# bypass which improves the ability to resist surging of relay contact

Posted on Feb 4, 2014

Generally, during power up of the apparatus, the capacitor is the main reason that surge current emerges, the synoptic diagram of the principle is shown in Fig. 1. Have it in the picture after K1 closes, the intersection of capacitor and C begin, charge, regard perfect condition direct current power supply can offer enough large electric current a

nd internal resistance for zero as direct current power supply, the intersection of switch and K1 and wire that connect, K1 contact resistance is zero, the wire thread is hindered as zero, At the time of condenser charge, the surge current produced can carry on approximate calculation according to formula 1. Though the electric capacity electric apparatus ESL has certain inhibit function on inputting the surge current, but inductance quantity is minor, inhibit function is minor, can neglect. Usually the capacitor is ESR smaller, for example, measure under 100kHz, ESR of the liquid tantalum capacitor is generally several hundred milliohms, polyester capacitive ESR is generally dozens of milliohms, and the pottery capacitive FSR is generally several milliohms. So instant in the power up of capacitor, will produce the greater surge current. The above is the analysis that the surge current for the capacitor and produced at the time of power up carries on, if other apparatuses or components and parts have similar characteristics with the capacitor at the time of power up, will produce the greater surge current too, for instance, the storage battery will produce more than one hundred amperes of surge current under charging the form to read too. After the driving signal is put through, the power up of coil, the sucking of electrical relay is combined into the mechanical movement course, dwell time 5- 15ms. Surging bypass...

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