CN106379819B - A motor speed control system - Google Patents

Abstract

The invention discloses a motor speed regulating system, which is suitable for hoisting machines of jib cranes. The motor speed regulating system includes a power supply, a frequency converter and a motor connected in sequence. The frequency converter first converts the power frequency AC power supply into a DC power supply, and then The DC power is converted into AC power with controllable frequency and voltage through the inverter to supply the motor so that the speed of the motor can be changed by changing the frequency. The frequency converter includes a rectifier circuit, a power factor correction circuit, a filter circuit, and an inverter circuit. And microprocessor circuit, man-machine interface circuit, rectifier circuit is used to convert alternating current to direct current, power factor correction circuit is used to improve power factor, filter circuit is used to complete filtering smoothing and energy storage of direct current, inverter circuit is used for direct current For conversion to three-phase alternating current, the microprocessor circuit is used to control the work of the power factor correction circuit and the inverter circuit according to the commands sent by the man-machine interface circuit. The invention can improve the product performance of the jib crane.

Description

A motor speed control system

The present invention is a divisional application of the Chinese invention patent application with the patent application number "201510256850.2" and the title "arm crane" filed by the applicant on May 20, 2015, and its entire content is incorporated in this application.

technical field

The invention relates to hoisting machinery, in particular to a jib crane and its subsystems or components.

Background technique

The jib crane includes a lifting mechanism, a luffing mechanism, a rotating mechanism, etc., relying on the cooperative actions of these mechanisms, heavy objects can be lifted and transported in a certain cylindrical space. The lifting mechanism of the jib crane includes a hoist, which lifts the workpiece by retracting and unwinding the steel rope wound on the drum. There are certain deficiencies in the design of the existing boom-type hoist: for example, the structure of the reel body and the reel shaft is relatively complicated, and the installation is not convenient; If it fails, it may cause a safety accident; for example, the winding method of the steel rope is not reasonable enough, and sometimes the steel rope is loosened or entangled, which increases the safety hazard; in addition, the speed of the winch cannot be adjusted conveniently; etc. . In view of the above-mentioned deficiencies in many aspects, it is necessary to improve the crane and its hoist.

Contents of the invention

In view of the defects in the prior art, the purpose of the embodiments of the present invention is to improve the whole machine, subsystems or components of the jib crane so as to improve the performance of the product.

In order to solve the above technical problems, the embodiment of the present invention provides a motor speed control system, which is suitable for the hoist of the jib crane, wherein the hoist is provided with a driving device, a winding device, a braking device and a control device: the driving device is provided with a motor, Coupling and reducer, the reducer is installed on the upper part of the frame, the high-speed shaft of the reducer is connected with the power output shaft of the motor through the coupling; the reel support structure of the winding device is installed on the upper part of the frame, one end of the reel Rotationally connected to the reel support structure, the other end of the reel is connected to the low-speed shaft of the reducer through the reel connection structure, the upper pulley block of the winding device is positioned on the frame, and the steel rope is wound on the drum, upper pulley block and lower pulley block , wherein the steel rope is wound counterclockwise from the first rope guide position of the reel, and then goes around the first lower pulley, the first upper pulley, the second lower pulley, and the second upper pulley counterclockwise, and then goes around the first pulley clockwise in turn. After the third lower pulley, the third upper pulley, and the fourth lower pulley, wind back clockwise to the second guide rope position of the reel, and the first end of the steel rope is wound around the first end of the reel and fixed to the first pressure rope position, the second end of the steel rope is wound around the second end of the reel and fixed at the second rope pressing position of the reel; the brake of the braking device is installed on the high-speed shaft of the reducer, and the deceleration is achieved by holding the brake wheel tightly The reel brake on the low-speed shaft of the machine; the control device sets the motor speed regulating system to regulate the speed of the motor, and the motor control circuit connects the contactor in series between the motor protection circuit breaker and the frequency converter, and the upper and lower limit switches are connected in series to the contactor The control circuit of the device, and the upper and lower limit switches are connected in parallel with the limit unlock knob; the motor speed control system includes a power supply, a frequency converter and a motor connected in sequence. The frequency converter first converts the power frequency AC power supply into a DC power supply, and then The DC power is converted into AC power with controllable frequency and voltage by the inverter to supply the motor, so that the speed of the motor can be changed by changing the frequency. The frequency converter includes a rectifier circuit, a power factor correction circuit, a filter circuit, an inverter circuit and Microprocessor circuit, man-machine interface circuit, rectifier circuit is used to convert alternating current to direct current, power factor correction circuit is used to improve power factor, filter circuit is used to complete filtering and smoothing of direct current and energy storage, and inverter circuit is used for direct current For the conversion of three-phase alternating current, the microprocessor circuit is used to control the work of the power factor correction circuit and the inverter circuit according to the commands sent by the man-machine interface circuit.

