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NWEMSDISTRIBUTIONTRANSFORMERCONNECTIONSRebekah WottonTacoma Public Utilitiesrwotton@ci.tacoma.wa.usEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 18931
NWEMS26 MVA SUBSTATION TRANSFORMER»High Voltage connected 115KV Delta»Distribution Voltage 7200/12,470 (12.5) Wye»26MVAAmperageEXCHANGING EXPERTISE SINCE 1893NWEMSVOLTAGE REGULATING TRANSFORMER»3 Single Phase Regulators»Distribution Voltage 7200»Each Regulator can raise or lower the voltage by 16, 5/8% stepsEXCHANGING EXPERTISE SINCE 18932
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 18933
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSBASICS»A conductor carrying current has a magnetic field around it.»With alternating current (ac), the magnetic field expands andcontracts, reversing polarity each half cycle.EXCHANGING EXPERTISE SINCE 18934
NWEMSBASICS»When more conductors are placed near the first conductorcarrying current, a current is induced in them and in theopposite direction.EXCHANGING EXPERTISE SINCE 1893NWEMSThe main purpose of a distributiontransformer is to transform theprimary voltage level (usuallyhigh) to a specific secondaryvoltage level which is required forspecific connected equipment.EXCHANGING EXPERTISE SINCE 18935
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSTRANSFORMER MAIN PARTS»The core, which is usually made of iron with lowmagnetic permeability.»Primary windings, a coil which receives the energyfrom the source.»Secondary windings, a coil that receives the energyfrom the primary and delivers it to the load.EXCHANGING EXPERTISE SINCE 18936
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSCOOLANT»For distribution transformers the coolant is almost always oil.»The electrical insulating qualities of oil is excellent, as well asthe ability of oil to transmit heat away from the core and coilsto the exterior radiating surfaces.EXCHANGING EXPERTISE SINCE 18937
NWEMSTURNS RATIO»The ratio is the number of turns on the primary winding to thenumber of turns on the coil of the secondary winding.»A primary coil with 600 turns at 7200 volts coupled with asecondary coil with 10 turns will deliver a secondary voltageof EXCHANGING EXPERTISE SINCE 1893NWEMSTRANSFORMER LOSSES»The transformer is not 100% efficient due to two types ofenergy losses.»No load losses are associated with magnetizing the iron core.»Load losses are associated with current flow.EXCHANGING EXPERTISE SINCE 18938
NWEMSEXCHANGING EXPERTISE SINCE ING EXPERTISE SINCE 18939
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSDELTA / DELTA»120/240/208 or 240/480/415 Volt 3‐Phase 4‐Wire, groundedneutral bushing.EXCHANGING EXPERTISE SINCE 189310
NWEMSNeutralEXCHANGING EXPERTISE SINCE 1893NWEMSNeutralEXCHANGING EXPERTISE SINCE 189311
NWEMSNeutralEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189312
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSNeutralEXCHANGING EXPERTISE SINCE 189313
NWEMSIf your transformer is:A) 8660v or higherorB) 200kVa or moreThen it is Subtractive PolarityEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189314
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189315
NWEMSOPEN WYE / OPEN DELTA»High Voltage Connected 2‐Phase Wye with Neutral»Secondary connected 3‐Phase 4‐Wire Open DeltaEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189316
NWEMSEXCHANGING EXPERTISE SINCE 1893NWEMSWYE – WYE»High Voltage Connected 3‐Phase 4‐Wire Wye.»Secondary Connected 3‐Phase 4‐Wire Wye.»The secondary voltage is 120/208 or 277/480 volts.EXCHANGING EXPERTISE SINCE 189317
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NWEMSNeutralNeutralEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189319
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NWEMSNEXCHANGING EXPERTISE SINCE 1893NWEMSEXCHANGING EXPERTISE SINCE 189321
2 EXCHANGINGEXPERTISESINCE1893 NWEMS 26 MVA SUBSTATION TRANSFORMER » High Voltage connected 115KV Delta » Distribution Voltage 7200/12,470 (12.5) Wye » 26MVA Amperage EXCHANGINGEXPERTISESINCE1893 NWEMS VOLTAGE REGULATING TRANSFORMER » 3 Single Phase
