Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE) PDF Download

In this article, we will explain how a rotating magnetic field is created. Imagine a part of an electric motor called the stator, where the wiring is set up in a way that each section is 120 degrees apart from the others.

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Even though the total of three electric currents in a balanced system adds up to zero, the resulting magnetic field they create doesn't add up to zero. Instead, it stays at a constant value and rotates in space as time passes.


The magnetic strength made by each current in every section can be shown with these equations. This is similar to how the current works in a three-part system, as the magnetic strength is in sync with the current.

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Where, φR, φY and φB are the instantaneous flux of corresponding RedYellow and Blue phase winding, φm amplitude of the flux wave. The flux wave in the space can be represented as shown below. 

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Here are the values of the magnetic strength at point 0 on the graph:

- Red (φR):

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- Yellow (φY):

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- Blue (φB):

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

At this point, the total of these strengths (φr) is 1.5 times the maximum (φm).

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Now, let's look at point 1 on the graph, where the angle is 30 degrees. At this point:

- Red (φR):
Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- Yellow (φY):

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- Blue (φB):

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

The total of these strengths (φr) is still 1.5 times the maximum (φm), but now it's rotated 30 degrees clockwise without changing its value.

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Now, looking at the graph of the magnetic strength waves, let's focus on point 2, where the angle is 60 degrees.

- The value of Red (φR) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- The value of Yellow (φY) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- The value of Blue (φB) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

At this moment, the total of these strengths (φr) is still 1.5 times the maximum (φm), and it's shown in the figure below. Here, we can see that the resulting magnetic direction has moved 30 degrees more clockwise without changing its strength.

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Next, let's look at point 3 on the graph, where the angle is 90 degrees.

- The value of Red (φR) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- The value of Yellow (φY) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

- The value of Blue (φB) is

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

Again, the total of these strengths (φr) is 1.5 times the maximum (φm), and it's shown in the figure below. Here, we see that the resulting magnetic direction has moved another 30 degrees clockwise without changing its strength.

Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE)

In this manner, we can demonstrate that when a balanced power is supplied to the three-phase stator wiring, a rotating or revolving magnetic field is created in space.

The document Rotating Magnetic Field | Electrical Machines - Electrical Engineering (EE) is a part of the Electrical Engineering (EE) Course Electrical Machines.
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FAQs on Rotating Magnetic Field - Electrical Machines - Electrical Engineering (EE)

1. What is a rotating magnetic field?
Ans. A rotating magnetic field is a magnetic field that changes direction over time and creates a rotating effect. It is produced by multiple magnetic field sources that are out of phase with each other, resulting in a rotating pattern.
2. How is a rotating magnetic field created?
Ans. A rotating magnetic field is created by using multiple phase windings in an electric motor or generator. These windings are energized with alternating current (AC) that is out of phase with each other, producing a rotating magnetic field.
3. What is the significance of a rotating magnetic field in electric motors?
Ans. The rotating magnetic field is essential in electric motors as it interacts with the rotor's magnetic field, producing a torque that causes the motor to rotate. This enables the conversion of electrical energy into mechanical energy, allowing motors to perform work.
4. Can a rotating magnetic field be used for wireless power transfer?
Ans. Yes, a rotating magnetic field can be utilized for wireless power transfer. By creating a rotating magnetic field, it is possible to induce an alternating current in a nearby coil, enabling the wireless transfer of energy.
5. Are there any practical applications of a rotating magnetic field?
Ans. Yes, the rotating magnetic field has various practical applications. It is extensively used in electric motors, generators, transformers, and induction heating systems. Additionally, it plays a crucial role in wireless power transfer, magnetic levitation, and magnetic resonance imaging (MRI) technology.
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