Compared with the prior art, the embodiment of the present invention improves the jib crane, thereby improving product performance, which is manifested in the following aspects: optimizing the hoist drum body, drum shaft and its drum support, and coupling structure, The layout of the reel is more reasonable, the structure is more compact, and the installation is more convenient; the structure of the reel body, the winding method of the steel rope and the structure of the rope are improved, which can better avoid the problem of loosening or entanglement of the steel rope, which is beneficial to Eliminate safety hazards; improve the brake, lifting limiter and motor stop control mechanism, and stop and brake in time according to the predetermined intention in the case of limit, emergency stop, etc., thereby effectively reducing safety accidents; Speed, the lifting speed can be fully controlled.

Description of drawings

Fig. 1 is the schematic diagram of jib crane of the present invention;

Fig. 2 is the front view of hoisting machine of the present invention;

Fig. 3 is the top view of winch of the present invention;

Fig. 4 is the right side view of hoisting machine of the present invention;

Fig. 5 is the schematic diagram of brake of the present invention;

Fig. 6 is a schematic diagram of the steel rope winding structure of the present invention;

Fig. 7 is a schematic diagram of the reel and the reel connection structure, the rope pressing structure and the reel support structure of the present invention;

Fig. 8 is the front view of the roll body of the present invention;

Fig. 9 is a longitudinal sectional view of the roll body of the present invention;

Fig. 10 is the schematic diagram of the reel shaft of the present invention;

Fig. 11 is a schematic diagram of the reel connection structure of the present invention;

Fig. 12 is a structural schematic diagram of the pressure rope of the present invention;

Fig. 13 is a schematic diagram of the support structure of the reel of the present invention;

Fig. 14 is a schematic diagram of the lift limiter of the present invention;

Fig. 15 is a schematic diagram of the internal structure of the lift limiter of the present invention;

Fig. 16 is the electrical schematic diagram of the motor shutdown control mechanism of the present invention;

17 is an electrical connection diagram of the limit switch of the motor shutdown control mechanism of the present invention;

Fig. 18 is the block diagram of motor speed control system of the present invention;

Fig. 19 is a circuit principle block diagram of the frequency converter of the present invention;

Fig. 20 is a schematic circuit diagram of the inverter of the present invention.

Detailed ways

In order to better understand the technical principle and working process of the embodiments of the present invention, the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

Figures 1 to 20 mark the structure of the winch, subsystems or components of the present invention, where the same symbols represent the same components.

Referring to Fig. 1, the structure of the jib crane of the present invention is shown. The jib crane includes chassis S1, turntable S2, hoist S3, lifting cylinder S4, arm frame S5, hook S6 and other components. Turntable S2 is installed on chassis S1, hoist S3 is installed on turntable, and the head end of boom S5 is The turntable S2 and the hook S6 are hung on the tail end of the jib S5, one end of the lift cylinder S4 is hinged to the turntable S2, and the other end of the lift cylinder S4 is hinged to the jib S5. The turntable S2 rotates to make the boom S5 rotate, the oil cylinder S4 expands and contracts to make the boom S5 take off and land, the variable speed cylinder (not shown in the figure) makes the boom S5 change its amplitude, and the hoist S3 is retracted and wound on the drum, the boom pulley block and the hook pulley block The steel rope to lift the workpiece on the hook S6. The present invention has made many improvements to the winch S3 and its subsystems and components, which will be further described below.

