KR102475393B1 - Apparatus for high efficiency power conversion of portable air pollution monitor - Google Patents

Abstract

The mobile air pollution monitor according to the present invention sucks air into the inside and drives the pump to discharge the sucked air to the outside along a certain line, a flowmeter that measures the flow rate of the air that is sucked in, and detects radioactivity or radiation in the air. A detection module that collects the detected radiation or radiation data and the measured flow rate, and a signal processing module that transmits the collected data, and provides DC power to the signal processing module based on the installed low-voltage battery and AC power to the pump. It includes a power module that provides.

Description

High efficiency power conversion device of mobile air pollution monitor {APPARATUS FOR HIGH EFFICIENCY POWER CONVERSION OF PORTABLE AIR POLLUTION MONITOR}

It relates to a high-efficiency power conversion device for a mobile air pollution monitor.

Air pollution monitors are used to continuously monitor radiation/radioactive substances in the air by acquiring air samples in a specific area.

In general, air pollution monitors are installed in fixed locations and monitor the air pollution level in the area in real time, but recently, a mobile air pollution monitor has been developed to increase the utilization of air pollution monitors.

Mobile air pollution monitors are put into spaces where fixed monitors are not installed in nuclear facilities and radiation-using facilities to monitor radiation/radioactive materials.

At this time, when a mobile air pollution monitor is introduced in the event of an accident, it plays an important role in ensuring the safety of workers from radiation and determining the degree of contamination at the site.

1 is an exemplary view showing a power module of a conventional mobile air pollution monitor.

As shown in FIG. 1, the mobile air pollution monitor implements the air pollution monitor on a mobile means for easy movement, and receives AC power from a commercial AC system (Electrical Utility) through a wire.

However, since low-voltage DC power is required for the electronic module of the mobile air pollution monitor and AC power is required for the pump, the mobile air pollution monitor operated by receiving power directly from the AC system requires a separate power supply for the electronic system that requires DC power. AC-DC converter (e.g. SMPS, Switching mode power supply) is required.

In this case, since the energy conversion efficiency is low because the rated power is always consumed, the operating time according to the energy consumption of the load is reduced, and the operation convenience is low because the flow control must be performed manually using the flow control valve.

As such, the existing power supply method has low utilization due to limitations in mobility of the mobile air pollution monitor, so a high-efficiency power conversion technology suitable for the mobile air pollution monitor is required.

As related prior literature, Korean Patent Registration No. 439,414 discloses "an isolated DC/DC power converter and an uninterruptible power supply using the same."

Korean registered patent 439,414

One embodiment of the present invention is to provide a power conversion device having high power conversion efficiency through a two-stage DC-AC converter composed of an insulated DC-DC converter and a full-bridge inverter by borrowing a low-voltage battery.

One embodiment of the present invention is to provide a power conversion device that automatically adjusts the flow rate according to the speed of the pump by adjusting the frequency of a single-phase inverter connected to the pump of the mobile air pollution monitor.

In addition to the above tasks, embodiments according to the present invention may be used to achieve other tasks not specifically mentioned.

A mobile air pollution monitor according to an embodiment of the present invention sucks air into the inside and drives the pump to discharge the sucked air to the outside along a certain line, a flowmeter measuring the flow rate of the sucked air, and radioactivity in the air. Alternatively, a detection module for detecting radiation, a signal processing module for collecting the detected radiation or radiation data and the measured flow rate, and transmitting the collected data, and providing DC power to the signal processing module based on the installed low-voltage battery, It includes a power module that provides AC power to the pump.

A power conversion device according to an embodiment of the present invention includes first power including a low voltage battery, a switching element connected to one end of the low voltage battery, a diode connected to the other end of the low voltage battery, and a filter connected at a point where the switching element and the diode are connected. A second power conversion module including a conversion module, an inductor connected in series to one end of the low voltage battery and the primary side of the transformer, a switch unit connected to one end of the inductor and the other terminal of the low voltage battery, and a dc-link unit connected to the secondary side of the transformer. and a power control module that performs feedback control on voltages of the first power conversion module and the second power conversion module based on the voltage of the low-voltage battery.

