The contact is the most important part of the relay, and the working reliability of the contact is affected by the contact material, the contact voltage and the current (especially the connection and disconnection voltage, the current waveform), the type of load, the pass - off ratio, and the environmental conditions. Contact voltage: inductive load will generate very high reverse voltage. The higher the voltage, the greater the energy, accelerating the contact corrosion and metal transfer. Contact current: the current at the closed and disconnected contacts has great influence on the contacts. When the load is a motor or a headlamp, the impact current of the closure is large, the loss of the contact and the amount of metal transfer will be greater. The contact transfer will result in the contact failure of the contact. The confirmation test should be carried out. 1, contact protection reverse voltage: disconnect the relay coil series circuit or electric motor, electromagnet and other inductive load must use the diode and other surge absorption to protect the contact. When the inductive load is cut off, the reverse voltage of hundreds to thousands of V will be generated, which will aggravate the electric corrosion and reduce the life of the contact. In addition, when the inductive current is less than 1A, the arc produced by the reverse voltage makes the inner coil of the relay and the organic gas of the plastic volatilized, and the acidification and carbonization are generated on the contact points, resulting in bad contact. Contact metal transfer: contact metal transfer is the transfer of contact material in a single direction by direct current. With the addition of the breaking times, the anode contact produces pits, the cathode contacts are raised, and the bumps and pits are easy to produce mechanical self locking to cause contact adhesion. Anti transfer contact materials or protective circuits should be selected. Contact protection absorption circuit: using contact protection element or protection circuit can reverse the reverse voltage, but if it is not used correctly, it will produce negative effects.
Fuda alloy， the partner of meishuo-the china Automotive Relay manufacturer。