How the motor works

The electromagnet is the basis of the motor. Suppose you create a simple electromagnet by winding 100 loops of wire around a nail and connecting them to a battery. When the battery is connected, the nail becomes a magnet and has the North and South poles.

Now suppose you pick up the nail magnet, pass an axis through it and hang it in the middle of the horseshoe magnet, as shown in the figure. If the battery is connected to the electromagnet and the north end of the nail is shown in the figure, the basic law of magnetism tells you what happens: the north end of the electromagnet is repelled by the north end of the horseshoe magnet and attracted to the south end of the horseshoe magnet. The southern end of the electromagnet will be excluded in a similar manner. The nail moves half a circle and then stops at the position shown.

Animated image of motor

You can flip the magnetic field by changing the direction of the electrons.

How's it going?

The key to the motor is to go further so that the magnetic field of the electromagnet is flipped when this half-circle of motion is complete. You can flip the magnetic field by changing the direction in which electrons flow through the wire, which means flipping the battery. Flipping causes the electromagnet to complete the other half of the circle. If the magnetic field of the electromagnet is flipped exactly at the right time at the end of each half circle of motion, the motor will rotate freely.

Working principle of DC motor

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Motor Diagram

There are two magnets in the motor: the rotor (green) is an electromagnet and the field magnet is a permanent magnet.

How's it going?

As we mentioned, you will encounter two types of motors: DC and AC. The latter is a DC or DC motor, which was developed in the mid-1800s and is still in use.

A simple motor has six parts:

stator

rotor

commutator

Brush

axis

DC power supply

The external part of the DC motor is the stator: a permanent magnet that is not moving. The inner part is the rotor, it will move. Here the rotor is like the nail in our previous example, and the stator is like a horseshoe magnet.

When DC passes through the rotor, it generates a temporary electromagnetic field that interacts with the magnetic field of the stator. The work of the commutator is to keep the polarity of the magnetic field flipped so that the rotator can keep rotating. This produces the torque required to generate mechanical power.

Toy motor

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Toy Motor Diagram

Outside you can see the steel can that forms the main body of the motor, a shaft, a nylon end cover and two battery leads.

How's it going?

The toy DC motor in the picture is small, about the size of a coin, with two battery leads. If the battery lead of the motor is connected to the battery, the shaft will rotate. If you reverse the traverse, it will rotate in the opposite direction.

The nylon end cap is fixed in place by two tabs. Inside the end cap, when the motor rotates, the brush of the motor transfers energy from the battery to the commutator. (Modern DC motors are usually brushless because brushes wear out and need to be replaced.)

The shaft fixes the rotor and the commutator. The rotor is a set of electromagnets, three in this case. The armature in the motor is a set of stacked thin metal plates with thin copper wires winding around the three poles of the rotor. Each end of the wire (one at each pole) is connected to one terminal, and each of the three terminals is connected to one pole of the commutator.

Part of any DC motor is the stator. In this motor, it is composed of the tank itself plus two curved permanent magnets. In a DC motor, the armature is the rotor and the magnetic field is the stator.

Rotor, commutator and brush

The contacts of the commutator are connected to the axis of the magnet, so they rotate with the magnet.

The contacts of the commutator are connected to the axis of the magnet, so they rotate with the magnet.

As we mentioned earlier, the rotor is like a nail in an electromagnet graph. The commutator is also connected to the shaft. The commutator is only a pair of plates connected to the shaft. These plates provide two connections for the coils of the electromagnet.

The "flip field" part of the motor is completed by two parts: commutator and brush.

The diagram shows how the commutator (green) and the brush (red) work together to let the current flow to the electromagnet and, at the appropriate time, flip the direction of the electron flow. The contacts of the commutator are connected to the axis of the magnet, so they rotate with the magnet. The brush is only two pieces of elastic metal or carbon that come into contact with the commutator contact.

Put them together

When you put all these parts together, you have a complete motor.

The key is that when the rotator passes through the horizontal position, the magnetic pole of the electromagnet flips. Because of the flip, the north pole of the electromagnet is always above the axis, so it repels the north pole of the stator and attracts the south pole of the stator.

Typically, the rotator will have three poles instead of the two as shown in this paper. The motor has three poles for two good reasons:

It gives the motor better power. In a bipolar motor, if the electromagnet is at the balance point and is completely horizontal between the two poles of the stator when the motor starts, you can imagine that the rotator will "get stuck" there. This will never happen with tripole motors.

Each time the commutator reaches the point where it flips the magnetic field in the bipolar motor, the commutator shortens the battery for a short time. This short circuit wastes energy and unnecessarily depletes the battery. Tripole motors also solve this problem.

There can be any number of poles, depending on the size of the motor and what it needs to do.

How AC motor works

Now let's take a look at the AC motor. AC motors use AC instead of DC. It shares many parts with DC motors and still relies on electromagnetic and inverted magnetic fields to generate mechanical power.

The parts inside the AC motor are:

stator

rotor

Solid axis

coil

Mouse cage

The stator winding in AC motor plays the role of DC motor rotator. In this case, it is a circle of electromagnets that are paired and sequentially charged to produce a rotating magnetic field.

Alternating current dynamo

An industrial AC motor with an electrical junction box on top, an output shaft on the left, and a rat shroud over it.

EGZON123/CC BY-SA 3.0/Wikimedia

You will remember that the rotors in the DC motor are connected to the batteries. However, there is no direct connection between the rotor in the AC motor and the power supply. It also has no brush. Instead, it often uses something called a squirrel cage. You're right.

A squirrel cage in an AC motor is a set of rotator bars connected to two rings, one at each end. It's a bit like a rat (or squirrel) running inside a cage. The squirrel cage rotator enters the stator. When AC is sent through the stator, it generates an electromagnetic field. The rods in the cage rotors are conductors, so they respond to the flipping of the stator poles. This is how the rotator rotates, and it produces its own magnetic field.

AC Rotor and Stator

The key to an AC influenza motor whose rotor magnetic field is induced by the stator magnetic field is that the rotator always tries to catch up. It is always looking for stagnation, so it spins to find stability. However, the electromagnetic field produced by the stator using AC power supply is always faster than that of the rotor. The rotation of the rotor is generating the torque required to generate mechanical power to turn the wheels or fans of the car.

Some AC motors use winding rotors, which are wound with wires instead of a squirrel cage. However, squirrel cages are more common. In either case, there is only one moving part in the AC motor, which means there is less to replace or maintain.