CN219322293U - Forward and reverse switching system - Google Patents

Abstract

The utility model discloses a forward and reverse switching system, wherein a stop switch K3 is respectively connected with a coil KM1-A of a forward relay KM1 and a coil KM2-A of a reverse relay KM2, the coil KM1-A of the forward relay KM1 is connected with an instantaneous normally-closed contact KM2-B of the reverse relay KM2, the instantaneous normally-closed contact KM2-B of the reverse relay KM2 is connected with a start switch K1, the coil KM2-A of the reverse relay KM2 is connected with an instantaneous normally-closed contact KM1-B of the forward relay KM1, and the instantaneous normally-closed contact KM1-B is connected with a reverse switch K2; the main contacts KM1-C of the forward relay KM1 are connected with the power line in the forward direction, and the main contacts KM2-C of the reverse relay KM2 are connected with the power line in the reverse direction.

Description

Forward and reverse switching system

Technical Field

The utility model relates to a forward and reverse switching system, and belongs to the technical field of motor control.

Background

In the field of wide application of automation equipment, it is required to drive by a single-phase ac motor. The single-phase alternating current motor needs to have forward and reverse functions, and can enable the belt conveyor to advance and retreat, the unloading trolley to advance and retreat, and the lifting platform to ascend and descend, so that a current commonly used alternating current motor control circuit controls the starting and stopping of the motor by using a relay K1, the running direction of the motor is switched by using relays K2 and K3, and the linkage normally-open contacts of three intermediate relays KA1, KA2 and KA3 are respectively 2 groups. Wherein 2 groups of linkage normally open contacts of the relay K1 are used for closing or opening the connection with the live wire L and the zero wire N of the single-phase alternating current. The 2 groups of linkage normally open contacts of the intermediate relay KA2 are used for closing or opening the connection with the 2 groups of normally open contacts of KA 1. The 2 groups of linkage normally open contacts of the intermediate relay KA3 are also used for closing or opening the connection with the 2 groups of normally open contacts of KA1, but 3 relays are needed in the circuit, and more relays can increase the cost of the circuit.

Disclosure of Invention

Aiming at the technical problems, the utility model provides a forward and reverse switching system with lower production cost.

The forward and reverse switching system comprises a forward relay KM1, a reverse relay KM2, a start switch K1, a reverse switch K2, a stop switch K3 and a motor M;

the first end of the stop switch K3 is connected with a first power line, the second end of the stop switch K3 is respectively connected with the first end of a coil KM1-A of a forward relay KM1 and the first end of a coil KM2-A of a reverse relay KM2, the second end of the coil KM1-A of the forward relay KM1 is connected with the first end of a transient normally-closed contact KM2-B of the reverse relay KM2, the second end of the transient normally-closed contact KM2-B of the reverse relay KM2 is connected with the first end of a start switch K1, the second end of the start switch K1 is connected with a second power line, the second end of the coil KM2-A of the reverse relay KM2 is connected with the first end of a transient normally-closed contact KM1-B of the forward relay KM1, the second end of the transient normally-closed contact KM1-B is connected with the first end of the reverse switch K2, and the second end of the reverse switch K2 is connected with a second power line;

the first end of the main contact KM1-C of the forward relay KM1 is connected with a first power line in a positive phase, the first end of the main contact KM2-C of the reverse relay KM2 is connected with the first power line in an opposite phase, the motor M is respectively connected with the second end of the main contact KM1-C of the forward relay KM1 and the second end of the main contact KM2-C of the reverse relay KM2, and the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 are instantaneous normally open contacts.

The technical scheme is further improved as follows: the upper port wiring sequence of the main contact KM1-C of the forward relay KM1 and the upper port wiring sequence of the main contact KM2-C of the reverse relay KM2 are the U phase, the V phase and the W phase of the first power line, the lower port wiring sequence of the main contact KM1-C of the forward relay KM1 is the U phase, the V phase and the W phase of the first power line, and the lower port wiring sequence of the main contact KM2-C of the reverse relay KM2 is the W phase, the V phase and the U phase of the first power line.

