5 technological solutions for diagnostic testing of industrial electric motors

There is a variety of diagnostic tests for electric motors that guarantee the useful life of these components, which, together with generators and rotating machines, are responsible for generating energy in industries. Therefore, it is necessary to bear in mind that, in order to plan maintenance effectively, it is essential to have accurate information on when assets should be repaired or replaced.

This is because premature failure can lead to significant economic losses as a result of unexpected outages and possible damage to the asset itself. Among the negative influences that can affect machines and undermine the reliability or useful life of this equipment are:

• Thermal stress, due to sudden changes in temperature, overload and hot spots.
• Electrical stress due to overvoltages, nominal voltage, partial high (PD).
• Environmental stress due to the presence of aggressive, reactive and abrasive chemicals, particle contamination.
• Mechanical stress due to vibration, oscillation in groove sections and at the end of winding sections.

Diagnostic tests on electric motors can reveal a great deal about their condition and are commonly performed after the machine has been manufactured, installed on site, or during repeated periods of operation. These assessments are reliable diagnostic methods for evaluating the condition of insulation and other components, and their results provide an indication of when maintenance should be performed.

Many of the diagnostic tools for monitoring of electric motor conditions They offer a comprehensive assessment to quickly identify potential problems and the risk of failure. Preventive and corrective measures that promote machine reliability and extend service life include the following:

• Perform regular or continuous condition assessments through the use of diagnostic tests on electric motors.
• Reverse the position of the starting point.
• Consider partial rewinding of worn parts.
• Replace the damaged components of the machine.
• Include tools in the maintenance plan for monitoring of electric motors and industrial frequency converters for the diagnosis of premature failures.

5 technological solutions for diagnostic testing of industrial electric motors

1. Instrumentation for performing voltage resistance testing

The voltage withstand test is a YES or NO investigation, so the instrumentation used for this type of test can indicate whether or not the insulation is adequate for service. The inherent resistance and healthy insulation capacity is well above the usual test value.

2. Technology for performing partial discharge measurement tests

Partial discharges (PD) occur in the insulation system of rotating machines, where the local electric field strength exceeds the electrical strength of the motor, causing progressive erosion of insulating materials that can lead to failure.

Unlike other dielectric tests on motors, partial discharge measurements are usually performed with devices that have a compensated reactor, which allows individual weak points in the insulation system to clearly identify the cause of recognisable patterns (e.g., slot discharges or end winding discharges).

Through the analysis of recognisable patterns, the main root causes identified with this type of diagnostic testing on electric motors are: contamination, gaps, cracks, ageing or general deterioration of different insulation components.

3. High-precision measurements, capacitance and dissipation factor/power factor

These types of measurements or tests are performed in order to identify defects that affect the condition of the machine's insulation. Healthy insulation is essential for safe operation, however, variations in capacitance and dissipation factor/power factor over time are often signs of partial discharges (PD) or insulation degradation, and trend data helps determine the speed of motor insulation.

4. Online monitoring for partial discharge testing

Compared to routine offline diagnostic testing, online partial discharge monitoring provides asset managers with the status of insulation conditions continuously, while electric motors and generators are operating under the influence of wearing forces.

Temporary monitoring of voltage onset and spread (VOS) activity is used to periodically observe changes in VOS activity, while permanent VOS monitoring continuously evaluates VOS activity throughout the entire service life of a machine.,

Machine operators can decide if and when it is necessary to schedule downtime and perform maintenance based on the information supported by the database collected through this type of diagnostic testing on electric motors.

5. Instrumentation for performing diagnostic tests on electric motors based on insulation resistance (IR), polarisation index (PI) and dielectric absorption ratio

These types of measurements and tests are useful for checking contamination of the machine windings, as well as deterioration of the motor insulation. They also assess the integrity of the insulation, ensuring safe operation, and check for moisture in the stator windings after a long period of inactivity.

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