Stress grading for high voltage motor and generator coils

Roberts, A.G.

doi:10.1109/57.400761

Cited by 91 publications

(40 citation statements)

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“…Exceedingly high electric field values (inside the insulation or at the surface) produce partial and/or surface discharges, which damage the insulation and lead to breakdowns and flashovers [13], [17]- [19].…”

Section: Introductionmentioning

confidence: 99%

Electrical shielding of MV/MF transformers subjected to high dv/dt PWM voltages

Guillod

Krismer

Kolar

2017

2017 IEEE Applied Power Electronics Conference and Exposition (APEC)

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Abstract-The introduction of Medium-Voltage (MV) SiliconCarbide (SiC) devices enables the usage of higher power converter operating voltages, switching frequencies, and commutation speeds. This implies that Medium-Frequency (MF) and High-Frequency (HF) transients are applied to passive components, and particularly to inductors and transformers. Together with the operation at medium voltage, this leads to challenging situations with respect to Common-Mode (CM) currents, parasitic resonances, insulation coordination, and EMI. The electrical field is the key parameter for the aforementioned effects. Therefore, this paper analyzes the electric field distribution (in the insulation, at the surface, and in the air) for a ±3.5 kV/±400 V, 50 kHz, 25 kW MV/MF transformer employed in a Solid-State Transformer (SST) demonstrator. For reducing the field, a suitable shield is designed. It is found that the shield drastically reduces the field at the surface of the transformer and in the air without increasing the losses.

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Section: Introductionmentioning

confidence: 99%

Electrical shielding of MV/MF transformers subjected to high dv/dt PWM voltages

Guillod

Krismer

Kolar

2017

2017 IEEE Applied Power Electronics Conference and Exposition (APEC)

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“…Furthermore, on top of the profile a layer with high permittivity is applied. This layer reduces surface impedance and, therefore, increases the forming of space charge [6]. The investigated combined field control method is shown in Figure 7.…”

Section: Combined Field Controlmentioning

confidence: 99%

“…To distribute the potential evenly, materials with relative permittivities significantly higher and lower than the wire insulation, ε wi , are necessary, while having a high electric breakdown strength as well. However, obtaining materials with the proper material characteristics might be difficult, since they are not widely available [6]. Furthermore, all capacitive layers should be void-free since voids in regions with high relative permittivity are prone to high levels of electric stress [14] and initiate partial discharge.…”

Section: Capacitive Field Controlmentioning

confidence: 99%

“…This method is applied in the linear actuator configuration by adding a layer with high permittivity adjacent to the inner and outer turn of the coil, as shown in Figure 4. The relative permittivity of this layer should be several times larger than the surrounding insulation materials for sufficient mitigation of the electric stress [6]. …”

Section: Refractive Field Controlmentioning

confidence: 99%

“…To decrease force disturbances and the cable mass, the operating voltage of the actuators is increased to above 2000 V. As a result, partial discharges occur during the expected lifetime of an inverter-fed actuator [1]. To ensure that the linear actuators reach their expected lifetime, electric field control methods have to be employed as is performed in cable accessories of medium and high-voltage networks [2][3][4][5] and high-voltage rotating machines [6][7][8]. These electric field control methods mitigate electric field stress and, therefore, ensure the partial discharge inception voltage is above the operating voltage.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of electric field control methods for foil coils in high-voltage linear actuators

Beek¹,

Jansen²,

Lomonova³

2015

Archives of Electrical Engineering

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This paper describes multiple electric field control methods for foil coils in high-voltage coreless linear actuators and their sensitivity to misalignment. The investigated field control methods consist of resistive, refractive, capacitive and geometrical solutions for mitigating electric stress at edges and corners of foil coils. These field control methods are evaluated using 2-D boundary element and finite element methods. A comparison is presented between the field control methods and their ability to mitigate electric stress in coreless linear actuators. Furthermore, the sensitivity to misalignment of the field control methods is investigated.

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