Motor Diagnostics (1)

Before start of motor diagnostics, we must know the scope of motor diagnostics itself.

The electric motor systems are consist of :
1. Controls
2. Motor
3. Coupling
4. Load

1. CONTROLS

Controls are consist of :

• MCCs (Motor Control Centers) and Disconnects (Starters, Overloads)
• Cabling

Common MCC/Disconnects problems :

• Loose connections
• Bad contacts
• Bad PF correction capacitors

Test methods that can be utilized to review the condition of these components include:

• Electrical Signature Analysis (ESA)
• Motor Circuit Analysis (MCA)
• Infrared Analysis
• Ultrasonics
• Volt/Amp Meter testing
• Ohm Meter testing
• Visual inspection

Common cable problems include:

• Thermal breakdown due to overloads or age.
• Contamination which can be even more serious in cables that pass underground through conduit.
• Phase shorts can occur as well as grounds. These can be caused by ‘treeing’ or physical damage.
• Opens due to physical damage or other causes.
• Physical damage is often a problem in combination with other cable problems.

Test instruments include motor circuit analysis, motor current signature analysis, infrared and insulation to ground testing.

Problems in the system before the electric motor can be broken down in the following order:

• Poor power factor
• Poor connections
• Undersized conductors
• Voltage unbalance
• Under or over voltage conditions

The most common equipment that covers all of these include motor circuit analysis, motor current signature analysis and infrared analysis.

to be continued...........

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