Motor drive system and elevator system

Abstract

A motor drive system (60) comprises a motor (15), an inverter (30), a motor cable (40), a bypass cable (50), and a surge suppression member (53). The inverter (30) drives the motor (15) by outputting a rectangular wave voltage from output terminals (32R-32T). The motor cable (40) extends from the output terminals (32R-32T) and is connected to connection terminals (15R-15T), and a rectangular wave voltage is transmitted. The surge suppression member (53) is disposed in the bypass cable (50). One end of the bypass cable (50) is connected to one or more of the connection terminals (15R-15T). The other end of the bypass cable (50) is connected to one or more of the output terminals (32R-32T).

Description

Motor drive system and elevator system

[0001] The present disclosure relates to a motor drive system and an elevator system.

[0002] A motor drive device (e.g., an inverter) drives a motor by outputting a square-wave voltage from its output terminals. However, when the square-wave voltage rises, a surge voltage may be applied between the motor's connection terminals due to a sudden voltage change. The surge voltage is larger than the square-wave voltage and may cause insulation breakdown in the motor. Designing a motor to be able to adequately withstand the surge voltage increases costs. Therefore, technologies have been proposed to protect motors from surge voltages using cost-effective surge suppression components.

[0003] For example, Japanese Patent Laid-Open Publication No. 4-251574 (Patent Document 1) discloses an inverter device including three output terminals and a three-phase reactor, which is disposed as a surge suppressor on three power lines extending from the output terminals to a motor.

[0004] Japanese Patent Application Publication No. 4-251574

[0005] When there is insufficient space around the power lines extending from the drive unit to the motor, it can be difficult to place surge suppression components on the power lines. Even in such cases, it is important to adequately protect the motor from surge voltages at low cost.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a motor drive system and an elevator system that can adequately protect a motor from surge voltages at low cost, even in cases where it is difficult to place a surge suppression member on the power line member extending from the drive device to the motor.

[0007] The motor drive system of the present disclosure includes a motor, a drive device, a power line member, a bypass power line member, and a surge suppression member. The motor has a plurality of connection terminals. The drive device has a plurality of output terminals and drives the motor by outputting a rectangular wave voltage from the plurality of output terminals. The power line member extends from the plurality of output terminals and is connected to the plurality of connection terminals, and the rectangular wave voltage is transmitted. The bypass power line member is disposed on the bypass power line member. One end of the bypass power line member is connected to one or more of the plurality of connection terminals. The other end of the bypass power line member is connected to one or more of the plurality of output terminals.

[0008] According to the present disclosure, even in cases where it is difficult to arrange a surge suppression member on a power line member extending from a drive device to a motor, the motor can be appropriately protected from surge voltages at low cost.

[0009] FIG. 1 is a diagram illustrating the configuration of an elevator system including a motor drive system according to a first embodiment. FIG. 2 is a diagram illustrating in detail the configuration of the motor drive system according to the first embodiment. FIG. 3 is a diagram illustrating in detail the configuration of the motor drive system according to the second embodiment. FIG. 4 is a diagram illustrating in detail an example of a result of a simulation of transition of voltage between connection terminals of a motor in the second embodiment. FIG. 5 is a diagram illustrating in detail the configuration of a motor drive system according to a modification of the second embodiment. FIG. 6 is a diagram illustrating in detail the configuration of a motor drive system according to a third embodiment. FIG. 7 is a diagram illustrating in detail another configuration of a motor drive system according to the fifth embodiment. FIG. 8 is a diagram illustrating in detail another configuration of a motor drive system according to the sixth embodiment. FIG. 9 is a diagram illustrating in detail the configuration of a motor drive system according to a seventh embodiment. FIG. 10 is a diagram illustrating in detail another configuration of a motor drive system according to the seventh embodiment. FIG. 11 is a diagram illustrating in detail another configuration of a motor drive system according to the seventh embodiment. FIG. 13 is a diagram for illustrating in detail the configuration of the motor drive system according to the eighth embodiment. FIG. 14 is a diagram for illustrating in detail another configuration of the motor drive system according to the eighth embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings will be denoted by the same reference numerals, and the description thereof will not be repeated. The embodiments and their modifications may be combined with each other as appropriate.

[0011] Embodiment 1. Figure 1 is a diagram showing the configuration of an elevator system including a motor drive system according to embodiment 1. Referring to Figure 1, elevator system 1 includes a hoisting machine 10, a rope 20, an elevator car 22, a counterweight 24, a control panel 25, a motor cable 40, and a surge suppression device 45. The vertically upward direction is also referred to as the +Z direction, and the vertically downward direction is also referred to as the -Z direction.

[0012] The hoisting machine 10 is provided inside a machine room MR. The machine room MR is located above the hoistway HW. The hoisting machine 10 includes a motor 15. The motor 15 is a three-phase AC motor. The rope 20 is wound up in response to the rotation of the motor 15. This causes the elevator car 22 to rise and fall within the hoistway HW.

[0013] The control panel 25 is located outside the machine room MR and, in this example, near the bottom of the elevator shaft HW. The control panel 25 includes an alternating current (AC) / direct current (DC) converter 26, an inverter 30, and a control device 35. The AC / DC converter 26 converts AC power supplied from an AC power source PS into DC power. The inverter 30 is a three-phase inverter located away from the motor 15. The inverter 30 converts DC power from the AC / DC converter 26 into AC power and supplies it to the motor 15. In this way, the inverter 30 functions as a drive device for driving the motor 15. The inverter 30 generates a current for driving the motor 15. This current is also referred to as a "motor drive current." The motor drive current is basically a large current. The control device 35 controls the inverter 30 using pulse width modulation (PWM) control, but may also control the inverter 30 using square wave control.

[0014] The motor cable 40 includes four covered electric wires. Three of these four electric wires are connected to the R-phase, S-phase, and T-phase output terminals (described below) of the motor 15. The remaining one is connected to the ground terminal of the motor 15 and the ground terminal of the inverter 30 (neither of which are shown). The motor cable 40 has a length of several meters or more. The motor cable 40 is provided near the elevator shaft HW and transmits AC power from the inverter 30 to the motor 15. A motor drive current flows through the motor cable 40. A surge suppressor 45 is provided to protect the motor 15 from surge voltages.

[0015] 2 is a diagram for explaining in detail the configuration of the motor drive system according to the first embodiment. Referring to Fig. 2, motor drive system 60 includes motor 15, inverter 30, power supply lines L1, L1a, motor cable 40, surge suppressor 45, and monitoring device 59.

[0016] The motor 15 has connection terminals 15R, 15S, and 15T. The connection terminals 15R, 15S, and 15T correspond to the R-phase terminal (U-phase terminal), the S-phase terminal (V-phase terminal), and the T-phase terminal (W-phase terminal) of the motor 15, respectively.

[0017] The inverter 30 is connected to DC buses 33a and 33b. The DC buses 33a and 33b are high-potential and low-potential power lines, respectively. The voltage between the DC buses 33a and 33b is also referred to as the "bus voltage BV." The bus voltage BV is a predetermined constant voltage. The inverter 30 is also connected to a power supply line L1. The power supply line L1 is laid from a power supply ps to the inverter 30 and transmits power to the inverter 30.

[0018] The inverter 30 has output terminals 32R, 32S, and 32T and multiple semiconductor switching elements (not shown). The inverter 30 operates by receiving power supplied from the power source ps via the power line L1 as operating power. The inverter 30 drives the motor 15, for example, by outputting a rectangular wave voltage from the output terminals 32R, 32S, and 32T. The multiple semiconductor switching elements are connected in series between the DC buses 33a and 33b. By switching these semiconductor switching elements on and off, the voltage of the corresponding output terminal switches between high and low potentials. This causes the output terminal to output a rectangular wave voltage. The nearby region VR corresponds to a region within a predetermined distance from the inverter 30. The nearby region VR is, for example, an area within the housing of the control panel 25 (FIG. 1).

