Coil Configuration The induced voltage of the relay coil can be limited using circuit technology by disconnecting the coil current (electromagnetic compatibility; protection of the control electronics). As the cut-off behavior can change adversely, particularly in simple diode configurations, the selection of configuration should be adapted to the application. Certain coil configurations can especially reduce the endurance. The configuration using a Zener diode proves to be particularly suitable. Coil suppression circuit Circuit to reduce the inductive switch off voltage peak of the relay coil (EMC protection, switch off voltage peak ). Note that most of the circuits reduce the armature release speed which can decrease the relay lifetime. From the various solutions, the use of Zener diode is particularly suitable (see figure above). Further information is available on request. Diode coil configuration A diode limits a cut-off spike to approx. 0.7 V. However, the energy caused by the flow of current increases the release time. Since some relay families can be reversed in their direction of movement by the armature returning to the rest position due to the current flow increasing once more. This c an cause the make contact to close again under certain circumstances and can lead to a increased arc duration. This can result in a considerable reduction in the endurance. For this reason, a diode configuration is not recommended for higher loads. Electrostatic screening Screening plate between coil and contact to provide electrostatic screening in reed relays. Energization, energizing value Sending a current through the relay coil to generate a magnetic field to move the armature. The energizing value is the product of the coil current and the number of wire turns of the coil. Parallel resistance The parallel resistance should be so rated that its value corresponds to approx. six tim es the coil resistance. In this way, the cut-off spike is limited to six times the operating voltage. At a nominal voltage of 12 V, the spike is approx. 80 V. Zener diode coil configuration A Zener diode limits the voltage peak across the coil and power source. This Zener diode control (see figure) is most advantageous since it does not significantly reduce the endurance. The Zener voltage of the Zener diode is rated at two or three times the level of the nominal voltage of the relay. At a nominal voltage of 12 V, 27 V Zener diodes are normally used. |