The six fault zones key to proper maintenance

A proper maintenance program goes beyond a visual inspection; instead it uses the proper tools and equipment necessary to check the six fault zones of a motor.


The 6 Fault Zones imperative to motor maintenance. Image courtesy: L&S ElectricEstablishing a routine maintenance program is the best way to ensure that your electric motors and other equipment will operate when you need them. The maintenance program must go beyond a visual inspection of the equipment. It needs to use the proper tools and equipment to both test and analyze your motors. Keeping a close tab on the motors is important, they have an impact on all equipment associated with them.

The six fault zones

Tests included in your maintenance program should assess the following six fault zones, which indicate the overall health of the motor:

1. Power circuit

Power circuit relates to the various components and connections that are downstream from the motor’s location, including fuses and circuit breakers, overloads, lug connections, disconnects, and contactors. It is possible to analyze the power circuit by measuring its health.

2. Power quality

To test power quality, consider both the current and the voltage. This fault zone comes from the electrical system, and when problems occur, they result in damage to the motor immediately or over time. Check the power quality by testing the crest factor, total RMS voltage, current harmonic voltage, and average voltage.

3. Rotor

There are several issues associated with the rotor fault zone. These include rotor laminations, bars, and end rings. It is unlikely that rotor faults result in direct issues with the motor, but they do cause parts of the motor to experience problems and eventually fail. Some of the tests for this zone include current demodulation, inductive imbalance, and inrush current.

4. Stator

The connections of the internal coil to the turn-to-turn insulation are associated with the stator fault zone. The tests in this region include analyzing inductive or impedance imbalances.

5. Insulation

Motor insulation is responsible for keeping different parts of the motor separated from each other. Heat has an adverse impact on insulation and significantly reduces the lifespan of the motor. Keeping the motor allows the insulation to do its job. In turn, this helps protect the windings and allows the motor to operate indefinitely. Other issues that affect the insulation include vibration, moisture, and contamination. Regular testing of the insulation indicates the overall health of the motor.

6. Air gap

The gap between the stator and the rotor is the air gap zone. Two types of faults exist in the air gap: dynamic and static. Analyze the air gap area by using a rotor influence check test (RIC) and current signature analysis.

These steps should be part of a routine maintenance program. Be sure that you are not just looking things over. Instead, use proper testing equipment to examine the six fault zones, which shows you just how healthy your motor is.

David Manney is marketing administrator at L&S Electric. This article originally appeared on Watts New L&S Electric's blog. L&S Electric is a CFE Media content partner.

Top Plant
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2017 Top Plant.
Product of the Year
The Product of the Year program recognizes products newly released in the manufacturing industries.
System Integrator of the Year
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
February 2018
2017 Product of the Year winners, retrofitting a press, IMTS and Hannover Messe preview, natural refrigerants, testing steam traps
March 2018
SCCR, 2018 Maintenance study, and VFDs in a washdown environment.
Jan/Feb 2018
Welding ergonomics, 2017 Salary Survey, and surge protection
April 2018
ROVs, rigs, and the real time; wellsite valve manifolds; AI on a chip; analytics use for pipelines
February 2018
Focus on power systems, process safety, electrical and power systems, edge computing in the oil & gas industry
December 2017
Product of the Year winners, Pattern recognition, Engineering analytics, Revitalize older pump installations
April 2018
Implementing a DCS, stepper motors, intelligent motion control, remote monitoring of irrigation systems
February 2018
Setting internal automation standards
December 2017
PID controllers, Solar-powered SCADA, Using 80 GHz radar sensors

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

The Maintenance and Reliability Coach's blog
Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
One Voice for Manufacturing
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Maintenance and Reliability Professionals Blog
The Society for Maintenance and Reliability Professionals an organization devoted...
Machine Safety
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
Research Analyst Blog
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Marshall on Maintenance
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
Lachance on CMMS
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
Maintenance & Safety
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
Industrial Analytics
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
IIoT: Operations & IT
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Randy Steele
Maintenance Manager; California Oils Corp.
Matthew J. Woo, PE, RCDD, LEED AP BD+C
Associate, Electrical Engineering; Wood Harbinger
Randy Oliver
Control Systems Engineer; Robert Bosch Corp.
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me