Investigation of Transformer-Based Solutions for the Reduction of Inrush and Phase-Hop Currents

Doğan, Rasim; Jazebi, Saeed; León, Francisco de

doi:10.1109/tpel.2015.2459032

Cited by 16 publications

(9 citation statements)

References 26 publications

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“…Several solutions external to the toroidal transformers had been proposed for inrush current mitigation such as; use of Negative Temperature Coefficient (NTC) thermistors in primary winding [6], pre-insertion resistors [7], and controlled switching [8]- [10], but all of them will increase the complexity of the system whilst reducing the reliability. Therefore, the robust transformer based solutions are always desirable in the industry [2].…”

Section: Engineermentioning

confidence: 99%

“…Transformer based solutions such as; the use of low grade (or non-annealed) electrical steel types, introducing air-gaps [11], and reducing the design flux density are always reliable and robust [2][4], but still these options have some drawbacks of being bulkier, higher cost, and most importantly they are compromising typical toroidal performance characteristics significantly. Therefore, the industry still needs a more developed transformer based solution for mitigating the inrush current.…”

Section: Engineermentioning

confidence: 99%

“…Generally, the inrush current does not last for a long time, but a few cycles of alternative current (See Figure 1). Magnitude of inrush current could be several times the rated current of the equipment, even closer to 30 times in extreme cases, especially with toroidal transformers [2]. The magnitude of the inrush current is based on several parameters like; switching angle, source impedance, magnitude of input voltage, residual flux on the magnetic core, saturation inductance, etc.…”

Section: Introductionmentioning

confidence: 99%

“…As a result, the overcurrent protection reacts for these high currents and trips the device from the source more often, resulting in inability to energize the equipment. Also the inrush current will result in significant voltage drops, and thus affect the power quality, reliability, and stability [2] [4].…”

Section: Introductionmentioning

confidence: 99%

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In-Rush Current Mitigation on Toroidal Transformers with Composite Cores

Perera¹,

Karunadasa

Zoysa³

et al. 2019

Engineer

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Toroidal transformers are high performance transformers used in high end applications. The unique toroidal construction drives them for such performance levels, but the gap less core construction itself makes them lag in controlling high inrush currents. Transformer based solutions are always favourable in the industry over the external solutions, but most of the existing transformer based solutions weaken the toroidal transformer's typical superior performance while mitigating the inrush current. This paper investigates an effective inrush current mitigating method with composite cores, while protecting the performance level of typical toroidal transformers and being competitive in the market. The proposed method has two cores made with different steel types which are positioned concentrically, where the inner core is uncut, but the outer core is cut with an air-gap. This paper investigates on the optimum air-gap that should be maintained to minimize the inrush current based on the transformer size and the particular two steel types. Further, this paper describes on the inrush current calculation on composite cores together with the formulae and derived characteristic curves. The results and formulae presented in this paper are verified with laboratory experiments with real transformers, built with composite cores.

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Section: Engineermentioning

confidence: 99%

Section: Engineermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

In-Rush Current Mitigation on Toroidal Transformers with Composite Cores

Perera¹,

Karunadasa

Zoysa³

et al. 2019

Engineer

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“…Additionally, the reconnection of the LV grid feeder after a tripped breaker causes inrush currents for the transformers. These inrush currents will stress the MV grid by injecting a zero sequence current with a magnitude, which can be several times higher than the nominal current designed for [33]. Due to the limited overloading capability of power semiconductors, this case is studied for the three phase short circuit on the LV grid side grid fed by the traditional transformer.…”

Section: Grid Faultsmentioning

confidence: 99%

Thermal Stress Analysis of Medium-Voltage Converters for Smart Transformers

Andresen

Carne

et al. 2017

IEEE Trans. Power Electron.

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A Smart Transformer (ST) can take over an important managing role in the future electrical distribution grid system and can provide many advanced grid services compared to the traditional transformer. However, the risk is that the advanced functionality is balanced out by a lower reliability. To address this concern, this work conducts thermal stress analysis for a Modular Multilevel Converter (MMC), which is a promising solution for the medium voltage stage of the ST. The focus is put on the mission profiles of the transformer and the impact on the thermal stress of power semiconductor devices. Normal operation at different power levels and medium voltage grid faults in a feeder fed by a traditional transformer are considered as well as the electrical and the thermal stress of the disconnection and the reconnection procedures. For the validation, the thermal stress of one MMC cell is reproduced on a laboratory setup with high speed temperature measurement. It is concluded, that the investigated conditions, including inrush currents and power variations, do not cause a significant lifetime reduction.

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