Master-slave switching system and method based on relay control

Abstract

A master-slave switching system and method based on relay control are characterized in that a host A is electrically connected with a host B, the host A is further electrically connected with one contact of a first relay and one contact of a second relay, and the host B is further electrically connected with the other contact of the first relay and the other contact of the second relay; a B machine big fault signal or B machine handle switching and touch screen B machine switching operation and a central control room B machine remote switching command are electrically connected with the first relay, and an A machine big fault signal or A machine handle switching and touch screen A machine switching operation and a central control room A machine remote switching command are electrically connected with the second relay. Two switching loops which are mutually independent and backup are formed, relay hardware control logic is added, backup of controller switching control is achieved through program judgment, and automatic switching under various working conditions is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of switching of hydropower units, and relates to a master-slave switching system and method based on relay control. Background Art

[0002] The existing hydropower station speed control system controller switching basically adopts the manual switching method, which requires manual operation of the switch to switch the controller between the master and slave. At this time, the handle position signal is used as the input signal source to trigger the master-slave switch. Its operation method is single and has great limitations. Secondly, when a major fault occurs in the speed regulator, it needs to automatically switch from the host to the slave. The fault signal is also used as the input signal source to trigger the master-slave switch, and there is no hardware control logic.

[0003] Firstly, it can only be operated on-site, that is, it is impossible to issue commands remotely to switch the speed regulator's controller from the master to the slave, which does not conform to the development trend of hydropower stations gradually realizing "few or no people on duty".

[0004] Secondly, once the switching switch fails, the controller will not be able to switch between the master and slave machines. If the main machine fails at this time, the speed governor will be in an uncontrollable state, and the turbine unit will not be able to perform frequency regulation and load regulation. The problem can only be solved by replacing a new switching switch. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a master-slave switching system and method based on relay control, which realizes automatic switching under various working conditions by adding relay hardware control logic and assisted by program judgment to realize the backup of controller switching control.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a master-slave switching system based on relay control, the switching system includes host A electrically connected to host B; host A is also electrically connected to one of the contacts of the first relay and the second relay, and host B is also electrically connected to the other contact of the first relay and the second relay; the major fault signal of machine B or the handle switching of machine B and the touch screen switching operation of machine B and the remote switching command of machine B in the central control room are electrically connected to the first relay, and the major fault signal of machine A or the handle switching of machine A and the touch screen switching operation of machine A and the remote switching command of machine A in the central control room are electrically connected to the second relay, forming two switching circuits that are independent of each other and serve as backup for each other.

[0007] The A machine handle switch or the B machine handle switch and the A machine major fault signal or the B machine major fault signal must pass through the A host and the B host to transmit the machine cutting signal to the controller, and then the controller completes the master-slave switch.

[0008] A new soft button "Switch xx unit speed regulator to use A / B machine as the main machine" is added to the computer operation window of the central control room; the pulse signal of this button is electrically connected to the local LCU control cabinet through the upper computer, and the signal is input to the monitoring system controller; the monitoring system controller receives the signal and issues a "Switch A machine as the main machine" order after program processing, or it is issued through the relay in the monitoring system control cabinet, and the speed regulator controller receives it and switches the master and slave machines.

[0009] Switching can only be achieved under the premise that both switching circuits can work normally. If one of the switching circuit controllers is set to the "STOP" state or fails to operate normally, controller switching cannot be achieved.

[0010] The method for triggering controller switching of a master-slave switching system based on relay control with a large fault signal as described above comprises the following steps: SA1, when a major fault occurs in machine A, the switch signal contact is connected to the power supply circuit of the relay that switches machine B to the main state. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signal is output to set machine B to the main state and machine A to the main state respectively; SA2, when a major fault occurs in machine B, the switch signal contact is connected to the power supply circuit of the relay that cuts machine A into the main mode. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to cut off the machine, and then the control signals are output to set machine A to the main mode and machine B to the main mode.

[0011] The method for triggering controller switching by a handle switching signal of the master-slave switching system based on relay control as described above comprises the following steps: SB1, when the control handle is switched to the A machine, the handle position signal contact is connected to the power supply circuit of the relay that switches the A machine to the main use. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of the A machine and the B machine, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set the A machine to the main use state and the B machine to the main use state respectively; SB2, when the control handle is switched to machine B, the handle position signal contact is connected to the power supply circuit of the relay that switches machine B to the main mode. Once the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main mode and machine A to the main mode.

[0012] The touch screen soft button switching method of the master-slave switching system based on relay control as described above comprises the following steps: SC-1, when the soft button "Switch to A machine as main" is clicked on the touch screen of the speed regulator control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches A machine to main use through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of A machine and B machine, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set A machine to the main state and restore B machine to the main state respectively; SC-2, when the soft button "Switch to B machine as main" is clicked on the touch screen of the speed regulator control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches B machine as the main machine through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main state and machine A to the main state.

