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The importance of phase sequence is related to the direction of rotation for a motor.
The three phases set up a rotating magnetic field, which runs the motor. Reverse the sequence, and most motors will run backwards, not necessarily a good thing.
There really are only two sequences; ABC, and ACB. All other sequences are permutations of one of these.
Wiki User
∙ 14y ago
Wiki User
∙ 11y agoIt's not 'necessary'; rather, it's a consequence of three-phase a.c. generation. When three potentials rise, in sequence, then the order in which they rise is the 'phase sequence' of those potentials.
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What is the symbol of phase sequence?
The symbol of phase sequence is RYB
How do you do for phase sequence protection at three phase motor operation?
motor is designed to operate in forward and reverse direction for the purpose of elevator. Phase sequence protection is not required.
What is phase sequence in 3-phase system?
The potential of each line of a three-phase system is displaced from the other two by 120 electrical degrees. The sequence, or order, in which the potential of each line reaches its peak value is termed the 'phase sequence' of the system. The 'normal' phase sequence of an alternator is considered to be the 'positive phase sequence', is arbitrarily assigned colours (e.g. red-yellow-blue, etc.), numbers (e.g. 1-2-3), letters (e.g. A-B-C), or a combination of letters or numbers (e.g. L1-L2-L3). If that alternator should run backwards, or (far more likely) if its terminals were disconnected and then incorrectly reconnected, the the sequence would be A-C-B (etc.), which would be considered to be 'negative phase sequence'. Before connecting two generators (or two complete transmission/distribution systems) together, their phase sequence must be confirmed as being the same. Reconnecting a three-phase motor with the wrong phase sequence would result in it running in the reverse direction and, possibly, damaging its load.
How do you check phase sequence?
It's outside the scope of this answer to go into the theory, but a 3 phase motor by convention normally rotates anticlockwise when viewed from the 'driven' end. To check phase sequence, the usual method is to use a phase sequence indicator. Originally these were like a miniature three phase motor encased in a hand-held device. If the flying leads were connected RYB, BRY, or YBR, the disc in the psi would rotate anticlockwise. If the flying leads were connected RBY, BYR, or YRB the disc would rotate clockwise. Nowadays, the mechanical aspect of the phase sequence indicator has been repalced with solid state devices that indicate on one of two leds if the sequence is c/w or ac/w. To check phase sequence you look for which phase out of the three phases peaks first. You could probably put each phase on an oscilloscope and see which one peaks first. Phase sequence is usually taken as positive anticlockwise from the reference voltage ( the phase that peaks the first).
How do you turn a 3 phase motor in to a generator?
We can convert a 3 phase ac motor into generator by changing phase sequence of the ac input cable of that motor
What is the difference between positive sequence and negative sequence arrangement?
The order in which the voltage of the coil reaches to the maximum value is called the Phase Sequence.POSITIVE PHASE SEQUENCE: If the coil is rotated in anticlockwise direction, the phase sequence will be Positive Phase Sequence, i.e., R-Y-B or A-B-C.NEGATIVE PHASE SEQUENCE: If the coil is rotated in clockwise direction, the phase sequence is called Negative Phase Sequence, i.e., R-B-Y or A-C-B.NOTE: Phase Sequence is of great importance in parallel operation of three phase transformers and alternators.
What is the symbol of phase sequence?
The symbol of phase sequence is RYB
How Negative phase sequence relay work?
How Negative phase sequence relay work
How the three phas e system generate?
Three coils ( Suppose: A, B and C ) are placed at 120 degree from each other in uniform magnetic field. The coils are rotated at uniform angular speed ( Suppose: omega ) ( unit: radian per second ). Emfs are induced in each coil. As coil B is placed at 120 degree from coil A, emf induced in coil B lags behind that of A by 120 degree. If the three phase voltage are equal in magnitude, the sum of the three phase voltage is zero. This can be shown by different ways. ( e.g. Vector sum ). The order in which the voltage of the coil reaches to the maximum value is called the phase sequence. ( Phase sequence is of great importance in parallel operation of three phase transformers and alternators ). Phase sequence R-Y-B is known as the positive sequence, while R-B-Y is known as the negative sequence. Phase sequence can be checked by using phase sequence indicator. Phase sequence can be reversed by interchanging any two terminals.
Sequence of phases in the cell cycle?
Interphase## G1SG2ProphasePrometaphaseMetaphaseAnaphaseTelophaseMitosisCytokinesis
Why to knw phase sequence?
If you reinstall a three-phase motor with two of the supply conductors interchanged, then the resulting negative phase sequence will cause the motor to run in reverse.
How do you do for phase sequence protection at three phase motor operation?
motor is designed to operate in forward and reverse direction for the purpose of elevator. Phase sequence protection is not required.
What the use of phase sequence indicator?
In indicator there is a led light source. It gives us the presence of the current source by indicate its light. If the phase of the indicator is not equal to the supply voltage then it can not give us the presence of current source by its led light off. If the phase of indicator is equal with the mane supply phase then its remaining bright and continuous gives us the indication of current source.ANSWER'Phase sequence' is the order, or sequence, in which each of the line voltages of a three-phase system reach their peak values. If 'normal' phase sequence is considered to be A-B-C (or R-S-T, etc.), then 'reverse phase sequence' would be A-C-B. Phase sequence is very important if, for example, you want to ensure that your three-phase motors rotate in the correct direction. So, after disconnecting them for maintenance, you can confirm the phase sequence of your incoming conductors by using a phase-sequence meter, before you reconnect that motor.
How is Negative phase sequence relay operated?
please see details in this site http://electricalandelectronics.org/2009/03/17/negative-phase-sequence-relay/
What is phase sequence in 3-phase system?
The potential of each line of a three-phase system is displaced from the other two by 120 electrical degrees. The sequence, or order, in which the potential of each line reaches its peak value is termed the 'phase sequence' of the system. The 'normal' phase sequence of an alternator is considered to be the 'positive phase sequence', is arbitrarily assigned colours (e.g. red-yellow-blue, etc.), numbers (e.g. 1-2-3), letters (e.g. A-B-C), or a combination of letters or numbers (e.g. L1-L2-L3). If that alternator should run backwards, or (far more likely) if its terminals were disconnected and then incorrectly reconnected, the the sequence would be A-C-B (etc.), which would be considered to be 'negative phase sequence'. Before connecting two generators (or two complete transmission/distribution systems) together, their phase sequence must be confirmed as being the same. Reconnecting a three-phase motor with the wrong phase sequence would result in it running in the reverse direction and, possibly, damaging its load.
How do you calculate negative phase sequence current?
4/4+4*4=20 is it correct by any means or not ? No this garbage has got nothing to do with negative phase sequence current in 3 phase electrical systems.
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.