Further, the electric bell also comprises an electric bell D, a relay KA and an electric bell switch K4; the first end of a coil KA-A of a relay KA is connected with a first power line, the second end of the coil KA-A of the relay KA is connected with the first end of an instantaneous normally-closed contact KM1-E of a forward relay KM1, the second end of the instantaneous normally-closed contact KM1-E of the forward relay KM1 is connected with the first end of an instantaneous normally-closed contact KM2-E of a reverse relay KM2, the second end of the instantaneous normally-closed contact KM2-E of the reverse relay KM2 is connected with the first end of an electric bell switch K4, the second end of the electric bell switch K4 is connected with a second power line, the first end of an electric bell D is connected with the first power line, and the second end of the electric bell is connected with the first end of an instantaneous normally-open contact KA-B of the relay KA; the second end of the instantaneous normally open contact KA-B of the relay KA is connected with a second power line.

Further, the electric bell switch further comprises a start button SF1, a start button SF2, a start button SF3, a stop switch SS1 and a stop switch SS2, wherein the start button SF1 is connected with the start switch K1 in parallel, the start button SF2 is connected with the reverse switch K2 in parallel, the start button SF3 is connected with the electric bell switch K4 in parallel, the stop switch SS1 is connected between the start switch K1 and the second power line, and the stop switch SS2 is connected between the instantaneous normally open contact KM2-E of the reverse relay KM2 and the second power line.

Further, the instantaneous normally open contact KM1-D of the forward relay KM1 is connected in parallel with the starting switch K1, the instantaneous normally open contact KM2-D of the reverse relay KM2 is connected in parallel with the reverse switch K2, and the starting button SF3 is connected in parallel with the instantaneous normally open contact KA-C of the relay KA.

Further, an instantaneous normally-open contact KA-D of a relay KA is connected between the start button SF1 and an instantaneous normally-closed contact KM2-B of the reverse relay KM2, and an instantaneous normally-open contact KA-E of the relay KA is connected between the start button SF2 and an instantaneous normally-open contact KM1-B of the forward relay KM 1; the instantaneous normally open contact KA-D of the relay KA is connected in series with the start button SF1 and then connected in parallel with the start switch K1, and the instantaneous normally open contact KA-E of the relay KA is connected in series with the start button SF2 and then connected in parallel with the reverse switch K2.

Further, the intelligent power supply device further comprises an indicator lamp HR1 and an indicator lamp HR2, wherein the first end of the indicator lamp HR1 is connected with a first power line, the second end of the indicator lamp HR1 is connected with the first end of an instantaneous normally open contact KM1-F of a forward relay KM1, the second end of the instantaneous normally open contact KM1-F of the forward relay KM1 is connected with a second power line, the first end of the indicator lamp HR2 is connected with the first end of an instantaneous normally open contact KM2-F of a reverse relay KM2, and the second end of the instantaneous normally open contact KM2-F of the reverse relay KM2 is connected with a second power line.

Further, a fuse FU1 is connected between the stop switch SS1, the stop switch SS2, and the second power supply line.

Further, a fuse FU2 is connected between the instantaneous normally open contact KA-B of the relay KA, the instantaneous normally open contact KM1-F of the forward relay KM1, the instantaneous normally open contact KM2-F of the reverse relay KM2 and the second power line.

Further, the main contacts KM1-C of the forward relay KM1 are interlocked with the main contacts KM2-C of the reverse relay KM 2.

According to the technical scheme, when the motor M is required to rotate forwards, the coil KM1-A of the forward relay KM1 can be electrified by closing the start switch K1, so that the main contact KM1-C of the forward relay KM1 is electrified, the motor M is connected with a power supply in a forward direction, forward rotation is realized, meanwhile, the instantaneous normally-closed contact KM1-B of the forward relay KM1 is disconnected, the coil KM2-A of the reverse relay KM2 is prevented from being electrified, the motor M is reversed, when the motor M is required to rotate reversely, the start switch K1 is closed, the coil KM1-A of the forward relay KM1 is closed, the reverse switch K2 is started again, the coil KM2-A of the reverse relay KM2 is electrified, so that the main contact KM2-C of the reverse relay KM2 is electrified, meanwhile, the instantaneous normally-closed contact KM2-B of the reverse relay KM2 is disconnected, the forward relay KM1-A is prevented from being electrified, and the forward relay M1-A is stopped when the motor M is required to rotate reversely, and the forward relay M1-A is stopped, and the forward relay M is required to stop the forward relay M1-A is stopped, and the forward relay M1 is required to rotate, and the forward relay M1 is stopped, and the forward relay M is required to stop the forward relay 1 is stopped, and the forward relay M is required to rotate, and the forward relay 1 is stopped, and the forward relay and the relay can be stopped.

