An additional condition for parallel operation of three-phase transformers over single-phase transformers is that

An additional condition for parallel operation of three-phase transformers over single-phase transformers is that
by

1 Answer

Answer :

An additional condition for parallel operation of three-phase transformers over single-phase transformers is that the transformers should belong to the same vector group

by

Related questions

For the parallel operation of single phase transformers it is necessary that they should have?

Last Answer : Necessary conditions required to be satisfied in order to ensure successful parallel operation of single phase transformers:  1. Only transformers having the same phase displacement between primary and secondary ... . 7. The phase sequence must be followed strictly on HV and LV side connection.

parallel operation of mosfet can be done more easily as compared to thyristor. why?

Description : parallel operation of MOSFET can be done more easily as compared to thyristor. why?

Last Answer : Parallel operation of MOSFET can be done more easily as compared to thyristor because the resistance of MOSFET is increases with increase in temperature. MOSFET have the positive temperature coefficient. In ... the parallel operation of MOSFET can be done more easily as compared to the thyristor.

Explain the series and parallel operation of MOSFET. Which is suitable and why ?

Description : Explain the series and parallel operation of MOSFET. Which is suitable and why?

Last Answer : Series operation of MOSFET: To increase voltage handling capability MOSFETs are connected in series. When the MOSFETs are connected in series each MOSFET should turn on and turn off ... on and turn off time and transconductance. Each MOSFET should share current equally.  

explain the parallel operation of IGBT?

Description : Also, highlight the problem faced during parallel operation.

Last Answer : Parallel operation of IGBT: Parallel operation of IGBT is done for obtaining high current rating. Paralleling of IGBT reduces conduction losses and thermal stress. IGBT combines the qualities of ... . IGBTs must share losses equally otherwise IGBT may get failure due to thermal differences.

For the parallel operation of two or more D.C. compound generators, we should ensure that?

Last Answer : For the parallel operation of two or more D.C. compound generators, we should ensure that series fields of all generators should be either on positive side or negative side of the armature.

Two transformers do not have equal percentage impedance. This is likely to result in?

Description : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?

Last Answer : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.

Single-phase mid-point controlled rectifier with RL load

Description : Single-phase mid-point controlled rectifier with RL load

Last Answer : Single-phase mid-point controlled rectifier with RL load : The circuit configuration of single-phase midpoint controlled rectifier is shown in the figure. During positive half-cycle of ... some part of next positive half-cycle of voltage with reversed polarity can appear across load.

Single-phase Midpoint controlled rectifier with Resistive load

Description : Single-phase Midpoint controlled rectifier with Resistive load

Last Answer : Single-phase Midpoint controlled rectifier with Resistive load:  1) During positive half cycle of AC supply, a is positive with respect to b , this makes T1 forward biased and T2 is reverse ... voltage reverses the polarity and T2 is turned off. The operation is as shown in waveforms.

When the firing angle a of a single-phase, fully controlled rectifier feeding constant direct current into a

Description : When the firing angle a of a single-phase, fully controlled rectifier feeding constant direct current into a load is 30°, the displacement power factor of the rectifier is

Last Answer : When the firing angle a of a single-phase, fully controlled rectifier feeding constant direct current into a load is 30°, the displacement power factor of the rectifier is √3/2

A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc

Description : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is (A) 4.5 V (B) 6.75 V (C) 9 V (D) 13.5 V

Last Answer : A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is 9 V

In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load,

Description : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is (A) sinusoidal current (B) constant dc current (C) continuous rectangular pulses (D) alternating rectangular pulses

Last Answer : In a 230 V, 50 Hz single-phase SCR bridge converter operating at a firing delay angle, α and with large R-L load, the input source current is alternating rectangular pulses

Two 3-phase transformers cannot be operated in parallel, if their :

Description : Two 3-phase transformers cannot be operated in parallel, if their :  (A) kVAs are different (B) phase sequences are different (C) % impedances are different (D) voltage ratios are different

Last Answer : Two 3-phase transformers cannot be operated in parallel, if their : phase sequences are different

State any two conditions for parallel operation of 3-phase transformer.

Description : State any two conditions for parallel operation of 3-phase transformer.

Last Answer : Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.