Referring to Fig. 2-Fig. 4 at the same time, the overall structure of the hoisting machine of the present invention is shown. The winch includes a driving device, a winding device, a braking device and a control device (not shown in the figure): the driving device is composed of a motor M01 (preferably a variable frequency motor), a shaft coupling 7, a speed reducer 1 and other components, and the motor M01, Coupling 7 and reducer 1 are connected sequentially; the winding device is composed of reel 2, upper pulley block 3, lower pulley block and steel rope and other components. The rope is wound on the drum 2, the upper pulley block 3 and the lower pulley block for retraction; the braking device is composed of a brake 5 and accessories, etc., and the brake 5 acts on the high-speed shaft or low-speed shaft of the reducer 1 for braking; the control device is set There is a motor stop control mechanism, and the motor stop control mechanism stops the motor when the preset upper limit or lower limit.

As shown in Figures 2-4, the specific structure of the winch is: the reducer 1 and the reel support structure 4 are installed on the upper part of the frame S01, one end of the reel 2 is rotatably connected to the reel support structure 4, and the reel 2 The other end is connected to the low-speed shaft of the reducer 1 through the reel connection structure 8, and the high-speed shaft of the reducer 1 is connected to the power output shaft of the motor M01 through the coupling (the coupling shell is provided outside) 7; the upper pulley block 3 Positioned on the frame S01, the steel rope is wound on the reel 2, the upper pulley block 3 and the lower pulley block in a certain pattern, and retracted and retracted when the motor M01 rotates forward or reversely; the brake 5 is installed on the reducer 1, During braking, the brake wheel 6 on the high-speed shaft of the reducer 1 can be tightly held and braked.

In this hoist, the drum body, drum shaft and its drum support and connection structure are optimized, the layout of the drum is more reasonable, the structure is more compact, and the installation is more convenient; the structure of the drum body and the winding method of the steel rope are improved And the rope pressing mechanism can better avoid the problem of loosening or entanglement of steel ropes, which is beneficial to eliminate potential safety hazards; the brake, lifting limiter and motor stop control mechanism have been improved, so that in the case of limit, emergency stop, etc. It can stop and brake in time according to the predetermined intention, thereby effectively reducing safety accidents. This is described further below.

Figures 2 to 4 show the installation structure of the brake. The brake 5 is installed on the high-speed shaft of the reducer 1. By holding the brake wheel 6, the reducer 1 is braked, and thus the low-speed shaft of the reducer 1 is braked. The reel 2 brake. The structure of the brake will be further described in detail below.

Referring to Fig. 5, the structure of the brake of the present invention is shown. In the brake 5, one end of the first brake arm 52, the second brake arm 53, the active telescopic rod (which can be an air cylinder or an oil cylinder) 59 with the driving device 50, and the driven telescopic rod 58 are respectively hinged on the brake seat 51. The other end of the first braking arm 52, the active telescopic link 59, and the driven telescopic link 58 are respectively hinged on an arm of the L-shaped connecting rod 57; the other end of the second braking arm 53 is hinged with the linear connecting rod 55, and the linear The other end of the connecting rod 55 is hinged with the other arm of the L-shaped connecting rod 57; the first brake block 56 is mounted on the inside of the first brake arm 52, and the second brake block 54 is mounted on the inside of the second brake arm 53. Inside, the inner arc surface of the first brake block 56 and the inner arc surface of the second brake block 54 hold the brake wheel 6 on the high speed shaft of the reducer 1 tightly during braking. This braking method has simple structure, fast braking response and good effect.

