporated, for example.

  For example, in order to obtain a predetermined rotational speed, a cooling tower fan is widely operated by incorporating a speed reduction device such as a belt or a gear and operating with a general-purpose three-phase motor. In this case, when the capacity is 7.5 kW or less, the three-phase motor is often started by directly putting it into a commercial three-phase AC power source. This is a cause of problems such as shortening.

  Therefore, as a countermeasure against such a problem, for example, a commercially available device called a soft starter and an inverter device are used as a driving device for a three-phase motor having a soft start function for slowly starting.

  Various types of three-phase motor drive devices having such a soft start function have been proposed.

  For example, Patent Document 1 discloses that a triangular wave synchronized with the zero cross point of an AC power supply is provided with a switching element such as a thyristor or triac that can be phase controlled in all three-phase power supply circuits from a three-phase AC power supply to a three-phase motor. Triangular wave generating means for generating a signal, command signal generating means for generating a command signal that changes along a time series, and conduction control of the switching element by phase control based on a level comparison between the triangular wave signal and the command signal A soft start control device configured to perform is described.

  In Patent Document 2, switching elements are interposed in two phases of a three-phase power supply circuit from a three-phase AC power source to a three-phase motor, and soft start control is performed by phase controlling these two-phase switching elements. A control device of a three-phase two-wire phase control system is described.

  In Patent Document 3, as in Patent Document 2, switching elements are interposed in two phases of a three-phase power supply circuit from a three-phase AC power source to a three-phase motor, and these two-phase switching elements are phase-controlled. In a device that performs soft start control, the firing angle of the switching element interposed in the two-phase power feeding circuit is deviated in order to suppress the generation of an unbalanced current between the phases and perform stable start-up. As described above, there is described a control device of a three-phase two-wire phase control system that includes a calculation means for controlling the gate trigger signal and gradually starts the three-phase motor while reducing the unbalance amount of the line voltage.

  In Patent Document 4, a starter is configured by interposing switching elements in all three-phase power supply circuits from a three-phase AC power source to a three-phase motor, and a bypass circuit that bypasses the starter is configured. The three-phase motor is started and stopped with a three-phase AC power source that is phase-controlled by the starter, and the three-phase AC power source is supplied from a bypass circuit that bypasses the starter by closing the electromagnetic switch during rated rotation. A drive device for a three-phase motor is described in which the phase motor is driven so that the power supply to the three-phase motor is switched between start / stop and rated rotation.

Furthermore, in Patent Document 5, a starter configured by interposing a switching element in all three-phase power supply circuits from a three-phase AC power source to a three-phase motor is installed in the motor terminal box, and the switching element is cooled. A starter having a configuration in which a large-scale cooling device is installed outside is described.
Japanese Patent No. 3279173 JP 2003-47289 A Japanese Patent No. 3998395 JP 2000-201490 A Japanese Patent Laid-Open No. 3-3685

  In order to use the soft start function as shown in Patent Documents 1 to 4, conventionally, a new control panel for accommodating a drive device having the soft start function is installed, or an existing control panel is installed. It was necessary to satisfy the condition that a space for installing the device could be secured or that the device could be added.

  Moreover, in the thing shown by patent document 5, since the starter is attached in the motor terminal box, a new control panel is installed, the space which installs an apparatus in the existing control panel is secured, or expansion However, it is necessary to cool the semiconductor device in the terminal box because the current always flows in the terminal box, and as a result, a large-scale cooling device is installed outside. It becomes a large-scale configuration.

  Therefore, in the present invention, it is not necessary to install a new control panel, to secure a space for installing the device in the existing control panel, or to add a device, and can be easily installed without being oversized. A first problem is to provide a three-phase motor integrated with a control device.

  On the other hand, in the above-described cooling tower fan or the like, an inverter power supply is sometimes used to perform variable speed operation, and it is assumed that a drive unit having a soft start function is installed in a terminal box. When the phase motor is connected to the inverter power source, neither the start by the inverter nor the start by the soft start function can be normally performed.

