Why Delta Star transformer Are Used For Lighting Loads?

Why Delta Star transformer Are Used For Lighting Loads?
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1 Answer

Answer :

For lighting loads, neutral conductor is must and hence the secondary must be star winding. and this lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta / star trformer is used for lighting loads.
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Related questions

Why Delta Star Transformers are used for Lighting Loads?

Description : Why Delta Star Transformers are used for Lighting Loads?

Last Answer : A. For lighting loads, neutral conductor is must and hence the secondary must be star winding.This lighting load is always unbalanced in all three phases. To minimize the current unbalance in the primary we use delta winding in the primary. So delta / star transformer is used for lighting loads.

Why Delta Star Transformers are used for Lighting Loads?

Description : Why Delta Star Transformers are used for Lighting Loads?

Last Answer : For lighting loads, neutral conductor is must and hence the secondary must be star winding and this lighting load is always unbalanced in all three phases.  To minimize the current unbalance in the primary we use delta winding in the primary So delta / star transformer is used for lighting loads.

What is the difference between delta-delta, delta-star transformer?

Description : What is the difference between delta-delta, delta-star transformer?

Last Answer : A. Delta-delta transformer is used at generating station or a receiving station for Change of Voltage (i,e) generally it is used where the Voltage is high & Current is low whereas Delta-star ... star neutral is taken as a return path and this configuration is used for Step down voltage phenomena.

Why input transformer of PUPS module 1 is delta-delta and module 2 is delta-star?

Description : Why input transformer of PUPS module 1 is delta-delta and module 2 is delta-star?

Last Answer : With the help of this arrangement, combined DC output from both chargers is equivalent to that from a 12-pulse rectifier. Advantage of 12-pulse rectifier is that the mains current is fairly close ... phase angle difference 30-degree between module 1 output and module 2 output give 12-pulse output. 

Why delta – delta CT’s are used for star – star transformer differential protection?

Description : Why delta – delta CT’s are used for star – star transformer differential protection?

Last Answer : Say primary neutral is not solidly earthed. Then for any earthfault on secondary terminal, the primary current distribution is so for external fault, the differential is likely to operate if sequence current ... into relay. The 2:1:1 distribution is possibly only for core type or delta tertiary.

In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.

Description : In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.

Last Answer : Ans: C This is vector group and has +30° displacement. Therefore, delta side leads by +30°.

When supplying emergency lighting loads, the storage battery initial voltage must not exceed the standard system voltage by more than _____________. A. 2% B. 3% C. 5% D. 10%

Description : When supplying emergency lighting loads, the storage battery initial voltage must not exceed the standard system voltage by more than _____________. A. 2% B. 3% C. 5% D. 10%

Last Answer : Answer: C

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.

Description : 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. 

Last Answer : Disadvantages: i) In this type of connection, the secondary voltage is not in phase with the primary. Hence it is not possible to operate this connection in parallel with star-star or delta-delta ... iv) As line current is equal to phase current the conductor size of winding should be large. 

A three-phase transformer, connected in star-delta, is composed of three single-phase transformers, each

Description : 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

Last Answer : 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: 220 / 13.2 kV 

A 4000 kVA, 11 kV/132 kV delta-star connected 3-phase transformer has reactance, x1 = 0.12 p.u.

Description : 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

Last Answer : 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 3.63 Ω

Delta/star transformer works satisfactorily when?

Last Answer : Delta/star transformer works satisfactorily when on balanced as well as unbalanced loads.

Why lighting isolation transformer is req.?

Description : Why lighting isolation transformer is req.? 

Last Answer : a) 3 wire to 4 wire conversion, since neutral is required for lighting load. b) Prevents transfer of E/F currents c) Reduces the fault level on secondary side and permits use of small sized cables / CB’s / fuses.

The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer

Description : The electrical schematic illustrated in figure A, depicts a/an _____________. EL-0059 A. autotransformer B. Delta Wye transformer C. primary EMF generator D. potential transformer

Last Answer : Answer: D

In a three-phase, open-delta connected transformer, the line current is equal to _____________. A. the phase current B. three times the phase current C. the sum of any two phase currents D. the difference of any two phase currents

Description : In a three-phase, open-delta connected transformer, the line current is equal to _____________. A. the phase current B. three times the phase current C. the sum of any two phase currents D. the difference of any two phase currents

Last Answer : Answer: A

If P is the power of a star connected system then what will be power of an equivalent delta connected system? A..P B. 3P C. P/3 D. None of the above

Description : If P is the power of a star connected system then what will be power of an equivalent delta connected system? A..P B. 3P C. P/3 D. None of the above

Last Answer : Ans: A

Disadvantages of Star-Delta Starting of Induction motor?