[0019] The motor cable 40 includes power lines 42R, 42S, and 42T. The power lines 42R to 42T are arranged in parallel with one another and correspond to an example of a "power line member" in the present disclosure. The rectangular wave voltage described above is transmitted through each power line to a corresponding connection terminal of the motor 15. The power line 42R extends from the output terminal 32R and is connected to the connection terminal 15R. The power line 42S extends from the output terminal 32S and is connected to the connection terminal 15S. The power line 42T extends from the output terminal 32T and is connected to the connection terminal 15T. That is, the power lines 42R to 42T extend from the output terminals 32R to 32T and are connected to the connection terminals 15R to 15T, respectively. R-phase current, S-phase current, and T-phase current flow through the power lines 42R to 42T, respectively, from the inverter 30 to the motor 15.

[0020] The surge suppression device 45 includes a bypass cable 50, a surge suppression member (surge suppression unit) 53, and a monitoring device 59. The bypass cable 50 includes bypass power lines 52R, 52S, and 52T. These bypass power lines are arranged in parallel with one another and correspond to an example of a "bypass power line member" in the present disclosure. The bypass power lines 52R to 52T are arranged so as to bypass the motor cable 40 (more specifically, the portion of the motor cable 40 surrounded by a cylinder in the figure (first portion)). The first portion is long enough to generate a surge voltage (described below).

[0021] One end of bypass power line 52R is connected to power line 42R at connection point p1R and is connected to connection terminal 15R through power line 42R. The other end of bypass power line 52R is connected to power lines 42R to 42T at connection points p2R to p2T, respectively. These other ends are connected to output terminals 32R to 32T through power lines 42R to 42T, respectively. Connectors (not shown) are provided at each of connection points p1R, p2R, p2S, and p2T. Bypass power line 52R branches at branch point BRR. Bypass power line 52S includes power line 55R and branch lines 55a, 55b, and 55c. Power line 55R connects connection point p1R and branch point BRR. Branch line 55a connects branch point BRR and connection point p2T. Branch line 55b connects branch point BRR and connection point p2S. The branch line 55c connects the branch point BRR and the connection point p2R.

[0022] One end of the bypass power line 52S is connected to the power line 42S at connection point p1S and is connected to connection terminal 15S through the power line 42S. The other end of the bypass power line 52S is connected to power lines 42R-42T at connection points p3R-p3T, respectively. These other ends are connected to output terminals 32R-32T through the power lines 42R-42T, respectively. Connectors (not shown) are provided at each of connection points p1S, p3R, p3S, and p3T. The bypass power line 52S branches at branch point BRS. The bypass power line 52S includes a power line 55S and branch lines 55d, 55e, and 55f. The power line 55S connects connection point p1S and branch point BRS. Branch line 55d connects branch point BRS and connection point p3T. Branch line 55e connects branch point BRS and connection point p3S. The branch line 55f connects the branch point BRS and the connection point p3R.

[0023] One end of the bypass power line 52T is connected to the power line 42T at connection point p1T and is connected to connection terminal 15T through the power line 42T. The other end of the bypass power line 52T is connected to power lines 42R-42T at connection points p4R-p4T, respectively. These other ends are connected to output terminals 32R-32T through power lines 42R-42T, respectively. Connectors (not shown) are provided at each of connection points p1T and p4R-p4T. The bypass power line 52T branches at branch point BRT. The bypass power line 52T includes a power line 55T and branch lines 55g, 55h, and 55i. The power line 55T connects connection point p1T and branch point BRT. Branch line 55g connects branch point BRT and connection point p4T. Branch line 55h connects branch point BRT and connection point p4S. The branch line 55i connects the branch point BRT and the connection point p4R.

[0024] Connection points p1R to p1T are located within a first reference distance from connection terminals 15R to 15T, respectively. Similarly, connection points p2R to p2T, p3R to p3T, and p4R to p4T are located within a second reference distance from connection terminals 15R to 15T, respectively. The first reference distance and the second reference distance are both less than, for example, 30% of the length of motor cable 40 in the Z direction.

[0025] The surge suppression member 53 is disposed on the bypass cable 50 within the vicinity region VR, and includes a group of surge suppression components 54R, 54S, and 54T.

[0026] The surge suppression component group 54R is provided on the bypass power line 52R and includes surge suppression components 56a, 56b, and 56c. Specifically, these surge suppression components are provided on the branch lines 56a to 56c, respectively.

[0027] The surge suppression component group 54S is provided on the bypass power line 52S and includes surge suppression components 56d, 56e, and 56f. Specifically, these surge suppression components are provided on the branch lines 56d to 56f, respectively.

[0028] The surge suppression component group 54T is provided on the bypass power line 52T and includes surge suppression components 56g, 56h, and 56i. Specifically, these surge suppression components are provided on the branch lines 56g to 56i, respectively.

[0029] Branch lines 55c, 55e, and 55g connect the same phase of motor 15 and inverter 30. Branch lines 55a, 55b, 55d, 55f, 55h, and 55i connect different phases of motor 15 and inverter 30. Each of surge suppression components 56a to 56i is a filter component including a circuit element such as a resistor, a capacitor, or a diode. The filter component may be configured to clamp the line voltage of power lines 42R to 42T. The combined impedance of bypass cable 50 and surge suppression member 53 corresponds to the impedance of surge suppression device 45.

[0030] The monitoring device 59 includes various sensors provided within the vicinity region VR. The monitoring device 59 is provided to monitor the status of the surge suppression member 53 (e.g., the voltage or temperature of each surge suppression component). The monitoring device 59 may further include a display device. The monitoring results of the monitoring device 59 are used for maintenance of the surge suppression member 53. The monitoring device 59 is connected to the power supply line L1a. The power supply line L1a is a power supply line for the monitoring device 59 that branches off from or is connected to the power supply line L1. The power supply line L1a is laid to the monitoring device 59 to transmit a portion of the power supplied from the power supply ps to the monitoring device 59. The monitoring device 59 operates by receiving power transmitted from the power supply ps through the power supply line L1a as operating power. The inverter 30, the surge suppression member 53, and the monitoring device 59 are provided within the vicinity region VR.

[0031] The surge voltage is described below. The surge voltage is applied between the connection terminals of the motor 15 due to the output of the aforementioned square-wave voltage. The magnitude of the surge voltage depends on various characteristics of the motor 15, inverter 30, and motor cable 40 (stray inductance, stray capacitance, stray resistance, electrical propagation speed, and characteristic impedance), as well as the voltage between the output terminals of the inverter 30. For example, the higher the rated output of the motor 15, the greater the stray capacitance of the motor 15, which tends to result in a higher surge voltage. The surge voltage is believed to result from (1) reflections caused by a mismatch between the characteristic impedance of the motor 15 and that of the motor cable 40, or (2) resonance between the inductance or stray capacitance of the motor 15 and the stray inductance or stray capacitance of the motor cable 40. Therefore, the motor cable 40 cannot be ignored when discussing surge voltage.

[0032] In many cases, surge voltages are applied between the connection terminals of the motor 15 when the motor cable 40 has a certain length (e.g., several meters or more). Therefore, the motor cable 40 can be modeled as a distributed parameter circuit from the perspective of an electrical circuit. In fact, the motor cable 40 has different potentials at both ends. As a result, the connection terminals 15R to 15T have a different potential from the output terminals 32R to 32T.

[0033] As an example, consider a transient state immediately after the state of the output terminals 32R to 32T switches from the first state to the second state. In the first state, all of the output terminals 32R to 32T are connected to the DC bus 33b. In the first state, the output terminals 32R to 32T have the same potential, so there is no potential difference between the output terminals. On the other hand, in the second state, only the output terminal 32R is connected to the DC bus 33a. In the second state, there is a potential difference between the output terminals 32R and 32S and between the output terminals 32R and 32T.