According to one embodiment of the present invention, the mobility of the mobile air pollution monitor is improved through miniaturization and light weight of the power module, and operation time can be secured to the maximum by power conversion efficiency.

According to one embodiment of the present invention, by borrowing a low-voltage battery and providing power to the signal processing module through a DC-DC converter, the low-frequency pulsating line is excluded, thereby reducing the size of the capacitor and improving output voltage reliability. .

According to one embodiment of the present invention, even if a flow control valve is not separately provided, the flow rate proportional to the rotational speed of the pump can be automatically controlled by controlling the rotational speed of the pump through an inverter.

1 is an exemplary view showing a power module of a conventional mobile air pollution monitor.
Figure 2 is a configuration diagram showing a mobile air pollution monitor according to an embodiment of the present invention.
3 is an exemplary diagram illustrating a power conversion module according to an embodiment of the present invention.
4 is an exemplary diagram showing an equivalent circuit of a dc-dc converter according to an embodiment of the present invention.
5 is a graph showing waveforms based on the operation of a dc-dc converter according to an embodiment of the present invention.
6 is an exemplary diagram illustrating a control algorithm according to an embodiment of the present invention.
7 is a graph showing a result according to a soft switching technique according to an embodiment of the present invention.
8 is a graph showing efficiency of a dc-dc converter according to load conditions according to an embodiment of the present invention.

With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. This invention may be embodied in many different forms and is not limited to the embodiments set forth herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of widely known known technologies, detailed descriptions thereof will be omitted.

Throughout the specification, when a certain component is said to "include", it means that it may further include other components without excluding other components unless otherwise stated.

Devices described in the present invention are composed of hardware including at least one processor, memory device, communication device, and the like, and a program to be executed in combination with the hardware is stored in a designated place. The hardware has the configuration and capability to implement the method of the present invention. The program includes instructions implementing the operating method of the present invention described with reference to the drawings, and implements the present invention in combination with hardware such as a processor and a memory device.

In this specification, “transmission or provision” may include direct transmission or provision as well as indirect transmission or provision through another device or by using a detour path.

Expressions written in the singular in this specification may be interpreted in the singular or plural unless an explicit expression such as “one” or “single” is used.

Figure 2 is a configuration diagram showing a mobile air pollution monitor according to an embodiment of the present invention.

As shown in FIG. 2, the mobile air pollution monitor 100 includes a detection module 110 for detecting radioactivity or radiation in an inhaled sample (air), a flow meter 120 for measuring the flow rate of the inhaled sample, and a sample Signal processing to process the signal generated by the single-phase induction motor-based pump 130, the detection module 110, or the flowmeter 120 to obtain , and provide the processed signal to a display device that performs data communication or interlocks module 140, and a power module 150.

The detection module 110 detects radioactivity or radiation in the air sucked in by driving the pump 130, measures the detected amount, and transfers the detected amount to the signal processing module 140.

The flow meter 120 measures the flow rate of air obtained from the detection module 110 and transmits it to the signal processing module 140, and does not include a separate valve for adjusting the flow unlike conventional devices.

The pump 130 drives air to be sucked into the detection module 110 to control the flow of air to the detection module 110, and drives the sucked air to be discharged to the outside via the flowmeter 120.

Here, the pump 130 receives AC power through the second power conversion module 153 of the power module 150, and the rotational speed of the pump is controlled by the second power conversion module 153.

The signal processing module 140 collects each radioactivity/radiation dose detected by the detection module 110 and the flow meter 120 and the flow rate of the inhaled sample, and processes them to detect only meaningful signals.

In addition, the signal processing module 140 transmits data to an external user terminal or an interlocking display device through data communication. Here, the display device may be mounted on the mobile air pollution monitor 100 to display a signal from the signal processing module 140.

The signal processing module 140 receives low voltage direct current power through the first power conversion module 152 .

The power module 150 uses a low voltage battery 151 to supply power to the signal processing module 140 and the pump 130 respectively. At this time, by borrowing the low-voltage battery 151, the mobile air pollution monitor can be independently operated even in a situation where some power lines are lost due to an accident.

