A power supply circuit for an electric motor of a construction machine and a construction machine

Abstract

The application relates to the technical field of vehicle power supply control, and discloses an engineering machinery motor power supply circuit and engineering machinery, which comprises a three-phase electric power supply, a rectifier module, an inverter module, a three-phase motor and a protection capacitor. The three-phase electric power supply is electrically connected with the rectifier module, the rectifier module is electrically connected with the inverter module, and the inverter module is electrically connected with the three-phase motor. Each output line of the three-phase electric power supply is connected with an input end of a protection capacitor through a branch, and the output ends of the three protection capacitors are connected to a target node. The target node is connected with the engineering machinery shell. The voltage between the three protection capacitors is 120 degrees, the voltage vector of the neutral point position is 0, and the voltage on the engineering machinery can be forcibly reduced after the neutral point is connected with the engineering machinery shell, so that the influence of the electric leakage on the engineering machinery on the user is reduced.

Description

Technical Field

[0001] This invention relates to the field of vehicle power supply control technology, specifically to a power supply circuit for an electric motor in engineering machinery and the engineering machinery itself. Background Technology

[0002] With the trend towards new energy sources, construction machinery is also becoming electrified. Currently, the commonly used technology involves using a frequency converter to rectify and invert the three-phase mains power, converting it into AC power to control the rotation of a permanent magnet synchronous motor. However, this type of construction machinery relies on grounding. If the entire vehicle is not grounded, the vehicle body may become electrified during operation. Often, there are numerous power distribution cabinets on the market without grounding points. When construction machinery draws power from these non-standard distribution cabinets, the equipment casing may become electrified, posing a certain safety hazard. Summary of the Invention

[0003] In view of this, the present invention provides a power supply circuit for an electric motor of engineering machinery and engineering machinery, so as to solve the problem of leakage when electric engineering machinery is not grounded.

[0004] In a first aspect, the present invention provides a power supply circuit for an electric motor of engineering machinery, comprising: a three-phase power supply, a rectifier module, an inverter module, a three-phase motor, and three protective capacitors; the three output lines of the three-phase power supply are electrically connected to the three input lines of the rectifier module, the two output lines of the rectifier module are electrically connected to the two input lines of the inverter module, and the three output lines of the inverter module are electrically connected to the three input lines of the three-phase motor; between the three-phase power supply and the rectifier module, each output line of the three-phase power supply has a branch line led out and electrically connected to the input terminal of a protective capacitor, and the output terminals of the three protective capacitors are connected together to a target node, the target node being connected to the wiring of the engineering machinery casing.

[0005] In some alternative embodiments, a first switch is provided on the line between the target node and the housing of the engineering machinery.

[0006] In some optional embodiments, the system further includes: a first relay and a second relay, the first relay including a first coil and a first switch, and the second relay including a second coil and a second switch; the two ends of the first coil are respectively connected to a first output line and a second output line, the first output line and the second output line being any two of the three output lines of the three-phase power supply; the second switch is connected in series at any one end of the first coil; the two ends of the second coil are respectively connected to a third output line and the first output line, or the two ends of the second coil are respectively connected to a third output line and the second output line, the third output line being a line other than the first output line and the second output line among the three output lines of the three-phase power supply.

[0007] In some alternative embodiments, an air switch is also provided on the three output lines of the three-phase power supply.

[0008] In some alternative implementations, the protective capacitor is 1uF.

[0009] In some alternative implementations, a filter capacitor is provided between the two output lines of the rectifier module.

[0010] In a second aspect, the present invention provides an engineering machinery, including an electric motor, a processor, a memory, an actuator, and a power supply circuit for the engineering machinery electric motor provided by any one of the first aspects.

[0011] The technical solution provided by this invention has the following advantages:

[0012] This invention connects three protective capacitors in a star configuration to the three-phase power supply and rectifier module, with the neutral point of each capacitor connected to the casing of the construction machinery. Because the voltages of the three protective capacitors are at 120-degree angles to each other, the vector sum of the voltages at the neutral point is zero. Connecting the neutral point to the casing of the construction machinery forcibly lowers the voltage on the machinery, reducing the impact of leakage current on the user. This also reduces common-mode voltage even when the electric construction machinery is not grounded, eliminating slight electric shock sensations. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1This is a schematic diagram of the power supply circuit for an electric motor in engineering machinery, based on relevant technologies.

[0015] Figure 2 This is a schematic diagram of the power supply circuit for an electric motor in another piece of engineering machinery, based on related technologies.

[0016] Figure 3 This is a schematic diagram of the power supply circuit for an engineering machinery electric motor according to an embodiment of the present invention.

