74
Varistor Products
©2009 Littelfuse, Inc.
Revision: November 5, 2009
TMOV
®
and
i TMOV
®
Varistor Series
Radial Lead Varistors > TMOV
®
and iTMOV
®
Series
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/tmov.html for current information.
1
2
3
3
2
1
Thermal
Fuse
Element
MOV
Thermal
Fuse
Element
MOV
Monitor Lead
Monitor Lead
Lead Configurations
TMOV
®
Varistor
iTMOV
®
Varistor
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.
R
LED
Line Fuse
iTMOV Varistor
Neutral
Line
To Protected Circuit
Note: MOVs are non-polarized passive elements
Application Example 1
In this case, the LED is normally on, and is off when the
thermal element opens.
Application Example 2
This circuit utilizes an optocoupler to provide
galvanic isolations between the iTMOV
®
varistor
and the indicating or alarm circuitry.
Application Example 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.
R
Line Fuse
iTMOV Varistor
Neutral
AC OPTOCOUPLER
TO STATUS
ANNUNCIATOR
LIGHT/ALARM
To Protected Circuit
Line
Line Fuse
iTMOV Varistor
Neutral
Fault LED
(Normallyoff)
"Load Powered"
neon lamp
Load Switch Relay
(loss of protection)
R
To Protected Circuit
Line
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.