Vacon 50X, User Manual

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37 vacon connections
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4
4.6 Reducing Current Surges and Voltage Transients
Inrush currents to coils of magnetic contactors, relays, and solenoids associated with or near the
drive can induce high current spikes in the power and control wiring, causing faulty operation. If this
occurs, a snubber network consisting of a series resistor and capacitor for AC loads, or a freewheeling
or 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 Solenoids
For magnetic contactors, relays, and solenoids energized from a DC source, use a free-wheeling diode of
the high-speed, fast-recovery type. Connect the diode across the coil as shown above in Figure 18. The
diode current and voltage should be selected using the following formulae:
For Main Circuit Contactors and Solenoids
C = 0.2 MFD, 500 VDC R = 500 5 Watts For Auxiliary Control Circuit Relays
C = 0.1 MFD, 500 VDC R = 200 2 Watts
RC Type
Snubber
AC
Coil Coil
DC
+
-
Freewheeling
Diode
Diode Current Rating (A)
Coil Capacity (VA)
Rated Voltage of Coil (V)
Rated Voltage of Coil (V) x 2 Diode Voltage Rating
=
=