Page 17 - C:\My Documents\Track N Times July 2020

TECHNICAL TRAINING

Loose Connections, Heat and Reliability

by Donald Dougherty, Senior Technician

As part of routine maintenance, the Tech Services department performs thermal or Infra-Red scans of the 480V
electrical system on our machines. These scans are useful tools detecting potential failure of components before
causing a serious breakdown and a possible machine delay.

Frequently during these scans, loose connections are found on circuit breakers, motor starters, and E3 modules.
Another one of these “Hot Spots” are the disconnects located just in front of many of the fan and auxiliary motors.

In this picture we see a couple of motor starters that have
loose connections as indicated by the bright areas. These
units appeared to have been recently replaced, as wires
had been twisted in order to get them to fit into the de-
vice being replaced.

Follow all L.O.T.O. procedures and verify zero energy
prior to servicing high voltage components!

Twisting wires while terminating them is not a good prac-
tice because a significant portion of the strands do not
make it into the device. As time goes by, these wires will
try to return to their natural state. This will eventually
result in frayed and poor connections. The best method is
to loosen the terminal screws of the device fully prior to
installation. This will provide ample room for the wires
and make it far easier to insert and connect them proper-
ly. It takes a little longer but saves much frustration when trying to get those pesky wires into the breaker or mo-
tor starter.
If you find wire ends frayed, twisted, dull looking, or otherwise heat-damaged, and have ample service loops, you
should cut off just the damaged portion of the wires, re-strip and insert the clean, un-twisted wire into the new
device. If sufficient wiring is not available, make every effort to clean, straighten and fully insert all of the exposed
wire into the device.

Bad connections are frequently the cause of “nuisance” tripping of circuit breakers. They can also cause poor over-
all machine performance, and difficulties troubleshooting intermittent problems.
If you are replacing a device in a 480V locker and still have the car locked out with zero energy verified, take a
few minutes to tighten up the other connections. The time spent is a good investment, and you will be surprised
how many loosened connections you will find. Even a quarter turn makes a big difference!
Last, but certainly not least. Remember to use a posi-lock screwriver on the Allen Bradley motor starters/devices
that have “Philips” head screws. This tool is specially designed for use with the terminal screws and provides the
positive transfer of torque when tightening the connections.
Making good solid connections is one of the best ways to keep a machine reliable, “A stitch in time saves nine…”!

PAGE 15 JULY 2020