Meanwhile, the forward and reverse switching system provided by the utility model starts the electric bell switch K4, the coil KA-A of the relay KA is electrified, the instantaneous normally open contact KA-B of the relay KA is closed, the electric bell D is electrified, sound information is output to the outside, when the equipment moves forward or moves reversely, the motor M rotates forward or reversely, the instantaneous normally closed contact KM1-E of the forward relay KM1 or the instantaneous normally closed contact KM2-E of the reverse relay KM2 is disconnected, the coil KA-A of the relay KA is deenergized, the instantaneous normally open contact KA-B of the relay KA is disconnected, the electric bell D is deenergized, and the outside sound information is stopped, so that when the equipment is about to start to operate, the alarm is given to the staff, the staff is far away from the equipment, or the equipment is stopped to give an alarm to the staff, and the staff is prompted to approach the equipment to work of the next working procedure.

Drawings

For a clearer description of embodiments of the utility model or of solutions in the prior art, the drawings which are used in the description of the embodiments or of the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.

Fig. 1 is a control schematic diagram of a forward and reverse switching system provided by the utility model.

Fig. 2 is a schematic diagram of a portion of a forward/reverse switching system according to the present utility model.

Fig. 3 is a schematic diagram of a signal generator of the forward and reverse switching system provided by the utility model.

Fig. 4 is a schematic diagram of PLC control of a signal generator of the forward and reverse switching system according to the present utility model.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to fall within the scope of the utility model.

Referring to fig. 1 and 2, a forward and reverse switching system includes a forward relay KM1, a reverse relay KM2, a start switch K1, a reverse switch K2, a stop switch K3, and a motor M;

the first end of the stop switch K3 is connected with a first power line, the second end of the stop switch K3 is respectively connected with the first end of a coil KM1-A of a forward relay KM1 and the first end of a coil KM2-A of a reverse relay KM2, the second end of the coil KM1-A of the forward relay KM1 is connected with the first end of a transient normally-closed contact KM2-B of the reverse relay KM2, the second end of the transient normally-closed contact KM2-B of the reverse relay KM2 is connected with the first end of a start switch K1, the second end of the start switch K1 is connected with a second power line, the second end of the coil KM2-A of the reverse relay KM2 is connected with the first end of a transient normally-closed contact KM1-B of the forward relay KM1, the second end of the transient normally-closed contact KM1-B is connected with the first end of the reverse switch K2, and the second end of the reverse switch K2 is connected with a second power line;

the first end of the main contact KM1-C of the forward relay KM1 is connected with a first power line in a positive phase, the first end of the main contact KM2-C of the reverse relay KM2 is connected with the first power line in an opposite phase, and the motor M is respectively connected with the second end of the main contact KM1-C of the forward relay KM1 and the second end of the main contact KM2-C of the reverse relay KM 2.

The starting switch K1 and the reversing switch K2 are normally open switches, the stopping switch K3 is normally closed switches, when the motor M is required to rotate forwards, the coil KM1-A of the forward relay KM1 can be electrified by closing the starting switch K1, and then the main contact KM1-C of the forward relay KM1 is electrified, the motor M is connected with a power supply forwards to realize forward rotation, meanwhile, the instantaneous normally closed contact KM1-B of the forward relay KM1 is disconnected, the coil KM2-A of the reversing relay KM2 is prevented from being electrified, the motor M is reversely rotated, when the motor M is required to rotate reversely, the starting switch K1 is closed, the coil KM1-A of the forward relay KM1 is electrified, the instantaneous normally closed contact KM1-B of the forward relay KM1 is closed, the reverse switch K2 is closed, the coil KM2-A of the reversing relay KM2 is electrified, and then the main contact KM2-C of the reversing relay KM2 is electrified, and meanwhile, the instantaneous normally closed contact KM2-B of the reversing relay KM2 is disconnected, and the motor M is prevented from being electrified, and the forward relay M1-A is prevented from being electrified when the motor M is required to rotate reversely, and the motor M is required to stop the forward relay M1, and the forward relay M1 is required to rotate reversely, and the forward relay M1 is prevented from being electrified, and the forward relay 1 is required to rotate, and the forward relay 1 to stop the forward relay is required to rotate, and the coil and the forward relay 1 is turned, and the forward relay and the relay 1 is turned.