The power module 150 includes a first power conversion module (DC-DC Converter, 152) and a second power conversion module (Two = stage DC-AC Converter, to supply power to the signal processing module 140 and the pump 130). 153) and a power control module (Power Converter Controller, 154).

The first power conversion module 152 is composed of a step-down converter and is connected to the signal processing module 140, and the second power conversion module is a two-stage DC composed of an isolated DC-DC converter and a full bridge inverter. -Connected with the pump 130 as an AC converter.

And the power control module 154 converts analog signals for the battery voltage (V _bat ), the DC-link voltage (V _dc ), the output voltage of the pump ( _vo ), and the output voltage (V _E ) of the signal processing module to power sensed in the circuit.

The power control module 154 performs feedback control on the DC-link voltage (V _dc ) until the battery voltage (V _bat ) decreases below the threshold value.

In detail, the power control module 154 controls a single-phase inverter connected to the pump 130 by following a preset flow rate reference value, and controls a step-down converter that supplies DC power based on the output voltage of the signal processing module 140. do.

At this time, the power control module 154 may control the speed of the pump by adjusting the applied frequency. At this time, the power control module 154 may perform variable voltage variable frequency (VVVF) control, and the flow rate reference value may be easily changed and set later by a manager.

In this way, as the power control module 154 controls the speed of the pump, it is possible to adjust the flow rate proportional to the rotational speed of the pump.

Hereinafter, configurations of power conversion modules will be described in detail with reference to FIG. 3 .

3 is an exemplary diagram illustrating a power conversion module according to an embodiment of the present invention.

As shown in FIG. 3 , the first power conversion module 152 and the second power conversion module 153 connected to the low voltage battery 151 are connected to the signal processing module 140 and the pump 130, respectively.

The first power conversion module 152 applies a step-down converter to supply power to the signal processing module 140, and the step-down converter means a buck converter, but is not necessarily limited thereto.

Here, since the buck converter has a linear relationship between control input (duty ratio) and output voltage, control performance is high, and a filter L _b exists on the output side to provide high-quality DC power to the signal processing module 140.

In the first power conversion module 152, a switching element S _b connected to one end of the low voltage battery 151 and a diode D _b connected to the other end of the low voltage battery 151 are connected to each other, and the switching element S _b ) and the diode (D _b ) are connected to the filter (L _b ).

In addition, since the first power conversion module 152 performs power conversion from a battery, which is a DC power source, a pulsation component corresponding to twice the frequency of the AC system is excluded, thereby reducing the size of the capacitor C _b and improving output voltage reliability. can make it

Meanwhile, the second power conversion module 152 is composed of an isolated DC-DC converter and a full-bridge inverter.

In detail, the isolated DC-DC converter includes a main switch (S ₁ ) and an active clamp switch (S _1a ) _a , a transformer T, a first diode (D ₁ ) and a second diode (D ₂ ), and a capacitor (C _r1 , C _r2 ).

The isolated DC-DC converter is connected in series to a transformer, a primary side of the transformer, an inductor (L _m ) connected to one end of the low voltage battery 151, one end of the inductor (L _m ) and the other end of the low voltage battery 151 It includes a switch unit connected to and a DC-link unit connected to the secondary side of the transformer.

The switch unit includes a main switch (S ₁ ) and an active clamp switch (S _1a ), and the DC-link unit includes a first diode (D ₁ ) and a second diode (D ₂ ) and is connected to the dc-dc transformer.

Here, the main switch (S ₁ ) and the active clamp switch (S _1a ) operate complementaryly, and when converted to an active state, a zero voltage switching operation is performed to eliminate switching loss.

In addition, the first diode (D ₁ ) and the second diode (D ₂ ) are zero current switching (ZCS) through a resonance circuit composed of leakage inductance (L _lk ) and capacitors (C _r1 ) and (C _r2 ) ) to achieve turn-off.

This mitigates the loss of diodes _D1 and _D2 's reverse recovery time issues.

The isolated DC-DC converter of this configuration serves to increase the low voltage of the low voltage battery 151 by the input voltage level of the full bridge inverter connected to the transformer.

And the full-bridge inverter converts high-voltage V _dc into AC power so that the pump can be driven.

