Keeping Motors Efficient
The operating costs of the typical motor are about 98
times its purchase price. These operating costs are often higher than
they need to be, due to inadequate or improper maintenance.
To get more efficiency from existing motors:
- Maintain the supply. Suppose someone asked you, "How much
current leaks to ground on your motor supply cables, and what level of
this is acceptable?" What would your answer be? How serious are you
about inspecting and maintaining cables at 480V and above? This is only
one aspect of maintaining the supply, but it's probably the most
- Maintain the input. Do you monitor the supply power current
to your large, high-energy usage motors? If you aren't using your power
monitoring system to look at motor feeder circuits, you are probably
passing up easy energy savings.
- Maintain the motor. Do you monitor and correct for motor
vibration? Do you check alignment as part of your PM procedures? Do you
inspect the mounting, grounding (bonding) connections, connection
resistance, and other factors that contribute to energy waste? What
about air filters? Do you follow the manufacturer's procedure for
- Maintain the motor/load interface. If the motor and load are
misaligned, you waste energy. Vibration monitoring and periodic
alignment inspection are essential.
- Maintain the load. Do you check the oil in motor gearboxes?
If the oil is low or dirty, you can actually detect the energy waste by
measuring the elevated temperature of the gearbox.
Power Factor Correction
This area of energy cost is seldom addressed correctly.
Don't overlook these important issues.
- If you are running the motor from a VFD, use a power factor
- If you are running the motor across the line, install power factor
correction at the motor. Consider doing this with a power factor
- If you have ruled out a VFD, consider a softstart device. For large
motors, this will provide a "domino effect" of failure prevention in
your whole system. By eliminating the spike/sag cycling caused by
starting large motors across the line, you'll extend the life of nearly
everything in your facility. You will be able to see this effect in
feeder cable insulation resistance tests on any motor that is large in
relation to your system.
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A motor failed in the main production line, causing it
to stop. You've already replaced the motor. Now you need to determine
the likely cause. How should you proceed?
The answer to this question appears at the end of this
Repairs and Root Cause
A motor fails, bringing production to a halt. Your team
swaps out the bad motor with a new one in what must be record time, and
production is humming along once again. But was this a real repair, or
simply a parts swap?
A real repair solves the problem. A parts swap doesn't
anything but the apparent cause of production stoppage and the
need to get running again. Thus, a parts swap won't prevent another
production stoppage. The smoke rolling out of a motor is a good clue
that its failure caused the production stoppage. But it doesn't tell
what caused that motor to fail. The real problem might even be in
another part of the facility.
Experts recommend root cause analysis, and we know this is the only
proven way to solve failures completely. So, why don't we do it every
time? One reason is urgency. Production managers want production up
now. They don't want to wait while you make wishbone diagrams,
conduct extensive testing, and develop a list of likely causes.
So, don't make them wait. Do this "thinking work" now, while the
equipment is running -- before you are in the pressure cooker.
a repair script for each item of critical equipment. The purpose of
script is to provide a sequence of troubleshooting steps that you can
employ quickly when a failure occurs. Your repair script can be in any
of several forms. The checklist format is simple, effective, and
efficient. The flowchart format is another option. Don't worry about
getting this perfect the first time.
NEC at the Facility
Article 100 defines "energized" as being electrically
connected to a source of voltage (or being the source of voltage). This
definition fits the scope of the NEC (defined in 90.2). But it falls
short when determining energy sources for purposes of safely working on
equipment. You may need to isolate non-electrical energy sources, such
as flywheels, gas cylinders, gravity-fed devices, hydraulic cylinders,
mechanical springs, and pneumatic circuits.
Most industrial accidents occur because of what people
do, not where they are. Here are three unsafe behaviors
your maintenance team should be aware of:
- Ignoring safety instructions. Signs, labels, checklists,
MSDS, and other sources of safety information help prevent injury, but
only if heeded.
- Assuming de-energization. Locking out a supply breaker
doesn't guarantee a circuit is de-energized. Trust, but verify (using a
meter rated for the power level in question).
- Hurrying. You've probably heard the expression, "Never
time to do it right but always enough time to do it over." It's also
true that your hurrying-related mistake can result in catastrophic
failure, injury, or death. Take the time to do it right.
Show & Events
Enter the "You Be the Electrical Inspector" Contest at the
Here's your chance to win a $100 American Express gift certificate and
to prove your knowledge of the National Electrical Code by acting as an
electrical inspector and citing every Code violation appearing in an
actual electrical installation. Visit the EC&M e-Tradeshow, a
virtual online exhibition and live conference center. Also available is
a live conference scheduled for February 15th on "Ground-Fault
Coordination" and a special presentation by Generac on "Sizing
Commercial Generators." And take a look at the archive of various past
conferences, such as "Claim Litigation" and "Harmonics: Causes,
Symptoms, and Remediation Techniques."
It's Time to Hit the Beach
If it's your job to make sure all systems are "go," you
need to go to Electric West. This show and conference offers the right
information and product mix to meet all of your information needs. Do
you maintain and operate electrical systems in a facility? If so, you
have to make plans to attend the Electric West conference program in
Long Beach, Calif. Check
out this event's 40+ seminars in the areas of power quality,
Code changes, and industrial applications, and make plans to meet 200+
leading suppliers. Or register
Answer to Electrical
This motor is obviously a critical one, or its failure
would not have stopped production. So, determining the likely cause is
also critical. The worst time to be thinking about the troubleshooting
procedure is when production is already down.
During a failure, you should be able to use a troubleshooting
procedure specific to this motor. Your first step in developing this
procedure is to develop a list of every asset (e.g., supply breaker,
motor drive, etc.) related to the motor. Note the asset ID and location
of each asset. Your next step is to develop the likely failure mode of
each of those assets and what tests to conduct for each failure mode.
While production is still up, you should walk through this procedure as
if you are actually troubleshooting. This will help you find
not apparent from your asset list.
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