In other embodiments, referring to fig. 3 and 4, the start switch K1, the reverse switch K2, and the stop switch K3 are remote switches, the signal transmitter in fig. 3 converts the switching value into a frequency wave signal, and the signal receiver in fig. 4 converts the signal decoding into the switching value output, so that the forward and reverse switching system can be remotely controlled, the equipment used in the environment with high altitude, limited space, severe operating environment and high manual operation risk can be remotely controlled, the potential safety hazard caused by the manual operation of the equipment requiring buttons is avoided, and the forward and reverse switching system is safer.

The motor can be rotated forward and backward by exchanging any two phases of the power supply, so in other embodiments, referring to fig. 2, the wiring sequence of the upper ports of the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 are all the U-phase, V-phase and W-phase of the first power supply line, the wiring sequence of the lower ports of the main contacts KM1-C of the forward relay KM1 is the U-phase, V-phase and W-phase of the first power supply line, and the wiring sequence of the lower ports of the main contacts KM2-C of the reverse relay KM2 is the W-phase, V-phase and U-phase of the first power supply line;

because the two phases are exchanged, the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 are ensured not to be closed at the same time, otherwise serious interphase short-circuit faults can occur, and therefore the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 are interlocked to ensure that the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 cannot be closed at the same time, the interlocking can be completed through mechanical components, and mechanical levers can be used to ensure that the main contacts KM1-C of the forward relay KM1 are blocked mechanically and cannot be closed.

In other embodiments, referring to fig. 1, the electric bell D, the relay KA, the electric bell switch K4 are further included; the first end of a coil KA-A of a relay KA is connected with a first power line, the second end of the coil KA-A of the relay KA is connected with the first end of an instantaneous normally-closed contact KM1-E of a forward relay KM1, the second end of the instantaneous normally-closed contact KM1-E of the forward relay KM1 is connected with the first end of an instantaneous normally-closed contact KM2-E of a reverse relay KM2, the second end of the instantaneous normally-closed contact KM2-E of the reverse relay KM2 is connected with the first end of an electric bell switch K4, the second end of the electric bell switch K4 is connected with a second power line, the first end of an electric bell D is connected with the first power line, and the second end of the electric bell is connected with the first end of an instantaneous normally-open contact KA-B of the relay KA; when the electric bell D is needed to prompt a worker, an electric bell switch K4 is started, if the coil KM1-A of the forward relay KM1 and the coil KM1-A of the reverse relay KM1 are both in power failure, the coil KA-A of the relay KA is powered on, the instant normally open contact KA-B of the relay KA is closed, the electric bell D is powered on, sound information is output to the outside, when the equipment moves forward or moves reversely, if one of the coil KM1-A of the forward relay KM1 and the coil KM1-A of the reverse relay KM1 is powered on, the motor M rotates forward or rotates reversely, the instant normally closed contact KM1-E of the forward relay KM1 or the instant normally closed contact KM2-E of the reverse relay KM2 is disconnected, the instant normally open contact KA-B of the relay KA is powered off, the electric bell D is powered off, the outside is stopped, the sound information is output, and therefore, the worker can be warned when the equipment starts to operate, or the equipment is kept away from the equipment, and the worker is warned, and the worker is kept close to the equipment, and the worker is close to the equipment is warned to the working procedure.