[0034] Before describing the advantages of the first embodiment, consider a first comparative example that does not include surge suppression device 45. In the first comparative example, immediately after switching from the first state to the second state, a rectangular wave voltage is output from output terminal 32R, and a current path is formed in which a current returns from output terminal 32R to output terminal 32S or 32T via power line 42R, connection terminal 15R, connection terminal 15S or 15T, and power line 42S or 42T.

[0035] In this current path, the voltage between output terminals 32R and 32S of inverter 30 and the voltage between output terminals 32R and 32T each have a step waveform. This step waveform depends on bus voltage BV and the speed at which the output voltage of output terminal 32R is switched. The potential change (rectangular wave voltage) at output terminal 32R that accompanies the switch from the first state to the second state propagates through power line 42R.

[0036] On the other hand, in the above current paths, the voltage between connection terminals 15R and 15S of motor 15 and the voltage between connection terminals 15R and 15T are each a superimposed voltage of the above step waveform voltage and a surge voltage (oscillating voltage) applied between the connection terminals. The maximum value of this superimposed voltage can be several times the phase-to-phase voltage between the corresponding output terminals of inverter 30. As a result, in the first comparative example, there is a possibility of dielectric breakdown in motor 15, and motor 15 cannot be protected from surge voltages.

[0037] Designing the motor 15 to be able to adequately withstand surge voltages would increase costs. Therefore, in the first comparative example, it is possible to provide a surge suppression member on the motor cable 40. However, due to spatial constraints in the building in which the elevator system 1 is installed, there may not be enough space around the motor cable 40 (e.g., near the hoistway HW in FIG. 1 ). In this case, it may be difficult to provide a surge suppression member on the motor cable 40. Even in such a case, it is important to adequately protect the motor 15 from surge voltages at low cost. In particular, because three-phase motors and three-phase inverters are widely used in industry, protecting the motor 15 as described above is extremely important from a practical perspective.

[0038] In this regard, in the first embodiment, a surge voltage is applied between connection terminals 15R and 15S and between connection terminals 15R and 15T immediately after switching from the first state to the second state (immediately after the rectangular wave voltage is output). This surge voltage propagates through bypass cable 50 and generates a potential difference in surge suppression member 53. As a result, a portion of the surge energy is returned to output terminal 32R through bypass cable 50 and surge suppression member 53, thereby suppressing the surge voltage. Similarly, the surge voltage applied between the connection terminals of motor 15 immediately after the rectangular wave voltage is output from output terminal 32S or 32T is also suppressed by surge suppression member 53. Furthermore, because surge suppression member 53 is disposed on bypass cable 50, it does not need to be disposed on motor cable 40. Disposing surge suppression member 53 on bypass cable 50 typically costs less than designing motor 15 to be able to adequately withstand surge voltages. From the above, according to embodiment 1, even if it is difficult to place surge suppression components on the motor cable 40 because there is not enough space around the motor cable 40, the motor 15 can be appropriately protected from surge voltages at low cost.

[0039] As described above, the surge suppression members 53 are disposed on the bypass power lines 52R-52T within the vicinity region VR. The reason for this is explained below. The position on the bypass power lines 52R-52T where the surge suppression members 53 can be disposed varies depending on the spatial constraints of the building in which the elevator system 1 is installed. However, in areas other than the vicinity region VR (hereinafter also referred to as the "non-vicinity region"), there is often insufficient space around the bypass power lines 52R-52T to dispose the surge suppression members 53. The non-vicinity region is, for example, the vicinity of the motor 15 (e.g., the area within the machine room MR) or the area near the center of the bypass cable 50. On the other hand, there is often space available within the vicinity region VR to dispose the surge suppression members 53. Therefore, the surge suppression members 53 are disposed on the bypass power lines 52R-52T within the vicinity region VR. This allows the motor 15 to be protected from surge voltages at low cost, even if there is insufficient space around the bypass power lines 52R-52T in the non-vicinity region. If the surge suppression member 53 can be placed in the non-neighborhood region VR, it may be placed in this region. This suppresses surge voltage to approximately the same extent as in the case where the surge suppression member 53 is placed in the neighborhood region VR, and protects the motor 15.

[0040] The monitoring device 59 is provided within the vicinity region VR. The advantages of this are described below. As a second comparative example, consider an example in which the surge suppression member 53 and the monitoring device 59 are installed within a non-proximity region (e.g., housed in a separate housing away from the housing of the control panel 25). In the second comparative example, the power line for the monitoring device 59 may be long and occupy a large amount of space. Depending on the surrounding space, it may be difficult to lay the power line to the monitoring device 59. In contrast, in the first embodiment, both the surge suppression member 53 and the monitoring device 59 are provided within the vicinity region VR (in this example, both are housed in the housing of the control panel 25, i.e., the same housing). This allows the operating power to be transmitted over a short distance from the power line L1 to the monitoring device 59 via the power line L1a. As a result, the monitoring device 59 can be operated without laying a long power line for the monitoring device 59. This allows for space-saving of the motor drive system 60 while enabling appropriate maintenance of the surge suppression member 53.

[0041] It is not necessary to provide components other than power lines 42R-42T and connectors at connection points p1R-p1T in the vicinity of motor 15. Therefore, motor drive system 60 can be applied even when there is not enough space in the vicinity of motor 15 to place various components.

[0042] The impedance of the surge suppression device 45 is preferably greater than the impedance of the motor cable 40. With this configuration, the current (hereinafter also referred to as the "return current") that flows back from the motor 15 to the output terminal of the inverter 30 through the bypass cable 50 and the surge suppression member 53 due to a surge voltage is smaller than the motor drive current. This eliminates the need for the surge suppression components of the surge suppression member 53 to be large enough to withstand a large current such as the motor drive current, and therefore allows them to be miniaturized. As a result, even if the placement of the surge suppression components 56a-56i is restricted by the space around the bypass cable 50, these surge suppression components can be easily placed in suitable locations.

[0043] Furthermore, when the return current is small, the amount of heat generated by the surge suppression components 56a-56i is reduced, making it easier to protect these surge suppression components from overheating. Additionally, since the bypass power lines 52R-52T do not need to be designed to withstand large currents, these bypasses can be thinner than the power lines 42R-42T. The diameter of the bypass cable 50 is determined based on the allowable current value flowing through the surge suppression member 53. A fuse may be attached to the bypass cable 50. This makes it possible to prevent overcurrent from flowing through the bypass cable 50, depending on the wiring state.

[0044] The surge suppression components 56a-56i do not have to be the same type of component. For example, surge suppression components (surge suppression components 56c, 56e, 56g) provided between the same phase of the motor 15 and the inverter 30 may experience momentary voltage fluctuations when a surge voltage is generated. To handle such voltage fluctuations, these surge suppression components may be, for example, diodes or resistive elements. If the surge suppression components 56c, 56e, 56g are diodes, these diodes are arranged so that forward currents flow from connection point p1R to connection point p2R, from connection point p1S to connection point p3S, and from connection point p1T to connection point p4T, respectively. On the other hand, surge suppression components (surge suppression components 56a, 56b, 56d, 56f, 56h, 56i) provided between different phases may experience voltage fluctuations over a relatively long time interval when a surge voltage is generated. To be able to cope with such voltage fluctuations, these surge suppression components may be formed by a capacitor and a resistive element connected in series with the capacitor.

