Insulation design of low voltage electrical motors fed by PWM inverters

L. Lusuardi, A. Cavallini, M. G. de la Calle, J. M. Martínez-Tarifa and G. Robles, “Insulation design of low voltage electrical motors fed by PWM inverters,” in IEEE Electrical Insulation Magazine, vol. 35, no. 3, pp. 7-15, May-June 2019.

doi: 10.1109/MEI.2019.8689431

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8689431&isnumber=8689426

Abstract— This paper proposes a model to determine the partial discharge inception voltage of magnet wires, including the effect of elevated temperatures, and shows its applicability to the complete range of wire geometries considered in IEC Standard 60317-13.

For long, the insulation of magnet wires used in low voltage motors was mostly stressed by temperature and vibrations. In addition, moisture sometimes hastened thermo-mechanical stress by hydrolyzing the insulation leading to crack formation. The ultimate breakdown mechanism was an excessive leakage current throughout cracks and pinholes in the insulation. Within this framework, the thickness of the insulation was dictated mostly by mechanical considerations, to prevent crack formation during manufacturing and operation. Electrical stress did not play a key role in the aging process.
Power electronics changed this picture…

Keywords— inverter-fed machine, partial discharges, insulation design.

Partial Discharge Signal Propagation in Medium Voltage Branched Cable Feeder

M. Shafiq, K. Kauhaniemi, G. Robles, G. A. Hussain and L. Kumpulainen, “Partial discharge signal propagation in medium voltage branched cable feeder,” in IEEE Electrical Insulation Magazine, vol. 34, no. 6, pp. 18-29, November-December 2018.

http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8507714&isnumber=8507707

doi: 10.1109/MEI.2018.8507714

Abstract— Rising global and regional electricity use is accelerating the need to upgrade networks. The adoption of sustainable ways of energy generation (renewables energy resources) is the top priority of today’s grid, and these resources are predominantly embedded within the distribution networks that are mostly connected by medium voltage (MV) cables. Driven by urbanization trends, negative land value impacts, public safety, environmental aesthetics, and network reliability, the resistance to overhead lines in distribution networks is gradually increasing in many countries. Either choosing the proactive path considering the operational superiority of underground cables compared with overhead lines or following the ongoing legislative policies, the use of cables has been increasing rapidly over the past 30 years. This trend is likely to accelerate.

Keywords— Power cables; Partial discharges; Power cable insulation; Cable shielding; Current measurement; Voltage measurement; Medium voltage; Condition monitoring; Cables; Branch; Joint; Diagnostic; Sensor},