[0017] Figure 4 This is another schematic diagram of the power supply circuit for an engineering machinery electric motor according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] With the trend towards new energy sources, construction machinery is also becoming electrified. Currently, the commonly used technology involves using a frequency converter to rectify and invert the three-phase mains power, converting it into AC power to control the rotation of a permanent magnet synchronous motor. However, this type of construction machinery relies on grounding. If the entire vehicle is not grounded, the vehicle body will become electrified during operation. Often, there are numerous power distribution cabinets on the market without grounding points. When construction machinery draws power from these non-standard distribution cabinets, the equipment becomes electrified, posing a certain safety hazard.

[0020] like Figure 1 The diagram shows a power supply circuit for an engineering machinery motor with a grounding line.

[0021] The three-phase power from the three-phase power supply is rectified into DC by the rectifier module of the frequency converter, and then inverted into AC by the inverter module to drive the three-phase motor of the construction machinery. Under normal circumstances, the motor windings and the casing are not completely insulated, and there will be a certain amount of distributed capacitance. Distributed capacitance is not a capacitor. The distributed capacitance of the motor casing refers to the capacitance generated between the motor casing and the internal circuit due to the non-ideal isolation between the conductors. When the voltage to ground of the neutral point n of the three-phase motor winding leaks through the distributed capacitance, a voltage to ground will appear on the casing of the construction machinery. When the user touches it, they may feel a slight electric shock. However, when the vehicle's ground wire PE is well grounded, the frame voltage is close to 0V, and touching the frame will not cause an electric shock.

[0022] However, many construction site electrical distribution cabinets lack a grounding (PE) terminal block, leaving the vehicle's PE wire unconnected. Figure 2 As shown. Furthermore, SVPWM (Space Vector Pulse Width Modulation) technology suffers from voltage asymmetry. Voltage asymmetry refers to the situation in a three-phase SVPWM inverter where the amplitudes of the positive and negative half-cycles of the output voltage are not equal. There are several reasons for this, such as: asymmetry in inverter switching states: During SVPWM modulation, the inverter's switching states directly affect the symmetry of the output voltage. Uneven switching will lead to output voltage asymmetry. Improper parameter settings: Incorrect settings of parameters such as the initial duty cycle and frequency can also cause voltage asymmetry. Hardware problems: Faulty hardware circuits or incorrect wiring can also cause voltage asymmetry. When the above problems exist simultaneously, a non-zero voltage to ground exists at the neutral point n of the motor winding at all times. Assuming the three-phase power frequency is 380V, the peak voltage U at the neutral point n of the motor winding is... ng As shown in Table 1 below.

[0023] Table 1. Schematic diagram of peak voltage variation of neutral point n to ground in motor windings

[0024]

[0025] Therefore, the voltage to ground at the neutral point n of the motor winding leaks through the distributed capacitance, resulting in a voltage to ground on the casing, causing a slight electric shock sensation when the user touches it. Therefore, it is essential to address the common-mode voltage when electric engineering machinery is not grounded.

[0026] According to an embodiment of the present invention, a power supply circuit for an engineering machinery motor is provided. Three star-connected capacitors are added to the front end of the inverter rectifier module. The neutral point of these three capacitors is close to 0V. This neutral point is connected to the inverter housing. Since the inverter housing and the vehicle frame are electrically connected, the vehicle frame voltage is significantly reduced, solving the problem of the vehicle frame being electrified. The specific circuit structure is as follows: Figure 3 As shown.

[0027] exist Figure 3 The power supply circuit for the electric motor of engineering machinery provided in this embodiment of the invention includes: a three-phase power supply S04, a rectifier module S01, an inverter module S02, a three-phase motor S05, and protection capacitors (C1, C2, C3).

[0028] The three output lines of the three-phase power supply S04 are electrically connected to the three input lines of the rectifier module S01, the two output lines of the rectifier module S01 are electrically connected to the two input lines of the inverter module S02, and the three output lines of the inverter module S02 are electrically connected to the three input lines of the three-phase motor S05.

[0029] Between the three-phase power supply S04 and the rectifier module S01, each output line of the three-phase power supply S04 leads out a branch and is electrically connected to the input terminal of a protection capacitor (C1, C2, or C3). The output terminals of the three protection capacitors (C1, C2, and C3) are connected to the target node, and the target node is connected to the wiring of the engineering machinery casing.

[0030] Specifically, three protective capacitors (C1, C2, C3) are added to the front end of the rectifier module S01 and connected in a star configuration. When powered on, the neutral point f (the target node) of the three protective capacitors (C1, C2, C3) is electrically connected to the inverter S03 casing and the vehicle frame. Because the voltage between the three protective capacitors (C1, C2, C3) comes from the three-phase power supply, and the protective capacitors (C1, C2, C3) allow AC while blocking DC, with each phase voltage changing at 120 degrees to the others, the vector sum of the voltages at the neutral point f (the target node) of the three protective capacitors (C1, C2, C3) is 0. Connecting the neutral point to the casing of the construction machinery forcibly lowers the voltage on the machinery, reducing the impact of leakage current (typically exceeding the safe voltage of 24V) on the user. Although leakage current cannot be completely eliminated, lowering the voltage can eliminate a slight electric shock sensation, thus reducing the common-mode voltage even when the electric construction machinery is not grounded. Even if the construction machinery casing is not like... Figure 1 With proper grounding, no perceptible voltage to ground will be generated on the outer shell of the construction machinery, and people standing on the ground will not feel an electric shock when touching the vehicle body or the crane hook.