Description : Disadvantages of Star-Delta Starting of Induction motor?

Last Answer : In Star-Delta starting induction motor stator is connected in star connection for starting after picking up speed it is connected to delta connection. When induction motor is connected in star connection ... . This also results in reduced starting torque (1/3 times compared to delta connection).

What advantage has the star connection over the delta connection ?

Description : What advantage has the star connection over the delta connection ?

Last Answer : A. Each star connection transformer is wound for only 57.7% of line voltage . In hv transmission, this admits of much smaller transformer being built for high voltage than possible with delta connection, because of less insulation.

State the voltage and current relation in star and delta connection.

Description : State the voltage and current relation in star and delta connection. 

Last Answer : In star connection line current is equal to the phase current and line voltage is √3 times that of phase voltage. In delta connection line voltage is equal to the phase voltage and line current is √3 times that of phase current. 

What are the value of voltage and current in star connection and in delta connection?

Description : What are the value of voltage and current in star connection and in delta connection?

Last Answer : Star connection a. IL = IPh. b. VL = √3 VPh. ∴ VPh = VL/√3. Note: in star connection we are getting neutral point and we can able to measure the phase as well as line voltage. Delta connection a. VL = VPh. b. IL = √3 IPh. ∴ IPh = IL/√3.

What are the advantages of star-delta starter with induction motor?

Description : What are the advantages of star-delta starter with induction motor?

Last Answer : The main advantage of using the star delta starter is reduction of current during the starting of the motor. Starting current is reduced to 3-4 times of current of Direct online starting Hence the starting current is reduced , the voltage drops during the starting of motor in systems are reduced

Why star delta starter is preferred with induction motor?

Description : Why star delta starter is preferred with induction motor?

Last Answer : Star delta starter is preferred with induction motor due to following reasons: Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less ... caused. In addition, starting torque is increased and it prevents the damage of motor winding.

The inverse definite mean time relays are used for over current and earth fault protection of transformer against (a) heavy loads (b) internal short-circuits (c) external short-circuits (d) all of the above

Description : The inverse definite mean time relays are used for over current and earth fault protection of transformer against (a) heavy loads (b) internal short-circuits (c) external short-circuits (d) all of the above

Last Answer : (b) internal short-circuits

48.During light loads, the transformer efficiency is low because A. Secondary output is low B. Transformer losses are high C. Fixed loss is high in proportion to the output D. Cu loss is small

Description : 48.During light loads, the transformer efficiency is low because A. Secondary output is low B. Transformer losses are high C. Fixed loss is high in proportion to the output D. Cu loss is small

Last Answer : C. Fixed loss is high in proportion to the output

The efficiency of a transformer, under heavy loads, is comparatively low because?

Description : The efficiency of a transformer, under heavy loads, is comparatively low because?

Last Answer : The efficiency of a transformer, under heavy loads, is comparatively low because copper loss becomes high in proportion to the output.

function of equipment’s used in sub-stations : (i) Earth Switch (ii) Relay (iii) Lighting Arrester (iv) Auxiliary transformer

Description : function of equipment’s used in sub-stations : (i) Earth Switch (ii) Relay (iii) Lighting Arrester (iv) Auxiliary transformer 

Last Answer : (i) Earth Switch   It's function is to discharge the ground capacitance when line is open circuited for maintenance purpose by isolator.) Earthing switch is inter - locked with isolator from the safety point ... 3-ph, 4wire, 400V) to give supply to control room, area lighting, staff quarters etc, 

Explain energy conservation method in lighting system by using installation of separate transformer / servo stabilizer.

Description : Explain energy conservation method in lighting system by using installation of separate transformer / servo stabilizer.

Last Answer : Energy conservation techniques by installation of separate transformer / servo stabilizer: The luminous efficiency of lamps depends upon the voltage applied across the terminals. It gives its best ... the voltage constant in that installation for giving best luminous efficiency of lamps.

The three non -inductive loads of 5 kW, 3 kW and 2 kW are connected in a star network between R, Y and B...

Description : 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

Last Answer : 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 11 A

Give any two advantages of open delta connection of 3-phase transformer.

Last Answer : Advantages of open delta connection of 3-phase transformer:  1. When one of the phase in case of delta-delta bank is out of order by any reason, the service will be continued till ... demand in future (about 33%) will be supplied by converting open delta connection to delta-delta connection.

The main application of delta/zig-zag connected 3-phase transformer is to supply

Description : 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

Last Answer : The main application of delta/zig-zag connected 3-phase transformer is to supply unbalanced loads

Write the formula from Star to Delta ?

Description : Write the formula from Star to Delta ?

Last Answer : Answer : Dividing the product of the resistors connected to the star by dividing the resistors of the opposite arm by taking two together, the quotient is equal to the value of each resistor connected.