[0013] The remote switching method of the central control room of the master-slave switching system based on relay control as described above comprises the following steps: SD1, click the soft button "Cut the speed governor of unit xx to the main use of unit A" on the computer operation window of the central control room. The pulse signal of this button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues the "Cut the speed governor of unit A to the main use" command after program processing, or it is opened by the relay in the monitoring system control cabinet, and its opening contact is connected to the power supply ends of the relay in the speed governor cabinet that cuts the speed governor to the main use. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of units A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed governor controller to cut the machine, and then the control signals are output to set the speed governor to the main use state and the speed governor to the main use state respectively; SD2. Click the soft button "Cut the speed regulator of unit xx to unit B as the main unit" on the computer operation window in the central control room. The pulse signal of this button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues an order to "cut unit B as the main unit" after program processing, or it is opened by the relay in the monitoring system control cabinet, and its opening contacts are connected to the power supply ends of the relay in the speed regulator cabinet that cuts unit B as the main unit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of units A and B, the states of the two pairs of normally open contacts of the relay are used as the criterion for the speed regulator controller to cut the machine, and then the control signals are output to set unit B to the main state and unit A to the main state.

[0014] The main beneficial effects of the present invention are: By adding relay hardware control logic and supplementing it with program judgment to realize the backup of controller switching control, automatic switching under various working conditions can be achieved.

[0015] It meets the demand that the turbine speed governor can automatically switch under various working conditions, solves the current problem of having to switch manually or trigger a serious fault, realizes the safety and stability of the master-slave switching process of the speed governor controller, and ensures the safe and stable operation of the turbine speed control system.

[0016] The designed loop and the original handle position signal are directly sent to the controller to trigger the master-slave switch, which are independent of each other and serve as backup for each other; automatic switching and rapid response; redundant control configuration and high reliability; saving labor costs and improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] Figure 1 This is the logic switching diagram of the original controller.

[0019] Figure 2 This is the system and logic switching diagram of the present invention.

[0020] In the figure, A host 1; B host 2; first relay 11; second relay 21. DETAILED DESCRIPTION

[0021] like Figure 1~2 In the invention, a master-slave switching system based on relay control is disclosed, wherein the switching system includes a host A 1 electrically connected to a host B 2; the host A 1 is also electrically connected to one of the contacts of a first relay 11 and a second relay 21, and the host B 2 is also electrically connected to the other contact of the first relay 11 and the second relay 21; a major fault signal of the B machine or a handle switch of the B machine and a touch screen switch operation of the B machine and a remote switch command of the B machine in the central control room are electrically connected to the first relay 11, and a major fault signal of the A machine or a handle switch of the A machine and a touch screen switch operation of the A machine and a remote switch command of the A machine in the central control room are electrically connected to the second relay 21, forming two switching circuits that are independent of each other and serve as backup for each other.

[0022] In the preferred solution, the A machine handle switch or the B machine handle switch and the A machine major fault signal or the B machine major fault signal all need to pass through the A host 1 and the B host 2 to transmit the machine cutting signal to the controller, and then the controller completes the master-slave switch.

[0023] In the preferred solution, a new soft button "Switch xx unit speed regulator to use A / B machine as the main machine" is added to the computer operation window of the central control room; the pulse signal of this button is electrically connected to the local LCU control cabinet through the upper computer, and the signal is input to the monitoring system controller; the monitoring system controller receives the signal and issues a "Switch A machine as the main machine" command after program processing, or it is issued through the relay in the monitoring system control cabinet, and the speed regulator controller receives it and switches the master and slave machines.

[0024] In the preferred solution, switching can be achieved only when both switching loops can operate normally. If one of the switching loop controllers is set to the "STOP" state or fails to operate normally, controller switching cannot be achieved.

[0025] As attached Figure 1 middle, The original speed regulator automatic switching control method has four operating conditions that can trigger the controller master-slave switch, which are all disturbance-free switching under normal conditions, as follows: 1.1. When the control handle is switched to machine A, the position signal will send out two signals at the same time after being judged by the program. The signal to machine A is defined as the master signal of this machine, and the signal to machine B is defined as the master signal of the slave machine. Then machine A will take over the master state, and machine B will return to the master state; 1.2. When the control handle is switched to the B machine, the position signal will send out two signals at the same time after being judged by the program. The signal to the A machine is defined as the slave machine master signal, and the signal to the B machine is defined as the master signal of the machine. Then the B machine will take over the master state, and the A machine will return to the master state. 1.3. When the A host is running and a major fault signal triggers the machine switching, the fault signal will send two signals at the same time after being judged by the program. The signal to the A host is defined as the slave host signal, and the signal to the B host is defined as the local host signal. Then the B host will take over the master state, and the A host will return to the master state. 1.4. When the host B is running and a major fault signal triggers the machine switching, the fault signal will also send out two signals at the same time after being judged by the program. The signal to the A machine is defined as the master signal of the local machine, and the signal to the B machine is defined as the slave master signal. Then the A machine will take over the master state and the B machine will return to the master state.

