AC motor has a stationary armature and rotating magnetic field. While DC motor has a stationary magnetic field and rotating armature.
Electric motors play a vital role in minimizing human effort in running various tasks in residential and industrial areas, as they are extremely efficient and automated. An electric motor is a machine that transforms electric energy into mechanical energy.
In this article, we will discuss the differences between two different types of electric motors based on the input power supplied to them as follows –
- AC Motor
- DC Motor
What is an AC motor?
An AC Motor is defined as a device that transforms AC input power supplied to it into output mechanical energy. The principle of operation of AC motors is based on the concept of electromagnetic induction.
An AC motor is comprised mainly of two components namely – the stator and rotor. The stator is the static or immovable part of the AC motor, which has a conducting coil called armature winding wound around it. This armature winding is responsible for generating the electromagnetic field which in turn cuts the rotor resulting in its rotation. The rotor is the rotating or moving part of the AC motor that drives the working of the machine.
Based on the phase in which the AC current is supplied, it can be divided into the following two types-
What is a DC motor?
A DC Motor is defined as a device that transforms DC input power supplied to it into output mechanical energy. The principle of operation of DC motors is based on the concept of Lorentz Law, according to which a conducting coil kept in an existing magnetic field experiences a force exerted on it.
Similar to an AC motor, a DC motor is also comprised mainly of two parts namely – the stator and rotor. The stator is the immovable part that remains static and is responsible for the production of the electromagnetic field. While the rotor is the rotatory part of the DC motor that starts rotating upon coming in contact with the stator’s magnetic field. As a result, the rotor of a DC motor is also referred to as the armature.
DC motors can be categorized into the following four types-
- Permanent Magnet DC Motor
- Series DC Motors
- Shunt DC Motors
- Compound DC Motors
Difference Between AC and DC Motor
The most notable differences between an AC motor and a DC motor are listed in the table given below –
| Parameter | AC Motor | DC Motor |
| Description | AC motor is a machine that runs on an alternating electric current source as input to produce mechanical energy from electrical energy. | DC motor is a machine that runs on direct electric current to produce mechanical energy from electrical energy. |
| Types of Motor | There are two types of AC motors – synchronous AC motors and induction motors. Induction motors can be of two main types namely – Single-phase AC motors and Three-phase AC motors. | DC motors can be broadly classified into 2 main types, viz. brushed and brushless DC motors. |
| Working Principle | AC motor works on the principle of Electromagnetic induction. | DC motor operates on the principle of Lorentz Law. |
| Supply source | AC motors are provided with a three-phase AC supply current from the main power grid. | DC motors are provided with DC current via DC generators, batteries, cells, converters, etc. |
| Type of current supplied at input | AC motor is supplied with alternating current at the input. | DC motor is supplied with direct current at the input. |
| Input supply phase | AC motors are supplied with a three-phase AC supply as the input source. | DC motors are supplied with only DC supply as the input source. |
| Starting of Motor | Three-phase AC motors are Self-starting. However, single-phase AC motors need a starting mechanism. | DC motors are self-starting. |
| Upkeep | Due to the absence of brushes, the AC motors do not require frequent maintenance or upgrade. | Due to the presence of brushes, DC motors require frequent maintenance or upgrades to function properly. |
| Input Terminals | There is three input terminals (RYB) present in the AC motor. | Two input terminals of DC supply (positive and negative) are present in DC motors. |
| Commutators and Brushes | No commutator and brushes | DC motors have commutators and brushes. |
| Performance | AC motors’ efficacy is comparatively lower than DC motors due to the occurrence of slip and eddy current losses. | The efficacy of DC motors is relatively higher than AC motors as issues arising due to eddy current losses and slip are absent. |
| Speed control | To control the speed of the AC motors, the input frequency of the current or the field poles has to be varied. | To control the speed of the DC motor, the armature voltage is varied. |
| Motor speed Reversal | By changing any one of the RYB phases at the stator terminal. | By reversing the armature or field supply in the case of a separately excited DC motor. In the case of the DC series and shunt motor, the polarity of the armature or field needs to be reversed. |
| Affordability | AC motors are comparatively cheaper than DC motors. | DC motors are comparatively more expensive than AC motors |
| Applications | AC motors find their applications in electronic devices or machines requiring fluctuating torque and high speed to operate. | DC motors find their applications in the operation of several electronic devices such as several home appliances such as mixers, microwaves, toys, etc. |
Conclusion
In conclusion, this article highlights the key differences between AC and DC motors and these differences help in choosing the right kind of motor for a particular application. Both AC and DC motors find a wide variety of applications in residential and commercial fields. The most significant difference is that AC motors operate on single-phase or three-phase alternating supply, while DC motors run on a direct current supply.