JP6880247B2 - Inverter controller - Google Patents

Description

The present invention relates to an inverter control device that drives a compressor of an air conditioner.

The inverter control device of the air conditioner drives the compressor using three-phase AC power supplied from the AC power supply. In the inverter controller, if the AC power supplied from the AC power supply is out of phase, the AC power will not be calculated correctly and the booster of the compressor will not be correctly boosted, causing step-out of the compressor and stopping of overcurrent interruption. Therefore, it is necessary to determine that it is abnormal and stop the compressor. Patent Document 1 discloses an inverter control device that detects open phase of AC power input from a three-phase AC power supply.

Japanese Unexamined Patent Publication No. 2008-101860

However, in the conventional inverter control device, if an abnormality occurs in the primary current detection process, the primary current may not be detected correctly. If the control unit continues to control the compressor while the primary current detection process is abnormal, the compressor may step out or stop overcurrent. Therefore, it is desirable that the inverter control device can detect an abnormality in the process of detecting the primary current.

The present invention has been made in view of the above, and an object of the present invention is to obtain an inverter control device capable of detecting an abnormality in a process of detecting a primary current.

In order to solve the above-mentioned problems and achieve the object, the inverter control device according to the present invention includes a converter unit that converts an alternating current, which is an alternating current supplied from an alternating current, into a direct current, and a first. To the first current detector that detects the first current value, which is the current value of the alternating current, and the compressor that converts the DC current to the second alternating current and transfers the second alternating current to the compressor that compresses the refrigerant. It includes an inverter unit to be applied, a second current detection unit that detects a second current value that is a current value of a second alternating current, and a control unit that controls the inverter unit. The control unit is a first unit. The first current value is the first current threshold , using the current value of, the second current value, the operating frequency of the compressor, and the compressor operating information indicating whether the compressor is operating or stopped. If the value is less than or equal to the value, the second current value is equal to or higher than the compressor current threshold value, the operating frequency of the compressor is equal to or higher than the operating frequency threshold value, and the compressor is operating, an abnormality occurs in the process of detecting the first current value. Performs an abnormality determination process for determining that is occurring.

The inverter control device according to the present invention has an effect that it is possible to obtain an inverter control device capable of detecting an abnormality in the process of detecting a primary current.

The figure which shows the inverter control device in embodiment The figure which shows the functional block of the control part in embodiment The figure which shows the structural example of the control circuit which concerns on embodiment The figure which shows the transition of the state about the control process in embodiment A flowchart showing the flow of control processing in the embodiment in a simplified manner. The figure which shows the timer operation in the normal state in an embodiment. The figure which shows the timer operation in the abnormality confirmation state and the abnormality grace state in an embodiment. A flowchart showing the flow of control processing in the embodiment in detail.

Hereinafter, the inverter control device according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment.
FIG. 1 is a diagram showing an inverter control device according to an embodiment of the present invention. The inverter control device 100 includes a noise filter board 10, a reactor 20, an inverter control board 30, and a connection line 50. The noise filter substrate 10 is also called a first substrate. The inverter control board 30 is also called a second board.

The noise filter substrate 10 is arranged separately from the inverter control substrate 30 in order to reduce the substrate size per substrate and enhance electromagnetic compatibility. Further, the noise filter substrate 10 removes the noise of the alternating current supplied from the alternating current power supply 1. The alternating current supplied from the alternating current power supply 1 is also called the first alternating current. A current transformer 11 and a first connector 12 are provided on the noise filter substrate 10. The current transformer 11 detects the primary current information which is the current value of the primary current of the AC power supplied from the AC power supply 1. In the present embodiment, the current transformer 11 detects the primary current information, but the current transformer 11 is not limited to the current transformer 11 as long as it can detect the primary current information. The functional unit that detects the current value of the primary current is also called the first current detection unit. The current value of the primary current is also called the first current value. The first connector 12 is connected to the second connector 34 provided on the inverter control board 30 by the connection line 50, and transmits the primary current information detected by the current transformer 11 to the control unit 35.

The reactor 20 is arranged between the noise filter board 10 and the inverter control board 30, and suppresses a momentary large current from flowing from the noise filter board 10 to the inverter control board 30.

