Siemens 6SR41 series Product User Manual page 68

Product Description
5.3 Cabinet Details
The transformer enclosure section primarily houses the transformer, polyglass air baffling,
and the secondary fuse block containing each power cell's A and C phase input fuses
(4160V only). The left front side of this section also serves as the access point for
input/output medium voltage cabling. The transformer core is grounded to the enclosure at
GND6.
Transformer
The 4160 V GenIV uses an isolating multi-winding nine secondary phase shifting transformer
(see Figure "GenIV Transformer").
It is configured for an 18-pulse power quality reaction to the utility by using +20°, 0°, and -20°
extended delta 750 V secondary windings with reference to the wye primary. The
transformer impedance is 6 - 8%. The 10000V GenIV uses an isolated multi-winding twenty-
four secondary phase shifting transformer. It is configured for a 48-pulse power quality
reaction to the utility by using +26.25 °, +18.75 °, +11.25 °, +3.75°, -3.75°,-11.25 °, -18.75 °, -
26.25 °.The transformer impedance is 8 - 12 %.
The transformer is a dry type forced air cooled unit, and polyglass air baffles are used to
direct air movement across the coils. Some transformers are equipped with secondary
winding coolers for improved thermal performance. The transformer is wound with 220°C
winding insulation and the BIL level depends on the input voltage rating. During Siemens'
assembly, the transformer and polyglass baffling are installed through the top of the
transformer section enclosure.
Adequate ventilation is provided by the centralized blower to maintain less than a 15°C rise
across the unit. A conservative winding design rise is used to ensure a 20-year life
expectancy given the non-linear secondary loading.
All connections to and from the transformer are made with insulated wire. For 4kV units, two
sets of normally closed thermal switches are mounted along the transformer air path and are
continuously monitored by NXG Control (typically 62.8° C and 70° C temperatures are used).
For 6000 V and 10units, two sets of normally closed thermal protectors are imbedded into
the transformer primary windings and are continuously monitored by NXG Control (typically
170°C and 190°C temperatures are used). The transformer is equipped with off-line taps to
accommodate utility line variations, +5%, 0%, and -5% are supplied on typical units (at
shipment, the units are placed on the 0% tap).
The default winding conductor is aluminum; however, some cases will require the use of a
copper winding, which is dependent upon the apparent power (kVA) size, input voltage,
frequency, and user preference. The transformer is optionally available with an electrostatic
shield and/or primary distribution class surge arresters. Several line voltages, apparent
powers (kVA), and frequencies are provided as customer options see Chapter "GenIV
Specifications" for applicable ranges and frames). Values outside these boundaries will be
considered CUSTOM and will be subject to engineering evaluation.
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Operating Instructions, Version AE 12/2009, A5E01454341C
Product User Manual