The synchronous reactance of the synchronous machme is the ratio between:...

The synchronous reactance of the synchronous machine is the ratio between: 

(A) open circuit voltage and short circuit current at Constant field current (B) short circuit Voltage and open circuit current at constant field current (C) open circuit voltage and short circuit current at different field current (D) short circuit voltage and open circuit current at different field current
by

1 Answer

Answer :

The synchronous reactance of the synchronous machine is the ratio between: open circuit voltage and short circuit current at constant field current 

by

Related questions

The synchronous reactance of the synchronous machine is ______________. (A) Ratio between open circuit voltage and short circuit current at constant field current (B) Ratio between short circuit voltage and open circuit current at constant field current (C) Ratio between open circuit voltage and short circuit current at different field current (D) Ratio between short circuit voltage and open circuit current at different field current

Description : The synchronous reactance of the synchronous machine is ______________. (A) Ratio between open circuit voltage and short circuit current at constant field current (B) Ratio between short circuit ... (D) Ratio between short circuit voltage and open circuit current at different field current

Last Answer : Ans. A The Synchronous reactance of a synchronous machine is a total steady state reactance, presented to applied voltage, when rotor is running synchronously without excitation. Therefore , XS = Ef / IS = Emf of OC for same If / short circuit current

A 3-phase star-connected 75 MVA, 25 kV 3-phase synchronous generator has a synchronous reactance of...

Description : 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.

Last Answer : 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 5/6 p.u.

The maximum possible power of a 3-phase synchronous motor with synchronous reactance 0.8 p.u. connected

Description : The maximum possible power of a 3-phase synchronous motor with synchronous reactance 0.8 p.u. connected to a bus-bar of 1.0 p.u. and excitation adjusted to 1.2 p.u. is (A) 0.5 p.u. (B) 0.96 p.u. (C) 1.5 p.u. (D) 1.8 p.u.

Last Answer : The maximum possible power of a 3-phase synchronous motor with synchronous reactance 0.8 p.u. connected to a bus-bar of 1.0 p.u. and excitation adjusted to 1.2 p.u. is 1.5 p.u.

Why synchronous generators are to be constructed with more synchronous reactance and negligible resistance?

Description : Why synchronous generators are to be constructed with more synchronous reactance and negligible resistance?

Last Answer : The presence of more resistance in the Synchronous generators will resist or oppose their synchronous operation. More reactance in the generators can cause good reaction between the two and help the ... to remain in synchronism in spite of any disturbance occurring in any one of the generators

What is synchronous reactance?

Description : What is synchronous reactance?

Last Answer : It is the combination of leakage reactance and armature reactance

The angular displacement between two interconnected stations is mainly due to (a) armature reactance of both alternators (b) reactance of the interconnector (c) synchronous reactance of both the alternators (d) all of the above

Description : The angular displacement between two interconnected stations is mainly due to (a) armature reactance of both alternators (b) reactance of the interconnector (c) synchronous reactance of both the alternators (d) all of the above

Last Answer : (a) armature reactance of both alternators

A three-phase synchronous motor has a terminal voltage of 460 V and a terminal current of 120 A at a power factor of 0.95 lagging, synchronous reactance of 1.68 ohm and the field current is 47 A. The field to armature mutual inductance of the synchronous motor is _____________.

Description : A three-phase synchronous motor has a terminal voltage of 460 V and a terminal current of 120 A at a power factor of 0.95 lagging, synchronous reactance of 1.68 ohm and the field current is 47 A. The field to armature mutual ... _____________.      (a). 20mH   (b). 16mH   (c). 24mH   (d). 22mH

Last Answer : 22

A 500 MVA, 11 KV synchronous generator has 0.2 p.u. synchronous reactance. The p.u. synchronous reactance

Description : A 500 MVA, 11 KV synchronous generator has 0.2 p.u. synchronous reactance. The p.u. synchronous reactance on the base values of 100 MVA and 22 KV is  A) 0.16 B) 0.01 C) 4.0 D) 0.25

