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22.05.2012 at 13:25

Track Report

HTT GiessharztransformatorIn July 2008 Schmid Silicon Technology GmbH (SST), the leading technology, equipment and EPC provider for high-end solar and electronic grade polysilicon and monosilane gas production plants, honored HTT Hochspannungstechnik und Transformatorbau in Hann. Münden / Germany with the order of one very special three- phase cast resin transformer for SST’s first Monosilane-based semi-industrial plant in Schwarze Pumpe, Saxony/Germany.

The three- phase cast resin transformer, type GDGN 2850/36-1, is a special design transformer which has been engineered and built in a close collaboration between SST’s plant engineers and the design engineers of HTT.

The challenge of this very specific transformer design was to meet the requirement of providing seven nominal low voltages, each with its individual current. Two adjacent phase voltages had to be able to conducting power at the same time, and the transformer had to be able to handle unsymmetrical load. All features had to be provided within one single transformer.

Technical specification in detail:


GDGN 2850 / 36 – 1

Nominal rating
kVA 1980
Nominal high voltage
V 30000
Tappings % +/-5
Tap changing to
V 20000
Tappings % +/-5

Nominal low voltage


1800 (183 A)
1200 (320 A)
810 (508 A)
600 (668 A)
420 (864 A)
360 (1076 A)
300 (1250 A)

Vector group

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The transformer was delivered to SST’s plant in December 2009. The production start at SST’s plant was in 2011. On June 12th 2011 First Silicon Out was announced by SST.

The transformer from the HTT factory in Hann. Münden greatly contributed to the successful start-up and operations. The transformer ensures that the process of silicon production is not interrupted by any power failures or any problems that can potentially result from a transformer.

The Transformer from HTT affords maximum operational safety and reliability.

Excellent teamwork between the process engineers of SST and the design engineers of HTT, precision in the production and HTT’s experience in manufacturing this kind of special transformers where among the key-factors in creating this mutually successful experience.