In other embodiments, referring to FIG. 1, the electric power meter further comprises a start button SF1, a start button SF2, a start button SF3, a stop switch SS1 and a stop switch SS2, wherein the start button SF1 is connected with the start switch K1 in parallel, the start button SF2 is connected with the reverse switch K2 in parallel, the start button SF3 is connected with the electric bell switch K4 in parallel, the stop switch SS1 is connected between the start switch K1 and the second power line, the stop switch SS2 is connected between the instantaneous normally open contact KM2-E of the reverse relay KM2 and the second power line, and if the start switch K1, the reverse switch K2, the stop switch K3 and the electric bell switch K4 are remote control switches, the start button SF1, the start button SF2, the start button SF3, the stop switch SS1 and the stop switch SS2 are manual buttons, and the coil KM1-A of the forward relay KM1 is electrified by pressing the start button SF1, further, the main contact KM1-C of the forward relay KM1 is closed, the motor M is connected with a power supply in the forward direction, forward rotation is realized, the start button SF2 is pressed, the coil KM2-A of the reverse relay KM2 is electrified, further, the main contact KM2-C of the reverse relay KM2 is closed, the motor M is connected with the power supply in the reverse direction, reverse rotation is realized, the start button SF3 is pressed, the coil KA-A of the relay KA is electrified, the instant normally open contact KA-B of the relay KA is closed, the electric bell D is electrified, sound information is output to the outside, the stop switch SS1 is pressed, the coil KM1-A of the forward relay KM1 and the coil KM1-A of the reverse relay KM1 are deenergized, the main contact KM1-C of the forward relay KM1 and the main contact KM2-C of the reverse relay KM2 are disconnected, the motor M is deenergized to stop rotation, the stop switch SS2 is pressed, the coil KA-A of the relay KA is deenergized, the instantaneous normally open contact KA-B of the relay KA is disconnected to enable the electric bell D to lose electricity, so that the forward and reverse switching system provided by the utility model can be controlled by remote control and manual operation.

In other embodiments, referring to fig. 1, the instantaneous normally open contact KM1-D of the forward relay KM1 is connected in parallel with the start switch K1, the instantaneous normally open contact KM2-D of the reverse relay KM2 is connected in parallel with the reverse switch K2, the start button SF3 is connected in parallel with the instantaneous normally open contact KA-C of the relay KA, when the start switch K1 is closed, the instantaneous normally open contact KM1-D of the forward relay KM1 is closed when the coil KM1-a of the forward relay KM1 is energized, when the start switch K1 is released, the circuit in which the coil KM1-a of the forward relay KM1 is located is guaranteed to remain energized, and similarly, the instantaneous normally open contact KM2-D of the reverse relay KM2 is guaranteed to remain energized when the reverse switch K2 is released.

In other embodiments, referring to FIG. 1, an instantaneous normally open contact KA-D of a relay KA is connected between a start button SF1 and an instantaneous normally closed contact KM2-B of a reverse relay KM2, and an instantaneous normally open contact KA-E of a relay KA is connected between the start button SF2 and an instantaneous normally open contact KM1-B of a forward relay KM 1; the instantaneous normally open contact KA-D of the relay KA is connected with the start button SF1 in parallel after being connected with the start button SF1 in series, and then connected with the reverse switch K2 in parallel, when the coil KM1-A of the forward relay KM1 and the coil KM1-A of the reverse relay KM1 are in power failure, the coil KA-A of the relay KA is powered on, the circuit where the instantaneous normally open contact KA-D of the relay KA and the instantaneous normally open contact KA-E of the relay KA are located is powered on, the start button SF1 and the start button SF2 are conveniently started, and when the equipment moves forward or moves reversely, if one of the coil KM1-A of the forward relay KM1 and the coil KM1-A of the reverse relay KM1 is powered on, the coil KA-A of the relay KA is powered off, the instantaneous normally closed contact KM1-E of the forward relay KM1 or the instantaneous normally closed contact KM2-E of the reverse relay KM2 is powered off, the circuit where the instantaneous normally open contact KA-D of the relay KA and the start button SF2 are located is powered off, and the circuit where the instantaneous normally open contact SF-D of the relay KA is located is started.