[0031] In some alternative implementations, a first switch K3 is provided on the line between the target node and the housing of the engineering machinery.

[0032] Specifically, in this embodiment of the invention, a first switch K3 is also installed on the line between the target node and the engineering machinery shell. When any phase of the three-phase power supply is missing, the vector sum of the three-phase voltages on the target node is not zero, and the target node becomes energized. At this time, the target node is connected to the engineering machinery shell, which may lead to a danger of the frame becoming energized. Therefore, this embodiment of the invention adds a first switch K3 between the target node and the engineering machinery shell, which can promptly avoid the danger of the frame becoming energized by disconnecting the first switch K3, thereby improving the reliability of the power supply circuit provided by this invention.

[0033] In some optional embodiments, the power supply circuit for the engineering machinery motor provided by the present invention further includes a first relay and a second relay. The first relay includes a first coil CL3 and a first switch K3, and the second relay includes a second coil CL2 and a second switch K2. The two ends of the first coil CL3 are respectively connected to a first output line and a second output line, which are any two of the three output lines of the three-phase power supply S04. The second switch K2 is connected in series at any one end of the first coil CL3. The two ends of the second coil CL2 are respectively connected to a third output line and a first output line, or the two ends of the second coil CL2 are respectively connected to a third output line and a second output line, where the third output line is a line other than the first and second output lines among the three output lines of the three-phase power supply S04.

[0034] Specifically, this invention implements phase loss protection for construction machinery when one phase of the three-phase power supply S04 is lost through two relays. When one phase of the three-phase power supply S04 is open-circuited, the voltage to ground of the neutral point of the star-connected three protective capacitors (C1, C2, C3) can reach 220V. If it is still connected to the housing of the construction machinery at this time, it will cause the frame to become electrified and dangerous. Therefore, if the connection between the neutral point of the star-connected protective capacitors (C1, C2, C3) and the housing of the construction machinery can be automatically disconnected when the three-phase power supply S04 is lost, it will be the best protection solution. Based on this, in this embodiment of the invention, the two ends of the first coil CL3 in the first relay are respectively connected to the first output line and the second output line. The first output line and the second output line are any two of the three output lines of the three-phase power supply S04. The second switch K2 in the second relay is connected in series at any one end of the first coil CL3. The two ends of the second coil CL2 in the second relay are respectively connected to the third output line and the first output line, or the two ends of the second coil CL2 are respectively connected to the third output line and the second output line. The third output line is the line other than the first output line and the second output line among the three output lines of the three-phase power supply S04.

[0035] For example Figure 3As shown, in an optional embodiment, the first coil CL3 corresponding to the first switch K3 is connected to the W and U phases of the three-phase power supply S04. The second switch K2 and the first coil CL3 are connected in series, and the second coil CL2 used to control the second switch K2 is connected to the W and V phases of the three-phase power supply S04. Based on this, when there is no phase loss in the three-phase power supply S04, the second coil CL2 is energized to generate a magnetic field, attracting the second switch K2 to close, and the circuit of the first coil CL3 is turned on. Then, the first coil CL3 is energized to generate a magnetic field, attracting the first switch K3 to close. The neutral point of the three protective capacitors (C1, C2, C3) connected in a star configuration is connected to the circuit of the inverter S03 casing, and then connected to the casing of the construction machinery. The voltage of the construction machinery casing is pulled down from the safety voltage of more than 24V to close to 0V, and the function takes effect. When at least one phase of the three-phase power supply S04 is lost, at least one circuit of the second coil CL2 or the third coil cannot be connected, thus preventing the generation of a magnetic field. The first switch K3 cannot be closed, or both the first switch K3 and the second switch K2 cannot be closed. The neutral point of the star-connected three protective capacitors (C1, C2, C3) cannot be connected to the circuit of the inverter S03 casing, and thus cannot be connected to the casing of the construction machinery. Therefore, this circuit can also disconnect the casing from the star-connected neutral point of the three protective capacitors (C1, C2, C3) when a phase is lost, thereby preventing the casing from becoming energized due to a phase loss.

[0036] In some alternative implementations, such as Figure 3 As shown, an air switch K1 is also installed on the three output lines of the three-phase power supply S04. When the user needs to power the construction machinery, the air switch K1 is closed; when it is not needed, the air switch K1 is opened to stop powering the construction machinery, further improving the reliability of the power supply circuit.

