A star arrangement of resistances has branch resistance of 3 Ω. The equivalent delta arrangement will...

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A star arrangement of resistances has branch resistance of 3 Ω. The equivalent delta arrangement will have resistance of values (1) 9 Ω (2) 6 Ω (3) 3 Ω (4) 1 Ω

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Three resistances of 3 Ω each are connected in delta. The value of the resistances in the equivalent star is : (A) 27 (B) 9 (C) 1.5 (D) 1 Ω

A star circuit has element of resistance R/2. The equivalent delta elements will be?

Each branch of Y-connected load has resistance of 10 Ω. The resistance of each branch of an equivalent ∆-connected load will be   (a) 30 Ω (b) 100 Ω (c) 110 Ω (d) None of these

If each branch of a Delta circuit has impedance √3 Z, then each branch of the equivalent Y circuit has impedance:  (A) Z/√3 (B) 3Z (C) 3√3Z (D) Z/3

What is the equivalent resistance of one limb A when delta connection is transformed in to star?  (A) R1R3/R1+R2+R3 (B) R2R3/R1+R2+R3 (C) R1R2R3/R1+R2+R3 (D) R1+R2+R3

A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u. The actual value of x1 referred to the low voltage side is (A) 0.85 Ω (B) 3.63 Ω (C) 36.3 Ω (D) 252 Ω

A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is (A) 9997 Ω (B) 10000 Ω (C) 997 Ω (D) 10003 Ω

DC ammeter has a resistance of 0.1 Ω and its current range is 0-100 A. If the range is to be extended to 0-300 A, what shunt resistance need to be connected?  A) 0.025 Ω B) 0.05 Ω C) 0.015 Ω D) 0.03 Ω

for Delta-Star connection of 3-phase transformer: i) Draw the connection diagram ii) List any two advantages of this connection iii) State its area of application.

A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 kV is (A) 2/15 p.u. (B) 5/6 p.u. (C) 1.0 p.u. (D) 1.2 p.u.

A DC shunt generator supplies 450 A at 230 V. The resistances of shunt field and armature are 50 Ω and 0.025 Ω respectively. What will be the armature voltage drop?  (A) 11.24 V (B) 22.7 V (C) 31.6 V (D) 38.4 V

A moving coli ammeter has a fixed shunt of 0.02 Ω with a coil circuit resistance of R=1 kΩ and needs potential of 0.5 V across it for full scale deflection. Calculate the value of shunt to give full scale deflection when the total current is 10 A. (1) 0.05 Ω (2) 0.005 Ω (3) 0.5 Ω (4) 0.0005 Ω

A 1mA D' Arsonval movement has resistance of 100 Ω. It is to be converted to a 10 V voltmeter. The value of multiplier resistance is  (A) 999 Ω (B) 9999 Ω (C) 9900 Ω (D) 990 Ω

Describe the power and control circuit for automatic Star-Delta starter for 3-phase induction motor.

Consider the following statements: Star delta starter is used in 3-phase induction motor because it  1. Prevents heating of the motor winding  2. Ensures permissible minimum starting current  3. Is regulated by electricity authority  4. Ensures smooth run up to full load   Of these statements (a) 1, 2 and 3 are correct (b) 2, 3 and 4 are correct (c) 1, 3 and 4 are correct (d) 1 and 2 are correct

When The dc converter in figure shown has a resistance load of R = 10 Ω and the input voltage is Vs 220 V the converter switch remains on, its voltage drop is Vo -2 V. The chopping frequency is fI K sW Vs If the duty cycle is 50%, determine: (a) the average output voltage V (b) the RMS output voltage Vo (c) the converter efficiency (d) the effective input resistance of the converter

A 10A DC Ammeter has a resistance of 0.1 Ω is to be extended to 50 A, the required shunt wire is A) Manganin wire of 20 m Ω B) Constantan wire of 20 m Ω C) Manganin wire of 25 m Ω D) Constantan wire of 25 m Ω

When a dipole antenna of 1/8 length has an equivalent total resistance of 1.5 Watt then the efficiency of the antenna is   (A) 0.89159% (B) 8.9159% (C) 89.159% (D) 891.59%

