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제     목 EchemNews 53: Current Density Distribution Measurement for Fuel Cell
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EChemNews No. 53 | 2007.6.12               주요내용: current density distribution measurement for fuel cell
 


    연료전지에서 전류분포를 측정할 수 있는 시스템에 대한 안내입니다.

    모델은 Current Scan High resolution (전류분포측정) 및 Current Scan Linear(전류분포 및 온도 분포 측정) 두가지입니다.

     

    User interface CurrentVIEW

    The user interface CurrentVIEW is easy to use and self-explanatory. It allows:

    + single and continuous measurements

    + visualization in 2D, 3D and as values

    + saving data as text files in spreadsheet format

    + saving data as pictures in jpg format

    + saving and reviewing of data streams.

     

    Also a dll can be introduced into an existing environment.

    Current Scan Lin

    Current density distribution and tempera-ture distribution measurement in fuel cell stacks.

    + detailed analysis of flow fields

    + detailed analysis of materials

    + optimization of fuel cells

    + fault diagnostics in fuel cells

    + resolution of about 7 x 7 mm

    + current range up to 2.5 A/cm²

    + temperature range up to 180°C

    + standard devices are available

    + special designs on request

    With the current scan lin, the current density distribution can be measured with a high resolution and it offers a linear complexity. So it is also applicable in large fuel cells. It is connected via USB to any computer and easy to use.

    In a fuel cell the locale conditions differ which leads to an inhomogeneous mass conversion re-sulting in an inhomogeneous current production. One of the keys to a deeper understanding of PEM fuel cells, DMFC and other electrochemical cells is the measurement of the current density distribu-tion. In large fuel cells this is important for a save and reliable operation as well as a high lifetime. Up to now the high complexity was a major problem.

    Application

    The device of type ?current scan lin“ shown on the first page has a resolution of 17 x 19 meas-urement cells and an active area of 150cm². It will be placed between the two half’s of a bipolar plate at an arbitrary place in the stack. The pictures be-low show a typical current distribution and a tem-perature distribution.

     

    Measurement Principle

    The permeability of a magnetic material is depend-ing on the magnetization and the temperature. The current Im, which has to be measured, flows through the coil L1 and causes a magnetization of the magnetic matrial (dashed line). An alter-nating current i(t), feed into L2, induces a voltage u(t) into the coil L3. This voltage depends upon the permeability of the magnetic material (dashed line). So it depends upon the current Im.

     

    The single measurement cells are conducted in series in rows and columns. This is shown in the following picture for example at 3 x 3 measurement cells.

    The alter-nating cur-rents i1(t) to in(t) will be feed con-secutively into the matrix to activate the rows 1 to n. At the col-umns the voltages u1(t) to un(t) will be acquired as measurement signals. The measurement cells which are not activated by an alternating current deliver nothing to the measure-ment signal. In general n² measurement points can be reached with 2 n wire pairs. So the complexity for connection wires, control and evaluation elec-tronics is linear! This way measurement devices for arbitrary large fuel cells can be build easily.

     

    Available standard devices

     

    The picture shows the standard devices Test25,

     

    Test50 and Test100 complete with 25cm², 50cm² and 100cm² single cell fuel cell and resistors to heat up the fuel cells.

     

    Also available is the shown universal design. Out-side the active area with measurement cells and a restricted area for the conductor paths, arbitrary holes may be drilled. Different electronics (pic-

    ture beside) which are able to drive up to 48 rows and 48 columns are available. They also differ in the number of inde-pendent input channels, influencing the speed.

     

    Custom made device

     

    The above picture shows custom made sensor plate with active area 800cm² and 46 x 36 measurement cells. Nearly any design is possible. The minimal size of the measurement cells is 7 x 7mm. The maximal size is restricted by the current they have to meas-ure and should not be much larger.

     

     

    Current Scan High Res

    Current density distribution measurement in fuel cells with high resolution.

