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.

O post Nishi takes part in the 38th Brazilian Congress on Maintenance and Asset Management, exhibiting products, services and equipment apareceu primeiro em Nishi.

More contents of NISHISAN tips: https://nishi.com.br/novo/en/blog/

O post GAP-N Electrical Testing Webinar: LOOP TEST apareceu primeiro em Nishi.

In this week’s webinar we present the electrical test using the PDMA MCEMAX MCEGold® for on-line analysis of motors.  In the video we perform a practical demonstration of performing an online test with expert explanation and commentary.

GAP-N: Predictive analysis of electric motors and generators

On-line tests:

• Partial discharges;
• Vibration analysis;
• Thermography;
• Power quality analysis;
• Current spectral analysis;
• Inrush current monitoring.

Watch the video on Youtube:

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

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 ENSAIO DE RESISTÊNCIA DE ISOLAMENTO:

Contact our team and request an assessment of the operational reliability of your equipment and avoid unplanned maintenance and decrease the downtime of your equipment.

O post GAP-N I PDMA MCEMAX MCEGold® PDMA electrical testing webinar ON-LINE PART 1 of 2 apareceu primeiro em Nishi.

The principle of an electrical machine is that the conduction of electric current is the basic condition for its operation. In order to conduct this current continuously through the various coils, there are electrical connections that connect one coil to another, both in the rotor and in the stator. These connections are made by soldering or brazing.

In brazing, the connection established between two metallic elements is made by means of an addition metal, which is in the liquid state and whose fusion temperature is higher than 450ºC and lower than the fusion temperature of the base materials, and the base metals do not participate in the constitution of the joint.

Welding, on the other hand, is a weak brazing, in which the melting temperature of the filler metal is below 450ºC. Normally, the filler metal penetrates by capillarity between the surfaces of the parts to be joined. Uniform heating of the surfaces should be promoted, because with the heating, the base material molecules get farther apart and the filler metal in liquid state penetrates between these molecules.

The goal to be achieved in the connections is that in this bridge, which connects the coils, there is no bad contact generating a high ohmic resistance value and consequent heat losses and Joule effect. The mechanical part is also important, because in addition to the Joule effect (electrical losses) there are centrifugal forces and thermal movements that generate stress in these connections, reasons that cause wear and malfunctions. Predictive and preventive maintenance is essential to identify the integrity of these connections and thus avoid unscheduled failures in them.

As an illustration, in an 8 160 hp, 13 800 V, 1 800 rpm motor, the client had a history of failures in the damping cage and requested a detailed inspection of the equipment for preventive evaluation and intervention, considering the need for high reliability of the equipment for operation. Through tests on the rotor circuit we concluded that the connections were intact, which enabled the return in operation, restoring peace of mind to the customer.

winding rotor connections

Inspection of electrical connections of a high voltage wound rotor	Wound rotor test to evaluate electrical connections

In another case, a 66 760 kVA, 13 800 V, 257.14 rpm hydro generator, a partial winding was performed on the stator winding with bar change. Since this generator had already failed due to problems in the brazing of the series connections of the bars, as a preventive measure, a general evaluation of all the connections was made before releasing the machine for operation.

Brazing process on electrical connection	Test to evaluate problems in the brazing of serial connections of the bars

Request a quote for a preventive evaluation of your equipment and count on our team of specialists in electrical machines!

O post Electrical connections apareceu primeiro em Nishi.

When we analyze the nominal voltage between turns of a machine, even for large equipment, the level is low and its operation is around 100/150 volts/turns. At this level, the electrical deterioration is low and the failures are due to thermal and mechanical actions on the insulating material. Because it is in direct contact with copper, the highest temperature point, it is the insulator that heats up first. Another wear factor is the movements by dilatation due to thermal cycles in operation. Electrically we can have deterioration coming from the impurities in the environment in which the machine is operating.

We have several switching sources inserted in the circuit that can generate voltage surge waves with fast rise time wavefronts. These waves, when they reach the winding, distribute the voltage (the circuit is seen as a capacitive divider) in an uneven way and concentrate high values in the first windings of the machine that can cause early deterioration by the appearance of electrical discharges due to the high voltage level. Remember that this insulation is made for a low voltage level, and is basically composed of the conductor’s own insulation (enamel and/or fiberglass) or in some projects an insulating layer is applied, but of only one turn.

Hardly ever does the machine go out of operation due to a short turn insulation. What normally happens is that this short deteriorates the main insulation, causing a short to ground that causes the protection to operate.

O post Surge Test apareceu primeiro em Nishi.

This phenomenon, voltage/current induced on the shaft, has worsened with the advent of PWM frequency converters, as motors are now fed by unbalanced waveforms with high frequency components.

The main cause of currents flowing through the bearings of the static converter-driven motor are common-mode voltages. The capacitive impedances become low at the high frequencies produced by the converter, causing current to flow through the path formed by the rotor, shaft, and bearing to ground.

These discharges wear out the balls and the raceway of the bearing or patent metal in the sliding bearing, giving rise to small holes, which begin to overlap and, if there are discharge currents for a long time, grooves (craters) will be formed. The erosion leads to reduced service life of the bearings and can cause machine failure.

To eliminate circulating currents, it is sufficient to isolate the motor bearings. As for the components of capacitive origin, it would be necessary to also isolate the bearings of the driven machine, to prevent the migration of electrical charges from the motor to the rotor of the driven machine through the electrically connected shafts in cases of non-isolated couplings. Another means of eliminating the capacitive component is to short-circuit the motor rotor by installing a graphite sliding brush in contact with the shaft.

Perform the maintenance of your motor operated with frequency inverter and avoid damage to bearings. Contact Nishi and request a quote to evaluate your equipment.

O post CURRENT CIRCULATING IN THE BEARINGS WHEN OPERATED WITH AC DRIVES apareceu primeiro em Nishi.