A 3-phase, 2 pole, 11 kV, 10000 kVA alternator has earthed neutral through a resistance of 7.0Ω. The machine has current balance protection which operates if out of balance current exceeds 20% of full load. Determine %age of winding protected against earth fault (1) 10.6% (2) 11.6% (3) 10.9% (4) 11.2%

If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then  (A) zero sequence currents are present on both sides of the transformer  (B) zero sequence currents are absent on both sides of the transformer  (C) zero sequence currents are present on the secondary side but not on the primary side  (D) zero sequence currents are present on the primary side but not on the secondary side

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For a balanced three phase star connected load for which line voltage is 230V and per phase resistance and reactance is 6 Ohm and 8 Ohm respectively. Calculate: 1) phase voltage 2) line current 3) power factor 4) total power absorbed

The three non -inductive loads of 5 kW, 3 kW and 2 kW are connected in a star network between R, Y and B phases and neutral. The line voltage is 400 V. The current in the neutral wire is nearly (a) 11 A (b) 14 A (c) 17 A (d) 21 A

The standing wave ratio of a 75 Ω transmission line used to feed a 300 Ω resistive load will be _____.

A 3-phase delta connected squirrel cage induction motor when started with a DOL starter has a starting torque of 600 NM. Its starting torque when star delta starter is used:

Consider a cube of material of sides 1 cm with a resistance of 0.003 Ω between its opposite faces. What is the resistance if the same volume of the material is drawn into a length of 50 cm with a uniform cross – section? A) 0.003 Ω B) 0.15 Ω C) 7.5 Ω D) None of these

A dc shunt motor runs at 500 r.p.m at 220 V. A resistance of 4.5 Ω is added in series with the armature for speed control. The armature resistance is 0.5 ohms. The current to stall the motor will be (1) 44 A (2) 50 A (3) 44.4 A (4) 60 A

In the equivalent circuit of a 3-phase induction motor, the mechanical load on the motor can be represented by a resistance of value (1) R2 (2) R2/S (3) R2(1-S)/S (4) (R2/S)+1

A balanced three phase Delta connected load consists of three resistances each of four ohm's connected to a 400 V 3 phase 50 Hz supply. Find 1) phase voltage, 2) phase current, 3) line current, 4) power consumed.

A lamp of 100W at 200V is supplied current at 100 volts. It will be equivalent to the lamp of:   a. 50W b. 40W c. 25W d. 10W

A three-phase transformer, connected in star-delta, is composed of three single-phase transformers, each rated 127/ 13.2 kV. The line-to-line voltage ratio for the three-phase transformer is: A) 220 / 13.2 kV B) 127 / 13.2 kV C) 127 / 220 kV D) 220 / 220 kV

What is the equivalent resistance of a network having 5 resistors of each 10ohm connected in parallel?  (A) 10 Ohms (B) 50 Ohms (C) 500 Ohms (D) 2 Ohms

The average power delivered to an impedance 4 − j 3 Ω by a current 5Cos(100πt + 100) Ampere is A) 44.2 W B) 50 W C) 62.5 W D) 125 W

Can you guys explain the advantages of frequency converter against the star delta or soft starter?

Three equal impedances are first connected in delta across a 3 -phase balanced supply. If the same impedances are connected in star across the same supply then,

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The main application of delta/zig-zag connected 3-phase transformer is to supply (A) balanced loads (B) unbalanced loads (C) furnace loads (D) single-phase loads

When ‘n’ resistances each of value ‘r’ are connected in parallel, then the resultant resistance is ‘x’. When these ‘n’ resistances are connected in series, total resistance is  (A) n2X (B) X/n (C) n2/X (D) nX2

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A 3-phase voltage source inverter operates in 180° conduction mode with a star connected resistive load. If input dc voltage is 100 V, then the peak to peak output line voltage is :

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What is the percentage error when 3 resistors with ratings 100 Ω at 5%, 150 Ω at 6% and 250 Ω at 8% respectively, are connected in series? A) 6.33% B) 6.80% C) 19% D) None of these

3.2 x 10-5 A, equivalent to: A. 32 µA B. 3.3 µA C. 320 Ma D. 3,200 mA