Electric Motor System Diagnostics Procedure

Electric Motor System Diagnostics Procedure

• The reliability and energy consumption of electric motors and the systems they drive has a direct financial impact to industrial and commercial enterprises.

• We will discuss the financial justification for a motor testing program, a general discussion of De-energized and Energized testing methods, and ideas for selling the service.

• Electrical Motor System testing is becoming an important part of a successful rotating equipment reliability testing program

What is a Motor System?

The Electric Motor System

Three-Phase Input Power Process Mechanical and Electrical Feedback

Motor System Faults

some common faults found within a motor system

Incoming Power
• Power Quality
o Harmonics (Voltage and Current)
o Over/Under Voltage
o Voltage Unbalance
o Power Factor
o Overload

Transformers
• Transformer Faults
o Insulation to Ground
o Winding Shorts
o Loose Connections
o Electrical Vibration

MCC – Controls and Disconnects

• MCC/Disconnect Problems
o Loose Connections
o Faulty Contacts
o Faulty Coils
o Faulty VFD
o Faulty Starter
o Bad PF Correction Capacitors

Cables (Before and After Controls)
• Cable Faults
o Thermal Breakdown
o Contamination (especially underground feeders)
o Shorts and Grounds
o Open
o Physical Damage

Electric Motor (Mechanical)

• Mechanical Faults
o Bearings
o Bad Shaft/Brg Housing
o Vibration

Electric Motor (Electrical)
• Electrical Faults
o Winding Shorts
o Insulation to Ground
o Contamination/Thermal Stress
o Rotor Faults
o Air Gap Faults

Coupling (Direct and Belted)
• Faults
o Misalignment
o Unbalance
o Belt/Insert Wear
o Tension Issues
o Sheave Wear

Load (Fans, Pumps, Compressors, Gearboxes, Etc.)

• Load Faults
o Worn parts (I.e. seals)
o Broken components (gears, fan, impeller blades, etc.)
o Bearings, etc

Where Electrical Faults Can Begin 
• End turns of windings
o Stresses are greatest
o Insulation is weakest
o Most exposed to contamination

About Motor Electrical Faults

• They start small and get worse
• They always end in failure
• Contributing factors

o Overloading

o Frequent start/stop cycling

o Vibration

o Contamination

o Age, Heat, VF Drives

Other Types Of Electrical Faults

• Open Phases
• Broken/Cracked Rotor Bars
• Air gap (eccentricity)
• Blown Capacitors
• Poor Connections
• Cable Faults
• Overload, Fuses, etc.

Meg-Ohm-Meter & Volt/Ohm Meter

When Used for Elec Motor Testing*

* Common electrical testing instruments   **Coil faults- turn to turn & coil to coil

Combined Technology Approach

Typical Electrical Contractor Today

Green indicates that a developing fault can be both detected and trended for Predictive Maintenance purposes.
Yellow indicates a fault can be detected, but is difficult to trend or cannot be detected at an early stage.

* When using a typical DMM to measure resistance.

Combined Technology Approach

Contractor with MCA and ESA

Green indicates that a developing fault can be both detected and trended for Predictive Maintenance purposes.
Yellow indicates a fault can be detected, but is difficult to trend or cannot be detected at an early stage.

Why Add Motor Testing?

• Generates additional billable hours for your business
• Improves your customers’ equipment reliability
• Provides a more accurate assessment of your customers’ equipment when compared to what you are doing now

Why Offer An Electrical Motor Testing Program?

• Many of your customers have motor system reliability issues
• Some will not have the resources to support an in-house motor testing program
• Some of your customers will gladly pay for this service
• Motor testing equals extra billing $$

• Multi-Technology Approach to Motor Diagnostics

o Electrical motor testing will also improve your ability to detect and eliminate causes of system

failure

• Use De-Energized MCA and Energized ESA testing to validate findings from Infrared & Power Analysis test methods

Why Your Company for Electrical Motor Diagnostics?

• Improve Rotating Equipment Reliability
• Lower Your Operating Costs
• Lower Energy Consumption
• Improve Product Quality
• Increase Company Profits
• Improve Employee Safety
• Reduce Reactive Repair Time When Equipment Does Fail