A small industrial plant draws an average load of 122 A at 0.73 power factor lagging from the secondary of its 2300/208 V, 60 kVA, star-delta transformer bank. Find: (iv) the rated transformer phase currents of the delta secondaries (v) percent of rated load on the transformers (vi) primary line and phase currents (vii) the kVA rating of each individual transformers

A small industrial plant draws an average load of 122 A at 0.73 power factor lagging from the secondary of its 2300/208 V, 60 kVA, star-delta transformer bank. Find: (iv) the rated transformer phase currents of the delta secondaries (v) percent of rated load on the transformers (vi) primary line and phase currents (vii) the kVA rating of each individual transformers

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.57P: A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when...

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A two-winding single-phase transformer rated 60kVA,240/1200V,60Hz, has an efficiency of 0.96 when operated at rated load, 0.8 power factor lagging. This transformer is to be utilized as a 1440/1200-V step-down autotransformer in a power distribution system. (a) Find the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the ratings as a two-winding transformer. Assume an ideal transformer. (b) Determine the efficiency of the autotransformer with the kVA loading of part (a) and 0.8 power factor leading.
An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
For the circuit element of Problem 2.3, calculate (a) the instantaneous power absorbed, (b) the real power (state whether it is delivered or absorbed). (c) the reactive power (state whether delivered or absorbed). (d) the power factor (state whether lagging or leading). [Note: By convention the power factor cos() is positive. If | | is greater than 90, then the reference direction for current may be reversed, resulting in a positive value of cos() ].
An industrial plant consisting primarily of induction motor loads absorbs 500 kW at 0.6 power factor lagging. (a) Compute the required kVA rating of a shunt capacitor to improve the power factor to 0.9 lagging. (b) Calculate the resulting power factor if a synchronous motor rated at 500 hp with 90 efficiency operating at rated load and at unity power factor is added to the plant instead of the capacitor. Assume constant voltage (1hp=0.746kW).
Three single-phase transformers, each rated 10MVA,66.4/12.5kV,60Hz, with an equivalent series reactance of 0.1 per unit divided equally between primary and secondary, are connected in a three-phase bank. The high-voltage windings are V-connected and their terminals are directly connected to a 115-kV three-phase bus. The secondary terminals are all shorted together. Find the currents entering the high-voltage terminals and leaving the low-voltage terminals if the low-voltage windings are (a) Y-connected and (b) - connected.
If the turn ratio of a step-down transformer is 10:1 and the series impedance (referred to the primary) of j50 ohm. If the no-load primary voltage is 230 kV (line-to-line), the secondary side is serving a Y-connected balance load of 1.5+ j0.25 ohms, the reactive power (per phase) absorbed by the load would be?
A single-phase 100-kVA, 2,400/240 V, 60-Hz distribution transformer is used as a step-down transformer. The load, which is connected to the 240 V secondary winding, absorbs 80 kVA at 0.8 power factor lagging and is at 230 V. Assuming an ideal transformer, calculate the following:(a) primary voltage;(b) load impedance;(c) load impedance referred to the primary;(d) the active and reactive power supplied to the primary winding.
1) A single-phase 100-kVA, 2,400/240 V, 60-Hz distribution transformer is used as a step-down transformer. The load, which is connected to the 240 V secondary winding, absorbs 80 kVA at 0.8 power factor lagging and is at 230 V. Assuming an ideal transformer, calculate the following: (a) primary voltage;(b) load impedance;(c) load impedance referred to the primary;(d) the active and reactive power supplied to the primary winding.
A 3-ph transmission line operating at 10 kV and having a resistance of 1 ohm and a reactance of 4 ohms is connected to the generating station bus-bars through a 5 MVA step-up transformer having a reactance of 5%. The busbars are supplied by a 10-MVA alternator having 10% reactance. Calculate the symmetrical short-circuit current if it occurs (a) at the receiving end of the line and (b) at the HV terminals of the transformer.
Given a 115kV/13.2kV distribution transformer rated at 30 MVA (OA) with an 8% nameplate impedance (Per Unit Transformer Impedance), calculate: The Full Load current in amps The Short Circuit current in amps The FA rating in MVA The FOA ratings in MVA.
If the turn ratio of a step-down transformer is 10:1 and the series impedance (referred to the primary) of j50 ohm. If the no-load primary voltage is 230 kV (line-to-line), the secondary side is serving a Y-connected balance load of 1.5+ j0.25 ohms, the real power (per phase) absorbed by the load would be: A. 142 MW B. None of the other choices are correct C. 94 MW D. 122 MW E. 49 MW
A 5,000-kVA, 3-phase transformer, 13.2/33-kV, A/Y, has a copper loss of 11 kW. The impedance drop at full-load is 7.5%. Calculate the primary voltage when a load of 4000 kW at 0.8 p.f. is delivered at 33 kv.