[0045] While a motor drive current flows through the motor cable 40, a return current flows through the bypass cable 50. Therefore, radiated noise may be generated due to these currents. Various measures may be implemented to reduce such radiated noise. These measures include, for example, twisting the power lines 42R-42T, twisting the bypass power lines 52R-52T, or twisting both the power lines and the bypass power lines. These measures may further include shortening the distance between the bypass power lines, shortening the distance between the motor cable 40 and the bypass cable 50, and attaching a high-resistance shield to the motor cable 40 and the bypass cable 50. These measures may further include encasing the motor cable 40 and the bypass cable 50 in a duct with high conductivity or magnetic permeability.

[0046] In the first embodiment, the inverter 30 and the surge suppression member 53 are housed in the same housing (the housing of the control panel 25). This housing may have a total of six output terminals. These six output terminals consist of three output terminals connected to the left side of the first section and three output terminals connected to the left side of the second section. The second section is the portion of the bypass cable 50 surrounded by the cylinder in the figure. When the housing has six output terminals, the first and second sections and their right sides are laid outside the housing and connected to connection terminals 15R to 15T.

[0047] In this example, the power lines 42R to 42T are included in the motor cable 40, and the bypass power lines 52R to 52T are included in the bypass cable 50. However, as long as the power lines 42R to 42T and the bypass power lines 52R to 52T are insulated from each other, these power lines may be included in a single cable. In this case, some of the same type of multiple litz wires may be used as power lines for the motor cable 40, and the remaining litz wires may be used as bypass power lines for the bypass cable 50.

[0048] One end (end in the +Z direction) of the bypass power lines 52R to 52T may be directly connected to the connection terminals 15R to 15T, respectively. In other words, the connection points p1R to p1T may be located at the connection terminals 15R to 15T, respectively. In this case, the power lines 42R to 42T and the bypass power lines 52R to 52T may be fastened together at these connection terminals, or these power lines may be joined together. Alternatively, terminal blocks for branching the bypass power lines 52R to 52T from the power lines 42R to 42T may be provided at these connection terminals. The closer the connection points p1R to p1T are to the connection terminals 15R to 15T, the more effectively surge voltages are suppressed. Therefore, when one end of the bypass power lines 52R to 52T is directly connected to the connection terminals 15R to 15T, respectively, surge voltages are particularly effectively suppressed.

[0049] Similarly, the other ends (ends in the −Z direction) of the bypass power lines 52R to 52T may be directly connected to the output terminals 32R to 32T, respectively. In other words, the connection points p2R to p2T, p3R to p3T, and p4R to p4T may be located at the output terminals 32R to 32T, respectively. The closer these connection points are to the connection terminals, the more the surge voltage is suppressed. Therefore, surge voltage is particularly effectively suppressed even when the other ends of the bypass power lines 52R to 52T are directly connected to the output terminals 32R to 32T, respectively.

[0050] As described above, according to the first embodiment, even if it is difficult to arrange the surge suppression member 53 on the motor cable 40 due to insufficient space around the motor cable 40, the motor 15 can be appropriately protected from a surge voltage at low cost. For example, even if there is insufficient space to arrange the surge suppression member 53 near the hoistway HW ( FIG. 1 ), the surge suppression member 53 can be arranged on the bypass cable 50 away from the hoistway HW, thereby suppressing the surge voltage. Therefore, the motor 15 can be protected from a surge voltage at low cost while appropriately addressing restrictions on the arrangement location of the surge suppression member 53.

[0051] Second Embodiment Fig. 3 is a diagram for explaining in detail the configuration of a motor drive system according to a second embodiment. Referring to Fig. 3, a motor drive system 70 is included in elevator system 1 in place of motor drive system 60 (Fig. 2) of the first embodiment. Motor drive system 70 differs from motor drive system 60 in that bypass power lines 52R to 52T do not branch off at branch points BRR to BRT, respectively.

[0052] Motor drive system 70 further differs from motor drive system 60 in that the ends of bypass cable 50 in the -Z direction are not connected to connection points p2S, p2T, p3R, p3T, p4R, and p4S, but are connected only to connection points p2R, p3S, and p4T. In other words, motor drive system 70 further differs from motor drive system 60 in that the ends of bypass power lines 52R to 52T in the +Z direction are connected to connection terminals 15R to 15T via connection points p2R, p3S, and p4T, respectively. Note that these ends may also be directly connected to these connection terminals.

[0053] Motor drive system 70 further differs from motor drive system 60 in that surge suppression member 53 includes resistive elements 62R, 62S, and 62T as surge suppression components instead of surge suppression component group 54R to 54T.

[0054] In other respects, unless otherwise specified, the hardware configuration of motor drive system 70 is the same as that of motor drive system 60. For example, the ends of bypass power lines 52R to 52T in the +Z direction are connected to connection terminals 15R to 15T via connection points p1R to p1T or directly, respectively.

[0055] Resistance elements 62R to 62T are disposed on bypass power lines 52R to 52T, respectively. The magnitude of the electrical resistance of resistance elements 62R to 62T can affect the magnitude of the motor drive current and the reflux current.

[0056] The magnitude of the motor drive current affects the amount of heat generated by these resistance elements. For example, the larger the motor drive current, the greater the amount of heat generated. Therefore, measures may be taken to reduce the amount of heat generated by the resistance elements 62R-62T. These measures include, for example, selecting resistance elements with high heat resistance as the resistance elements 62R-62T and providing heat sinks near these resistance elements.

[0057] The following describes how these resistive elements function in the motor drive system 70. As an example, consider a transient situation immediately after the operation of the inverter 30's switching elements causes the output terminals 32R-32T to switch from a first state to a second state, resulting in a rectangular wave voltage being output from the output terminal 32R and a surge voltage being applied between the connection terminals of the motor 15. In this situation, an instantaneous potential difference may be generated between the same-phase terminals of the motor 15 and the inverter 30 (e.g., the connection terminal 15R and the output terminal 32R) due to the operation of the inverter 30's switching elements. This causes a portion of the surge energy to return to the output terminal 32R through the bypass cable 50 and the resistive elements 62R-62T. As a result, the surge energy is dissipated by the resistive elements 62R-62T. This reduces the peak surge voltage, thereby suppressing the surge voltage.

[0058] Another advantage of motor drive system 70 is described below. Essentially, resistive elements (1) tend to have a relatively long lifespan among circuit elements and (2) a relatively small stray capacitance. Advantage (1) allows motor 15 to be protected from surge voltages over a relatively long period of time. Furthermore, advantage (2) reduces inconveniences caused by the discharge of electric charge stored in the stray capacitance of surge suppression components when installing surge suppression components on bypass power lines 52R-52T (or when connecting surge suppression device 45 to output terminals 32R-32T and connection terminals 15R-15T, or power lines 42R-42T).

[0059] Another advantage of the motor drive system 70 will be described below. In this example, the number of power lines of the bypass cable 50 (bypass power lines 52R-52T) is equal to the number of power lines of the motor cable 40 (power lines 42R-42T). The bypass power lines 52R-52T are connected to the power lines 42R-42T at connection points p1R and p2R, connection points p1S and p3S, and connection points p1T and p4T, respectively. Resistive elements 62R-62T are provided on the bypass power lines 52R-52T, respectively, as surge suppression components. Therefore, surge voltages applied between the connection terminals of the motor 15 are suppressed by these surge suppression components. As a result, surge voltages between all connection terminals of the motor 15 are suppressed in the same manner, thereby enabling appropriate protection of the motor 15. An example in which the number of power lines of the bypass cable 50 is different from the number of power lines of the motor cable 40 will be described in detail later.

[0060] In the second embodiment, the impedance of the surge suppressor 45, i.e., the combined impedance of the bypass cable 50 and the resistor elements 62R to 62T, can be easily increased due to the electrical resistance of the resistor elements 62R to 62T. This reduces the return current and the heat generation of these resistor elements. This makes it easy to prevent these resistor elements from overheating.