Referring to Fig. 6, it shows the steel rope winding structure of the present invention. In this steel rope winding structure, the steel rope 10 is wound on the reel 2, the upper pulley (arm frame pulley) group 3 and the lower pulley (hook pulley) group 9 in the following manner: the first end of the steel rope 10 is wound on the reel The first end of the drum 2 is fixed at the first rope pressing position 2a, the second end of the steel rope 10 is wound around the second end of the drum 2 and fixed at the second rope pressing position 2d of the drum 2, and the steel rope 10 is self-winding The first rope guide position 2b of cylinder 2 is wound out in the counterclockwise direction, bypassing the first lower pulley 91, the first upper pulley 31, the second lower pulley 92, and the second upper pulley 32 counterclockwise in turn, and then bypassing the first lower pulley 91 in turn clockwise. After the three lower pulleys 93, the third upper pulley 33, and the fourth lower pulley 94, turn back clockwise to the second guide rope position 2c of the drum 2. The steel rope 10 adopts this winding method, which can reduce the occurrence probability of undesirable phenomena such as winding and loosening of the steel rope.

Referring to Fig. 7, it shows the reel and the reel connection structure, the rope pressing structure and the reel support structure of the present invention. The reel 2 includes a reel body 21 and a reel shaft 22, the first end of the reel shaft 22 is fixedly supported on the second end of the reel body 21, and the first end of the reel body 21 is connected by a reel connection structure (Fig. Part I in 7) is connected with the low-speed shaft of the reducer 1, and the second end of the reel shaft 22 is supported on the reel support structure (Part III among Fig. 7), which is very convenient to install. In addition, the upper parts of both ends of the reel body 21 are respectively provided with pressure rope structures (II part in FIG. 7 ), which can better fix the ends of the steel rope 10 .

Referring to Figs. 8-9 at the same time, the structure of the reel of the present invention is shown. The reel body 21 is provided with a first end plate 25, a second end plate 24 and a support plate 23. The first end plate 25 of the reel body 21 is connected to the low-speed shaft of the reducer 1 through a reel connection structure. The reel body 21 The second end plate 24 and the support plate 23 fixedly support the reel shaft 22, and the reel shaft 22 is installed on the reel support structure, which is very convenient to install.

As shown in FIGS. 2-9 , a steel rope guide groove 211 is provided on the reel body 21 to facilitate the introduction/extraction of the steel rope 10 along the steel rope guide groove 211 , thereby facilitating the orderly winding of the steel rope 10 .

Referring to Fig. 10, the structure of the spool shaft of the present invention is shown. The reel shaft 22 includes a reel shaft main body 222, the first end of the reel shaft main body 222 is provided with a first shaft shoulder 221, and the second end of the reel shaft main body 222 is provided with a second shaft shoulder 224 and a third shaft shoulder 225, Wherein, the outer diameters of the reel shaft main body 222 , the first shaft shoulder 221 , the second shaft shoulder 224 and the third shaft shoulder 225 are successively reduced, and a tapered transition is provided between the reel shaft main body 222 and the second shaft shoulder 224 Part 223, this spool shaft 22 has better structural strength and is also convenient for installation.

Referring to Fig. 11, it shows the reel connection structure of the present invention. In this reel connection structure, the connecting half shaft 84 is supported on the connecting plate 82 by the cylindrical roller bearing 87, and the inner end of the connecting half shaft 84 is provided with a baffle plate 86, and the connecting half shaft 84, the cylindrical roller bearing 87 and the connecting plate 82 is blocked with an inner cover plate 85, and the outer joint portion connecting the half shaft 84, cylindrical roller bearing 87 and connecting disc 82 is sealed with an outer cover plate 83, and the connecting disc 82 is fixed to the flange 81. The blue plate 81 is fastened to the first end plate 25 on the drum body 21 . This structure is reliable in connection and convenient in installation.

Referring to Fig. 12, it shows the rope pressing structure of the present invention. The rope pressing structure 11 includes a steel rope pressing plate 111, and a steel rope pressing groove 1121 is provided on the lower surface of the steel rope pressing plate. It is fixed on the reel body 21 without falling out, thereby increasing the safety factor.

Referring to Fig. 13, it shows the reel supporting structure of the present invention. In the reel support structure 4 , the support base 41 is provided with a machine base bearing seat 43 , the reel bearing seat 44 is supported on the machine base bearing seat 43 , and the reel shaft 22 is supported on the reel bearing seat through a tapered roller bearing 45 44. The inner joint of machine base bearing seat 43, reel bearing seat 44 and tapered roller bearing 45 is sealed with inner cover plate 42, machine base bearing seat 43, reel bearing seat 44 and tapered roller bearing 45 The outer joint part is blocked with an outer cover plate 47. This structure is compact and easy to install.

