On September 27 at 11:30 a.m. in the Parque Barigui room, engineer Fabio Toshio Nakatani will give a presentation on: Hybrid analysis (man+technology) in predictive maintenance of rotating electrical machines. Discussing Industry 4.0 in the area of maintenance in relation to industrial automation and the integration of different technologies. Artificial intelligence, robotics, neural networks and big data with the aim of improving processes and increasing productivity and reliability. But where does this technological evolution leave the role of man (specialist)? How will integrated work between technology and specialists increase the degree of reliability of rotating electrical machines?

Register at https://cbmga.abramanoficial.org.br/ and visit the Nishi stand during your participation in the country’s main Maintenance and Asset Management event.

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What is corrective maintenance?

Still very present in companies, corrective maintenance is only used when some equipment breaks down or fails. This method does not use maintenance planning, which leads to the need for parts inventory and availability of professionals, since the failures are not foreseen and cause the idleness of machines and labor.

For example, a machine seems to be in perfect condition and in constant production, but at some point a part presented a failure and the production had to be stopped. Since there was no planning, the maintenance professional, before correcting it, needs to understand the problem, check if the part can be replaced and if there is in stock. This situation will cause the company to make the machine unavailable, which will generate costs per machine stopped, part that needs to be replaced, and labor costs.

When performed without planning, corrective maintenance generates huge inconveniences, compromising the fulfillment of deadlines and especially operational profitability.

What is preventive maintenance?

When we talk about maintenance planning, one of the best paths to follow is certainly the preventive maintenance. It is the maintenance that corrects problems and failures even before they happen, thus reducing costs, machine unavailability, and increasing maintenance efficiency. Its main characteristic is the possibility of scheduling maintenance, avoiding problems with parts inventory, idle machines, and lack of production.

The tip we leave in this maintenance is to focus on the expected result, to evaluate the condition and operational reliability of the equipment, and not to focus only on the execution of the tasks pre-established by the planning. In an electrical machine, the electrical and mechanical tests and visual inspection are conditions to analyze its results and from there make a critical analysis and conclude potential problems and the degree of reliability that it is, that is, for this the presence of an electrical machine specialist is essential.

In the market we also commonly hear the term “rejuvenation” for preventive maintenance, which can lead to a misinterpretation. There is no way to rejuvenate what is already aging. We can prevent accelerated aging.

What is predictive maintenance?

It is safe to say that predictive maintenance is a step ahead of preventive maintenance. It is the most accurate follow-up and planning maintenance, requires greater qualification of the professional and aims to prevent any failure of parts before they even present a defect. It is characterized by monitoring equipment parameters, such as partial discharges, vibration, temperature, etc.

Predictive maintenance uses the monitoring of the parameters of the parts so that their replacement can be done before the end of their useful life. By inspecting the machine, the maintenance professional – based on the monitoring parameters – identifies the need to change components and schedules the best moment for maintenance, which is done without intervention in production, facilitating maintenance and avoiding higher costs with machine idleness.

What company wants to stop its production because of a failure or defect? Very similar to preventive maintenance, predictive maintenance has as a positive point the possibility of programming its actions. Planning and follow-up of the parts are important factors, which working together, reduce costs with losses and increase the effectiveness in the production of the machines.

NISHI offers solutions for all types of maintenance. Contact us and request an evaluation of reliability and operational warranty of your electric machine.

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In this week’s webinar we present the second part of the electrical test using the PDMA MCEMAX MCEGold® for off-line analysis.  In the video we perform a hands-on demonstration. We present how to identify broken bars in rotor cage performing the Rotor Influence Test and complete explanation about each type of off-line test.

GAP-N: Predictive Analysis of Electric Motors and Generators

Off-line testing:

Standard Test:

• Ohmic Resistance between Phases;
• Inductance between Phases;
• Insulation resistance corrected to 40ºC;
• Capacitance;
• Polarization Graphical Index;
• Step Voltage DC;
• Rotor Influence Test.

Watch the videos below via Nishi’s Youtube channel:

Webinar de ensaios elétricos GAP-N I PDMA MCEMAX®powered by MCEGold® PDMA OFF-LINE PARTE 2 de 2:

Webinar de ensaios elétricos GAP-N I PDMA MCEMAX MCEGold® PDMA ON-LINE PARTE 1 de 2:

Webinar de ensaios elétricos GAP-N I ENSAIO DE RESISTÊNCIA DE ISOLAMENTO:

Contact our team and request an assessment of your equipment’s operational reliability and avoid unplanned maintenance on your equipment.