[0026] It can be seen that the above switching methods are all local switching methods.

[0027] Embodiment 1, like Figure 2 In the control method of speed governor master-slave switching, touch screen soft button switching operation and remote control in the central control room are added on the basis of the original switching logic. All four switching methods need to transmit the machine cutting signal to the controller CPU through relay control. First, take the controller switching triggered by a major fault signal as an example for specific explanation: 2.1. When a major fault occurs in the A machine, the switch signal contact is connected to the power supply circuit of the relay that switches the B machine to the main state. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of the A and B machines, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signal is output to set the B machine to the main state and the A machine to the main state; 2.2. When a major fault occurs in machine B, the switch signal contact is connected to the power supply circuit of the relay that switches machine A to the main state. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine A to the main state and machine B to the main state.

[0028] Embodiment 2, like Figure 2 In the speed regulator master-slave switching control method, the handle switching also needs to be controlled by the relay to transmit the machine cutting signal to the controller CPU. This is different from the original control method that directly sends the position signal to the controller to trigger the master-slave switching. The new handle switching signal triggers the controller switching method as follows: 3.1. When the control handle is switched to the A machine, the handle position signal contact is connected to the power supply circuit of the relay that switches the A machine to the main state. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of the A and B machines, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set the A machine to the main state and the B machine to the main state respectively; 3.2. When the control handle is switched to machine B, the handle position signal contact is connected to the power supply circuit of the relay that switches machine B to the main function. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main function state and machine A to the main function state.

[0029] Embodiment 3, like Figure 2 In the speed regulator master-slave switching control method, the touch screen soft button switching operation is a new control operation. This operation also needs to be controlled by the relay to transmit the machine cutting signal to the controller CPU. The touch screen soft button switching operation is described as follows: 4.1. When the soft button "Switch to A machine as the main machine" is clicked on the touch screen of the speed regulator control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches A machine to the main machine through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of A and B machines, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set A machine to the main state and restore B machine to the main state respectively; 4.2. When the soft button "Switch to B machine as main" is clicked on the touch screen of the speed regulator control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches B machine as the main machine through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main state and machine A to the main state.

[0030] Embodiment 4, like Figure 2 In the speed regulator master-slave switching control method, the remote operation in the central control room is a newly added control operation. This operation also needs to be controlled by the relay to transmit the machine cutting signal to the controller CPU. The specific description of the remote operation in the central control room is as follows: 5.1. Click the soft button "Cut the speed governor of unit xx to the main unit A" on the computer operation window in the central control room. The pulse signal of the button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues a "cut the A unit to the main unit" command after program processing, or it is opened by the relay in the monitoring system control cabinet, and its opening contacts are connected to the power supply ends of the relay in the speed governor cabinet that cuts the A unit to the main unit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of the A unit and the B unit, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed governor controller to cut the machine, and then the control signals are output to set the A unit to the main state and the B unit to the main state respectively; 5.2. Click the soft button "Cut the speed regulator of unit xx to the main unit B" on the computer operation window in the central control room. The pulse signal of this button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues a "Cut the B unit to the main unit" command after program processing, or it is opened by the relay in the monitoring system control cabinet, and its opening contact is connected to the power supply ends of the relay in the speed regulator cabinet that cuts the B unit to the main unit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of the A and B units, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to cut the machine, and then the control signals are output to set the B unit to the main unit state and the A unit to the main unit state. This switching method can realize remote switching.

[0031] In the above embodiments, the requirement that the turbine speed governor can automatically switch under various working conditions can be met, and the current problem of having to switch manually or trigger a serious fault can be solved to achieve the safety and stability of the master-slave switching process of the speed governor controller, thereby ensuring the safe and stable operation of the turbine speed control system.

[0032] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The embodiments and features in the embodiments of the present application can be arbitrarily combined with each other without conflict. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A master-slave switching system based on relay control, characterized in that: The switching system comprises an A host (1) electrically connected to a B host (2); the A host (1) is also electrically connected to one of the contacts of a first relay (11) and a second relay (21); the B host (2) is also electrically connected to the other contact of the first relay (11) and the second relay (21); a major fault signal of the B machine or a B machine handle switch and a touch screen B machine switch operation and a central control room B machine remote switch command are electrically connected to the first relay (11), and a major fault signal of the A machine or a A machine handle switch and a touch screen A machine switch operation and a central control room A machine remote switch command are electrically connected to the second relay (21), forming two switching circuits that are independent of each other and serve as backup for each other.