  Therefore, a second object of the present invention is to provide a controller-integrated three-phase motor that can operate normally regardless of whether the connected power source is a commercial power source or an inverter power source.

  In order to solve the above-described problems, in the present invention, phase-controllable switching elements are interposed in at least two phases of a three-phase power feeding circuit from a connection portion with a three-phase AC power source to a three-phase motor. And a switching circuit for bypassing these switching elements, switching means for operating or not operating the bypass circuit, and feeding frequency detecting means connected to the two phases of the feeding circuit. And a control means for selecting the operation of the bypass circuit by the soft start means and the switching means based on the power supply frequency detected by the power supply frequency detection means, and the elements of each circuit and each means are connected to the terminals of the three-phase motor. We propose a three-phase motor with integrated control device installed in the box.

  In the present invention, it is proposed that in the above configuration, the soft start means includes a voltage zero cross detection circuit connected to two phases of the power feeding circuit and a phase control drive circuit of the switching element.

  Further, the present invention proposes that, in the above-described configuration, the switching element is interposed in two phases of the power feeding circuit, and the control unit is configured to control the soft start unit by two-phase control.

  In the present invention, in the above configuration, the soft start means is provided with a switching element conduction time detection circuit, and the control means is phase-controlled so that the conduction times of the switching elements detected by the conduction time detection circuit are equal. We propose a controller-integrated three-phase motor that is configured to operate a circuit.

  Further, the present invention proposes that, in the above configuration, at least a part of the wall of the terminal box is configured as an external heat radiating portion, and a switching element is attached to the inside of the wall.

  The present invention also proposes that, in the above configuration, the switching element is a power semiconductor element such as a thyristor or a triac, and the switching means of the bypass circuit is a relay.

  Further, the present invention proposes that, in the above configuration, the three-phase motor is for driving a cooling tower fan in which a reduction gear is incorporated.

  The present invention also proposes that the three-phase motor is an induction motor in the above configuration.

  In the present invention, since the above-described circuits and means from the connection portion with the three-phase AC power source to the three-phase motor are installed in the terminal box of the three-phase motor, for example, the installation in the cooling tower or the like is installed at a predetermined position. After that, the power supply line of the three-phase AC power source may be connected to the connection terminal in the terminal box, and installation is very easy.

  When the operation is started with the power turned ON, the control means detects the power supply frequency by the power supply frequency detection means, determines whether the frequency is the frequency of the commercial AC power supply, and if the frequency is the frequency of the commercial AC power supply, The operation of the start means is selected and the bypass circuit is not operated.

  When the soft start means operates, the switching element interposed in at least two phases of the three-phase power feeding circuit is phase-controlled to start the three-phase motor by the soft start operation, which occurs in the three-phase motor and the speed reducer. It is possible to suppress problems such as the impact at the time of start-up, the generation of noise due to belt slip, and the shortening of the service life.

  When starting by the soft start operation and reaching the rated rotation, the control means operates the bypass circuit by the switching means, and thereafter, the feeding current flows only through the bypass circuit and does not flow to the switching element. Therefore, since the switching element only needs to be cooled at the time of starting, it is easy to perform sufficient cooling even if it is mounted in the terminal box. That is, it is possible to perform sufficiently good cooling by configuring at least a part of the wall of the terminal box as an external heat radiating portion and attaching a switching element inside the wall.

  On the other hand, if it is determined at the start of operation that the power supply frequency detected by the power supply frequency detection means is not the frequency of the commercial AC power supply, the control means operates the bypass circuit operation / non-operation switching means to operate the bypass circuit. To work.

  In this case, the three-phase AC power source connected to the three-phase motor is an inverter power source, and the feeding current flows through the feeding circuit of the phase not provided with the bypass circuit and the switching element and does not flow to the switching element. The operation and the start operation by the soft start function do not interfere with each other, and normal operation by the inverter is performed.

  As described above, a switching element using a power semiconductor element such as a thyristor or a triac may be interposed in at least two phases of a three-phase power feeding circuit from a connection portion with a three-phase AC power source to a three-phase motor. From the viewpoint of installation in the terminal box, it is more advantageous to interpose only in two phases than in all three phases. In this case, the control means uses three-phase two-wire phase control. Control by method.

