M&C rewinds compressor motor stator
1 October 2019
Electrical switching & drive systems & components
Marthinusen & Coutts (M&C) recently provided a solution to an irregularity that occurred in the stator of a large 36 MW compressor motor deployed at Sasol’s Secunda plant.The results of final tests, conducted by HV Test Filed Services on the stator after M&C; had completed all the necessary repairs on it, were found to be the best among many such tests conducted on similar equipment over a period of several decades.
Initially a Sasol maintenance team discovered during a routine inspection in January 2018 that the flux shield mountings on the stator were faulty, whereupon Sasol awarded M&C; a contract to identify the cause of the irregularity and offer a remedy.
“We tested the stator winding, which we found to be fine, but confirmed that there was a defect in the flux shield and recommended that it be repaired, as there was a risk of it damaging the winding if left to continue operating in its existing condition. To repair the flux shield meant also having to remove the winding and perform a rewind on the stator,” said Rob Melaia, M&C’s engineering and technical executive.
Sasol accepted M&C’s recommendation and in August last year assigned it to perform the required repairs. “In addition to replacing the old bars with new bars purchased from a reputable coil manufacturer in the US, we did a very specific modification to repair the flux shield to prevent a recurrence of the defect in the future,” Melaia added. “On investigating the defect we found that the electrical current, instead of flowing only in the flux shield as it ought to have done to prevent the core from overheating, had started flowing in the mounting bolts, so causing wear by electrical arcing in the mounting holes and the mounting studs.”
The solution M&C’s repair team provided was to fit copper braid straps from several points on the flux shield to the stator body to reroute the current in such a way as to prevent a repeat of the damage as witnessed. To confirm the effectiveness of the solution M&C; arranged to have the refurbished stator tested by local independent test authority HV Test Field Services.
Partial discharge and Tan Delta tests were conducted, being the recognised tests for determining the integrity and efficiency of medium voltage windings. The results were:
• A maximum partial discharge of below 250 PicoCoulombs (pC) at 120% of phase voltage.
• In the Tan Delta tests the dielectric dissipation factor was found to be 65 x 10-4 at 20% of phase voltage and 105 x 10-4 at 100% of phase voltage.
“These test results were the best ever to be achieved among the numerous machines on which HV Test has conducted tests of this kind!” Melaia concluded. “We have every reason to be proud of this outcome as it says volumes about M&C’s expertise in this field, both in terms of correctly diagnosing and repairing faults in a wide range of large rotating equipment, as well as providing the appropriate and most effective solutions for them,”
Further reading:
Precise detection of complex rotational movements
Beckhoff Automation
Electrical switching & drive systems & components
The EP3751-0260 EtherCAT Box module by Beckhoff connects an acceleration sensor with an inertial measurement unit - a gyroscope. This provides accurate detection of acceleration and rotational motion in addition to shock, vibration and tilt measurement, both as preprocessed values and as raw sensor data.
Read more...
Energy management system for electrohydrostatic actuation systems
Electrical switching & drive systems & components
In the machine manufacturing industry, more drive systems are being converted from servo-hydraulic throttle to electrohydrostatic actuation systems. The four-quadrant capability of the electrohydrostatic pump unit and servo drive used in this technology, in combination with the new Moog energy management system, allows regenerative power flows generated during braking or pressure relief to be stored and reused.
Read more...
Drive solution for stacker reclaimer
Electrical switching & drive systems & components
Hägglunds Drives South Africa recently completed a retrofit project on the bucket wheel of a stacker reclaimer at Richards Bay Coal Terminal. The project entailed replacing a gearbox drive solution with a direct drive solution from Hägglunds Drives SA.
Read more...
Kamoa-Kakula power pack order for SEW-EURODRIVE
SEW-EURODRIVE
Electrical switching & drive systems & components
With well over 100 units already delivered, SEW-EURODRIVE is set to continue supplying Ivanhoe Mines’ prestigious Kamoa-Kakula Copper Complex in the Democratic Republic of Congo.
Read more...
Seven ways to reduce production downtime on the plant
Electrical switching & drive systems & components
Production downtime is one of the biggest risks in the manufacturing industry. Follow these seven tips to reduce machine downtime in your production line.
Read more...
The time is now to implement a motor management strategy
Schneider Electric South Africa
Editor's Choice Electrical switching & drive systems & components
Motor management plays an all-important role in controlling motor energy costs in various industries, segments and applications. Research and practical experience have consistently shown that effective motor management practices can result in significant energy savings, reduced operational costs, and improved overall system reliability.
Read more...
Rapid overhaul of compressor motors
ACTOM
Electrical switching & drive systems & components
Marthinusen & Coutts Zambia was requested by a smelter based in the Copperbelt to provide an in-country repair solution for its two critical 4,5 MW compressor motors. The company was given only three weeks in which to overhaul and commission the motors.
Read more...
PC-based motion control on a labelling machine
Beckhoff Automation
Editor's Choice Electrical switching & drive systems & components
For 50 years, Bausch+Ströbel in Germany has been developing packaging and production systems for the pharmaceutical industries. The company’s goal is to offer the best technical and economical solutions for the challenges of modern industry. Its new ESA1025 labelling machine shows how this is achieved with PC-based control from Beckhoff as the central motion controller.
Read more...
Thrust for hybrid electric flying
Editor's Choice Electrical switching & drive systems & components
Several leading academic institutes in Germany are collaborating on the future of hybrid electric flying. The partners are researching an entirely new propulsion system for medium-range aircraft with up to 35 passengers.
Read more...
Precise knowledge for precise applications
Electrical switching & drive systems & components
Aerotech has been supplying standard product solutions such as motors, drives, controls and positioning tables since 1970. Customised motion subsystems include positioning systems on granite structures with undercarriage and vibration isolation, and also external measurement systems.
Read more...
printer friendly version