Last Answer : A 500 MVA, 11 KV synchronous generator has 0.2 p.u. synchronous reactance. The p.u. synchronous reactance on the base values of 100 MVA and 22 KV is 0.01

The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and

Description : The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is (A) 0.25 pu (B) 0.5 pu (C) 1.0 pu (D) 1.5 pu

Last Answer : The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is 0.5 pu

The ratio of the effective value of the counter EMF in volts, to the effective value of the current in amperes is called _____________. A. impedance factor B. capacitive reactance C. inductive reactance D. root mean square

Description : The ratio of the effective value of the counter EMF in volts, to the effective value of the current in amperes is called _____________. A. impedance factor B. capacitive reactance C. inductive reactance D. root mean square

Last Answer : Answer: C

Ratio of the rotor reactance X to the rotor resistance R for a two-phase servo motor

Description : Ratio of the rotor reactance X to the rotor resistance R for a two-phase servo motor (A) is equal to that of a normal induction motor (B) is less than that of a normal induction motor (C) ... than that of a normal induction motor (D) may be less or greater than that of a normal induction motor

Last Answer : C

Capacitive reactance formula

Description : Capacitive reactance

Last Answer : Capacitive reactance formula

Parallel Reactance and Resistance Example 1

Description : Parallel Reactance and Resistance Example 1

Last Answer : Parallel Reactance and Resistance Example 1

Circuits with capacitive reactance X C alone

Last Answer : Circuits with capacitive reactance X C alone. Capacitive reactance X C values in series. There is no resistance or inductive reactance only capacitive reactance is there. Let two capacitive ... horizontal in phasor diagram. The total current I T leads voltage V A by 90 degree.

AC Circuits with Resistance but No Reactance

Description : AC Circuits with Resistance but No Reactance

Last Answer : AC Circuits with Resistance but No Reactance AC Circuits with Resistance but No Reactance Series resistances let two resistances R 1 and R 2 are connected in series as shows in figure and there ... voltage. Voltage V A is common to both the branch hence voltage V A is common reference.

Potier reactance of an alternator is almost the same as

Description : Potier reactance of an alternator is almost the same as   (a) Field winding reactance (b) Total armature reactance (c) Leakage reactance of field winding (d) Armature leakage reactance

Last Answer : Potier reactance of an alternator is almost the same as Armature leakage reactance 

The operating characteristics of a reactance type distance relay (A) a stepped waveform for increasing

Description : The operating characteristics of a reactance type distance relay (A) a stepped waveform for increasing reactance (B) a straight line for a constant reactance (C) a circle for a constant reactance (D) a set of circles for variable reactances

Last Answer : The operating characteristics of a reactance type distance relay a straight line for a constant reactance

What is the reactance of a 3H inductor when the frequency is 120 Hz?

Description : What is the reactance of a 3H inductor when the frequency is 120 Hz? A. 2260 ohm B. 2060 ohm C. 360 ohm D. 0  

Last Answer : 2260 ohm is the reactance of a 3H inductor when the frequency is 120 Hz.

If X is the system reactance and R is its resistance, the power transferred is maximum when

Description : If X is the system reactance and R is its resistance, the power transferred is maximum when (1) X=R (2) X=1.414 R (3) X=1.732 R (4) X=2R 

Last Answer : x = 1.732R

In an induction motor, if the rotor resistance is equal to stand-still reactance then the maximum torque is_________.

Last Answer : In an induction motor, if the rotor resistance is equal to stand-still reactance then the maximum torque is equal to starting torque.

Capacitive reactance is more when?

Description : Capacitive reactance is more when?

Last Answer : Capacitive reactance is more when capacitance is less and frequency of supply is less.

The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q....

Description : The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms.

Last Answer : The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes 10 ohms.

What is the unit of reactance?

Description : What is the unit of reactance?

Last Answer : Unit of reactance is Ohms ( Ω ) .Reactance is denoted by X .

What is the inverse of reactance?

Description : What is the inverse of reactance?

Last Answer : Inverse of reactance is Susceptance .Unit of Susceptance is Siemens.

what is the reciprocal of reactance?