If the percentage impedances of the two transformers working in parallel are different, then?

Description : If the percentage impedances of the two transformers working in parallel are different, then?

Last Answer : If the percentage impedances of the two transformers working in parallel are different, then parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load.

The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be :

Description : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be :  (A) 34.64 kVA (B) 75 kVA (C) 20 kVA (D) None of the above

Last Answer : The kVA rating of Three-phase transformer with Voltage = 200V and Current = 100A will be : 34.64 kVA

The speed of a three-phase induction motor is controlled by variable voltage variable frequency control

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Last Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to

Description : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be

Last Answer : Torque developed by a three-phase, 400V, induction motor is 100 N -m. If the applied voltage is reduced to 200-V, the d'veloped torque will be 25 N -m

A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for

Description : A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for

Last Answer : A 400 V, 50 Hz three-phase induction motor rotates at 1440 rpm on full -load. The motor is wound for 4 poles

The sending end and receiving end voltages of a three-phase transmission line are 10 kV/ph and 9.5 kV/ph,

Description : The sending end and receiving end voltages of a three-phase transmission line are 10 kV/ph and 9.5 kV/ph, respectively. If the resistance drop is 150 V/ph and receiving end power factor is 0.8, the sending end power factor is (A) 0.745 lagging (B) 0.775 lagging (C) 0.8 lagging (D) 0.85 lagging

Last Answer : Vscos¢s-Vrcos¢r=IR

In case one phase of a three-phase synchronous motor is short-circuited the motor will?

Last Answer : In case one phase of a three-phase synchronous motor is short-circuited the motor will not start.

With neat sketch explain four modes of operation of a TRIAC?

Description : With neat sketch explain four modes of operation of a TRIAC? 

Last Answer : Modes of operation of a TRIAC: There are four different operating modes of TRIAC:  1) MT2 and gate are positive with respect to terminal MT1(Mode1) : Here terminal MT2 is positive ... junction P2-N2 is forward biased, current carriers are injected and therefore, the TRIAC is turned on. 

Explain the operation of UPS with a neat block diagram.

Description : Explain the operation of UPS with a neat block diagram.

Last Answer : Uninterruptible-Power-Supplies (UPS): A block diagram of UPS system is shown in figure. It essentially consists of four major components: i)Rectifier (or battery charger) ii) ... . Due to fast action requirement, transfer switch can be implemented by fast acting semiconductor devices.

Which of the following thyristors can be used for high frequency of operation?

Description : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO 

Last Answer : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO 

A four -quadrant operation requires two full converters connected in

Description : A four -quadrant operation requires two full converters connected in  (1) Series (3) Back to back (2) Parallel (4) Series Cascade

Last Answer : A four-quadrant operation requires two full converters connected in Parallel 

In a single-phase induction motor, the operating direction is determined by the ________

Description : In a single-phase induction motor, the operating direction is determined by the ________ A) Rotor B) Stator C) Starting circuit D) None of these

Last Answer : In a single-phase induction motor, the operating direction is determined by the Starting circuit

The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a

Description : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) ... proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

Last Answer : The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ directly proportional to α and inversely proportional to Φ

The sequence components of current of a single-phase load connected to a 3-phase system are

Description : The sequence components of current of a single-phase load connected to a 3-phase system are (A) equal positive and negative sequence components (B) equal positive, negative and zero sequence components (C) vector sum of sequence currents is zero (D) algebraic sum of sequence currents is zero

Last Answer : The sequence components of current of a single-phase load connected to a 3-phase system are equal positive, negative and zero sequence components

In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then

Description : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then (A) the flux is constant (B) the flux first decreases and then increases in ... increases and decreases in the opposite direction with the same magnitude (D) current flows through the rotor

Last Answer : In a single-phase induction motor when the rotor is stationary and voltage is applied to the stator, then the flux first decreases and then increases in the same direction

A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred

Description : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is (A) 216 V (B) 226 V (C) 234 V (D) 236 V

Last Answer : A 230 V/460 V single-phase transformer operating at 20 A and unity power factor has primary referred resistance of 0.2 Ω and reactance of 0.5 Ω. The approximate primary induced emf is 226 V

In a single-phase transformer, the magnetizing current is

Description : In a single-phase transformer, the magnetizing current is (A) in phase with the no-load current (B) in quadrature with the no-load current (C) the product of no-load current and power factor (D) in phase with the flux in the core

Last Answer : In a single-phase transformer, the magnetizing current is in phase with the flux in the core

The starting winding of a single-phase motor is placed in?

