37 z vacon connectionsTel. +358 (0)201 2121 • Fax +358 (0)201 21220544.6 Reducing Current Surges and Voltage TransientsInrush currents to coils of magnetic contactors, relays, and solenoids associated with or near thedrive can induce high current spikes in the power and control wiring, causing faulty operation. If thisoccurs, a snubber network consisting of a series resistor and capacitor for AC loads, or a freewheelingor flyback diode for DC loads, can be placed across the relay coil to prevent this condition.The following component values should be used for 115 VAC or 230 VAC relays or solenoids.Figure 18: Connection Diagram for AC and DC Relay Coils and SolenoidsFor magnetic contactors, relays, and solenoids energized from a DC source, use a free-wheeling diode ofthe high-speed, fast-recovery type. Connect the diode across the coil as shown above in Figure 18. Thediode current and voltage should be selected using the following formulae:For Main Circuit Contactors and SolenoidsC = 0.2 MFD, 500 VDC R = 500 5 WattsFor Auxiliary Control Circuit RelaysC = 0.1 MFD, 500 VDC R = 200 2 WattsRC TypeSnubberACCoil CoilDC+-FreewheelingDiodeDiode Current Rating (A) Coil Capacity (VA)Rated Voltage of Coil (V)Rated Voltage of Coil (V) x 2Diode Voltage Rating==