The inverter control board 30 is a board for controlling the compressor 40. A converter unit 31, an inverter unit 32, a current detection unit 33, a second connector 34, and a control unit 35 are provided on the inverter control board 30. The converter unit 31 converts the alternating current supplied from the noise filter substrate 10 into a direct current. The inverter unit 32 converts the direct current converted by the converter unit 31 into a three-phase alternating current for driving the compressor 40 and applies it to the compressor 40. The three-phase alternating current for driving the compressor 40 is also called a second alternating current. The current value of the three-phase alternating current for driving the compressor 40 output by the inverter unit 32 is also called a second current value. The current detection unit 33 detects the current value of two phases of the three-phase current flowing from the inverter unit 32 to the compressor 40. The current detection unit 33 is also called a second current detection unit. The current detection unit 33 may detect the currents of the three phases of the compressor 40, respectively. Alternatively, the current detection unit 33 may use a method of detecting a direct current obtained by combining the currents of the three phases of the compressor 40, and is not limited to the current detection method. The second connector 34 is connected to the first connector 12 by the connection line 50, and inputs the primary current information acquired from the first connector 12 to the control unit 35. The control unit 35 controls the voltage applied from the converter unit 31 to the inverter unit 32. The control unit 35 generates a PWM (Pulse Width Modulation) signal that controls on or off of the switching element constituting the inverter unit 32 based on the primary current information, and applies the PWM signal to the inverter unit 32 to inject the inverter. The unit 32 is controlled. Further, the control unit 35 controls the inverter unit 32 when the current value of the primary current obtained from the primary current information increases above the threshold value in order to prevent step-out of the compressor 40 and stop of overcurrent interruption. , Implement protection control to prevent step-out and overcurrent interruption. The compressor 40 compresses the refrigerant, and heat exchanges the compressed refrigerant with a heat exchanger (not shown).

FIG. 2 is a diagram showing a functional block of the control unit 35 in the embodiment. The control unit 35 includes a determination processing unit 351, a storage unit 352, and a signal control unit 353. The determination processing unit 351 performs control processing using the primary current information, the compressor current information, the compressor operating frequency, the compressor operating information, and the abnormality determination data stored in the storage unit 352. The control process determines whether an abnormality has occurred in the detection process of the primary current acquired by the control unit 35 due to a failure of the transmission path or a failure of the current transformer 11, and controls the inverter control device 100 based on the result of the determination. It is a process. The transmission path is a primary current from the current transformer 11 to the control unit 35 formed by the first connector 12, the second connector 34, and the connection line 50 connecting the first connector 12 and the second connector 34. It is a route through which information is transmitted. The compressor current information is information on the current value of the current flowing from the inverter unit 32 to the compressor 40 detected by the current detection unit 33. The compressor operating frequency is information obtained from a drive command value for driving the compressor 40, which is output by the inverter unit 32. The compressor operation information is information on the operating state of the compressor 40, and is information indicating that the compressor 40 is operating or stopped.

The storage unit 352 holds the primary current threshold value, the compressor current threshold value, the frequency threshold value, the first time threshold value, the second time threshold value, and the number of determination graces, which are abnormality determination data. .. The primary current threshold, compressor current threshold, frequency threshold, first time threshold, second time threshold, and number of judgment graces determine the abnormal state of the primary current detection process. Used for. Further, the storage unit 352 determines that the primary current detection process is in an abnormal state, and holds the number of transitions to the abnormal confirmed state as the number of abnormal occurrences.

The frequency threshold value, compressor current threshold value, primary current threshold value, first time threshold value, second time threshold value, and number of determination graces held in the storage unit 352 are determined by the inverter control device. After operating the 100 and the compressor 40 and confirming the performance during operation, the threshold values corresponding to the information acquired by the inverter control device 100 are set respectively.

The storage unit 352 includes an abnormality determination counter. The abnormality determination counter is data to be used for control processing in the control program written to the control unit 35. Further, the storage unit 352 includes an abnormal state timer and a normal state timer, which are timers for counting the elapsed time used for the control process. The abnormal state timer is a timer for determining whether or not the primary current detection process is in an abnormal state. The normal state timer is a timer for determining whether or not the primary current detection process is in the normal state. The abnormal state timer and the normal state timer have a time threshold for determining the abnormal state or the normal state, and by using this threshold, the primary current detection process is in the abnormal state or the normal state. Is determined to be.

