This "near hands-on" training uses clear and concise presentations and eighty-seven interactions to convey the knowledge of three-phase transformer bank connections your workers need to build and service a bank. Recognize and explain the phasor diagrams used to illustrate delta and wye systems. List and explain basic requirements for connecting transformers to delta and wye systems. Single-Phase Transformer Connections. RGC*75/480 = 4kV, 3 bank, 3-75kVA transformers, 277/480V NOTE: Only plates DGC*25/208, DGC*50/208, and DGC*75/208, supply transformers that have already had their secondary internal taps changed to provide 208V. This General Electric lineman's pocket hand book (GE-2485 ) includes commonly used distribution transformer connections and related information including reference tables, voltages, diagrams, etc. Use these worksheets to draw the primary and secondary vector diagrams, then to sketch the physical connections on a transformer bank. The four basic connections are: Y-Y, Y-∆, ∆-Y, and ∆-∆. Generator Step-Up Auto-transformer Step-down pads transformer transformer 115/10 or 20 kV 500/230 230/13.8 132 345/161 161 161 230/115 132 230 230/132 115 345 69 500 34 GENERATION TRANSMISSION SUB … Clearing up confusion on bonding and grounding solidly grounded transformers. GE Manual GET-2485T FOR ELECTRICAL POWER LINEMEN - Books by General Electric.
A three-phase transformer is built for a specific connection and voltage transformation and the unit will have a nameplate with the internal connections shown. The banking of these units results in a 240/120V, 3-phase, 4-wire secondary. Transformer Polarity, Terminal Markings, and Connections Single-Phase Transformers Primary and secondary terminals of a single-phase transformer have the same polarity when the current enters the primary terminal and at the same time leaves the secondary terminal. Transformers are constructed with subtractive and additive polarities.
Note how a center-tap terminal is used on the secondary of one transformer to ground the entire system. When a balanced delta bank has a single phase load with unity power factor connected, the in phase transformer will supply half the current and the virtual open delta transformer will supply half the current. Also suppose the primary coil has Npturns of wire.
When a single unit or bank of three is used, there are four types of connections.
The rating of the transformer bank is reduced to 58% of that of the actual bank. Transformer Connections Worksheets These worksheets exercise your skills at drawing vector diagrams and wiring up transformer banks. Transformer connection diagrams . 13. a delta bank may be considered as a virtual transformer formed by two transformers in open delta in parallel with a third transformer. This demonstration will help build understanding around the two transformer rules that apply to Wye-Wye banks. The secondary voltage would then be 62.6V. Considering that a Δ configuration can operate satisfactorily missing one winding, some power system designers choose to create a three-phase transformer bank with only two transformers, representing a Δ-Δ configuration with a missing winding in both the primary and secondary sides: Three-Phase Transformer Winding Connections The primary and secondary windings of a three-phase transformer can be connected in different configuration to meet just about any voltage requirement. A free training video from Northwest Lineman College www.lineman.edu. GE Distribution Transformer Books. Vector Diagrams for Linemen shows how to quickly and correctly draw voltage vector diagrams for any transformer bank. If one transformer of delta-delta connection is damaged or accidentally opened, then the defective transformer is removed, and the remaining transformer continues to work as a three phase bank. One might be tempted to say that, given this is a 50kVA unit then the permissible current draw on the secondary side would now be 50,000/62.6=798.6A. One of the coils is connected to the AC source of voltage Vp (or current Ip) and this coil is called the primary coil. This dot represents the matching polarity on the primary and secondary sides of the single phase transformer.