As shown in Figure 13, this embodiment shows the installation structure of the lift limiter. In Fig. 12, the reel shaft connecting plate 46 is arranged on the reel shaft 22, in order to install the driving end of the lift limiter 12 (such as the rocking bar of the screw type lift limiter 12), when the reel 2 rotation angle exceeds a predetermined When the value (number of revolutions) is reached, the electrical connection can be disconnected to prevent further rotation of the drum, which can limit the lifting height. Further details will be described below in conjunction with FIGS. 12-14 .

Referring to Fig. 14-Fig. 15, the structure of the lift limiter of the present invention is shown. Referring to Fig. 12 at the same time, the lift limiter 12 includes a U-shaped bracket 121, a rocker 122, a screw 123, a runner 124, a limiter housing 125, a guide rod 126, a push plate 127, a movable conductive column 128, a limiter Switch 129 and fixed conductive column 120: U-shaped bracket 121 is fixed on the outer cover plate 47 connected with the reel shaft 22, the limiter housing 125 is fastened to the U-shaped bracket 121 by screws, and the screw rod 123 is supported on the limiter shell On the body 125, the push plate 127 is installed on the screw rod 123, one end of the movable conductive column 128 is connected to the push plate 127, and the other end of the movable conductive column 128 is supported on an arm of the limit switch 129 fixedly connected with the limiter housing 125 , the fixed conductive column 120 is fixed on the other arm of the limit switch 129, the runner 124 is installed on the end of the screw rod 123, one end of the rocker 122 is connected to the runner 124 eccentrically, and the other end of the rocker 122 is connected to the reel shaft The connecting plate 46 is connected.

In addition, a guide rod 126 is installed on the limiter housing 125 , the guide rod 126 is arranged parallel to the screw rod 123 , and the push plate 127 slides through the guide rod 126 to ensure smooth movement.

In this embodiment, the position of the push plate 127 can be adjusted in advance. When the reel 2 rolls, the rocker 122 rotates with the reel shaft connecting plate 46, and the screw rod 123 rotates through the runner 124, and the translation of the push plate 127 drives the movable conductive column 128 to break away from the fixed conductive column 120, thereby disconnecting the electrical connection And play a position-limiting role, thereby improving safety performance.

Figures 14-15 illustrate the structure of the lift limiter 12, which can be used for both upper limit and lower limit. The limit switch of the lifting limiter is connected to the control circuit of the motor M01 of the winch, and the motor M01 is stopped by triggering the motor protection circuit breaker in the motor control circuit, thus playing a role of safety protection.

The present invention aims at preventing the upper and lower limit from occurring, and at the same time improves the electrical control system, which is specifically described as follows.

Referring to Fig. 16-Fig. 17 at the same time, it shows the circuit structure of the motor shutdown control mechanism of the present invention. The motor shutdown control mechanism can be used for winches and other types of lifting devices. Its electrical structure is: in the control circuit of the motor M01, a contactor KM01 is added between the motor protection circuit breaker QF01 and the frequency converter VF01; The limit switches SQ01 and SQ02 are connected in series to the control loop of the contactor KM01. Here, terminals 1-6 of motor protection circuit breaker QF01, A1 and A2 (three groups of terminals 1 and 2) of contactor KM01, terminals R, S, T, V, W and PE of inverter VF01, limit switch The terminals 11 and 12 of SQ01 and SQ02, and the terminals 13 and 14 of the limit unlocking key knob SB01 are connected according to Fig. 15 and Fig. 16, and will not be further described in detail.

When the limit switch SQ01 or SQ02 is triggered, the coil power of the contactor KM01 is directly cut off, and the contactor KM01 is released, thereby cutting off the power supply of the VF01 circuit of the inverter, thereby quickly stopping the operation of the motor M01; after that, unlock by rotating the limit The key knob SB01 can be unlocked. This control method reduces the intermediate links for processing limit signals, so that when a fault occurs, the motor can be stopped immediately, avoiding equipment damage and personnel casualties.