And in the case of a full-bridge inverter directly connected to the pump 130, it consists of four switches (S ₂ , S ₃ , S ₄ , S ₅ ) and performs a bipolar switching operation.

Here, the bipolar switching operation improves stability and reliability of the system because there is no common mode noise unlike the unipolar switching method.

At this time, the rotation speed of the pump may be controlled according to the frequency applied to the full-bridge inverter by the power control module 154 .

Since the measured value of the flow rate is proportional to the rotational speed of the pump, the flow rate can be adjusted by controlling the rotational speed of the pump. In other words, even if a flow control valve is not separately provided, the flow rate can be controlled by controlling the number of revolutions of the pump by an inverter.

Since the rotational speed of the pump and the measured value of the flow rate are proportional, it can automatically act as a flow control valve by controlling the rotational speed of the pump.

As such, the first power conversion module 152 and the second power conversion module 153 connected in parallel with the low voltage battery 151 supply power to the signal processing module 140 and the pump 130, respectively.

4 is an exemplary diagram showing an equivalent circuit of a dc-dc converter according to an embodiment of the present invention, and FIG. 5 is a graph showing waveforms based on the operation of the dc-dc converter according to an embodiment of the present invention.

As shown in FIG. 4, the main switch (S ₁ ) and the active clamp switch (S _1a ) of the isolated dc-dc converter operate complementaryly, and four detailed operation modes exist during one switching cycle.

Here, the detailed operation modes are the same as mode1, mode2, mode3, and mode4, the current i _s before mode1 is 0, and no current flows in the secondary side of transformer T.

Mode 1 starts when the main switch (S ₁ ) turns on at t ₀ , and when the main switch (S ₁ ) is turned on, since the current flows through the reverse diode of the switch S ₁ , both ends of the main switch (S ₁ ) The voltage applied to is turned on in a zero voltage state as 0.

Since it is turned on at zero voltage, switching loss is reduced.

And in Mode 1, when power is delivered from the battery to the DC-link side through the transformer (T), the current i _s flows through the diode (D ₁ ) on the secondary side of the transformer (T), and the leakage inductance (L _lk ) and Resonance occurs due to the resonance capacitors C _r1 and C _r2 .

Mode 2 starts when the secondary side current (i _s ) becomes 0 at t ₁ and resonance ends. Since the current (i _s ) becomes 0 while the diode (D ₁ ) is conducting, in Mode 2, the diode (D ₁ ) is turned off in a zero current state. Therefore, losses due to diode reverse recovery time problems are reduced.

Mode 3 starts when the main switch (S ₁ ) is turned off and the active clamp switch (S _1a ) is turned on, and the current flowing through the switch at the time (t ₂ ) when the active clamp switch (S _1a ) is turned on is Since the current flows through the diode in the reverse direction of the active clamp switch S _1a , the active clamp switch S _1a is also turned on in the zero voltage state.

In Mode 3, resonance occurs as in Mode 1, and the energy stored in the active clamp capacitor is transferred to the DC-link side through the transformer (T) and diode (D ₂ ), and the leakage inductance (L _lk ) and the resonance capacitor (C _r1 , C _r2 ) causes a second resonance.

Mode 4 starts when the secondary side current (i _s ) becomes 0, and as in Mode 2, the diode (D ₂ ) is turned off in a zero current state. Therefore, the diode (D ₂ ) also reduces the loss due to the diode's reverse recovery time problem.

And FIG. 5 shows waveforms for the four modes of FIG. 4, where t0 to t1 indicates Mode 1, t1 to t2 indicates Mode 2, t2 to t3 indicates Mode 3, and t3 to t4 indicates Mode 4.

Hereinafter, a configuration in which the flow rate is adjusted according to the control of the power module 150 without the flow control valve will be described in detail using FIG. 6 .

6 is an exemplary diagram illustrating a control algorithm according to an embodiment of the present invention.

As shown in FIG. 6, the power module 150 includes the battery voltage (V _bat ), the DC-link voltage (V _dc ), the output voltage ( _vo ) of the pump 130 and the output of the signal processing module 140. The analog signal for the voltage (V _E ) is sensed in the power circuit.

