Rewound Motors Research Articles

Estimation efficiency of rewound induction motors in situ using a numerical model

This paper presents an effective technique for determining the impact of rewinding practices on the motor efficiency and characterizing the efficiency reduction when electrical motors are rewound several times. This technique focuses on a new approach and a statistical study to find a numerical model for the estimation efficiency of rewound induction motors in the field. The experimental results from 101 induction motor tests are analyzed. A numerical model is determined and compared with different methods: separate losses method, modified current method and simple current method. An error analysis is conducted to examine the level of uncertainty by testing three asynchronous motors at 110 kW, 160 kW, and 300 kW. The results show that this approach can predict and estimate the efficiency reduction in rewound motors without expensive tests and can help the energy manager make effective cost decisions in replacing the rewound motors with more efficient ones by using an assessment of overconsumption and maintenance costs. Another advantage of this model is that it can be used to improve the software tools and can also be a very strong indicator to audit the repair quality

Energy Efficiency Labelling System for Industrial Motors

This paper presents an energy efficiency labelling system for industrial motors used in Sri Lanka. Industrial sector in Sri Lanka consumes 3,880 GWh of electricity, i.e. 33% out of 11,741 GWh of total electricity consumption (2015). Induction motors account for a high share of energy used in industry. The energy efficiency labelling system proposed will enable improved efficiency of industrial motors by reducing energy losses. The automatic efficiency testing program is developed using the LabView development platform based on IEC 60034-2-1 standard. Subsequently, a test bench design was also developed. It will be helpful in purchasing motors from the international market and thereby motor driven systems will achieve the next level of efficiency in the industrial sector. It also helps to cross check the efficiency level of repaired or rewound motors. An economic calculation model (tariff based) is developed to analyse the economic benefits of higher efficiency levels. This economic calculation model assists in decision-making of replacement of a motor or an upgrade of a system.

Investigation and Comparison of Three-Phase and Six-Phase Cage Motor Energy Parameters

Factory-produced three-phase 2,2 kW power cage motor with single-layer preformed winding and the same motor after its original winding was replaced with a single-layer preformed six-phase winding was investigated in this work. Electromagnetic properties of the stator windings of the analyzed motors were determined after performing the harmonic analysis of their generated rotating magnetomotive forces and by calculating the electromagnetic efficiency factors according to the results of this analysis. Electromagnetic efficiency factors of both single-layer preformed three-phase, and six-phase windings are equal under the same pole count but unequal number of pole and phase slots (kef = 0,914). All energy parameters of factory-made cage motor and rewound motor were calculated after completing their no-load and load tests and by using the segregated-losses method. It was estimated that under the rated load the phase electric current of rewound cage motor with six-phase stator winding decreased by 16,4 %, power input from electric grid decreased by 4,4 %, power losses decreased by 13,5 %, efficiency factor increased by 3,8 %, and power factor increased by 4,7 %, compared to identically loaded factory-made cage motor with respective energy parameters. Research has shown that energy parameters of the six-phase cage motor are noticeably better compared to the three-phase motor, even though the electromagnetic efficiency factors of their windings were equal. DOI: http://dx.doi.org/10.5755/j01.eee.21.3.5876

A Novel Algorithm for Estimating Refurbished Three-Phase Induction Motors Efficiency Using Only No-Load Tests

Induction motors fail due to many reasons, and many are rewound two or more times during their lifetimes. It is generally assumed that a rewound motor is not as efficient as the original motor. Precise estimation of efficiency of a refurbished motor or any existing motor is crucial in industries for energy savings, auditing, and management. Full-load and partial-load efficiency can be measured by using the dynamometer. This paper presents a novel technique for estimating refurbished induction motors’ full-load and partial-load efficiencies from only no-load tests. The technique can be applied in any electric motor workshop and eliminates the need for the dynamometer procedure. It also eliminates the need for the locked-rotor test. Experimental and field results of testing eight induction motors are presented, and the degree of accuracy is shown by comparing the estimated efficiencies against the measured values. To provide the necessary credits to the proposed technique, an error analysis is conducted to investigate the level of uncertainty through testing three induction motors, and the results of uncertainty of the direct measurements and no-load measurements using the proposed technique are presented.

Performace Evaluation & Life Cycle Costs In Rewound Induction Motors Used In Spinning Units

Induction motors being the major energy consumer in the plant offer opportunities of energy saving. In the spinning unit many induction motors are in-house rewound. This paper reports the analysis done on the rewound induction motors to determine its efficiency and life cycle cost comparison. Practical comparisons between rewound motors and the new motors are shown.

The Motor Rewind Issue-A New Look

Motor users have always been concerned about how long a rewound motor would last but never knew what to do about it. As power costs become higher and higher, a new and related question is cost. What happens to the efficiency and operating cost of a motor that is rewound two to three tithes during, its lifetime? The answers will depend upon how the motor is repaired. How motor losses can be changed during the rewind process is reviewed, along with what precautions should be taken to prevent an increase in operating costs and a decrease in motor life. The positive steps the motor user can take to protect his motor investment will also be explored.