iTMOV Varistor Application Examples
The application examples below show how the indicator lead on the
iTMOV can be used to indicate that the thermal element has been
opened. This signifies that the circuit is no longer protected from
transients by the MOV.
Application Example 1 (Figure 1)
In this case, the LED is normally on, and is off when the thermal
element opens.
Application Example 2 (Figure 2)
This circuit utilizes an optocoupler to provide galvanic isolations
between the iTMOV varistor and the indicating or alarm circuitry.
Application Example 3 (Figure 3)
This circuit illustrates the use of the monitoring lead of the iTMOV
varistor to ensure that equipment is only operated when overvoltage
protection present. In normal operation the load switch relay solenoid is
powered via the indicator lead of the iTMOV varistor. In the event of the
thermal element being activated, the relay will de-activate, cutting power
to the protected circuit and the fault LED will illuminate.
Please note: Indicator circuits are provided as a guideline only.
Verification of actual indicator circuitry is the responsibility of the end
user. Component values selected must be appropriate for the specific
AC line voltage service and application.
R
LED
Line Fuse
iTMOV Varistor
Neutral
Line
Figure 1. Application example 1
R
Line Fuse
iTMOV Varistor
Neutral
Figure 2. Application example 2
AC OPTOCOUPLER
TO STATUS
ANNUNCIATOR
LIGHT/ALARM
Line Fuse
iTMOV Varistor
Neutral
Figure 3. Application example 3
Fault LED
(Normallyoff)
"Load Powered"
neon lamp
Load Switch Relay
(loss of protection)
R
To Protected Circuit
To Protected Circuit To Protected Circuit
Line
Line