Description : what is the reciprocal of reactance?

Last Answer : reciprocal of reactance is susceptance.

A synchronous machine with low value of short-circuit ratio has?

Last Answer : A synchronous machine with low value of short-circuit ratio has lower stability limit.

What will happen if the induction motor runs at synchronous speed ?

Description : What will happen if the induction motor runs at synchronous speed ?

Last Answer : Since there is always slip present in rotor it cannot run at synchronous speed no current will be developed hence no torque will developed

Compare characteristics of asynchronous and synchronous transmission mode.

Description : Compare characteristics of asynchronous and synchronous transmission mode (four points). 

Last Answer : Synchronous transmission Asynchronous transmission 1. Synchronous transmission are synchronized by an external clock. 1. Asynchronous transmission are synchronized by special signals along the transmission ... for transferring a small amount of data as it is simple and economical.

Compare synchronous and asynchronous counter.

Description : Compare synchronous and asynchronous counter.

Last Answer : Asynchronous Counter Synchronous Counter In an Asynchronous Counter the output of one Flip Flop acts as the clock Input of the next Flip Flop. In a Synchronous Counter all the Flip Flop's are ... Also called as serial counter Also called as Parallel Counter

What is synchronous speed

Last Answer : this term sychronous speed related to AC  machines.. The speed depends on the EMF frequency and number of poles...

The synchronous motor can be used as a capacitor

Description : The synchronous motor can be used as a capacitor • By increasing excitation • By decreasing excitation • By increasing speed • By decreasing speed

Last Answer : The synchronous motor can be used as a capacitor By increasing excitation

A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously

Description : A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased  1. The power factor decreases upto a certain value of field current and thereafter it increases.  2. The armature current ... the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

Last Answer : A synchronous motor operates at 0.8 pf lagging. If the field current of the motor is continuously increased  1. The power factor decreases upto a certain value of field current and thereafter it increases.  2. The armature current ... the correct answer is (a) 1, 2 (b) 3, 4 (c) 1, 3 (d) 2, 4

The swing equation for a synchronous machine is based on

Description : The swing equation for a synchronous machine is based on (A) relative motion between load angle and stator magnetic field (B) maximum power flow possible through a particular point (C) net torque and angular displacement (D) relation between excitation voltage and excitation current

Last Answer : The swing equation for a synchronous machine is based on (A) relative motion between load angle and stator magnetic field (B) maximum power flow possible through a particular point (C) net torque and angular displacement (D) relation between excitation voltage and excitation current

A synchronous capacitor is

Description : A synchronous capacitor is (A) an unloaded and under excited 3-phase synchronous motor (B) a loaded and over excited 3-phase synchronous generator (C) an unloaded and over excited 3-phase synchronous motor (D) a 3-phase synchronous generator loaded with a capacitor bank

Last Answer : A synchronous capacitor is an unloaded and over excited 3-phase synchronous motor

A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now...

Description : A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now increased. It will feed (a) The same power but at a leading power factor (b) The same power ... a lagging power factor (c) More power at unity power factor (d) Less power at unity power factor

Last Answer : A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now increased. It will feed The same power but at a lagging power factor 

A 12 -pole, 440 V, 50 Hz, 3 -phase synchronous motor takes a line current of 100 A at 0.8 pf leading....

Description : A 12 -pole, 440 V, 50 Hz, 3 -phase synchronous motor takes a line current of 100 A at 0.8 pf leading. Neglecting losses, the torque developed will be

Last Answer : A 12 -pole, 440 V, 50 Hz, 3 -phase synchronous motor takes a line current of 100 A at 0.8 pf leading. Neglecting losses, the torque developed will be 1165 Nm

Consider the following statements regarding capability curves of a synchronous generator :

Description : Consider the following statements regarding capability curves of a synchronous generator :  1. The MVA loading should not exceed the generator rating.  2. The field current should not be allowed to exceed a ... 4. The load angle must be more than 90°.  Which of the above statements are correct ?