  In the control by the three-phase two-wire phase control system, the soft start means is provided with a switching element conduction time detection circuit so that the control means has the same conduction time of each switching element detected by the conduction time detection circuit. If the phase control drive circuit is configured to operate, a smooth soft start can be realized by reducing the unbalance of the current flowing in each phase.

Next, an embodiment of a three-phase motor integrated with a control device according to the present invention will be described with reference to the accompanying drawings.
First, FIG. 1 is a perspective view showing an appearance of a cooling tower as an example of a device using a three-phase motor integrated with a control device according to the present invention, and FIG. 2 is an enlarged partially cutaway perspective view of a main part. .
Reference numeral 1 denotes a cooling tower. In this case, a plurality of cooling towers 1 are arranged in a row, and control with increasing or decreasing the number of operating units is possible. A fan cylinder 3 that rotatably supports a fan 2 is provided in the upper part of the cooling tower 1. A belt speed reducer 4 that rotates the rotating shaft of the fan 2 on the fan cylinder 3 and a three-phase electric motor 5 for rotational driving. In this case, a three-phase motor is installed.

  The cooling tower 1 is a device that dissipates heat generated in air conditioning equipment and industrial equipment to the atmosphere. The heat is carried by the cooling water and is brought into contact with a large amount of air obtained by the fan 2 in the cooling tower 1. Heat is dissipated and the cooled cooling water is recycled.

  The cooling capacity of the cooling tower 1 is in contact with the atmosphere to dissipate its heat, so the summer is the most severe in the summer when the temperature of the atmosphere is the highest. When the temperature is lowered or when the heat load is lowered, the cooling water temperature is lowered more than necessary, resulting in overcooling. Therefore, there is a method of reducing the number of operating units as a method of lowering the cooling performance of the cooling tower 1 and raising the cooling water temperature. . When the cooling water temperature increases due to a decrease in the number of operating units, the number of operating units increases, and when the cooling water temperature decreases too much, an ON-OFF operation is performed in which the operating unit number is decreased.

  3 is a perspective view showing a three-phase motor 5 according to the present invention, FIG. 4 is a front view, FIG. 5 is a cross-sectional view taken along line AA of FIG. 4, and the three-phase motor 5 according to the present invention is A terminal box 6 is provided on the side, and this terminal box 6 includes a lid 7.

  In the three-phase motor 5 according to the present invention, the terminal box 7 includes a connection portion 8 for connecting to a three-phase AC power source, in this case, each circuit and each means to be described later from the connection terminal to the three-phase motor 5 in the terminal box 6. Next, each of these circuits and each means will be described in detail.

FIG. 6 is a system diagram showing an embodiment of a control device applied to the three-phase motor 5 according to the present invention.
Reference numeral 8 is a connection terminal which is a connection portion 8 to the three-phase AC power supply as described above, and two phases of the three-phase power supply circuits 9r, 9s, and 9t extending from the connection portion 8 to the three-phase motor 5, in this case , R-phase and T-phase power supply circuits 9r and 9t, phase-controllable switching elements 10r and 10t, and in this embodiment, thyristors are interposed, and these switching elements 10r and 10t are respectively connected in parallel. The bypass circuits 12r and 12t provided with the bypass relay 11 including the contact portions 11r and 11t are connected. The phase interposing the switching elements 10r and 10t is not limited to the R phase and the T phase, and may be an appropriate two phase. Further, switching elements may be interposed in all three phases.

  When a switching element is interposed in the three-phase power supply circuits 9r, 9s, and 9t of the power supply circuits 9r, 9s, and 9t, for example, a three-phase three-wire phase control method as described in Patent Document 1 described above is applied. Further, as in this embodiment, switching elements 10r and 10t capable of phase control are interposed only in the two-phase, R-phase, and T-phase power supply circuits 9r and 9t of the power supply circuits 9r, 9s, and 9t. In this case, for example, a three-phase two-wire phase control system described in Patent Document 2 and Patent Document 3 described above can be applied.

