Some energy is always lost (to heat, friction and windage) when motors convert electricity into useful (mechanical) work. To improve motor efficiency, manufacturers have found ways to reduce these losses—not by changing raw materials or production methods, but through design modifications: first with higher-efficiency EPACT motors and, more recently, with NEMA Premium models.
Compared with standard-efficiency motors, for example, some higher-efficiency models have longer stator and rotor cores to reduce core losses, and more copper wire area in the windings to decrease copper losses. Using the smallest fan that can keep the winding temperature within design limits also minimizes windage losses in totally enclosed, fan-cooled (TEFC) models.
Repaired motor efficiency
The mistaken view that motors—including energy-efficient and NEMA Premium models—cannot be repaired or rewound without a loss of efficiency was scientifically disproven by a study in 2003 that identified good practices that maintain the energy efficiency of repaired motors. Commissioned by the Electrical Apparatus Service Association (EASA, United States) and the Association of Electrical & Mechanical Trades (AEMT, United Kingdom), the study tested the efficiencies of motors ranging from the original EPACT level to NEMA Premium and IEC IE3 levels.
Conducted at the University of Nottingham under the direction of engineering executives from motor manufacturers in the U.S. and U.K., the study measured the efficiencies of 22 motors ranging in size from 50hp to 200hp (37kW to 150kW) before and after multiple winding burnout processes and rewinds. A 1998 study by AEMT also proved that the efficiency of motors with lower hp/kW ratings can be maintained during repair, dispelling the notion that, of themselves, winding burnout and removal damage the core.
Among the good repair practices identified by the two studies were making certain the overall length of the turns in the winding does not increase (more resistance increases loss), and increasing the wire area (lower resistance means lower loss) when slot fit allows it. These steps maintain, or may even reduce, the copper losses (I2R) in the winding.
Service centres that follow the guidelines in ANSI/EASA AR100-2010 “Recommended Practice for the Repair of Rotating Electrical Apparatus” and the more-specific recommendations of the EASA/AEMT Rewind Study’s “Good Practice Guide” will provide repairs that have a proven record of maintaining motor efficiency. Both documents are available as free downloads at www.easa.com/energy to assist service centres, end users and energy advocates in obtaining this critical information.
It is on this basis that GIL Automations Limited has recently invested in an ATEX Motor Service Center in Port Harcourt Nigeria as part of our local capacity development. We also carry out Vibration Analysis and Transformer Filtration Services under our Rotating Equipment Services.
Our service centre is rated to repair, certify and Rewind Electric Motors up to 500KW (600HP) and covers as found and as left data. We also cover Onsite Motor Repairs for MV and HV Motors with our partners.
We Service Vendors such as GE, ABB, Siemens, Toshiba, Worlong among other Motors.
Our technicians are trained and certified to repair ATEX Motors.
FULLY EQUIPPED WORKSHOP INCLUDES:
- BURN OFF OVEN
- CURING OVEN
- MILLING MACHINES
- WINDING ANALYSERS
- MOTOR TEST SYSTEMS
- ELECTRICAL PANEL SHOP
- COIL EXTRACTOR MACHINE
- BEARING HEATERS
- DYNAMIC BALANCINGMACHINE
- CORE LOSS TESTERS ETC
At Gil service centre, you can be sure to repair your motors and obtain same efficiency as designed by the manufacturers. We have EASA membership, hence our guiding principle and playbook is the
ANSI/EASA AR100-2010
