Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and the Yahoo Answers website is now in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
what is a rotating magnetic field?
would it be used in a d.c motor or a transformer or a alternator
- Eddie WLv 71 decade agoFavorite Answer
How about a little background information first? If you have 2 magnets, like charges would repel each other and opposite charges would attract each other. That is; N & N, S & S would repels each other. N & S would attract each other. This is a natural phenomenon.
Further more, if you wrap an iron core with an insulated winding and apply current (voltage) to it, this iron core would become an electro-magnet.
Now, consider 2 magnets are placed in a housing. One piece of magnet is fixed in place and the other piece is pivoted in the center so that it is free to rotate. When the like charges come together, the pivoted piece cannot move backwards. It has no choice but to rotate.
Now, consider if there are 2 iron-cored coils, called the field winding, you have one fixed in place, called the stator, and you have the other one pivoted in the center, called the armature. When you applying current to them separately, these 2 fields are electrically magnetized, as explained in the background information. If the current for the fileds are 180 degree out of phase, ie, the + always meet the + and the - always meet the -. The + always tries to chase the - and the - always tries chase the +. This phenomenon create a rotating motion. This is called the rotating magnetic field.
- Poor oneLv 61 decade ago
A rotating magnetic field is what happens in the stator of a 3 phase motor or generator.
If you imagine the generator as a magnet spinning within 3 coils placed 120 degrees apart. As the N of the magnet approaches a coil, it induces a voltage. So each coil will see a voltage as the Magnet passes. This voltage is then used to create a rotating magnetic field in the 3 coils of a motor to drive the shaft.
- ChuckLv 61 decade ago
A rotating magnetic field is required in AC (induction) motors and alternators. In the case of an alternator, the field winding itself is usually on the rotating armature. When it is energized with direct current and the shaft rotated, it induces voltage in the stationary (stator) windings, and the shaft experiences mechanical resistance to being rotated if there is current flowing in the stator windings - its a motor in reverse.
For an AC induction motor, the three phases are 120 degrees out of phase with one another, which produces a rotating magnetic field around the axis of the motor (since the windings are spaced at 120 degrees with respect to each other). A single phase induction motor achieves a rotating magnetic field by having two windings, and one of them has a capacitor to alter the phase of the current in that winding.
- shaunLv 46 years ago
A rotating magnetic field is a magnetic field that has moving polarities in which its opposite poles rotate about a central point or axis. Ideally the rotation changes direction at a constant angular rate. This is a key principle in the operation of the alternating-current motor.
Rotating magnetic fields are often utilized for electromechanical applications such as induction motors and electric generators. However, they are also used in purely electrical applications such as induction regulators.
- Anonymous5 years ago
The 3 phases of the motor are physically wound 120 degrees apart. Where the motor is powered, each phase produces a magnetic field. These are all added together vectorially. When you do this, you end up with one vector that rotates as the line voltages change.
- Anonymous1 decade ago
The rotating magnetic field is a key principle in the operation of alternating-current motors. A permanent magnet in such a field will rotate so as to maintain its alignment with the external field. This effect was conceptualized by Nikola Tesla, and later utilised in his, and others, early AC (alternating-current) electric motors. A rotating magnetic field can be constructed using two orthogonal coils with 90 degrees phase difference in their AC currents. However, in practice such a system would be supplied through a three-wire arrangement with unequal currents. This inequality would cause serious problems in standardization of the conductor size and so, in order to overcome it, three-phase systems are used where the three currents are equal in magnitude and have 120 degrees phase difference. Three similar coils having mutual geometrical angles of 120 degrees will create the rotating magnetic field in this case. The ability of the three-phase system to create a rotating field, utilized in electric motors, is one of the main reasons why three-phase systems dominate the world's electrical power supply systems.Source(s): http://en.wikipedia.org/wiki/Magnetic_field