  Reference numeral 13 denotes a switching element driving circuit corresponding to the phase control driving circuit, in this case, a thyristor driving circuit. The switching elements 10r and 10t are phase-controlled by receiving a gate trigger signal from the thyristor driving circuit 13. Each switching element 10r, 10t is connected to a thyristor conduction time detection circuit 14 for detecting a voltage at both ends and detecting a conduction time, and the R-phase and S-phase power supply circuits 9r, 9s are connected to each switching element 10r, 10t. The voltage zero-cross detection circuit 15 of these interphase voltages and the frequency detection circuit 16 are connected, and these thyristor drive circuit 13, voltage zero-cross detection circuit 15 and frequency detection circuit 16 are connected to a microcomputer as the control means 17. It is connected. Reference numeral 18 denotes a bypass relay open / close circuit that operates the bypass relay 11 to open and close the contact portions 11r and 11t. Reference numeral 20 denotes a current detection circuit that detects the current of the S-phase feeding circuit 9s by the current detection unit 19. The bypass relay switching circuit 18 and the current detection circuit 20 are also connected to the microcomputer as the control means 17.

  In the present invention, each circuit and each means described above are installed in the terminal box 6, and elements and circuits constituting them can be configured as the circuit board 21. As shown in FIG. 5, a radiation fin 22 is provided on a part of the wall of the terminal box 6, in this case, the side wall in the same direction as the axial direction of the three-phase motor 5. Elements 10r and 10t, for example, thyristor modules are fixed.

  In the above configuration, the three-phase motor 5 according to the present invention is fixed to a predetermined portion of the belt speed reducer 4 of the fan cylinder 3 of the cooling tower 1, for example, and then the three-phase AC power supply line is connected to the terminal box 6. What is necessary is just to connect to the connection terminal 8, and installation is very easy. Reference numeral 24 denotes a support cylinder for drawing the power supply line into the terminal box 6.

  In the above configuration, when the power is turned on and the operation of the three-phase motor 5 is started, the control means 17 detects the power supply frequency by the power supply frequency detection circuit 16, determines whether the frequency is the frequency of the commercial AC power supply, When the frequency of the commercial AC power source is 50 Hz or 60 Hz, the soft start start operation is selected and the bypass circuit is not operated. That is, the control means 17 is configured so that the bypass relay switching circuit 18 maintains the contact portions 11r and 11t of the bypass relay 11 in the open state, and from the voltage zero cross detection circuit 15, the thyristor conduction time detection circuit 14, and the switching element drive circuit 13. The three-phase motor 5 is started by a soft start operation by controlling the phases of the two-phase switching elements 10r and 10t by the soft start means 25.

  As described above, the phase control of the two-phase switching elements 10r and 10t is performed by the method described in Patent Document 3, that is, from the integrated value of the line voltage in order to reduce the voltage imbalance in the soft start operation. A method of deriving an optimal control pattern and performing a soft start operation by shifting the firing angles of the two phases according to this control pattern can be applied. In the embodiment of the present invention, the thyristor conduction time detection circuit 14 is used. By detecting the conduction time of the switching elements 10r and 10t of each phase and controlling the conduction time to be equal for each control period, the voltage imbalance is reduced without requiring a specific control pattern. It is something to be made.

The soft start operation according to the embodiment of the present invention will be described with reference to a control pattern in the method of Patent Document 3.
First, FIG. 7 shows a control pattern in the method of Patent Document 3, in which the black circles indicate the firing angles of the switching elements of each phase per unit time. A soft start is performed by shifting the firing angle from 180 ° to a firing angle of 0 °.
8 to 12 show current waveforms of the switching elements 10r and 10t of the respective phases, R phase and T phase under the conditions of the firing angles of points A, B, C, D and E in FIG. The solid line represents the R-phase current, and the broken line represents the T-phase current.