The signal control unit 353 controls whether or not to output a PWM signal based on the abnormality determination of the determination processing unit 351 to control the inverter unit 32 when an abnormal state is detected.

The hardware configuration of the determination processing unit 351, the storage unit 352, and the signal control unit 353 according to the embodiment will be described. The determination processing unit 351 and the signal control unit 353 are realized by a processing circuit which is an electronic circuit that performs each processing.

The processing circuit may be dedicated hardware or a control circuit including a memory and a CPU (Central Processing Unit) that executes a program stored in the memory. Here, the memory corresponds to, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), or a flash memory, a magnetic disk, an optical disk, or the like. When the processing circuit is a control circuit including a CPU, the control circuit is, for example, the control circuit 200 having the configuration shown in FIG.

As shown in FIG. 3, the control circuit 200 includes a processor 200a which is a CPU and a memory 200b. When it is realized by the control circuit 200 shown in FIG. 3, it is realized by the processor 200a reading and executing the program corresponding to each process stored in the memory 200b. The memory 200b is also used as a temporary memory in each process performed by the processor 200a.

When the processing circuit is dedicated hardware, the processing circuit is, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

The storage unit 352 is a non-volatile memory such as a ROM or a flash memory.

A flowchart of control of the inverter control device 100 according to the embodiment will be described.

FIG. 4 is a diagram showing a state transition related to the control process in the embodiment. The inverter control device 100 can transition between three control states: a normal state, an abnormal grace state, and an abnormal confirmed state. The normal state is a state in which no abnormality has occurred in the process of detecting the primary current. The abnormal grace state is a state in which it is confirmed that the primary current detection process is abnormal, but it is not determined that an abnormality has occurred in the primary current detection process. The abnormality confirmed state is a state in which it is determined that an abnormality has occurred in the process of detecting the primary current. The details of the state transition process will be described later.

When the operation of the inverter control device 100 is started, it is set to a normal state as an initial state. When the control process determines that the primary current detection process is in an abnormal state, the inverter control device 100 transitions to an abnormal grace state. In the abnormal grace state, the inverter control device 100 can transition to the normal state. Further, when the inverter control device 100 is in the abnormal grace state and the setting condition for determining the abnormal state is satisfied, the inverter control device 100 transitions to the abnormal confirmed state. Once the inverter control device 100 transitions to the abnormally determined state, the operation of the compressor 40 cannot be restored unless the condition for canceling the abnormally determined state is satisfied. The condition for canceling the abnormality confirmation state is when the power is turned on again after the power is turned off or when the abnormality release signal is received from the indoor unit.

By providing an abnormal grace state in the control process, even when the determination processing unit 351 momentarily or accidentally detects an abnormality in the primary current detection process, it is subsequently determined to be in the normal state, so that the compressor 40 is operated. Can be continued. Therefore, it leads to improvement of comfort when using the product. Further, when it is determined that the abnormal state is confirmed even in the situation where the abnormal grace state is provided, the product life of the inverter control device 100 is controlled by stopping the operation of the compressor 40 and controlling the operation so as not to restart the operation. And leads to improved safety.

FIG. 5 is a flowchart showing a simplified flow of control processing in the embodiment. The control process is composed of an abnormality determination process, a state transition process, an abnormality determination process, an abnormality grace process, and a normal process. Further, in the abnormality determination process, the abnormality determination process, the abnormality grace process, and the normal process, a timer process is performed to determine the abnormal state of the primary current detection process over time.

The determination processing unit 351 executes the abnormality determination process based on the acquired information (step S1). The acquired information is primary current information, compressor current information, compressor operating frequency, compressor operating information, primary current threshold value, compressor current threshold value, and frequency threshold value. The abnormality determination process is a process for determining whether or not an abnormality has occurred in the process of detecting the primary current.

