The Research Of Current Skin Effect On Proton Exchange Membrane Fuel Cell

The skin effect is the electromagnetic phenomenon caused by alternate current, which makes the electron going to the surface of the conductor, so it makes the current density denser at the edge while it is sparser in the center.The major obstacle for the PEM (Proton Exchange Membrane) fuel cell commercialization is the durability. Especially during the dynamic status, attenuation of cell performance becomes stronger. When the outputs changed rapidly, according to Fourier transformation, the current is actually the vector sum of one steady direct current component and numerous cosine alternating current components, and in Maxwell theory, sine alternate current (have the different phase position to cosine current) can cause skin effect in conductor. Because all the high frequency components are cosine alternating currents and the alternate current can cause skin effect in the conductor, so it's confirmed that when the direct triangle pulse current passes through the conductor, skin effect can be produced.In this paper, the polar plates of graphite and stainless steel have been researched, finding the current density distribution under the direct impulse wave and direct sine wave currents. Using the coil probe to detects the induced electromotive force (E M F) in the materials. At last, the current density calculated by the current integral formula, and the regularity of current density distribution is found.The test divided into two parts:the direct impulse wave and direct sine wave flow through the graphite and stainless steel collection plate materials independently. The results found that:(1)When the two kinds of currents flow through the graphite and stainless steel collection plate materials, the current density increased from the center to outward;(2) The higher the frequency of currents, the more obvious of skin effect, the more nonuniform current density distribution;(3) The greater the amplitude of high frequency currents, the more obvious of skin effect and the more nonuniform of current density distribution; (4) In the same conditions, the more nonuniform of current density distribution in stainless steel material is more than that of in graphite material.Therefore, in the design and use of fuel cells, it must be considered the current density distribution caused by skin effect, and then influences the cells' performance and life.