    + detailed analysis of flow fields

    + detailed analysis of materials

    + optimization of fuel cells

    + fault diagnostics in fuel cells

    + resolution of about 1 x 1 mm

    + current range up to 2A/cm²

    + standard devices are available

    + special designs on request

    With the current scan high res, the cur-rent density distribution can be measured with a very high resolution. It is connected via USB to any computer and easy to use.

    In a fuel cell the locale conditions differ which leads to an inhomogeneous mass conversion re-sulting in an inhomogeneous current production. One of the keys to a deeper understanding of PEM fuel cells, DMFC and other electrochemical cells is the measurement of the current density distribu-tion. This is important for a save and reliable op-eration as well as a high lifetime.

    Application

     

    The device of type ?current scan high res“ shown on the first page has a resolution of 32 x 36 meas-urement cells and an active area of 25cm². The picture below shows a sectional view of the setup.

    The gas diffusion layer will be placed directly on the segments. The channels of the flow field are milled between the segments. The device is usable as anode or cathode of a single cell.

    The picture below shows a typical current distribution.

     

    Measurement Principle

    The devices of this series use a segmented electrode with segments of about 1mm² connected to single electronic loads trough a multilayered printed circuit board.

    An electronic load, connected to a segment, is shown in the following picture.

     

    The electronic loads are realized with operational amplifiers which work as current source or sink. So the device can be used on the anode or optionally on the cathode side. The voltage after the resistor R is feed back to the operational amplifier OP. So the voltage Uout at the segment is held constant at the voltage of the input Uin. The voltage Um is measured and the current which flows out of the segment or into the segment is calculated with help of the formula

     

    Many of these electronic loads are connected with a multiplexer which switches the voltages Um to an Analog-to-Digital converter. The inputs are connected together and the voltage Uin is provided by an Digital-to-Analog converter. This is shown in the following picture.

    The size of the device is limited, because the complexity grows quadratically with the size or resolution. For large fuel cells there is another principle available which is realized in the devices of the series “current scan lin”.

     

    Available standard device

    The available standard device is designed for a 25cm² ECF 25 single cell fuel cell from Electro Chem. It has 32 x 36 segments of 1.47 x 1.64mm on a base plate. 18 boards with 64 electronic loads and a data-acquisition system with USB interface are pluged into the base plate. The power supply is in a 19” housing.

    Custom made devices

    Nearly any custom made design is possible. The minimal size of the measurement cells is 1 x 1mm. The maximal size is restricted by the current the operational amplifiers are able to deliver. But be-cause of the quadratic complexity the devices of the series ”current scan high res” are restricted to small devices. For large fuel cells or fuel cell stacks please ask for a device of the series “current scan lin”.

     

    Specification

     

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WonATech 취급품목

 

수입품

  • Electrochemical Analyzer
  • Electrochemical Impedance Spectroscopy
  • Fuel Cell Monitor (Impedance System for Fuel cell at High Current)
  • Electrochemical Quartz Crystal Microbalance
  • Scanning ElectroChemical Microscope
  • DC Corrosion Measurement System
  • Portable(Field) Electorchemical Analyzer
  • Electronic Load
  • SCC(Stress corrosion cracking) measurement system
  • Autoclave
  • CER(Contact Electric Resistance) Measurement system
  • Electrochemical Accessories
  • Current Distribution Measurement System for fuel Cell
  • Fuel cell station

생산품

  • Automatic Battery Charge/Discharge Test System
  • Fuel Cell Test Station
  • Electronic load for fuel cell test
  • Multi-channel Potentiostat/Galvanostat
  • Potentiostat/Galvanostat
  • Portable Potentiostat/Galvanostat
  • EIS analysis software
     

    Copyright WonATech Co.,Ltd 2006. All rights reserved.
    http://www.wonatech.com sales@wonatech.com P: 02)578-6516,  F: 02)576-2635

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