[0037] In some optional embodiments, the protective capacitors (C1, C2, C3) provided by the present invention are 1uF. Specifically, the effectiveness of the protective capacitors (C1, C2, C3) in eliminating induced voltage on the casing of engineering machinery varies depending on their size. Excessively large capacitors result in wasted cost and space, while excessively small capacitors have a limited effect on eliminating induced voltage on the casing of engineering machinery. Therefore, based on the actual scenario, the optimal protective capacitor (C1, C2, C3) parameters of the embodiments of the present invention are determined to be 1uF, balancing elimination capability and low cost.

[0038] In some alternative implementations, such as Figure 3As shown, the present invention also includes a filter capacitor between the two output lines of the rectifier module S01. The capacitor between the rectifier module S01 and the inverter module S02 plays a crucial role in the power electronic system. This filter capacitor can be used to filter and smooth the DC output of the rectifier module S01, reducing ripple during the AC to DC conversion process; while for the inverter module S02, the filter capacitor can also be used to stabilize the output voltage and reduce harmonic interference, improving the quality of AC power.

[0039] In addition, in some alternative implementations, the aforementioned relays and protective capacitors are not limited to being implemented inside the frequency converter, but can also be implemented by external installation of independent modules, for example... Figure 4 This facilitates the modification of the power supply circuit of engineering machinery, allowing for the addition of independent protective modules as needed.

[0040] This invention also provides an engineering machinery, including an electric motor, a processor, a memory, an actuator, and the power supply circuit for the engineering machinery electric motor provided in the above embodiments.

[0041] The processor may include one or more processors, memory, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other using different buses and may be mounted on a common motherboard or otherwise installed as needed. The processor can process instructions that execute within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interface). In some alternative implementations, multiple processors and / or multiple buses may be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices may be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system).

[0042] The processor can be a central processing unit, a network processor, or a combination thereof. The processor may further include hardware chips. These hardware chips can be application-specific integrated circuits (ASICs), programmable logic devices (PLDs), or combinations thereof. The programmable logic devices can be complex programmable logic devices (CLPs), field-programmable gate arrays (FPGAs), general-purpose array logic (GDAs), or any combination thereof.

[0043] The memory stores instructions executable by at least one processor to cause the at least one processor to perform the method shown in the above embodiments.

[0044] The memory may include a stored program area and a stored data area, wherein the stored program area may store the operating system and application programs required for at least one function; the stored data area may store data created based on the use of the computer device, etc. Furthermore, the memory may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory may optionally include memory remotely located relative to the processor, which can be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0045] The memory may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory may also include a combination of the above types of memory.

[0046] The computer device also includes a communication interface for communicating with other devices or communication networks.

[0047] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0048] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0049] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A power supply circuit for an electric motor in engineering machinery, characterized in that, include: Three-phase power supply, rectifier module, inverter module, three-phase motor, protection capacitor; The three output lines of the three-phase power supply are electrically connected to the three input lines of the rectifier module, the two output lines of the rectifier module are electrically connected to the two input lines of the inverter module, and the three output lines of the inverter module are electrically connected to the three input lines of the three-phase motor. Between the three-phase power supply and the rectifier module, each output line of the three-phase power supply has a branch line that is electrically connected to the input terminal of a protection capacitor. The output terminals of the three protection capacitors are connected to the target node, which is connected to the wiring of the engineering machinery casing.

2. The power supply circuit for the electric motor of engineering machinery according to claim 1, characterized in that, A first switch is installed on the line between the target node and the outer shell of the engineering machinery.

3. The power supply circuit for the electric motor of engineering machinery according to claim 2, characterized in that, Also includes: A first relay and a second relay, wherein the first relay includes a first coil and a first switch, and the second relay includes a second coil and a second switch; The two ends of the first coil are respectively connected to the first output line and the second output line, and the first output line and the second output line are any two of the three output lines of the three-phase power supply. The second switch is connected in series at any one end of the first coil; The two ends of the second coil are respectively connected to the third output line and the first output line, or the two ends of the second coil are respectively connected to the third output line and the second output line. The third output line is the line other than the first output line and the second output line among the three output lines of the three-phase power supply.

4. The power supply circuit for the electric motor of engineering machinery according to claim 1, characterized in that, An air switch is also installed on the three output lines of the three-phase power supply.

5. The power supply circuit for the electric motor of engineering machinery according to claim 1, characterized in that, The protective capacitor is 1uF.

6. The power supply circuit for the electric motor of engineering machinery according to claim 1, characterized in that, A filter capacitor is installed between the two output lines of the rectifier module.

7. An engineering machinery, characterized in that, It includes an electric motor, a processor, a memory, an actuator, and a power supply circuit for an engineering machinery electric motor as provided in any one of claims 1-6.

Images