The determination processing unit 351 performs a state transition process after the abnormality determination process (step S2). The state transition process uses the first time threshold value, the second time threshold value, the abnormality determination counter, and the number of determination graces stored in the storage unit 352. The determination processing unit 351 performs each process of normal processing (step S3), abnormality grace processing (step S4), or abnormality determination processing (step S5) based on the state transitioned by the state transition processing. The normal process is a process performed when the inverter control device 100 is in a normal state. The abnormal grace process is a process performed when the inverter control device 100 is in the abnormal grace state. The abnormality determination process is a process performed when the inverter control device 100 is in the abnormality determination state.

Next, the operation of the timer processing according to the embodiment will be described. The timer processing is executed in the abnormality judgment processing, the normal processing, the abnormality grace processing, and the abnormality confirmation processing, and whether the primary current detection process is in the abnormal state or the normal state is checked with the abnormal state timer. Judgment is made using the state timer, the first time threshold value, and the second time threshold value. The timer processing includes a first timer processing, a second timer processing, a third timer processing, a fourth timer processing, a fifth timer processing, and a sixth timer processing. .. In each timer process, the abnormal state timer and the normal state timer are increased or the timers are cleared. When the abnormal state timer exceeds the first time threshold value, it is determined that the primary current detection process is in an abnormal state. When the normal state timer exceeds the second time threshold value, it is determined that the primary current detection process is in the normal state.

FIG. 6 is a diagram showing a timer operation in a normal state according to the embodiment. In the first timer processing, both the abnormal state timer and the normal state timer stop increasing in value. The second timer process increases the value of the normal state timer and stops the increase of the value of the abnormal state timer. The fourth timer process clears the timer value to 0 for both the abnormal state timer and the normal state timer, and stops the increase of the value.

FIG. 7 is a diagram showing timer operation in the abnormal confirmation state and the abnormal grace state in the embodiment. The third timer process clears the value of the normal state timer to 0, stops the increase of the value of the normal state timer, and starts the increase of the value of the abnormal state timer. In the fifth timer process, after clearing the value of the abnormal state timer to 0, the value of the abnormal state timer is increased with the start of operation of the compressor 40. Also, the value of the normal state timer is cleared to 0. The sixth timer process clears the timer value to 0 for both the abnormal state timer and the normal state timer, and stops the increase of the value.

FIG. 8 is a flowchart showing in detail the flow of the control process according to the embodiment. The numbers attached to each step correspond to those in FIG. 5. For example, step S1-1 is a process included in the abnormality determination process of step S1 in FIG.

The determination processing unit 351 acquires the acquired information and determines whether the compressor 40 is in operation or stopped from the compressor operation information (step S1-1). When the compressor 40 is in the stopped state (steps S1-1 and No), the determination processing unit 351 executes the first timer processing (step S1-5). After that, the control process proceeds to step S2-1. When the compressor 40 is in operation (steps S1-1, Yes), the determination processing unit 351 compares the compressor operating frequency with the frequency threshold value (step S1-2). In step S1-1, the determination processing unit 351 confirms whether or not the compressor 40 is operating, even if it is in an abnormal state when the compressor 40 is not operating, the product comfort and the product life. , And does not affect safety.

When the compressor operating frequency is less than the frequency threshold value (steps S1-2, No), the determination processing unit 351 executes the second timer processing (step S1-6), and thereafter, the control processing is performed. The process proceeds to step S2-1. When the compressor operating frequency is equal to or higher than the frequency threshold value (steps S1-2, Yes), the determination processing unit 351 compares the compressor current value obtained from the compressor current information with the compressor current threshold value. (Step S1-3).

When the compressor current value is less than the compressor current threshold value (steps S1-3, No), the determination processing unit 351 executes the second timer processing (step S1-6), and then the control processing. Goes to step S2-1. When the compressor current value is equal to or higher than the compressor current threshold value (steps S1-3, Yes), the determination processing unit 351 compares the primary current value obtained from the primary current information with the primary current threshold value. (Step S1-4). Here, the reason why the primary current value and the primary current threshold value are compared is that if the primary current value is equal to or less than the primary current threshold value, there is a possibility that an abnormality has occurred in the primary current detection process. Because it is expensive. Therefore, in the present embodiment, whether or not the primary current value is equal to or less than the primary current threshold value is used to determine whether or not an abnormality has occurred in the process of detecting the primary current. However, when the operating load of the compressor 40 is light, the primary current itself becomes small, so that the process of detecting the primary current may be determined to be abnormal even if it is actually normal. Therefore, in order to suppress erroneous judgment when the primary current is below the primary current threshold value, it is determined whether or not an abnormality has occurred in the process of detecting the primary current using the compressor operating frequency and the compressor current value. It is carried out.

