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Why trefoil formation for single core cable?
Voltages are induced in the sheath of cables running in parallel which result in circulating currents flowing in the sheaths. The distances between single core cables running in parallel determine the voltages induced. With single core cables in trefoil formation (touching each other) the distances between the cables are minimum and thus the voltages induced are minimised and hence the circulating currents.The circulating currents cause localised heating.
What are the relations between individual voltages and the total voltages when resistors are connected in series and in parallel?
-- The current in each individual resistor is (voltage across the whole circuit) divided by (the resistance of the individual resistor). -- The current in any individual resistor is less than the total current in the circuit. -- The total current in the circuit is the sum of the currents through each individual resistor.
What is the RMS volts formula for 3 phase system?
In three-phase systems, we always consider individualline or phase currents, or individual line or phase voltages. In other words, we treat currents and voltages no differently from single-phase currents or voltages (i.e. we don't 'combine' them because they are three-phase quantities). So these quantities are expressed in r.m.s. values.
What is the difference between line to line voltage to line to ground voltage?
A three-phase, four-wire, system consists of three 'hot' conductors which are called line conductors, and a neutral conductor, sourced from a wye (or 'star') connected alternator or transformer. For this type of system, line voltages exist between line conductors, and phase voltages exist between any line conductor and the neutral conductor.A three-phase, three-wire, system consists of three 'hot' conductors which are called line conductors, sourced from a delta (or 'mesh') connected alternator or transformer. For this type of system, the phases are connected between lines. Line voltages exist between line conductors, and these are numerically equal to the phase voltages.
Differentiate delta to delta connection of the transformer to delta to Y connection?
In delta to delta there will be no ground on both primary and secondary sides. Leave the primary side but we take care on secondary side. If there any fault occurs on the secondary then there will be unbalanced voltages between the phases results in the flow of current through the secondary windings so only we are using star on the secondary side while having neutral to prevent such a current flow.
Does the formula used to calculate the turns ratio uses the phase voltages and phase current?
No, the turns ratio formula calculates the ratio of the primary to secondary winding turns on a transformer using the number of turns on each winding. Phase voltages and currents are not directly used in this calculation.
What is the voltage phase shift between primary and secondary line voltages in star-delta transformer connection?
The voltage phase shift between primary and secondary connections in a transformer is 180 electrical degrees.
What are the standard voltages for transmission?
The standard voltage for transmission is about 115 to 1,200 kV (long-distance transmission). The extreme high voltages are measured more than 2,000 kV and it is exists between conductor and ground.Answer for UKThe standard transmission voltages in the UK are 400 kV and 275 kV. Primary distribution voltages are 132 kV and 33 kV, and secondary distribution voltages are 11 kV and 400 V. These are all line voltages -i.e. voltages measured between line conductors.
Why trefoil formation for single core cable?
Voltages are induced in the sheath of cables running in parallel which result in circulating currents flowing in the sheaths. The distances between single core cables running in parallel determine the voltages induced. With single core cables in trefoil formation (touching each other) the distances between the cables are minimum and thus the voltages induced are minimised and hence the circulating currents.The circulating currents cause localised heating.
What are the relations between individual voltages and the total voltages when resistors are connected in series and in parallel?
-- The current in each individual resistor is (voltage across the whole circuit) divided by (the resistance of the individual resistor). -- The current in any individual resistor is less than the total current in the circuit. -- The total current in the circuit is the sum of the currents through each individual resistor.
What is the RMS volts formula for 3 phase system?
In three-phase systems, we always consider individualline or phase currents, or individual line or phase voltages. In other words, we treat currents and voltages no differently from single-phase currents or voltages (i.e. we don't 'combine' them because they are three-phase quantities). So these quantities are expressed in r.m.s. values.
What is the difference between lap windings and wave windings?
Lap windings has four current paths, the same as the number of the field poles, while the Wave windings has only two paths, regardless of the number of poles. Lap windings are also used for applications requiring lower voltages at higher currents, while Wave windings are used for applications requiring higher voltages at lower currents
What is the difference between line to line voltage to line to ground voltage?
A three-phase, four-wire, system consists of three 'hot' conductors which are called line conductors, and a neutral conductor, sourced from a wye (or 'star') connected alternator or transformer. For this type of system, line voltages exist between line conductors, and phase voltages exist between any line conductor and the neutral conductor.A three-phase, three-wire, system consists of three 'hot' conductors which are called line conductors, sourced from a delta (or 'mesh') connected alternator or transformer. For this type of system, the phases are connected between lines. Line voltages exist between line conductors, and these are numerically equal to the phase voltages.
Describe the similarities and differences between gyres and currents?
A difference between gyres and currents is that currents are formed by the wind, but gyres are formed by currents.
What is difference between balanced and unbalanced load?
three phase load is said to be balanced when the impedance and power factor of each load is equal.in this condition phasor sum of currents and phase voltages add up to zero.
Differentiate delta to delta connection of the transformer to delta to Y connection?
In delta to delta there will be no ground on both primary and secondary sides. Leave the primary side but we take care on secondary side. If there any fault occurs on the secondary then there will be unbalanced voltages between the phases results in the flow of current through the secondary windings so only we are using star on the secondary side while having neutral to prevent such a current flow.
What is the Difference between relation schema and relation instance?
difference between relation sehema and relation instance in dbms