For reference, in FIG. 6, V _dc ^* is the reference value of the DC-link voltage, f ₀ ^* is the output The reference frequency of the voltage ( _vo ), _VE ^* is the reference value of the output voltage of the signal processing module 140, v _o ^* is the reference value of the output voltage of the pump 130, f ^* represents the reference flow rate.

Here, the flow rate f can be obtained from the flow meter 120 or the signal processing module 140 through a digital communication method such as serial communication or Ethernet communication.

In general, since air pollution monitors measure real-time radioactivity measurement values and flow rates, the flow rate (f) value can be shared according to the connection between each component.

The power module 150 performs feedback control on the DC-link voltage supplying power to the pump 130 until the voltage of the low-voltage battery 151 decreases below a threshold value.

In addition, the power module 150 performs feedback control on the output voltage of the step-down converter that supplies the serial current to the signal processing module 140.

At this time, as the power control module 154 that performs the control, for example, a proportional-integral controller (PI controller) may be used.

In addition, the power module 150 performs control based on a variable voltage variable frequency (VVVF) algorithm for the single-phase inverter connected to the pump.

In other words, the power module 150 may adjust the flow rate by controlling the speed of the pump 130 by adjusting the frequency applied to the inverter.

In detail, the power module 150 adjusts the rotational speed of the pump by following a preset flow rate reference value based on a variable voltage variable frequency algorithm.

For example, when using an inverter method, the power consumption of the pump is proportional to the third power of the pump rotational speed, so the following relational expression can be obtained.

[Equation 1]

P ₁ : P ₂ = N ₁ ³ : N ₂ ³

Here, P ₁ is the rated power consumption, P ₂ is the power consumption when an inverter is applied, N ₁ is the rated rotational speed, and N ₂ is the pump rotational speed under inverter control.

When power is received directly from the existing alternating current system, the rated power corresponding to P ₁ is always consumed, whereas when the inverter method is used as in the present invention, the frequency of the output voltage can be adjusted, so that the rotation of the pump 130 number can be controlled. Accordingly, in the case of the pump 130 having a rated frequency of 60 Hz, an average energy saving of 20% when operating at a frequency of 55 Hz and an average of 70% when operating at 40 Hz is possible.

As such, according to the power conversion module proposed in the present invention, high power efficiency is obtained for a limited energy source such as a battery.

Hereinafter, power efficiency will be confirmed using FIGS. 7 and 8 .

7 is a graph showing results according to a soft switching technique according to an embodiment of the present invention, and FIG. 8 is a graph showing efficiency of a dc-dc step according to a load condition according to an embodiment of the present invention.

(a) of FIG. 7 shows values of v and i for a state in which the main switch S ₁ is turned on, and (b) shows values of v and i for a state in which the diode D ₁ is turned off.

Looking at (a) of FIG. 7, it can be seen that a zero voltage switching operation is performed, and looking at (b), the diode D ₁ is turned off while the current is 0, and the zero current switching ( Zero Current Switching (ZCS) turn-off is achieved.

8, it can be seen that the maximum efficiency of the DC-DC converter according to the load condition is 98.1%.

Table 1 also shows the output power and flow rate of the inverter using the VVVF algorithm.

As such, it can be seen that the soft switching technology of the dc-dc stage and the VVVF performance of the inverter stage have high efficiency characteristics.

Output voltage/frequency Output power, P ₀ Flow rate, f 120V/27.5Hz 94.5W 26.5L/min 150V/37.2Hz 119W 36L/min 180V/47Hz 154W 43L/min 200V/53Hz 190W 47.4L/min 220V/60Hz 240W 52L/min

As described above, according to the present invention, as power is supplied to the signal processing module through a DC-DC converter by borrowing a low-voltage battery, the low-frequency pulsating line is excluded, thereby reducing the size of the capacitor and improving output voltage reliability.

According to the present invention, the flow rate proportional to the rotational speed of the pump can be automatically controlled by controlling the rotational speed of the pump through an inverter even if the flow rate control valve is not separately provided.

A program for executing a method according to an embodiment of the present invention may be recorded in a computer readable recording medium.

