0
Still curious? Ask our experts.
Chat with our AI personalities
Coach
Beau
LaoAdd your answer:
Earn +20 pts
What is the effect of Phase sequence change in 3 phase supply?
It is important to keep the phase sequence the same throughout the system but it is more important to connect the transformers up with the right polarities. Never close a delta connection without a test fuse wire first, for correct transformer polarity connection.
What is neutral negetive sequence current?
Negative sequence current is defined as 3I2 = (phase 1)*(1angle 0) + (phase 2)*(1angle 240) + (phase 3)*(1angle 120) Negative sequence current is seen in three phase power systems due to natural system imbalance. Also during unbalanced fault conditions such as line to line, Line to ground, and line to line to ground faults. It is not seen in purely balanced three phase faults.
What is negative phase current?
Negative Phase Sequence is Phenomena generally found in motors,the formula for positive phase sequence is : Ip= Ir + a * Iy + a^2*Ibthe formula for negative phase sequence is : In= Ir + a ^2* Iy + a*IbAs the name suggest the sequence of current or the mmf is in reverse order, a reverse order current in stator will produce a reverse order mmf, now this reverse order mmf is rotating in direction opposite to the rotor of the motor, thus the mmf cut is very high and so current induced in stator is considerably high; as for normal mmf it is in direction of rotor so mmf cut is very small thus current induced is very small.this high current in your rotor leads to overheating of your motor and finally burning of your windings.CommentNegative phase sequence is not 'generally found in motors'. But one of the effects of negative phase sequence would be to cause a three-phase motor to reverse direction.
What are the procedures for the connection of single and 3 phase circuits?
Single phase connection has 1 phase wire and a neutral wire. Another wire for protective earth. In three phase system, motor can be connected in star or delta. Most AC induction motors are in Delta. Power distribution system is generally 3 phase 4 wire. Transmission system is 3 phase high voltage. Industry uses 3 phase system, where as 1 phase is for domestic, commercial applications. Both 1 and 3 phase system has a frequency. It is either 50 Hz or 60 Hz, depending upon the country or region.
Why is important for three phase supply voltage to be in-phase?
The phase voltages (i.e. line-to-neutral in a 4-wire system, or line-to-line in a 3-wire system) of a three-phase system are displaced from each other by 120 electrical degrees. Each phase voltage, in fact, is rarely in phase with its phase current, as the phase-angle (the angle by which a phase current lags or leads its phase voltage) is determined by the load not by the supply.In general, most loads are resistive-inductive so the phase current usually lags the phase current.So, to answer your question, it's not important that a phase current is in phase with its phase voltage -if that is what you are asking.