In order to change the speed of the winch S3 conveniently, the present invention adopts motor frequency conversion speed regulation control. It will be explained below.

Referring to Fig. 18, it shows a block diagram of the motor speed regulating system of the present invention. The motor speed control system includes power supply M03, frequency converter M02 and motor M01 connected in sequence. The frequency converter M02 adopts the AC-DC-AC mode. The DC power is converted into AC power with controllable frequency and voltage by the inverter to supply the motor M01, so that the speed of the motor M01 can be changed by changing the frequency.

As shown in Figure 18, the input stage of the inverter M02 is provided with a filter decoupling circuit, which is preferably an RC filter decoupling circuit, which is composed of a current-limiting resistor R and a filter capacitor C connected in series, thus making the power supply M03 The positive output terminal and the output ground terminal are connected to the current limiting resistor R and the filter capacitor C connected in series. The filter decoupling circuit is used as a pre-analog low-pass filter of the AC signal input channel, and has the function of anti-interference; the decoupling capacitor is connected between the two terminals of the AC and DC signal input channel, which can provide bypass for high-frequency differential mode interference signals. road.

Referring to Fig. 19, it shows a block diagram of the circuit principle of the frequency converter of the present invention. The frequency converter M02 of this embodiment includes a rectification circuit M021, a power factor correction circuit M022, a filter circuit M023, an inverter circuit M024, a microprocessor circuit M025, a human-machine interface circuit M026, etc., wherein: the rectification circuit M021 is composed of a rectification diode or The bridge stack (preferably a full-bridge rectifier circuit), including the necessary interference filtering circuit, its main function is to convert alternating current into direct current; the power factor correction circuit M022 is an optional component, composed of power semiconductors and control chips, it also Connected to the power factor correction terminal of the microprocessor circuit M025, the function is to make the input current close to a sine wave, reduce the harmonic content of the grid, and achieve the purpose of improving the power factor; the filter circuit M023 (preferably an RC filter circuit) is mainly composed of electrolytic capacitors, etc. It is composed of components to complete the filtering and smoothing of direct current and energy storage; the inverter circuit M024 is composed of a power module and a drive circuit, and its power module can be an intelligent power drive tube chip, which is also connected to the drive signal terminal of the microprocessor circuit , its main function is to complete the conversion of direct current to three-phase alternating current, and realize the purpose of frequency modulation and voltage regulation; the microprocessor circuit M025 is composed of a microprocessor (DSP) and peripheral circuits, and according to the commands sent by the man-machine interface circuit M026, Send corresponding command signals to control the power factor correction circuit M022 and inverter circuit M024 to work, and perform necessary circuit protection and fault handling according to circuit feedback information. In this way, this embodiment controls the output mode of the frequency converter M02 through the microprocessor circuit, which is beneficial to flexibly output voltage according to predetermined requirements, thereby meeting the needs of different users.

Referring to FIG. 20 , it shows the schematic circuit diagram of the inverter of the present invention. Specifically, it is an example of the inverter circuit M024 and the microprocessor circuit used for the motor M01. Its working method is: the mains power is converted into direct current through the rectification circuit M021, filtered by the electrolytic capacitor, and then connected to the power input terminal of the inverter circuit M024 , the filter capacitor is connected between the input terminals of the power supply. The microprocessor of the microprocessor circuit controls the motor M01 according to the setting signal of the man-machine interface circuit.

In this embodiment, the inverter circuit M024 includes a power tube driver chip, which is connected to the microprocessor (MCU/DSP) of the microprocessor circuit, so as to drive the corresponding The power tubes are turned on and off alternately. Specifically, the inverter circuit M024 includes six power transistors Q1-Q6, which are divided into three groups, and each group of power transistors controls one phase winding of the three-phase motor M01.