[0061] 4 is a diagram showing an example of the results of a simulation of the transition of voltage between the connection terminals of motor 15 in embodiment 2. Referring to FIG. 4, line 102 represents the results of a simulation of the transition of voltage between output terminals 32R and 32S of inverter 30. Line 104 represents the results of a simulation of the transition of voltage between connection terminals 15R and 15S of motor 15 in a third comparative example. The motor drive system of the third comparative example differs from motor drive system 70 of embodiment 2 in that it does not include surge suppression device 45, but is otherwise the same as motor drive system 70. Line 106 represents the results of a simulation of the transition of voltage between connection terminals 15R and 15S of motor 15 in embodiment 2.

[0062] In the simulation, the motor 15 was modeled as a circuit having a capacitor between each phase and ground. The motor cable 40 was modeled as multiple ladder circuits, each having inductance, electrical resistance, and capacitance. The value of this electrical resistance was determined based on the assumed value of the surge frequency, which was in the range of several hundred kHz to several MHz. The bypass cable 50 was modeled as multiple ladder circuits with characteristics similar to those of the motor cable 40.

[0063] Between time t0 and time t1, the voltages at the output terminals 32R and 32S and the voltage between the connection terminals 15R and 15S were all zero. At time t1, the inverter 30 output a rectangular wave voltage from the output terminal 32R (line 102).

[0064] In the third comparative example, immediately after time t1, a surge voltage was applied between the connection terminals 15R and 15S (line 104). This surge voltage was approximately twice the square wave voltage described above. The voltage oscillation of the surge voltage disappeared at time t2. In this comparative example, the surge voltage was large, and it took a long time for the voltage oscillation to disappear. This is undesirable from the viewpoint of protecting the motor 15.

[0065] On the other hand, in the second embodiment, a surge voltage was applied between the connection terminals of the motor 15 (line 106) immediately after time t1, but this surge voltage was smaller than that in the third comparative example. The voltage oscillation of the surge voltage disappeared at time t2a (<t2). In other words, in the second embodiment, the voltage oscillation of the surge voltage disappeared earlier than that in the third comparative example. Therefore, it was confirmed that the motor 15 can be more appropriately protected from surge voltages compared to the third comparative example.

[0066] As described above, according to the second embodiment, motor 15 can be protected from surge voltages for a relatively long period of time. Furthermore, it is possible to reduce the inconvenience caused by electric charge discharge when surge suppression components are arranged on bypass power lines 52R to 52T.

[0067] Modification of Second Embodiment. FIG. 5 is a diagram for explaining in detail the configuration of a motor drive system according to a modification of the second embodiment. Referring to FIG. 5, motor drive system 75 is included in elevator system 1 in place of motor drive system 70 (FIG. 3) of the second embodiment. Motor drive system 75 differs from motor drive system 70 in that surge suppression member 53 further includes capacitors 67R, 67S, and 67T as surge suppression components. In other respects, the hardware configuration of motor drive system 75 is the same as that of motor drive system 70 unless otherwise specified. Therefore, detailed description will not be repeated.

[0068] The capacitors 67R to 67T are connected in series with the resistor elements 62R to 62T, respectively. The advantages of this will be explained below.

[0069] Immediately after the rectangular wave voltage is output from connection terminal 15R (immediately after the rectangular wave voltage rises), inverter 30 begins supplying a motor drive current to motor cable 40. Some of this motor drive current may flow into bypass cable 50. Capacitors 67R-67T block the DC component of this motor drive current. This prevents the DC component of the motor drive current from flowing into resistor elements 62R, 62S, or 62T. As a result, it is possible to prevent these resistor elements from overheating due to an unnecessary increase in the amount of heat generated by the DC component.

[0070] Third Embodiment. FIG. 6 is a diagram for explaining in detail the configuration of a motor drive system according to a third embodiment. Referring to FIG. 6, motor drive system 80 is included in elevator system 1 in place of motor drive system 70 (FIG. 3) of the second embodiment. Motor drive system 80 differs from motor drive system 70 in that surge suppression member 53 includes diodes 65R, 65S, and 65T as surge suppression components instead of resistor elements 62R to 62T. In other respects, the hardware configuration of motor drive system 80 is the same as that of motor drive system 70 unless otherwise specified. Therefore, detailed description will not be repeated.

[0071] Diodes 65R to 65T are arranged on bypass power lines 52R to 52T, respectively. Diode 65R is arranged so that a forward current flows from connection point p1R to connection point p2R. Diode 65S is arranged so that a forward current flows from connection point p1S to connection point p3S. Diode 65T is arranged so that a forward current flows from connection point p1T to connection point p4T.

[0072] The following describes how these diodes function in the motor drive system 70. As an example, consider a transient situation immediately after the state of the output terminals 32R-32T switches from the first state to the second state due to the operation of the switching elements of the inverter 30 and a rectangular wave voltage is output from the output terminal 32R. In this situation, the rectangular wave voltage has not yet propagated to the connection terminal 15R. Therefore, the voltage at the connection terminal 15R remains at zero. In this case, because the voltage at the output terminal 32R is higher than the voltage at the connection terminal 15R, a reverse voltage is applied to the diode 65R. Therefore, no forward current flows through the diode 65R. On the other hand, after the rectangular wave voltage propagates to the connection terminal 15R, a surge voltage is applied between the connection terminals 15R and 15S. This causes the voltage at the connection terminal 15R to become higher than the voltage at the output terminal 32R. As a result, a potential difference is generated between the connection terminal 15R and the output terminal 32R.

[0073] Therefore, after a surge voltage is generated, a forward voltage is applied to diode 65R, causing a forward current to flow. In this case, a portion of the surge energy is returned to output terminal 32R through bypass power line 52R and diode 65. This suppresses the surge voltage and protects motor 15. Furthermore, no forward current flows through diode 65R before the rectangular wave voltage propagates to connection terminal 15R. This prevents unnecessary power consumption by diode 65R before the surge voltage is generated. Therefore, with the above configuration, motor drive system 80 can protect motor 15 from a surge voltage while appropriately reducing power consumption. For the same reason, diodes 65S and 65T can also suppress a surge voltage immediately after a rectangular wave voltage is output from output terminal 32S or 32T.

[0074] Another advantage of motor drive system 80 will now be described. Basically, diodes, like resistor elements, tend to (1) have a relatively long life among circuit elements and (2) have a relatively small stray capacitance. Therefore, motor drive system 80 has the same advantages as advantages (1) and (2) described in the second embodiment.

[0075] Another advantage of motor drive system 80 is described below. Because motor drive system 80 does not include a resistive element in surge suppression member 53, the amount of heat generated by surge suppression member 53 can be reduced compared to embodiment 2. Furthermore, the current flowing through bypass cable 50 is essentially the forward current of diodes 65R-65T alone. Therefore, for example, if the impedance of surge suppression device 45 is equal to the impedance of power lines 42R-42T, the effective value of the current flowing through bypass power lines 52R-52T is less than half that of power lines 42R-42T. Therefore, bypass power lines 52R-52T can be made thinner than power lines 42R-42T, making it easier to address space constraints.

[0076] FIG. 7 is a diagram showing an example of the results of a simulation of the transition of voltage between the connection terminals of motor 15 in embodiment 3. Referring to FIG. 7 , line 202 represents the results of a simulation of the transition of voltage between output terminals 32R and 32S of inverter 30. Line 204 represents the results of a simulation of the transition of voltage between connection terminals 15R and 15S of motor 15 in a fourth comparative example. The motor drive system of the fourth comparative example differs from motor drive system 80 of embodiment 3 in that it does not include surge suppression device 45, but is otherwise the same as motor drive system 80. Line 206 represents the results of a simulation of the transition of voltage between connection terminals 15R and 15S of motor 15 in embodiment 3.