In other embodiments, referring to fig. 1, the device further includes an indicator lamp HR1 and an indicator lamp HR2, where a first end of the indicator lamp HR1 is connected to a first power line, a second end of the indicator lamp HR1 is connected to a first end of an instantaneous normally open contact KM1-F of the forward relay KM1, a second end of the instantaneous normally open contact KM1-F of the forward relay KM1 is connected to a second power line, a first end of the indicator lamp HR2 is connected to a first end of an instantaneous normally open contact KM2-F of the reverse relay KM2, a second end of the instantaneous normally open contact KM2-F of the reverse relay KM2 is connected to a second power line, when a coil KM1-a of the forward relay KM1 is energized, the instantaneous normally open contact KM1-F of the forward relay KM1 is closed, the indicator lamp HR1 is energized to emit light, and the device is operated in a forward direction, and the indicator lamp HR2 is energized to emit light to the outside.

In other embodiments, referring to fig. 1, a fuse FU1 is connected between the stop switch SS1, the stop switch SS2 and the second power line, when the loop current of the stop switch SS1 or the stop switch SS2 is large, the bimetallic strips with different expansion coefficients in the fuse FU1 deform to push the connecting rod to act, so that the loop is disconnected, and the short-circuit protection is performed on the stop switch SS1 and the stop switch SS2.

In other embodiments, referring to fig. 1, a fuse FU2 is connected between an instantaneous normally open contact KA-B of a relay KA, an instantaneous normally open contact KM1-F of a forward relay KM1, an instantaneous normally open contact KM2-F of a reverse relay KM2, and a second power line, and when a loop current in which the instantaneous normally open contact KA-B of the relay KA, the instantaneous normally open contact KM1-F of the forward relay KM1, and the instantaneous normally open contact KM2-F of the reverse relay KM2 are located is large, bimetallic strips with different expansion coefficients in the fuse FU2 deform to push a connecting rod to act so as to disconnect the loop, thereby performing short-circuit protection on the instantaneous normally open contact KA-B of the relay KA, the instantaneous normally open contact KM1-F of the forward relay KM1, and the instantaneous normally open contact KM2-F of the reverse relay KM 2.

In other embodiments, referring to fig. 2, main contacts KM1-C of forward relay KM1 and main contacts KM2-C of reverse relay KM2 are connected between motor M with thermal relay KH, which overload protects motor M.

The utility model has been further described with reference to specific embodiments, but it should be understood that the detailed description is not to be construed as limiting the spirit and scope of the utility model, but rather as providing those skilled in the art with the benefit of this disclosure with the benefit of their various modifications to the described embodiments.

Claims (10)

1. The forward and reverse switching system is characterized in that: the motor comprises a forward relay KM1, a reverse relay KM2, a start switch K1, a reverse switch K2, a stop switch K3 and a motor M;

the first end of the stop switch K3 is connected with a first power line, the second end of the stop switch K3 is respectively connected with the first end of a coil KM1-A of the forward relay KM1 and the first end of a coil KM2-A of the reverse relay KM2, the second end of the coil KM1-A of the forward relay KM1 is connected with the first end of an instantaneous normally-closed contact KM2-B of the reverse relay KM2, the second end of the instantaneous normally-closed contact KM2-B of the reverse relay KM2 is connected with the first end of the start switch K1, the second end of the start switch K1 is connected with a second power line, the second end of the coil KM2-A of the reverse relay KM2 is connected with the first end of an instantaneous normally-closed contact KM1-B of the forward relay KM1, the second end of the instantaneous normally-closed contact KM1-B is connected with the first end of the reverse switch K2, and the second end of the reverse switch K2 is connected with the second power line;

the first end of the main contact KM1-C of the forward relay KM1 is positively connected with the first power line, the first end of the main contact KM2-C of the reverse relay KM2 is reversely connected with the first power line, the motor M is respectively connected with the second end of the main contact KM1-C of the forward relay KM1 and the second end of the main contact KM2-C of the reverse relay KM2, and the main contact KM1-C of the forward relay KM1 and the main contact KM2-C of the reverse relay KM2 are instantaneous normally open contacts.

