Installing Additional Suppression; Installing Suppression At The Power Supply; Installing Suppression For Devices In An Enclosure; Periodic Inspection And Replacement Of Movs - GE VersaMax Manual

2

Installing Additional Suppression

For agency compliance, external MOV suppression is required from both the positive and
negative input to frame ground or at the power line input of a system enclosure (see
below). The axial-leaded ZA series of MOVs from Harris is often used. The 20mm size,
model V36ZA80 rated at 160 joules is sufficient for both supply types. The MOV should
be able to handle most line transients. Measurement of actual transients may be required in
extreme cases to decide what MOV is best.

Installing Suppression at the Power Supply

Typical power and ground connections are shown below.
DC: +
DC: -
or or
AC: H
AC: N

Installing Suppression for Devices in an Enclosure

For a group of devices installed in an enclosure, MOVs can be installed at the point where
the power lines enter the enclosure. Ideally, MOVs should be used at each cabinet in the
system for maximum protection. The following illustration shows suppression on both
power lines and a communications bus entering an enclosure.
Enclosure
Power
to
Modules
Short Length of
Communications
Bus Cable

Periodic Inspection and Replacement of MOVs

MOVs do a good job of absorbing transients on communications, control, and power lines,
provided the total energy of those transients does not exceed the rating of the device.
However, if the energy of the transient exceeds the rating of the device, the MOV may be
either damaged or destroyed. This failure may not be visibly or electrically evident. MOVs
should be regularly inspected for signs of damage to assure continued protection against
transients. For some applications, periodic replacement of critical MOVs is recommended,
even if they do not show signs of damage.
2-14 VersaMax® Modules, Power Supplies, and Carriers User's Manual – March 2003 GFK-1504K