Efficient Plant October 2017 - 37

feature | equipment reliability

Knowing what
issues to look for
and where will
lead to better management of your
site's motor fleet.
Image courtesy of
Fluke Inc.

Reflections are generated when there is
an impedance mismatch between the
source and load. Impedance mismatches can occur as a result of improper
installation or component selection, or
equipment degradation over time. Note:
In a motor-drive circuit, the peak of the
reflection could be as high as the DC bus
voltage level.
Criticality: High
5. Sigma current. Sigma currents are
essentially stray currents that circulate in
a system. The sigma currents are created
as a result of the signal frequency, voltage
level, capacitance, and inductance in
conductors. These circulating currents
can find their way through protective
earth systems causing nuisance tripping
or, in some cases, excess heat in windings. Sigma current can be found in
the motor cabling and is the sum of the
current of the three phases at any one
point in time. In a perfect situation, the
sum of the three currents would equal
zero. In other words, the return current
from the drive would be equal to the

OCTOBER 2017

current to the drive. Note: Sigma current
can also be understood as asymmetrical signals in multiple conductors that
capacitively couple currents into the
ground conductor.
Criticality: Low
6. Operational overloads. Motor overload
occurs when a motor is under excessive
load. The primary symptoms are excessive current draw, insufficient torque,
and overheating. Excessive motor heat
is a major cause of motor failure. In the
case of an overloaded motor, individual
motor components, including bearings,
motor windings, and other components,
may be working fine, but the motor will
continue to run hot. For this reason, it
makes sense to begin your troubleshooting by checking for motor overload.
Note: Overload is the cause of 30% of
motor failures.
Criticality: High

MECHANICAL FACTORS

7. Misalignment. Misalignment, be it
angular, parallel, or compound, occurs

when the motor drive shaft is not in
correct alignment with the load, or the
component that couples the motor to the
load is misaligned. Many professionals
believe that a flexible coupling eliminates
and compensates for misalignment, but
a flexible coupling only protects the coupling from misalignment. Even with a
flexible coupling, a misaligned shaft will
transmit damaging cyclical forces along
the shaft and into the motor, leading to
excess wear and increasing the apparent
mechanical load. Note: Misalignment
may also feed vibration into the load and
the motor drive shaft.
Criticality: High
8. Shaft imbalance. Imbalance is a condition of a rotating part in which the mass
center does not lie on the axis of rotation.
In other words, there is a "heavy spot"
somewhere on the rotor. This condition
can be caused by numerous factors,
i.e., dirt accumulation, missing balance
weights, manufacturing variations, uneven mass in motor windings, and other
wear-related issues. Note: Although
EFFICIENTPLANTMAG.COM |

37


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Table of Contents for the Digital Edition of Efficient Plant October 2017

Editorial
Implementations
Profitable Reliability Control On Your Horizon
Experts Provide IIoT Insights
Integrating Automation Into Shade Manufacturing
Fluid-Flow Challenges
Looking For Failure In All The Wrong Places
Closer Human/Robot Collaboration
Note These Causes Of Motor Failure
Reliable Pumping Supplement: Food & Beverage Processing
On The Floor
Uptime
IIoT
Pump 'Cavitation' Might Not Be
Never Too Late For Basic Navigation
Audit or Assess? Understand The Difference
A Perfect Pair: Barcodes and Your CMMS
Lubrication Strategies
Products
Ad Index
Showcase
Efficiency Insight
Efficient Plant October 2017 - 1
Efficient Plant October 2017 - Cover1
Efficient Plant October 2017 - Cover2
Efficient Plant October 2017 - 1
Efficient Plant October 2017 - 2
Efficient Plant October 2017 - 3
Efficient Plant October 2017 - 4
Efficient Plant October 2017 - 5
Efficient Plant October 2017 - 6
Efficient Plant October 2017 - 7
Efficient Plant October 2017 - Editorial
Efficient Plant October 2017 - 9
Efficient Plant October 2017 - Implementations
Efficient Plant October 2017 - 11
Efficient Plant October 2017 - Profitable Reliability Control On Your Horizon
Efficient Plant October 2017 - 13
Efficient Plant October 2017 - 14
Efficient Plant October 2017 - 15
Efficient Plant October 2017 - Experts Provide IIoT Insights
Efficient Plant October 2017 - Integrating Automation Into Shade Manufacturing
Efficient Plant October 2017 - 21
Efficient Plant October 2017 - 22
Efficient Plant October 2017 - 23
Efficient Plant October 2017 - 17
Efficient Plant October 2017 - 18
Efficient Plant October 2017 - 19
Efficient Plant October 2017 - Integrating Automation Into Shade Manufacturing
Efficient Plant October 2017 - 21
Efficient Plant October 2017 - 22
Efficient Plant October 2017 - 23
Efficient Plant October 2017 - 24
Efficient Plant October 2017 - Fluid-Flow Challenges
Efficient Plant October 2017 - 26
Efficient Plant October 2017 - 27
Efficient Plant October 2017 - 28
Efficient Plant October 2017 - Looking For Failure In All The Wrong Places
Efficient Plant October 2017 - 30
Efficient Plant October 2017 - 31
Efficient Plant October 2017 - 32
Efficient Plant October 2017 - 33
Efficient Plant October 2017 - Closer Human/Robot Collaboration
Efficient Plant October 2017 - 35
Efficient Plant October 2017 - Note These Causes Of Motor Failure
Efficient Plant October 2017 - 37
Efficient Plant October 2017 - 38
Efficient Plant October 2017 - Reliable Pumping Supplement: Food & Beverage Processing
Efficient Plant October 2017 - 40
Efficient Plant October 2017 - 41
Efficient Plant October 2017 - 42
Efficient Plant October 2017 - 43
Efficient Plant October 2017 - 44
Efficient Plant October 2017 - 45
Efficient Plant October 2017 - 46
Efficient Plant October 2017 - On The Floor
Efficient Plant October 2017 - 48
Efficient Plant October 2017 - Uptime
Efficient Plant October 2017 - IIoT
Efficient Plant October 2017 - Pump 'Cavitation' Might Not Be
Efficient Plant October 2017 - Never Too Late For Basic Navigation
Efficient Plant October 2017 - Audit or Assess? Understand The Difference
Efficient Plant October 2017 - A Perfect Pair: Barcodes and Your CMMS
Efficient Plant October 2017 - Lubrication Strategies
Efficient Plant October 2017 - 56
Efficient Plant October 2017 - 57
Efficient Plant October 2017 - 58
Efficient Plant October 2017 - 59
Efficient Plant October 2017 - Products
Efficient Plant October 2017 - 61
Efficient Plant October 2017 - Ad Index
Efficient Plant October 2017 - Showcase
Efficient Plant October 2017 - Efficiency Insight
Efficient Plant October 2017 - Cover3
Efficient Plant October 2017 - Cover4
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