2. The forward-reverse switching system according to claim 1, wherein: the wiring sequence of the upper ports of the main contacts KM1-C of the forward relay KM1 and the main contacts KM2-C of the reverse relay KM2 is U-phase, V-phase and W-phase of the first power line, the wiring sequence of the lower ports of the main contacts KM1-C of the forward relay KM1 is U-phase, V-phase and W-phase of the first power line, and the wiring sequence of the lower ports of the main contacts KM2-C of the reverse relay KM2 is W-phase, V-phase and U-phase of the first power line.

3. The forward-reverse switching system according to claim 1, wherein: the electric bell also comprises an electric bell D, a relay KA and an electric bell switch K4; the first end of a coil KA-A of the relay KA is connected with the first power line, the second end of the coil KA-A of the relay KA is connected with the first end of an instantaneous normally-closed contact KM1-E of the forward relay KM1, the second end of the instantaneous normally-closed contact KM1-E of the forward relay KM1 is connected with the first end of an instantaneous normally-closed contact KM2-E of the reverse relay KM2, the second end of the instantaneous normally-closed contact KM2-E of the reverse relay KM2 is connected with the first end of an electric bell switch K4, the second end of the electric bell switch K4 is connected with the second power line, the first end of the electric bell D is connected with the first power line, and the second end of the electric bell switch KA is connected with the first end of an instantaneous normally-open contact KA-B of the relay; and the second end of the instantaneous normally open contact KA-B of the relay KA is connected with the second power line.

4. A forward and reverse switching system as claimed in claim 3 wherein: still include start button SF1, start button SF2, start button SF3, stop switch SS1, stop switch SS2, start button SF1 with start switch K1 connects in parallel, start button SF2 with reverse switch K2 connects in parallel, start button SF3 with bell switch K4 connects in parallel, start switch K1 with be connected with between the second power cord stop switch SS1, reverse relay KM 2's instantaneous normally open contact KM2-E with be connected with between the second power cord stop switch SS2.

5. The forward-reverse switching system of claim 4, wherein: the instantaneous normally open contact KM1-D of the forward relay KM1 is connected with the starting switch K1 in parallel, the instantaneous normally open contact KM2-D of the reverse relay KM2 is connected with the reverse switch K2 in parallel, and the starting button SF3 is connected with the instantaneous normally open contact KA-C of the relay KA in parallel.

6. The forward-reverse switching system of claim 5, wherein: an instantaneous normally-open contact KA-D of the relay KA is connected between the start button SF1 and an instantaneous normally-closed contact KM2-B of the reverse relay KM2, and an instantaneous normally-open contact KA-E of the relay KA is connected between the start button SF2 and an instantaneous normally-open contact KM1-B of the forward relay KM 1; the instantaneous normally open contact KA-D of the relay KA is connected in series with the start button SF1 and then connected in parallel with the start switch K1, and the instantaneous normally open contact KA-E of the relay KA is connected in series with the start button SF2 and then connected in parallel with the reverse switch K2.

7. The forward-reverse switching system of claim 6, wherein: the intelligent power supply device comprises a forward relay KM1, an indicator lamp HR1 and an indicator lamp HR2, wherein the first end of the indicator lamp HR1 is connected with a first power line, the second end of the indicator lamp HR1 is connected with a first end of an instantaneous normally open contact KM1-F of the forward relay KM1, the second end of the instantaneous normally open contact KM1-F of the forward relay KM1 is connected with a second power line, the first end of the indicator lamp HR2 is connected with the first power line, the second end of the indicator lamp HR2 is connected with a first end of an instantaneous normally open contact KM2-F of the reverse relay KM2, and the second end of the instantaneous normally open contact KM2-F of the reverse relay KM2 is connected with the second power line.

8. The forward-reverse switching system of claim 4, wherein: and a fuse FU1 is connected between the stop switch SS1 and the second power line as well as between the stop switch SS2 and the second power line.

9. The forward-reverse switching system of claim 7, wherein: a fuse FU2 is connected between the instantaneous normally open contact KA-B of the relay KA, the instantaneous normally open contact KM1-F of the forward relay KM1, the instantaneous normally open contact KM2-F of the reverse relay KM2 and the second power line.

10. The forward-reverse switching system of claim 7, wherein: the main contacts KM1-C of the forward relay KM1 interlock with the main contacts KM2-C of the reverse relay KM 2.

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