[0077] As in the third embodiment, the motor 15, the motor cable 40, and the bypass cable 50 were modeled as a capacitor circuit, multiple ladder circuits, and multiple ladder circuits, respectively. It was confirmed that the surge voltage was smaller and the voltage oscillation of the surge voltage disappeared earlier in the third embodiment than in the fourth comparative example. Therefore, it was confirmed that the third embodiment can protect the motor 15 from the surge voltage.

[0078] As described above, according to the third embodiment, it is possible to protect the motor 15 from surge voltages while appropriately reducing power consumption in the motor drive system 80. Furthermore, since the bypass power lines 52R-52T can be made thinner than the power lines 42R-42T, it is easier to deal with the constraints of the surrounding space.

[0079] Modification of Third Embodiment. FIG. 8 is a diagram for explaining in detail the configuration of a motor drive system according to a modification of the third embodiment. Referring to FIG. 8, motor drive system 85 is included in elevator system 1 in place of motor drive system 80 (FIG. 6) of the third embodiment. Motor drive system 85 differs from motor drive system 80 in that surge suppression member 53 further includes resistance elements 66R-66T as surge suppression components. In other respects, the hardware configuration of motor drive system 85 is the same as that of motor drive system 80, unless otherwise noted. Therefore, detailed description will not be repeated.

[0080] Resistance elements 66R to 66T are connected in series with diodes 65R to 65T, respectively. This increases the impedance (resistance component) of surge suppression device 45 compared to the third embodiment. As a result, the current flowing into bypass cable 50, out of the motor drive current, can be further reduced. This reduces the amount of heat generated by surge suppression member 53 as a whole. This holds true even when the amount of heat generated by resistance elements 66R to 66T due to the current flowing into bypass cable 50 is taken into account. In addition, because the current flowing through bypass cable 50 is reduced as described above, bypass power lines 52R to 52T can be made thinner.

[0081] Fourth Embodiment Fig. 9 is a diagram for explaining in detail the configuration of a motor drive system according to a fourth embodiment. Referring to Fig. 9, motor drive system 90 is included in elevator system 1 in place of motor drive system 60 (Fig. 2) of the first embodiment. Motor drive system 90 differs from motor drive system 60 in that bypass power lines 52R to 52T do not branch off at branch points BRR to BRT, respectively.

[0082] Motor drive system 90 further differs from motor drive system 60 in that the ends of bypass cable 50 in the -Z direction are not connected to connection points p2R, p2T, p3R, p3S, p4S, and p4T, but are connected only to connection points p2S, p3T, and p4R. In other words, motor drive system 90 further differs from motor drive system 60 (FIG. 2) in that the ends of bypass power lines 52R to 52T in the -Z direction are connected to output terminals 32S, 32T, and 32R via connection points p2S, p3T, and p4R, respectively. Note that these ends may also be directly connected to these connection terminals.

[0083] Motor drive system 90 further differs from motor drive system 60 in that surge suppression member 53 includes filter components 68RS, 68ST, and 68TR as surge suppression components instead of surge suppression component group 54R to 54T.

[0084] In other respects, unless otherwise specified, the hardware configuration of motor drive system 90 is the same as that of motor drive system 90. For example, the ends of bypass power lines 52R to 52T in the +Z direction are connected to connection terminals 15R to 15T via connection points p1R to p1T or directly, respectively.

[0085] Filter components 68RS to 68TR are provided on bypass power lines 52R to 52T, respectively. Filter component 68RS includes a resistor element 62RS and a capacitor 67RS. Filter component 68ST includes a resistor element 62ST and a capacitor 67ST. Filter component 68TR includes a resistor element 62TR and a capacitor 67TR. Capacitors 67RS to 67TR are connected in series with resistor elements 62RS to 62TR, respectively.

[0086] When the motor cable 40 is only a few meters long, the entire motor cable 40 and surge suppression device 45 can be modeled as an LCR series circuit to a first-order approximation. The inductance component of this LCR series circuit is derived from the inductance of the power lines 42R-42T and the bypass power lines 52R-52T. The capacitance component of the LCR series circuit is derived from the capacitance of the capacitors 67RS-67TR. The combined capacitance of these capacitances is preferably equal to or greater than the stray capacitance of the motor 15. The inductance and capacitance are related to the frequency of the surge voltage. The resistance component of the LCR series circuit is derived from the electrical resistance of the resistor elements 62RS-62TR. These electrical resistances are related to the degree of surge voltage reduction.

[0087] The following describes how filter components 68RS-68TR function in motor drive system 90. As an example, consider a transient situation immediately after the operation of the switching elements of inverter 30 causes output terminals 32R-32T to switch from a first state to a second state, a rectangular wave voltage is output from output terminal 32R, and a surge voltage is applied between the connection terminals of motor 15. In this situation, a potential difference may be generated between terminals of different phases of motor 15 and inverter 30 (e.g., connection terminal 15R and output terminal 32S) for a longer time interval than in the second embodiment or its modified example.

[0088] If the motor drive system 90 did not include the surge suppression device 45, a surge voltage would be applied between the connection terminals of the motor 15, potentially causing dielectric breakdown in the motor 15. In contrast, according to the fourth embodiment, a portion of the surge energy is returned from these connection terminals to the filter components 68RS-68TR through the bypass cable 50. As a result, the surge energy is dissipated by the resistor elements 62RS-62TR. This reduces the peak of the surge voltage, thereby suppressing the surge voltage. Furthermore, even if a potential difference occurs between the terminals of different phases of the motor 15 and the inverter 30 over a long period of time, it is possible to prevent the power consumption of the resistor elements 62RS-62TR from increasing due to overheating, which would be caused by the function of the capacitors 67RS-67TR.

[0089] Fifth Embodiment In the above, the case has been mainly described where the number of power lines in the bypass cable 50 is equal to the number of power lines in the motor cable 40. However, the number of bypass power lines in the bypass cable 50 may be smaller than the number of power lines in the motor cable 40. According to the fifth embodiment, even in such a case, the motor 15 can be protected from surge voltages.

[0090] Fig. 10 is a diagram for explaining in detail the configuration of a motor drive system according to embodiment 5. Referring to Fig. 10, motor drive system 100 is included in elevator system 1 in place of motor drive system 70 (Fig. 3) of embodiment 2. Motor drive system 100 differs from motor drive system 70 in that bypass cable 50 does not include bypass power line 52T and surge suppression member 53 does not include resistive element 62T.

[0091] In other respects, unless otherwise specified, the hardware configuration of motor drive system 100 is the same as that of motor drive system 70. For example, the ends of bypass power lines 52R and 52S in the +Z direction are connected to connection terminals 15R and 15S via connection points p1R and p1S or directly, respectively. Similarly, the ends of bypass power lines 52R and 52S in the −Z direction are connected to output terminals 32R and 32S via connection points p2R and p3S or directly, respectively.

[0092] In this example, surge suppression member 53 is made up of resistive elements 62R and 62S, but may further include capacitors 67R and 67S, as in the modified example of embodiment 2. Alternatively, surge suppression member 53 may be made up of diodes 65R and 65S (FIG. 6). Surge suppression member 53 may further include resistive elements 66R and 66S.

[0093] Fig. 11 is a diagram for explaining in detail another configuration of a motor drive system according to embodiment 5. Referring to Fig. 11, motor drive system 105 is included in elevator system 1 in place of motor drive system 90 (Fig. 9) of embodiment 4. Motor drive system 105 differs from motor drive system 90 in that bypass cable 50 does not include bypass power line 52T and surge suppression member 53 does not include filter component 68TR.

