Page 8 - Issue 3 2023

NEWS

How a few good test tools saved sporadic fault or the motor is tripping
out because it’s pulling too many amps
expensive motor replacements or it doesn’t have enough resistance,
you have to investigate further,” he
adds.
Because the machines run 24 hours
ew things are as disposable as paper towels. But the next time you nonchalantly a day, troubleshooting is done with the
toss away (or compost) a paper towel, keep in mind that there’s a lot more to machines running if at all possible. “If
Fit than meets the eye. Paper towels are manufactured through a finely tuned it’s a smaller component, a lot of times
system of electrical, electronic and mechanical components. Coordinating all those you can isolate it and just fix that one
components and keeping them running productively 24 hours a day is challenging to say area while the machines are running,”
the least. Rob notes.
Rob, an electrical engineer at an American paper mill, knows those challenges well. The environment in a pulp and paper
He’s responsible for electrical and electronic issues related to two large tissue machines mill is not easy on tools or people. It’s
that generate several tons of paper towels an hour. wet, steamy and dusty. Technicians have
Installing and troubleshooting those systems was great preparation for the to climb ladders to reach some of the
gargantuan tissue machines he works on today. Each machine is run by coordinated equipment so tools need to be easy to
drive systems with about 12 drives and motors plus auxiliary equipment that adds carry, rugged and above all reliable.
another 100 motors or so to each machine. The motors range from a small 375 W unit Rob has found that Fluke tools
to a 4500 kW behemoth. perform well in that environment.
“I troubleshoot everything from variable frequency drives (VFDs) and motors to He was first introduced to Fluke by
programmable logic controllers (PLCs) and instrumentation. We’ve got a lot of valves, a his father, who is an electrician for a
lot of instrument sensors, and a lot of coordinated drive systems,” Rob says. hydroelectric power company. Today the
On any given day Rob gets trouble calls ranging from nuisance issues to potential list of Fluke test tools Rob uses reads like
catastrophic failures. a mini catalogue – about 18 items at last
count.
Starting with the basics
Motor and drive problems are the most common calls. “Normally your first check is to Responding to sensitive VFDs
do an insulation check on the motor and wiring to make sure it’s not shorting to ground One tool Rob is almost never without is
somewhere,” Rob explains. “If the insulation check is reading low, that’s usually a dead his Fluke 87V DMM. Whether he’s doing
giveaway that it’s time to change out the motor.” first-line troubleshooting or delving
Sometimes, however, the problems are a bit more complicated. “If you’ve got a down into more complex problems, the
87V is usually the first tool he turns to. A
case in point: one night a VFD-controlled
motor kept tripping. Technicians were
concerned that they’d have to replace
the motor. That would have taken about
eight hours plus another two hours to
restart the machine.
“Using my trusty Fluke 87V, I was
able to determine that the motor was
fine, but the real issue was a 5-volt
instrument supply module,” Rob recalls.
“Older VFDs have a very low tolerance
for these modules. The 87V was reading
4,77 V on the supply module. The lowest
possible voltage this drive can handle
from the supply is 4,8 V.” The solution
was to replace the communication
power supply board which cost about
$300 and took just 15 minutes.
“Had it not been for the accuracy
of the Fluke meter we probably would

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