  Referring to FIG. 8 showing a state in which the firing angle of the R phase and the T phase is 120 ° (point A), in the section where the firing angle of the R phase and the T phase is 180 ° to 120 °, both firings are performed. It can be seen that even if the corners are the same, the respective conduction times are equal.

  However, referring to FIG. 9 showing a state where the firing angles of the R phase and the T phase are 90 ° (point B), in the section where the firing angles of the R phase and the T phase shift from 120 ° to 90 °, both When the firing angles are the same, a difference in conduction time begins to occur, and at point B, a difference of 30 ° in conduction time occurs.

  On the other hand, referring to FIG. 10 where the R-phase and T-phase firing angles are 90 ° and 60 ° (point C), respectively, the R-phase firing angle is maintained at 90 ° and the T-phase firing angle is maintained. It can be seen that in the section where the angle shifts from 90 ° to 60 °, the difference in conduction time gradually decreases, and at point C, each conduction time becomes equal.

  Furthermore, referring to FIG. 11 showing the states of the R-phase and T-phase firing angles of 60 ° and 30 ° (point D), respectively, the R-phase firing angle is 90 ° to 60 °, and the T-phase firing angle. It can be seen that in the section where the angle shifts from 60 ° to 30 °, a difference starts to occur in the conduction time, and at point D, a difference of 30 ° occurs in the conduction time.

  On the other hand, referring to FIG. 12, which shows the R-phase and T-phase firing angles of 60 ° and 0 ° (point E), respectively, the R-phase firing angle is maintained at 60 ° and the T-phase firing angle is maintained. In the section where the angle shifts from 30 ° to 0 °, the difference in conduction time gradually decreases. At point E, each conduction time becomes equal, and thereafter the firing angles of the R phase and the T phase are both It can be seen that the respective conduction times are equal until 0 ° is reached.

  Therefore, in the embodiment according to the present invention, when the firing angle is gradually reduced in the soft start operation, the thyristor conduction time detection circuit 14 detects the conduction time of the switching elements 10r and 10t of the respective phases, and the conduction thereof. Since the control is performed so that the time becomes equal for each control cycle, after the firing angles of the R phase and the T phase are both 180 °, the point reaches the point A along the solid line in the figure, and then the point A After reaching the point C through the locus of the middle broken line and then to the point E through the locus of the broken line in the figure, the firing angles of the R phase and the T phase both reach the point of 0 ° along the solid line. . The transition from point A to point E will be explained. First, from point A to point C, the manipulated value of the T-phase firing angle is twice as large as the manipulated value of the R-phase firing angle. Next, when transitioning from point C to point E, if the firing angle of the T phase is smaller than 60 °, the conduction time of the R phase is instantaneously increased by 30 °. The operation amount of the firing angle changes greatly.

  As shown in the above-mentioned Patent Document 3, if the ignition angle is controlled by a specific control pattern, the change operation of the ignition angle on one phase side is stopped at a certain ignition angle, and the operation on the other phase side is stopped. A section that operates only the firing angle occurs, and when the firing angle on the other phase side is manipulated while the operation on the firing angle on the other phase side is stopped, it deviates from the optimum value. End up.

  However, in the embodiment according to the present invention, since the operation of the firing angle of each phase is controlled so that the conduction time becomes equal for each control cycle, the operation on one phase side does not stop, A very smooth soft start operation is realized because of the movement to reduce the unbalance.

  Next, when it is determined that the power supply frequency detected by the frequency detection circuit 16 is not the frequency of the commercial AC power supply at the start of the operation described above, the control means 17 uses the bypass relay switching circuit 18 to each of the bypass relays 11. The bypass circuits 12r and 12t are operated by closing the contact portions 11r and 11t.

  In this case, the three-phase AC power source connected to the connection portion 8 of the three-phase motor 5 is an inverter power source, but the feeding current from the three-phase AC power source is provided with bypass circuits 12r and 12t and switching elements 10r and 10t. Since the current does not flow to the switching elements 10r and 10t through the non-feeding power supply circuit 9s, the start operation by the inverter and the start operation by the soft start function do not interfere, and normal operation by the inverter, that is, soft start A series of operations from operation to normal operation is performed.