[0094] In other respects, the hardware configuration of motor drive system 105 is the same as that of motor drive system 90 unless otherwise specified. For example, the ends of bypass power lines 52R and 52S in the +Z direction are connected to connection terminals 15R and 15S via connection points p1R and p1S or directly, respectively. The ends of bypass power lines 52R and 52S in the -Z direction are connected to output terminals 32S and 32T via connection points p2S and p3T or directly, respectively. In the fifth embodiment, bypass power lines 52R and 52S correspond to the "bypass power line members" of this disclosure.

[0095] According to the fifth embodiment, the number of power lines (power lines 42R to 42T) of the motor cable 40 is three, while the number of power lines (bypass power lines 52R, 52S) of the bypass cable 50 is two. Even in such a case, part of the surge energy is returned to the surge suppression member 53 through the bypass cable 50. This makes it possible to reduce the number of power lines of the bypass cable 50, thereby saving costs, while protecting the motor 15 from surge voltages.

[0096] Sixth Embodiment Fig. 12 is a diagram for explaining in detail the configuration of a motor drive system according to a sixth embodiment. Referring to Fig. 12, a motor drive system 110 is included in elevator system 1 in place of motor drive system 105 (Fig. 11) of the fifth embodiment. Motor drive system 110 differs from motor drive system 105 in that bypass cable 50 does not include bypass power line 52R, specifically, in that the power line of bypass cable 50 is a single bypass power line (bypass power line 52S). In this example, bypass power line 52S corresponds to the "bypass power line member" of the present disclosure.

[0097] Motor drive system 110 further differs from motor drive system 105 in that surge suppression member 53 does not include filter component 68RS as a surge suppression component. Motor drive system 110 further differs from motor drive system 105 in that motor drive system 110 further includes reactor 72.

[0098] In other respects, the hardware configuration of motor drive system 110 is the same as that of motor drive system 105, unless otherwise specified. For example, the end of bypass power line 52S in the +Z direction is connected to connection terminal 15S via connection point p1S or directly. The end of bypass power line 52S in the −Z direction is connected to output terminal 32T via connection point p3T or directly.

[0099] The reactor 72 is disposed on the power line 42R. The reactor 72 is disposed to suppress surge voltage and reduce noise. The reactor 72 may be disposed in the non-proximal region described above, but is preferably disposed in the proximal region VR.

[0100] Depending on the environment around the motor cable 40, it may be preferable to place a reactor on each power line of the motor cable 40 (particularly within the vicinity region VR) to suppress surge voltages and effectively reduce noise. However, if there is insufficient space around the motor cable 40, it may be difficult to place a reactor on each power line as described above. As a result, in this example, the reactor 72 is placed only on the power line 42R, while a reactor cannot be placed on each of the power lines 42S and 42T.

[0101] According to the sixth embodiment, the surge voltage between connection terminals 15S and 15T is suppressed by filter component 68ST. Furthermore, because reactor 72 is disposed on power line 42R, noise caused by the motor drive current flowing through power line 42R is reduced, and the surge voltage between connection terminals 15R and 15S and the surge voltage between connection terminals 15R and 15T are suppressed. Therefore, even if there is insufficient space around motor cable 40 (particularly within the vicinity region VR) to accommodate three reactors, motor 15 can be protected from the surge voltage between the respective connection terminals while reducing noise caused by the motor drive current flowing through power line 42R. In addition, motor cable 40 has three power lines, while bypass cable 50 has only one power line. Therefore, motor 15 can be protected from surge voltage while minimizing the number of power lines in bypass cable 50.

[0102] Seventh Embodiment Fig. 13 is a diagram for explaining in detail the configuration of a motor drive system according to a seventh embodiment. Referring to Fig. 13, motor drive system 120 is included in elevator system 1 in place of motor drive system 60 (Fig. 3) of the second embodiment. Motor drive system 120 differs from motor drive system 60 in that it includes a single-phase motor 17 and a single-phase inverter 31 instead of motor 15 and inverter 30.

[0103] Motor drive system 120 further differs from motor drive system 60 in that motor cable 40 includes power lines 42L and 42N instead of power lines 42R to 42T. Power lines 42L and 42N correspond to an example of a "power line member" in the present disclosure. Motor drive system 120 further differs from motor drive system 60 in that the power line of bypass cable 50 is only bypass power line 52a instead of bypass power lines 52R to 52T. Bypass power line 52a corresponds to a "bypass power line member" in the present disclosure. Motor drive system 120 further differs from motor drive system 60 in that surge suppression member 53 includes filter component 57 as a surge suppression component instead of resistor elements 62R, 62S, and 62T.

[0104] In other respects, the hardware configuration of motor drive system 120 is the same as that of motor drive system 60 unless otherwise specified, and therefore detailed description will not be repeated.

[0105] The single-phase motor 17 has connection terminals 17L and 17N. The single-phase inverter 31 has output terminals 32L and 32N. The single-phase inverter 31 functions as a drive device that drives the single-phase motor 17 by outputting a square-wave voltage from the output terminal 32L. The single-phase inverter 31 may drive the single-phase motor 17 by outputting a square-wave voltage from the output terminal 32N. After the single-phase inverter 31 outputs the square-wave voltage, a surge voltage may be applied between the connection terminals 17L and 17N. Such a surge voltage may cause insulation breakdown in the single-phase motor 17.

[0106] The power lines 42L, 42N are arranged in parallel with each other. The power line 42L extends from the output terminal 32L and is connected to the connection terminal 17L. The power line 42N extends from the output terminal 32N and is connected to the connection terminal 17N. In other words, the power lines 42L, 42N extend from the output terminals 32L, 32N and are connected to the connection terminals 17L, 17N, respectively. In this example, a rectangular wave voltage is output from the output terminal 32L, and this rectangular wave voltage is transmitted on the power line 42L. Note that when a rectangular wave voltage is output from the output terminal 32N, this rectangular wave voltage is transmitted on the power line 42N.

[0107] The end of bypass power line 52a in the +Z direction is connected to connection terminal 17L via connection point p1L. This end may be directly connected to connection terminal 17L. A connector (not shown) is provided at connection point p1L.

[0108] The end of the bypass power line 52a in the -Z direction is connected to the output terminal 32L via a connection point p2L. The connection point p2L is preferably located within the vicinity region VR. A connector (not shown) is provided at the connection point p2L. The end may be directly connected to the output terminal 32L.

[0109] The filter component 57 is disposed on the bypass power line 52a. The filter component 57 is a resistive element 58. The filter component 57 may further include a capacitor (not shown) connected in series with the resistive element 58. Alternatively, the filter component 57 may be a diode (not shown) arranged so that a forward current flows from the connection point p1L to the connection point p2L. The filter component 57 may further include a resistive element (not shown) connected in series with the diode.

[0110] In this example, the power lines 42L, 42N are included in the motor cable 40, and the bypass power line 52a is included in the bypass cable 50, but as long as the power lines 42L, 42N and the bypass power line 52a are insulated, these power lines may be included in a single cable.

[0111] FIG. 14 is a diagram illustrating in detail another configuration of a motor drive system according to the seventh embodiment. Referring to FIG. 14, a motor drive system 125 is included in elevator system 1 in place of motor drive system 120 (FIG. 13) of the second embodiment. Motor drive system 125 differs from motor drive system 120 in that the end of bypass power line 52a in the −Z direction is connected to connection point p2N instead of connection point p2L. In this example, filter component 57 includes a resistive element 58 and a capacitor 58a. Capacitor 58a is connected in series with resistive element 58.

[0112] In other respects, the hardware configuration of motor drive system 125 is the same as that of motor drive system 120 unless otherwise specified, and therefore detailed description will not be repeated.

[0113] In both the examples of Figures 13 and 14, the number of power lines (power lines 42L, 42N) of the motor cable 40 is two, while the number of power lines (bypass power line 52a) of the bypass cable 50 is one.