Last Answer : The starting winding of a single-phase motor is placed in stator.

The capacitors used in single-phase capacitor motors have no?

Last Answer : The capacitors used in single-phase capacitor motors have no polarity marking.

If starting winding of a single-phase induction motor is left in the circuit, it will?

Last Answer : If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.

A single-phase induction motor is?

Last Answer : A single-phase induction motor is inherently non-self-starting with low torque.

The power factor of a single-phase induction motor is usually?

Last Answer : The power factor of a single-phase induction motor is usually lagging.

In a capacitor start single-phase motor, when capacitor is replaced by a resistance?

Last Answer : In a capacitor start single-phase motor, when capacitor is replaced by a resistance motor will continue to run in same direction.

In a shaded pole single-phase motor, the revolving field is produced by the use of?

Last Answer : In a shaded pole single-phase motor, the revolving field is produced by the use of shading coils.

The rotor developed by a single-phase motor at starting is?

Last Answer : The rotor developed by a single-phase motor at starting is zero.

In capacitor start single-phase motors?

Last Answer : In capacitor start single-phase motors current in the starting winding leads the voltage.

If the capacitor of a single-phase motor is short-circuited?

Last Answer : If the capacitor of a single-phase motor is short-circuited the motor will not start.

74)Power transformers are generally designed to have maximum efficiency around A. No load B. Half load C. Near full load D. 10% overload

Description : 74)Power transformers are generally designed to have maximum efficiency around A. No load B. Half load C. Near full load D. 10% overload

Last Answer : C. Near full load

[23] Transformers are rated in KVA instead of KW because A. load power factor is often not known B. KVA is fixed whereas KW depends on load power factor C. Total transformer loss depends on volt ampere D. It has become customary

Description : [23] Transformers are rated in KVA instead of KW because A. load power factor is often not known B. KVA is fixed whereas KW depends on load power factor C. Total transformer loss depends on volt ampere D. It has become customary

Last Answer : C. Total transformer loss depends on volt ampere

TRANSFORMERS MCQ

Description : TRANSFORMERS MCQ

Last Answer : 101. A shell-type transformer has (a) high eddy current losses (b) reduced magnetic leakage (c) negligibly hysteresis losses (d) none of the above Ans: b 102. A transformer can have regulation closer to zero (a ... (6) much smaller (c) much higher (d) somewhat smaller (e) none of the above Ans: c

What are the schedules of maintenance done on transformers?

Description : What are the schedules of maintenance done on transformers?

Last Answer : Ans. Following are the schedules of maintenance on transformers. a. Daily maintenance. b. Monthly maintenance. c. Quarterly maintenance. d. Half yearly maintenance. e. Yearly maintenance. f. 5 Yearly maintenance.

Why a transformer requires cooling. What are the methods of cooling transformers?

Description : Why a transformer requires cooling. What are the methods of cooling transformers?

Last Answer : Ans. Transformers requires cooling as they get heated up due to various losses taking place in the transformer. (like iron of copper losses) Following are the methods of cooling of transformer. a. Natural ... . Forced oil air Natural Cooling (OFAN). d. Forced oil and forced Air cooling (OFAF).

What are the loses in Transformers, Explain?

Description : What are the loses in Transformers, Explain?

Last Answer : Ans. (1) Iron loses (2) Copper loses Iron Loss : Iron loss occurs in the transformers Iron core due to hysteresis and eddy currents taking place. They are almost fixed irrespective of ... losses in the primary and the secondary windings of the transformer which with the loading of transformer.

Classify the transformers based on the construction, frequency and power.

Description : Classify the transformers based on the construction, frequency and power.

Last Answer : Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled. 

Which of the following connection of transformers will give highest value of secondary voltage ?

Description : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Last Answer : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Two transformers A and B having equal outputs and voltage ratios but unequal percentage

Description : Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 

Last Answer : Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 33%