  In the present invention, the control device is housed and integrated in the terminal box, and normal operation is performed even if the three-phase AC power source connected to the three-phase motor 5 is a commercial power source or an inverter power source. Therefore, it is possible to provide a control device-integrated three-phase motor that can be installed very easily and is very easy to use.

  The control device-integrated three-phase motor of the present invention is most suitable for driving a cooling tower fan in which a speed reducer is incorporated, but is highly applicable to other appropriate applications.

It is a perspective view which shows the external appearance of a cooling tower as an example of the apparatus using the control apparatus integrated three-phase motor which concerns on this invention. It is an expansion partially notched perspective view of the principal part. It is a perspective view which shows the three-phase motor 5 which concerns on this invention. It is a front view which shows the three-phase motor 5 which concerns on this invention. It is the sectional view on the AA line of FIG. It is a systematic diagram which shows embodiment of the control apparatus applied to the three-phase motor 5 which concerns on this invention. It is explanatory drawing which shows the soft start operation | movement in embodiment of this invention compared with the operation | movement by a control pattern. It is explanatory drawing which shows the current waveform of each phase in A point of FIG. It is explanatory drawing which shows the current waveform of each phase in B point of FIG. It is explanatory drawing which shows the current waveform of each phase in C point of FIG. It is explanatory drawing which shows the current waveform of each phase in D point of FIG. It is explanatory drawing which shows the current waveform of each phase in E point of FIG.

Explanation of symbols

1 Cooling tower 2 Fan 3 Fan cylinder 4 Belt reducer 5 Three-phase motor (three-phase induction motor)
6 Terminal box 7 Lid 8 Connection (connection terminal)
9r, 9s, 9t Feed circuit 10r, 10t Switching element 11r, 11t Contact 11 Pass relay 12r, 12t Bypass circuit 13 Phase control drive circuit (thyristor drive circuit)
14 Thyristor conduction time detection circuit 15 Voltage zero cross detection circuit 16 Frequency detection circuit (means)
17 Control means (microcomputer)
18 Bypass relay switching circuit 19 Current detection unit 20 Current detection circuit 21 Circuit board 22 Radiation fin 23 External heat dissipation unit 24 Support cylinder 25 Soft start means

Claims (8)

At least two phases of the three-phase power supply circuit from the connection with the three-phase AC power source to the three-phase motor are provided with phase-controllable switching elements, and the soft-start means is configured with these switching elements as elements. The bypass circuit for bypassing these switching elements, the switching means for the operation and non-operation of the bypass circuit, the feed frequency detecting means connected to the two phases of the feed circuit, and the feed frequency detected by the feed frequency detecting means A control device comprising a soft start means and a control means for selecting the operation of the bypass circuit by the switching means, and each circuit and elements of each means are installed in a terminal box of a three-phase motor. Body type three-phase motor. The control device integrated three-phase motor according to claim 1, wherein the soft start means includes a voltage zero cross detection circuit connected to two phases of the power supply circuit and a phase control drive circuit of the switching element. 3. The three-phase control device integrated type according to claim 2, wherein the switching element is interposed in two phases of the power supply circuit, and the control means is configured to control the soft start means by phase control of two phases. Electric motor. The soft start means is provided with a switching element conduction time detection circuit, and the control means is configured to operate the phase control drive circuit so that the conduction time of each switching element detected by the conduction time detection circuit is equal. A three-phase motor integrated with a control device according to claim 3 .
5. The controller-integrated type according to claim 1, wherein at least a part of the wall of the terminal box is configured as an external heat radiating portion, and a switching element is attached to the inside of the wall. Three-phase motor. 6. The controller-integrated three-phase motor according to claim 1, wherein the switching element is a thyristor or a triac , and the switching means of the bypass circuit is a relay.


The three-phase motor integrated with a control device according to any one of claims 1 to 6, wherein the three-phase motor is for driving a cooling tower fan in which a reduction gear is incorporated. The three-phase motor integrated with a control device according to any one of claims 1 to 7, wherein the three-phase motor is an induction motor.

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