2. The master-slave switching system based on relay control according to claim 1 is characterized in that: The A machine handle switch or the B machine handle switch and the A machine major fault signal or the B machine major fault signal all need to pass through the A host (1) and the B host (2) to transmit the machine cut-off signal to the controller, and then the controller completes the master-slave switch.

3. The master-slave switching system based on relay control according to claim 1 is characterized in that: A new soft button "Switch xx unit speed regulator to A / B machine as master" is added to the computer operation window of the central control room; the pulse signal of this button is electrically connected to the local LCU control cabinet through the host computer, and the signal is input to the monitoring system controller; the monitoring system controller receives the signal and issues a "Switch A machine as master" order after program processing, or it is issued through the relay in the monitoring system control cabinet, and the speed regulator controller receives it and switches the master and slave machines.

4. The master-slave switching system based on relay control according to claim 1 is characterized in that: Switching can only be achieved under the premise that both switching circuits can work normally. If one of the switching circuit controllers is set to "STOP" state or fails to operate normally, controller switching cannot be achieved.

5. The method for triggering controller switching of a master-slave switching system based on relay control by a large fault signal according to any one of claims 1 to 4, characterized in that: The steps include: SA1, when a major fault occurs in machine A, the switch signal contact is connected to the power supply circuit of the relay that switches machine B to the main state. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signal is output to set machine B to the main state and machine A to the main state respectively; SA2, when a major fault occurs in machine B, the switch signal contact is connected to the power supply circuit of the relay that cuts machine A into the main mode. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to cut off the machine, and then the control signals are output to set machine A to the main mode and machine B to the main mode.

6. The method for triggering controller switching by a handle switching signal of a master-slave switching system based on relay control according to any one of claims 1 to 4, characterized in that: The steps include: SB1, when the control handle is switched to the A machine, the handle position signal contact is connected to the power supply circuit of the relay that switches the A machine to the main use. When the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of the A machine and the B machine, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set the A machine to the main use state and the B machine to the main use state respectively; SB2, when the control handle is switched to machine B, the handle position signal contact is connected to the power supply circuit of the relay that switches machine B to the main mode. Once the signal comes, the relay is energized and its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main mode and machine A to the main mode.

7. The touch screen soft button switching method of the master-slave switching system based on relay control according to any one of claims 1 to 4, characterized in that: The steps include: SC-1, when the soft button "Switch to A machine as main" is clicked on the touch screen of the speed governor control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches A machine to main use through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of A machine and B machine, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed governor controller to switch the machine, and then the control signals are output to set A machine to the main state and restore B machine to the main state respectively; SC-2, when the soft button "Switch to B machine as main" is clicked on the touch screen of the speed regulator control cabinet, the pulse signal of the button is connected to the voltage-stabilizing diode to convert the pulse signal into a stable voltage signal, and then the voltage is output to the two ends of the power supply of the relay that switches B machine as the main machine through the voltage divider circuit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to switch the machine, and then the control signals are output to set machine B to the main state and machine A to the main state.

8. The remote switching method in the central control room of the master-slave switching system based on relay control according to any one of claims 1 to 4, characterized in that: The steps include: SD1, click the "Switch xx unit speed governor to A as the main unit" soft button on the computer operation window of the central control room. The pulse signal of this button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues a "Switch A unit as the main unit" command after program processing, or it is switched through the relay in the monitoring system control cabinet, and its switching contacts are connected to the power supply ends of the relay in the speed governor cabinet that switches A unit as the main unit. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of A unit and B unit, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed governor controller to switch the machine, and then the control signals are output to set A unit to the main state and B unit to the main state respectively; SD2, click the "Cut xx unit speed regulator to B machine as the main" soft button on the computer operation window in the central control room. The pulse signal of this button is transmitted through the communication between the upper computer and the local LCU control cabinet, and the signal is input to the monitoring system controller. The monitoring system controller receives the signal and issues a "Cut B machine as the main" command after program processing, or it is opened by the relay in the monitoring system control cabinet, and its opening contacts are connected to the power supply ends of the relay in the speed regulator cabinet that cuts B machine as the main machine. After the relay is energized, its normally open auxiliary contacts are closed. In the control programs of machines A and B, the states of the two pairs of normally open contacts of the relay are used as the judgment criteria for the speed regulator controller to cut the machine, and then the control signals are output to set B machine to the main state and A machine to the main state.

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