What equipment are star delta starters used in?

Description : What equipment are star delta starters used in?

Last Answer : Star Delta starter is used to start the AC motors with rating generally higher than 11 kw, depending upon the type of load.

What is star / delta ?*

Description : What is star / delta ?*

Last Answer : In star VL = √3 VΦ In delta VL = VΦ

Is the alternator connected star or delta

Description : Is the alternator connected star or delta

Last Answer : Look up in Dennis T Hall. Also in your ship ask E/O. Normally star.

If a motor is wound star and you want to change to delta what should you do?

Description : If a motor is wound star and you want to change to delta what should you do?

Last Answer : Open the terminal connection box. Remove the shorting link connecting the common connection (star) point of A2, B2 and C2. With the 3 phase windings marked A1A2, B1B2, C1C2, connect A2 to B1, B2 to C1 and C2 to A1.

Is the ship's alternator Star wound or Delta wound?

Description : Is the ship's alternator Star wound or Delta wound?

Last Answer : Refer Dennis T Hall

What is the meaning of Star winding/ Delta winding?

Description : What is the meaning of Star winding/ Delta winding?

Last Answer : Refer Dennis T Hall

Draw the star and delta connection. State any one conversion formula.

Description : Draw the star and delta connection. State any one conversion formula.

Last Answer : star and delta connection

Convert the delta network into equivalent star network.

Description : Convert the delta network into equivalent star network.

Last Answer : Delta to start network R1 = 4x6/ 4+6+2 = 24/12 =2/1= 2Ω R2 = 2x6/ 4+6+2 = 12/12= 1 = 1Ω R3 = 4x 2/ 4+6+2 = 8/12= 2/3= 0.66Ω

Derive an expression for delta to star transformation.

Description : Derive an expression for delta to star transformation. 

Last Answer : For delta network the resistance between the terminals 1 and 2 consists of R12 in parallel with  (R23+R31) Hence ,the resistance between the terminals 1 and 2 is In case of star network the ... equation( ii) from( i),we get Adding equations (iii) and( iv),we have 

Calculate the equivalent resistance between A & B using star-delta conversion

Description : Calculate the equivalent resistance between A & B using star-delta conversion

Last Answer : Solution :  Converting Inner star in to delta-  Resistances 4 and 6 are in parallel in all branch so

Develop the control circuit for star-delta starter used for starting a 3 ∅ induction motor.

Description : Develop the control circuit for star-delta starter used for starting a 3 ∅ induction motor.

Last Answer : Control Circuit for Star-Delta Starter: 1) Automatic Star-Delta Starter: OR 2) Semi- automatic Star-Delta Starter:

Delta to Star Conversion Example

Description : Delta to Star Conversion Example

Last Answer : Delta to Star Conversion Example

Wye (Star) to Delta Conversion

Description : Wye (Star) to Delta Conversion

Last Answer : Wye (Star) to Delta Conversion

Star to delta conversion examples

Description : Star to delta conversion examples

Last Answer : Star to delta conversion example 1

Draw and explain star delta starter for 3 phase induction motor

Description : Draw and explain star delta starter for 3 phase induction motor

Last Answer : Star Delta Starter for 3 Phase Induction Motor:  Diagram Explanation: The stator winding of the motor which is designed for delta operation is connected in star during starting ... which connects stator windings in delta connection. Now each stator phase gets full line voltage VL.

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

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

Last Answer : Power circuit: Control circuit: 

Compare star and Delta Connection.

Description : Compare star and Delta Connection.

Last Answer : Compare Star and Delta connected system:  Star connected system Delta connected system   In STAR connection, the starting or finishing ends (Similar ends) of three coils are connected together to form the ... VPH Line Current is √3 times of Phase Current. i.e. IL = √3 IPH

What are the advantages of the use of frequency converter instead of star-delta or soft starter?

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

Last Answer : ¬Soft starters  A soft starter is, as you would expect, a device which ensures a soft starting of a motor. A softstarter has different characteristics to the other starting ... at rated current from zero to full speed. Frequency converters are becoming cheaper all the time.

Consider the following statements: Star delta starter is used in 3-phase induction motor

Description : 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 ... and 4 are correct (c) 1, 3 and 4 are correct (d) 1 and 2 are correct 

Last Answer : 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 ... and 4 are correct (c) 1, 3 and 4 are correct (d) 1 and 2 are correct 

If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded

Description : 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) ... side  (D) zero sequence currents are present on the primary side but not on the secondary side

Last Answer : If an unsymmetrical line to ground fault occurs at the secondary terminals of a delta/star, ungrounded transformer, then zero sequence currents are absent on both sides of the transformer