Last Answer : Consider the following statements regarding capability curves of a synchronous generator :  1. The MVA loading should not exceed the generator rating.  2. The field current should not be allowed to exceed a ... .  Which of the above statements are correct ? 1, 2 and 3 only

When a synchronous motor is started, the field winding is initially :

Description :  When a synchronous motor is started, the field winding is initially :  a)excited by a d.c. sources b) short circuited c) open circuited d) none of these

Last Answer :  When a synchronous motor is started, the field winding is initially : short circuited

A synchronous motor is essentially a motor with

Description : A synchronous motor is essentially a motor with   (a) Constant speed (b) Leading power factor (c) Unity power factor (d) Lagging power factor 

Last Answer : a

A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. ...

Description : A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. The field excitation of the motor is first decreased to zero and then increased in the ... 2) First decrease and then increase, (3) Increases continuously (4) First increase and then decreased

Last Answer : A 3~phase synchronous motor, connected to infinite bus, is operating at no load at normal excitation. The field excitation of the motor is first decreased to zero and then increased in the reverse direction. The armature current of the synchronous motor will: Increases continuously.

In a 3-phase synchronous motor; ...

Description : In a 3-phase synchronous motor;  (A) the speed of the stator MMF is always more than that of the rotor MMF (B) the speed of the stator MMF is always less than that of the rotor MMF (C) the ... that of the rotor MMF is zero (D) the rotor and the stator MMF are stationary with respect to each other

Last Answer : In a 3 -phase synchronous motor:  the rotor and the stator MMF are stationary with respect to each other

What type of excitation is given to the rotor winding of a synchronous motor?

Description : What type of excitation is given to the rotor winding of a synchronous motor?  (A) DC supply at 100 -250 V (B) AC supply at 400 V (C) Revolving field (D) Induction from stator currents 

Last Answer : Dc supply of 100 to 250v is applied on the field circuit to make stable magnetic field which thens follow the rotating magnetic feild of stator or armature circuit.

The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

Last Answer : Ns         equals        f/pair pole 50/4      - 12.5

What is the effect of resistance and reactance on power factor ?

Description : What is the effect of resistance and reactance on power factor ?

Last Answer : Power factor depends on resistance and reactance. As the resistance of the circuit increases, the phase angle between the current and the voltage decreases, resulting in an increase in the power factor ... current and the voltage increases, resulting in a decrease in the power factor of the circuit.

What is the expression of capacitive reactance ?

Description : What is the expression of capacitive reactance ?

Last Answer : Capacitive reactance = XC

In a series `LCR` circuit the frequency of a `10 V`, `AC` voltage soure is adjusted in such a fashion that the reactance of the inductor meausers `15

Description : In a series `LCR` circuit the frequency of a `10 V`, `AC` voltage soure is adjusted in such a fashion that the reactance of the inductor meausers `15

Last Answer : In a series `LCR` circuit the frequency of a `10 V`, `AC` voltage soure is adjusted in such a ... the series combination of `L` and `C`will be:

Why is there no inductive reactance in DC circuits?

Description : Why is there no inductive reactance in DC circuits?

Last Answer : Inductive reactance is a resistance by inductors to the changeof current flow, and is dependent on the frequency at which thecurrent oscillates. DC current flows in only one direction so aninductor's impedance remains the same.

Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop

Description : Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop

Last Answer : Answer: D

An AC circuit has a capacitive reactance of 30 ohms in addition to an inductive reactance of 40 ohms connected in series. What is the reactance of the circuit? A. 8.37 ohms B. 10.00 ohms C. 50.00 ohms D. 70.00 ohms

Description : An AC circuit has a capacitive reactance of 30 ohms in addition to an inductive reactance of 40 ohms connected in series. What is the reactance of the circuit? A. 8.37 ohms B. 10.00 ohms C. 50.00 ohms D. 70.00 ohms

Last Answer : Answer: B

The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip increases, rotor reactance decreases. B. The pullout point on the torque curve is about seven times the normal full load torque value. C. At stand still, stator current is 150% of normal. D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Description : The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip ... D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Last Answer : Answer: D