When the primary current value is larger than the primary current threshold value (steps S1-4, No), the determination processing unit 351 executes the second timer process (step S1-6), after which the control process is performed in steps. Move to S2-1. When the primary current value is equal to or less than the primary current threshold value (steps S1-4, Yes), the third timer process is executed (step S1-7), after which the control process shifts to step S2-1. ..

After the abnormality determination process, the control process shifts to the state transition process (step S2) shown in FIG. In the abnormality determination process, the abnormal state in the process of detecting the primary current is determined momentarily, but in the state transition process, it is determined whether the abnormal state in the process of detecting the primary current continues.

The determination processing unit 351 compares the abnormal state timer with the first time threshold value (step S2-1). When the abnormal state timer is equal to or greater than the first time threshold value (steps S2-1 and Yes), the determination processing unit 351 updates the abnormality determination counter (step S2-2). When the abnormal state timer is less than the first time threshold value (steps S2-1 and No), the determination processing unit 351 compares the normal state timer with the second time threshold value (step S2-4). ).

To update the abnormality determination counter, 1 is added to the abnormality determination counter as the number of abnormality determinations. After that, the determination processing unit 351 compares the updated abnormality determination counter with the number of determination graces (step S2-3). When the abnormality determination counter is equal to or greater than the number of determination graces (steps S2-3, Yes), the control process shifts to the abnormality determination process (step S5-1). When the abnormality determination counter is less than the number of determination graces (steps S2-3, No), the control process shifts to the abnormality grace process (step S4-1). Since it is determined that the abnormal state is in step 2-3, there is no means for shifting to the normal process in the control process.

When the normal state timer is less than the second time threshold value (steps S2-4, No), the determination processing unit 351 cannot determine whether the primary current detection process is in the abnormal state or the normal state. The control process shifts to the abnormality determination process (step S1), and the abnormality determination process is performed again. When the normal state timer is equal to or higher than the second time threshold value (steps S2-4, Yes), the determination processing unit 351 determines that the primary current detection process is in the normal state, and the control process proceeds to the normal process. The transition (step S3-1).

When the process shifts to the normal process, the determination processing unit 351 determines that the normal state has been determined, and executes the fourth timer process (step S3-2). After that, the determination processing unit 351 clears the abnormality determination counter (step S3-3).

In the process of step S2-3, when the abnormality determination counter is less than the number of determination graces (steps S2-3, No), this process shifts to the abnormality grace process (step S4-1). The determination processing unit 351 determines in step S2-1 that it is in an abnormal state, but since the abnormality determination counter is not equal to or greater than the number of determination graces, a fifth timer process is performed (step S4-2). After that, the determination processing unit 351 once stops the operation of the compressor 40 and restarts it (step S4-3). After that, the control process shifts to the abnormality determination process (step S1), and the abnormality determination process is performed again. When the abnormal state continues in the abnormality determination process and the state transition process again and the abnormality determination counter increases, the condition of step S2-3 is satisfied, that is, the abnormality determination counter is equal to or greater than the determination grace number (step S2). In −3, Yes), the control process shifts to the abnormality determination process (step S5). When the normal state is determined by the abnormality determination process and the state transition process again, this process shifts to the normal process. Alternatively, when the abnormality determination process and the state transition process determine that the abnormality is in the abnormal grace state, the abnormality determination counter is updated and the process proceeds to the abnormality determination process again.

When the process shifts to the abnormality determination process (steps S2-3, Yes), the determination processing unit 351 determines that the abnormal state in the primary current detection process has been determined, and executes the sixth timer process (step S5-2). ). After that, the determination processing unit 351 stops the compressor 40. Further, the determination processing unit 351 restricts the compressor 40 from being restarted (step S5-3). The determination processing unit 351 clears the abnormality determination counter (step S5-4). The determination processing unit 351 updates the number of occurrences of an abnormality and adds 1 to the number of occurrences of an abnormality as an abnormality history (step S5-5). Further, the determination processing unit 351 executes an abnormality report to the indoor unit (step S5-6) so that the indoor unit can also determine the abnormal state, and then ends the control process.