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In machines that work at high temperatures (close to the temperature limit of the insulating material), the insulation between the plates deteriorates over time, causing the appearance of eddy currents or “eddy currents”, which circulate between the plates of the core that are shorted. The temperature at this location can often be 30 to 40ºC higher than the average core temperature.

The test commonly used to detect possible “hot spots” is the “Loop Test”. We wind coils around the magnetic core where the number of turns is calculated to achieve a flux similar to the nominal flux. We leave the core fed until its temperature stabilizes, and by thermovision we evaluate the temperature differences.

If one or more points are identified where the temperature variation is above average (10ºC or more), these points must be investigated and/or repaired. The repair is done by completely disassembling the core, stripping the insulation material, applying the new insulation, and assembling it.

Learn more about the services provided by Nishi and contact one of our experts for information about maintenance and standards applied to electrical tests of rotating machines.

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A common first question is what determines motor life? Is it determined by the lifetime of the insulation material? By the wear period of the bearings? By the deterioration of the steel? Others?

When we “explode” a motor and stratify its components we see in its composition basically steel, copper and insulating materials. When comparing the materials, we conclude that the insulating material is the most fragile in relation to the others. Is it correct to say that the life span of the motor is determined by the life span of the insulating material? What about the bearings that wear out over time, is it correct to say that the end of their life is the end of the motor’s life?

With good maintenance practices, ensuring the integrity of the insulation system can be a determining factor for long motor life. In medium and high voltage motors, predictive and preventive maintenance will prevent the acceleration of the aging of the insulation system. Statistics show that the stator winding alone accounts for almost 40% of failures.

Having knowledge of the failure mechanisms of a motor’s insulation system and intervening in them will ensure long-lasting uptime. We list below the main causes of failure or accelerated aging:

• high motor temperature;
• electrical stress;
• high contaminant environment.

It is common for all three phenomena to act simultaneously.

Learn more about the services provided by Nishi and contact one of our experts for information about failure modes of insulation systems.

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“Partial Discharge” and “Corona” are terms commonly reported in the electrical and maintenance fields, they are commonly confused as being similar terms. They have in common that they do not immediately cause a complete path in the dielectric for the electric current.

According to the IEEE, a partial discharge is an incomplete or “partial” discharge that occurs between insulators and also between conductor and insulator. In contrast, a full discharge is one that crosses the space between conductors, causing what is known as an electrical fault, by forming a conductive bridge.

Corona, on the other hand, occurs when the gases adjacent to an energized conductor ionize and produce normally visible discharges. Thus, partial discharges inside the insulating wall cannot be called corona.

Visit our Predictive Maintenance page and contact our team for more information on partial discharge monitoring and predictive diagnostics. Evaluate the advantages of unscheduled shutdowns, reducing costs in equipment maintenance and increasing the efficiency of the production process.

*Illustrative images taken from the IEC 60034-27-2 standard.

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This subject is very important for users of large motors and generators. In machines with voltage higher than 6 kV, operating at the frequency of the electrical system (50 or 60 Hz), the coils (market standard) have a semi-conductive material (tape or paint) on the straight side in order to avoid partial discharges that deteriorate the insulating system. The fit between coil and slot is never perfect and we always have small voids in this contact. In this situation, we have electrically a circuit with 2 (two) capacitors connected in series of different dielectric constants (air and insulating).

The semi-conductive material, applied over the insulator, aims to short-circuit the air capacitance and thus eliminate possible discharges. It is unlikely that machines with voltage below 6 kV will present the problem of discharges, taking into account that the working voltage applied to the insulator will be lower than 3.4 kV (phase x ground) and would not reach the disruptive voltage of the air.

Contact our team and request an evaluation of your technical specification with the requirements of materials and manufacturing processes for coils and bars for motors and generators.

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In maintenance we have no way to make the machine “younger”. An insulating system, a bearing system, or others do not become younger after an intervention of this nature. Only in complete corrective maintenance can we rejuvenate it. By replacing the coils, the bearings and other items with new ones, we will be restoring the useful life of these components.

We consider preventive maintenance, which we prefer to call Overhaul (act or effect of reviewing or revising; inspection to correct or prevent failures). With the improvement of predictive techniques is increasingly common to preventive intervention as a complement to the indications and trends evaluated in predictive intervention.

In this work, the “keen eye” of the technical expert is fundamental to see, inspect, test, and systemically evaluate the components. To detect potential loss of life and also intervene at points that may be accelerating the aging process.

Inspections of the cooling system, insulation system, winding tie system, corona and partial discharges, wedges, bearings have avoided early and unexpected losses when detected and corrected. However, as we said, there is no way to “rejuvenate” if they are already aged.

Read more about the GAP-N electrical predictive analysis methodology for rotating electrical machines by clicking on the link:

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