Question

Questions: 1. Delta-Wye and Wye-Delta configurations both produce: a) Increases in secondary voltages and currents. b) Decreases in the secondary voltages and currents. c) Phase shift between the incoming and outgoing line voltages. d) Additional V3 increases in the secondary voltages and currents. ANSWER: Choose an item. 2. The line voltage at the secondary of a 10:1 wye-delta connected transformer will be: a) Equal to the line voltage at the primary times b) Equal to the line voltage at the primary times V3. C) Equal to the line voltage at the primary times 0.1 times d) ual to the line voltage at the primary times 0.1 times V3. ANSWER: Choose an item. 3. The line voltage at the secondary of a delta-wye connected transformer is: a) greater than it is with a wye-delta connection. b) less than it is with a wye-delta connection. c) the same as it is with a wye-delta connection. d) only dependent on the turns ratio. ANSWER: Choose an item. 4. The sum of the phase voltages in three-phase transformers: a) depends on the connection. b) equal zero when the transformers are properly connected. C) is V3 times the turns ratio. d) can only be determined when a load is connected to the secondary ANSWER: Choose an item. 5. Before three-phase transformers are put into service: b) the load must be balanced. a) the phase sequence of the incoming line must be verified. c) the winding connections must be checked to ensure proper phase relationship. ANSWER: Choose an item. d) the phase shift must be measured.

What is the answer for questions 2-5?

Answer 1

We will use the concept of three phase transformer connection.

The voltage transfer for three phase transformer occurs phase to phase.

Detailed solution is given below:

PAGE-01 Ane 2.1 10:11 mon will KV = 0.lv i vo - Linie voltage vacuou secondary Detta conmuted V X O|x| V K = Nz = Ool too Guven N1 = 60 Holtage drama fue detaren poumany to Lecondary scarie phace to phase. Thue, Lune Voltage vacuore Delta connected Lecondary vi - Lucie woltage at the frunavy X 0.1% te flence, option (c) is correct. K=No Ni Ane 3. The KV, 3 dok vi sine voltage vatio feu Delta- wye transfoumee = STB KU = VÕK. line voltage matro for Wye - Delta brane foumee - [Refue figure of Ane 2) oo BBK > 1K Thue lor same twin ratio (k), the livie woltage at the secondary of selta - Wye ne greater than a Wye-Delta connection Option (al is correct.

PAGIE-02 Ane 4. + Uploo - con & Up Loo Vp L120 m VpZ240 Vp 224003 como Up/120° DELTA CONNECTION STAR CONNECTION Helding the phone woltagu un Star - Connection, Up L120° + Vp 2240° + Up L120° Adding the khau voltage an Delta Connection Vp Loº + Up L240° + Vp L120° = 0. =0 the sum of the Thue in a three khase transfoumor phase voltages in equal to zero. & Option (b) is connect. Ane 5. Before three-phase transformou are put in service the phase sequence of the incoming lere must be wrified. Otherwise due to wincovieet connection were culating wwwuent will oss flow with in the transform. & Option (a) is correct.