As described above, according to the present invention, it is possible to determine the abnormal state of the primary current detection process, and when the primary current detection process is in the abnormal state, the control unit 35 can stop the operation of the compressor 40. it can. This leads to protection of the operation of the compressor 40 and prevention of breaker interruption, as well as protection of the capacitor on the inverter control board 30, so that there is an effect that the product life can be prevented from being shortened and the product safety can be improved.

Further, according to the present invention, the control unit 35 performs an abnormality determination process based on a plurality of threshold values and a state transition process capable of providing a grace period for the abnormality determination, whereby an abnormal state in the primary current detection process is performed. Prevents the operation of the compressor 40 from being stopped due to false detection. Further, when the abnormal state of the primary current detection process is determined, the cause of the failure of the inverter control device 100 can be grasped by recording it as an abnormality history. Further, since the control unit 35 does not use a database or the like for the data used for the abnormality determination, the number of set values can be suppressed to a small number and the data capacity can be reduced. Therefore, it is possible to secure a data capacity for controlling the software.

In the present invention, the noise filter board 10 and the inverter control board 30 are composed of two boards. However, if the inverter control board 30 is provided, the other boards do not have to be the noise filter board 10, and the type of board may be different. Not limited. Further, if the primary current detection device such as the current transformer 11 and the control unit 35 are connected by a transmission path such as a connector and a connection line 50 or a pattern on a substrate, a plurality of substrate configurations or a single substrate is used. The present invention can also be implemented in the configuration.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 AC power supply, 10 noise filter board, 11 current transformer, 12 first connector, 20 reactor, 30 inverter control board, 31 converter section, 32 inverter section, 33 current detector section, 34 second connector, 35 control section, 40 compressor, 50 connection line, 100 inverter control device, 200 control circuit, 200a processor, 200b memory, 351 judgment processing unit, 352 storage unit, 353 signal control unit.

Claims (5)

A converter unit that converts the first alternating current, which is the alternating current supplied from the alternating current, into a direct current, and
A first current detection unit that detects a first current value, which is a current value of the first alternating current, and a first current detection unit.
An inverter unit that converts the direct current into a second alternating current and applies the second alternating current to a compressor that compresses the refrigerant.
A second current detection unit that detects a second current value, which is the current value of the second alternating current, and a second current detection unit.
A control unit that controls the inverter unit and
With
Wherein the control unit uses the first current value, said second current, compressor operation information indicating the operation frequency of the compressor, and the compressor is or stopped during operation, the The first current value is equal to or lower than the first current threshold, the second current value is equal to or higher than the compressor current threshold, the operating frequency of the compressor is equal to or higher than the operating frequency threshold, and the compressor is An inverter control device that performs an abnormality determination process for determining that an abnormality has occurred in the first current value detection process during operation. The control unit
After the abnormality determination process
A normal state in which no abnormality has occurred in the first current value detection process, an abnormality confirmation state in which it is determined that an abnormality has occurred in the first current value detection process, and the first current. The inverter control device according to claim 1, which performs a state transition process of transitioning to either an abnormal grace state in which it is not determined that an abnormality has occurred in the value detection process. The control unit
After the state transition process
In the normal state, the normal process of executing the abnormality determination process again is performed.
In the abnormality confirmation state, the abnormality confirmation process of stopping the compressor and not restarting the compressor is performed.
The inverter control device according to claim 2, wherein in the abnormal grace state, the compressor is stopped, the compressor is restarted, and the abnormal grace process is performed to execute the abnormality determination process again. The control unit
In the abnormality determination process, the normal process, the abnormality grace process, and the abnormality determination process, a timer process is performed to determine whether or not an abnormality has occurred in the first current value detection process using a timer. The inverter control device according to claim 3. The first connector that transmits the first current value and
A second connector that acquires the first current value from the first connector and transmits the first current value to the control unit.
A connection line connecting the first connector and the second connector,
With
The first current detector and the first connector are provided on the first substrate.
The inverter control device according to any one of claims 1 to 4 , wherein the inverter unit, the control unit, and the second connector are provided on a second substrate.

Images