Computer readable media may include program instructions, data files, data structures, etc. alone or in combination. The medium may be specially designed and constructed or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and ROMs, RAMs, flash memories, and the like. A hardware device specially configured to store and execute the same program instructions is included. Here, the medium may be a transmission medium such as light, a metal wire, or a waveguide that transmits a signal designating a program command or data structure. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter or the like as well as machine language codes such as those produced by a compiler.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also made according to the present invention. falls within the scope of the rights of

Claims (11)

A pump that drives air to be sucked into the inside and discharged to the outside along a certain line;
A flow meter for measuring the flow rate of the air to be sucked in;
A detection module for detecting radioactivity or radiation in the air;
A signal processing module that collects the detected radioactivity or radiation data and the measured flow rate and delivers the collected data, and
A power module providing DC power to the signal processing module and AC power to the pump based on the installed low-voltage battery
including,
The power module includes a two-stage dc-ac converter that boosts the voltage of the low-voltage battery, converts the boosted voltage into AC power, and provides it to the pump;
The two-stage DC-AC converter includes an isolated DC-DC converter and a full-bridge inverter,
The isolated DC-DC converter includes an inductor connected to one end of the low-voltage battery, a main switch and an active clamp switch connected to one end of the inductor and the other end of the low-voltage battery, and a first diode connected to the secondary side of the transformer. Including a DC -link part composed of 2 diodes,
The isolated DC-DC converter performs a zero voltage switching operation when the main switch and the active clamp switch operate complementary to each other to turn on, and when the first diode and the second diode are turned off, zero A mobile air pollution monitor that boosts the voltage of the low-voltage battery to the operating voltage of the full-bridge inverter while performing a current switching operation.
In paragraph 1,
The power module,
a step-down converter for stepping down the voltage of the low-voltage battery and providing DC power to the signal processing module; and
A mobile air pollution monitor comprising a control module that senses the voltage of the low-voltage battery and performs feedback control on the voltage of the DC-DC converter or step-down converter until the sensed value decreases below a threshold value.
In paragraph 2,
The control module,
A mobile air pollution monitor that controls the frequency applied to the full-bridge inverter through variable voltage variable frequency (VVVF) control that follows a predetermined flow rate reference value based on the measured flow rate.
In paragraph 2,
The step-down converter,
A switching element connected to one end of the low-voltage battery and a diode connected to the other end of the low-voltage battery are connected to each other, and a filter is included at a point where the switching element and the diode are connected;
A mobile air pollution monitor providing DC power to the signal processing module through the filter.
delete delete In paragraph 1,
The full bridge inverter,
A mobile air pollution monitoring system in which 4 switches perform bipolar switching operation.
low voltage battery,
A first power conversion module including a switching element connected to one end of the low-voltage battery, a diode connected to the other end of the low-voltage battery, and a filter connected at a point where the switching element and the diode are connected;
A second power conversion module comprising an inductor connected in series to one end of the low voltage battery and a primary side of the transformer, a switch unit connected to one end of the inductor and the other terminal of the low voltage battery, and a dc-link unit connected to the secondary side of the transformer. , and
A power control module performing feedback control on voltages of the first power conversion module and the second power conversion module based on the voltage of the low voltage battery.
including,
The switch unit includes a main switch and an active clamp switch,
The dc-link unit includes a first diode and a second diode,
When the main switch and the active clamp switch operate complementary to each other to perform a zero voltage switching operation when turned on, and to perform a zero current switching operation when the first diode and the second diode are turned off, the full bridge inverter A power conversion device for boosting the voltage of the low-voltage battery to an operating voltage of
In paragraph 8,
The first power conversion module steps down the voltage of the low-voltage battery to deliver DC power to a signal processing device;
The second power conversion module boosts the voltage of the low-voltage battery, converts the boosted voltage into AC power, and transmits it to a pump.
In paragraph 9,
The power control module,
Collecting the flow rate by the pump,
A power converter for controlling the second power conversion module to adjust the frequency applied to the pump through variable voltage variable frequency (VVVF) control that follows a predetermined flow rate reference value based on the collected flow rate. .
In paragraph 10,
The power control module,
The power conversion device for controlling the second power conversion module to calculate power consumption according to the rotational speed of the pump to follow the flow rate reference value and to apply a frequency equal to the calculated power consumption.

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