34
The dielectric strength of the capacitor generally needs to be between 200 and
300 V. Use an AC capacitor (without polarity) in an AC circuit.
Inductive load
C
R
Power supply
Diode Method (DC Only)
The energy stored in the coil is impressed on the coil as a current by the action of
the parallel diode and converted to Joule heat by the resistance of the inductive
load. Here, the reset time will be increased even more than for the CR method.
The reverse dielectric strength of the diode must be 10 times the circuit voltage
and the forward current must be at least as high as that of the load. If the circuit
voltage is low enough, as it is for most electronic circuits, then the reverse dielec-
tric strength of the diode can be as low as 2 to 3 times the circuit voltage.
Inductive load
Power supply
Varistor (AC or DC)
The method uses the fixed voltage characteristics of a varistor to prevent high
voltages from being applied to the contacts. Here, as well, the reset time will be
increase somewhat.
Connect the varistor between the load connections for 24-V and 48-V power
supply voltages and between the contact connections for 100 to 200-V power
supply voltages.
Inductive load
Power supply
Output Surge Current
When connecting an output device having a high surge current (such as an
incandescent lamp), use one of the following circuit configurations to protect the
Output Unit.
The following circuit lets the load draw a small current (about one third the rated
current) while the output is OFF, significantly reducing the surge current.
OUT
COM
L
R
+
Wiring and Connections
Section 2-5
