Question

What is the working principle of AC DC motor?

Answer 1

The working principle of both AC (Alternating Current) motors and DC (Direct Current) motors is based on the interaction between a magnetic field and a current-carrying conductor, which results in a force that causes rotation. However, the way this interaction happens differs slightly between AC and DC motors.

Working Principle of a DC Motor:

1. Magnetic Field and Current:
   

   - A DC motor consists of a stator (which provides a magnetic field) and a rotor (the rotating part, also called an armature) that carries a current.
   - When DC voltage is applied to the motor, current flows through the armature winding, and a magnetic field is created.

1. Force on the Rotor:
   

   - According to Lorentz's law, when a current-carrying conductor is placed in a magnetic field, it experiences a force. The direction of the force is given by the right-hand rule (thumb pointing in the direction of current, fingers in the direction of the magnetic field, and the palm shows the direction of the force).
   - This force causes the rotor to rotate.

1. Commutator:
   

   - To keep the motor running continuously, the direction of the current in the rotor must be reversed every half turn (to prevent the rotor from stopping). This is done by the commutator, a device that reverses the current in the rotor windings as it rotates, ensuring continuous rotation in the same direction.

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Working Principle of an AC Motor:

In AC motors, the working principle depends on whether the motor is a synchronous motor or an induction motor. The most common type is the induction motor.

Induction Motor (the most common type of AC motor):

1. Magnetic Field Interaction:
   

   - An AC current is supplied to the stator (the stationary part) of the motor, creating a rotating magnetic field.
   - The rotor (the rotating part) is placed within this rotating magnetic field. Due to electromagnetic induction, a current is induced in the rotor.

1. Rotation of the Rotor:
   

   - The magnetic field produced by the stator interacts with the induced current in the rotor, causing a force to act on the rotor.
   - This force makes the rotor rotate in the same direction as the rotating magnetic field.

1. No Commutator:
   

   - Unlike DC motors, AC motors do not require a commutator. Instead, the rotor in an induction motor "follows" the rotating magnetic field, but there is always a slight lag, which is known as the slip.

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Key Differences Between AC and DC Motors:

1. DC Motors: Require a commutator to reverse current in the rotor and maintain continuous rotation. They operate on a constant DC supply.
   

1. AC Motors: Operate using a rotating magnetic field produced by AC power. No commutator is required for the rotor.
   

Both types of motors utilize the same basic principle — the interaction between magnetic fields and electric currents to produce mechanical motion — but they differ in how the current is supplied and how the rotation is maintained.