The specific connection method of each power tube is: the sources of power tubes Q1, Q2, and Q3 are connected to one end of the DC power supply, the drains of power tubes Q4, Q5, and Q6 are connected to the other end of the DC power supply, and the drain of power tube Q1 is connected to the other end of the DC power supply. Connect the connection point with the source of the power transistor Q4 to the U-phase terminal of the motor, connect the connection point between the drain of the power transistor Q2 and the source of the power transistor Q5 to the V-phase terminal of the motor, and connect the drain of the power transistor Q3 to the power transistor Q6 The source connection point of the power tube is connected to the W-phase terminal of the motor; the gates of the power transistors Q1, Q2, Q3, Q4, Q5, and Q6 are respectively connected to an output end of the power tube driver chip, and each input end of the power tube driver chip is respectively controlled by One of the output pulse width adjustment signals PWM1, PWM2, PWM3, PWM4, PWM5 and PWM6 of the microprocessor circuit is controlled. The sources and drains of the six power transistors Q1 - Q6 are correspondingly connected with diodes D1 - D6 .

When starting up, the microprocessor generates corresponding 6-channel pulse width modulation signals according to the set motor speed, that is, the driving signals PWM1~PWM6; the six power tubes (MOSFET or IGBT) Q1 of the inverter M024 are driven by the power tube drive chip ~Q6; These power tubes are alternately turned on and off to generate three-phase modulation waveforms, and output three-phase alternating current with adjustable voltage and variable frequency, which is output to the U, V, and W terminals of the motor M01, thereby realizing the motor M01 Stepless frequency conversion speed regulation.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention.

Claims (3)

1. A motor speed control system, which is suitable for the winch of the jib crane, wherein the winch is provided with a driving device, a winding device, a braking device and a control device: the driving device is provided with a motor, a coupling and a reducer, and the reducer Installed on the upper part of the frame, the high-speed shaft of the reducer is connected to the power output shaft of the motor through a coupling; the reel support structure of the winding device is installed on the upper part of the frame, and one end of the reel is rotatably connected to the reel support structure. The other end of the drum is connected to the low-speed shaft of the reducer through the drum connection structure. The upper pulley block of the winding device is positioned on the frame, and the steel rope is wound on the drum, the upper pulley block and the lower pulley block. The position of the guide rope is wound out counterclockwise, and the first lower pulley, the first upper pulley, the second lower pulley, and the second upper pulley are passed counterclockwise in turn, and then the third lower pulley, the third upper pulley, and the third upper pulley are passed clockwise in turn. After the fourth lower pulley, wind back clockwise to the second guide rope position of the reel, and the first end of the steel rope is wound around the first end of the reel and fixed at the first pressure rope position, and the second end of the steel rope is wound At the second end of the reel and fixed at the second rope pressing position of the reel; the brake of the braking device is installed on the high-speed shaft of the reducer, and the reel on the low-speed shaft of the reducer is braked by holding the brake wheel ;The control device is equipped with a motor speed regulation system to regulate the motor speed, and the motor control circuit is connected in series with the contactor between the motor protection circuit breaker and the frequency converter, and the upper and lower limit switches are connected in series with the control circuit of the contactor, and the upper and lower limit switches The position switch is connected in parallel with the limited position unlocking knob; it is characterized in that the motor speed control system includes a power supply, a frequency converter and a motor connected in sequence, and the frequency converter first converts the power frequency AC power supply into a DC power The frequency converter can be converted into AC power with controllable frequency and voltage to supply the motor so that the speed of the motor can be changed by changing the frequency. The frequency converter includes a rectifier circuit, a power factor correction circuit, a filter circuit, an inverter circuit and a microprocessor circuit. Man-machine interface circuit, rectifier circuit is used to convert AC to DC, power factor correction circuit is used to improve power factor, filter circuit is used to complete filtering and smoothing of DC and energy storage, and inverter circuit is used to convert DC to three-phase AC The microprocessor circuit is used to control the work of the power factor correction circuit and the inverter circuit according to the commands sent by the man-machine interface circuit. 2. The motor speed control system according to claim 1, wherein the rectifier circuit is a full-bridge rectifier circuit. 3. The motor speed control system according to claim 1 or 2, characterized in that the filter circuit is an RC filter circuit.