Interlaminar Insulation Faults Detection and Quality Assessment of Magnetic Cores Using Flux Injection Probe

Abstract

Inter-laminar faults between laminations of the magnetic cores increase core losses and could cause major damage to electrical machines. A system has been developed to detect inter-laminar fault between the laminations of the magnetic cores by means of Flux Injection Probe (FIP). Experimental work was carried out to calibrate the measuring system and qualify its accuracy over a wide measurement range. Application of a prototype FIP to quality assessment of transformer laminations was investigated in two stages: inspection of stack of laminations with known inter-laminar faults applied by artificial shorts and inspection of stack of laminations with unknown quality. The experimental results show that the developed system is capable to detect inter-laminar fault between as few as 2 laminations.

An Experimental Approach for Condition Monitoring of Magnetic Cores With Grain-Oriented Electrical Steels

“…Quality of the magnetic cores are determined by electrical and magnetic properties of the magnetic materials, coating of the laminations which determine the inter-laminar resistance between the laminations, clamping pressure, manufacturing processes, etc. Key amongst these are manufacturing processes which have direct impacts on properties of the materials and hence normal operation of the magnetic cores and related devices [1][2][3][4][5][6][7].…”

“…In this regards, practical methods have been introduced and successfully employed to evaluate ILF of rotating machines [4][5][6][7][8][9][10][11][12] and transformers [13][14][15][16], and other magnetic devices with laminated cores. An overall review of these methods is performed in [1].…”

Development of a new approach to core quality assessment of modern electrical machines

“…Mechanical, magnetic and electric properties of electrical steels can be deteriorated by manufacturing process, e.g. cutting, pressing and welding, which has a direct impact on normal operation of the magnetic cores [3,4]. Quality of the magnetic cores is an important factor for the designers, manufacturers and users of the magnetic devices.…”

Efficient finite element method to estimate eddy current loss due to random interlaminar contacts in electrical sheets

“…1,2 There are both experimental and analytical approaches to model the interlaminar short circuits of lamination stacks. 3,4 In some studies, 5,6 artificial galvanic contacts are applied at the opposite sides of a transformer limb and additional losses are quantified through a measurement. However, the interlaminar galvanic contacts are random in nature and introduce uncertainties in the electromagnetic field solution.…”

“…These burrs also deteriorate the insulation of adjacent sheets and make random galvanic contacts between the sheets . There are both experimental and analytical approaches to model the interlaminar short circuits of lamination stacks . In some studies, artificial galvanic contacts are applied at the opposite sides of a transformer limb and additional losses are quantified through a measurement.…”