[0114] According to the seventh embodiment, even when a surge voltage is applied between connection terminals 17L, 17N of single-phase motor 17, part of the surge energy is returned to output terminals 32L, 32N through bypass power line 52a and surge suppression member 53. This makes it possible to protect single-phase motor 17 from surge voltages while minimizing the number of power lines in bypass cable 50 and saving costs.

[0115] Variation of Seventh Embodiment. FIG. 15 is a diagram for explaining in detail the configuration of a motor drive system according to a variation of the seventh embodiment. Referring to FIG. 15, motor drive system 130 is included in elevator system 1 in place of motor drive system 120 of the seventh embodiment (FIG. 13). Motor drive system 130 differs from motor drive system 120 in that it includes DC motor 18 and power supply device 37 instead of single-phase motor 17 and single-phase inverter 31. In other respects, the hardware configuration of motor drive system 130 is the same as that of motor drive system 120 unless otherwise specified. Therefore, detailed description will not be repeated.

[0116] The DC motor 18 includes connection terminals 18L and 18N, which are a high-potential terminal and a low-potential terminal, respectively. The power supply 37 is an AC / DC converter or a DC / DC converter and includes output terminals 37L and 37N. The power supply 37 drives the DC motor 18 by outputting a square-wave voltage from either of the output terminals 37L and 37N. After the power supply 37 outputs the square-wave voltage, a surge voltage may be applied between the connection terminals 18L and 18N. Such a surge voltage may cause insulation breakdown in the DC motor 18.

[0117] Fig. 16 is a diagram for explaining in detail another configuration of a motor drive system according to this modification. Referring to Fig. 16, motor drive system 135 is included in elevator system 1 in place of motor drive system 125 (Fig. 14) of embodiment 7. Motor drive system 135 differs from motor drive system 125 of embodiment 7 in that it includes power supply device 37 and DC motor 18 instead of single-phase inverter 31 and single-phase motor 17. In other respects, the hardware configuration of motor drive system 135 is the same as that of motor drive system 125 unless otherwise specified. Therefore, detailed description will not be repeated.

[0118] 15 and 16, when a surge voltage is applied between connection terminals 18L and 18N, part of the surge energy is returned to surge suppression member 53 through bypass power line 52a. Therefore, according to this modification, the number of power lines in bypass cable 50 can be minimized to save costs, while protecting DC motor 18 from surge voltage.

[0119] Eighth Embodiment. Figures 17 and 18 are diagrams for explaining in detail the configuration of a motor drive system according to an eighth embodiment. Referring to Figure 17, motor drive system 140 differs from motor drive system 120 (Figure 13) in that the power lines of bypass cable 50 further include bypass power line 52b, and surge suppression member 53 further includes a filter component 57 provided on bypass power line 52b. In this eighth embodiment, single-phase motor 17 can also be appropriately protected from surge voltages. Note that single-phase motor 17 and single-phase inverter 31 in Figure 17 may be replaced by DC motor 18 and power supply device 37, respectively (see Figure 18).

[0120] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0121] 1 elevator system, 10 hoisting machine, 15 motor, 15R to 15T, 17L, 17N, 18L, 18N connection terminal, 17 single-phase motor, 18 DC motor, 30 inverter, 31 single-phase inverter, 32R to 32T, 32L, 32N, 37L, 37N output terminal, 37 power supply device, 40 motor cable, 50 bypass cable, 53 surge suppression member, 59 monitoring device, 60, 70, 75, 80, 85, 90, 100, 105, 110, 120, 125, 130, 135 motor drive system.

Claims

1. A motor drive system comprising: a motor having a plurality of connection terminals; a drive device having a plurality of output terminals and configured to drive the motor by outputting a rectangular wave voltage from the plurality of output terminals; power line members extending from the plurality of output terminals and connected to the plurality of connection terminals, to which the rectangular wave voltage is transmitted; a bypass power line member; and a surge suppression member disposed on the bypass power line member, wherein one end of the bypass power line member is connected to one or more of the plurality of connection terminals, and the other end of the bypass power line member is connected to one or more of the plurality of output terminals.

2. The motor drive system according to claim 1, wherein a combined impedance of the bypass power line member and the surge suppressor member is greater than an impedance of the power line member.

3. A motor drive system as described in claim 1 or claim 2, wherein the power line member includes: a first power line extending from a first output terminal of the plurality of output terminals and connected to a first connection terminal of the plurality of connection terminals; and a second power line extending from a second output terminal of the plurality of output terminals and connected to a second connection terminal of the plurality of connection terminals, the second power line being parallel to the first power line, the one end of the second power line being connected to the first connection terminal, and the other end of the second power line being connected to the first output terminal.

4. The motor drive system according to claim 3, wherein the surge suppression member includes a resistive element.

5. The motor drive system according to claim 4, wherein the surge suppression member further includes a capacitor connected in series with the resistive element.

6. The motor drive system according to claim 3, wherein the surge suppression member includes a diode, and the diode is arranged so that a forward current of the diode flows from the one end to the other end.

7. The motor drive system according to claim 6, wherein the surge suppression member further includes a resistive element connected in series with the diode.

8. A motor drive system as described in claim 1 or claim 2, wherein the power line member includes: a first power line extending from a first output terminal of the plurality of output terminals and connected to a first connection terminal of the plurality of connection terminals; and a second power line extending from a second output terminal of the plurality of output terminals and connected to a second connection terminal of the plurality of connection terminals, the second power line being parallel to the first power line, the one end of the second power line being connected to the first connection terminal, and the other end of the second power line being connected to the second output terminal.

9. The motor drive system according to claim 8, wherein the surge suppression member includes: a resistive element; and a capacitor connected in series with the resistive element.

10. A motor drive system according to any one of claims 1 to 9, wherein the power line member includes a plurality of power lines, the bypass power line member includes a plurality of bypass power lines, and the number of the plurality of bypass power lines is equal to the number of the plurality of power lines.

11. A motor drive system according to any one of claims 1 to 9, wherein the power line member includes a plurality of power lines, the bypass power line member includes one or more bypass power lines, and the number of the one or more bypass power lines is smaller than the number of the plurality of power lines.

12. The motor drive system according to claim 11, wherein the motor includes a three-phase motor, and the drive device includes a three-phase inverter that drives the three-phase motor.

13. The motor drive system according to claim 12, wherein the plurality of power lines include: a first power line extending from a first output terminal among the plurality of output terminals and connected to a first connection terminal among the plurality of connection terminals; a second power line extending from a second output terminal among the plurality of output terminals and connected to a second connection terminal among the plurality of connection terminals, the second power line being parallel to the first power line; and a third power line extending from a third output terminal among the plurality of output terminals and connected to a third connection terminal among the plurality of connection terminals, the third power line being parallel to the first power line and the second power line; the motor drive system further includes a reactor disposed on the first power line; and the one or more bypass power lines are a single bypass power line, one end of the single bypass power line is connected to the second connection terminal, and the other end of the single bypass power line is connected to the third output terminal.

14. The motor drive system according to claim 11, wherein the motor includes a single-phase motor, and the drive device includes a single-phase inverter that drives the single-phase motor.

15. The motor drive system according to claim 11, wherein the motor includes a DC motor, and the drive device includes a power supply device that drives the DC motor.

16. The motor drive system according to any one of claims 1 to 15, wherein the surge suppression member is disposed on the bypass power line member within a region adjacent to the drive device.

17. The motor drive system according to claim 16, further comprising a monitoring device provided in the vicinity area for monitoring the state of the surge suppression member.

18. An elevator system comprising: a motor drive system according to any one of claims 1 to 17; and an elevator car that is raised and lowered within a hoistway in response to rotation of the motor.

19. The elevator system of claim 18, wherein the motor is provided inside a machine room above the hoistway, and the drive device is provided outside the machine room.

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