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The Comparison between AC and DC Motors

Oct. 09, 2021
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Electric motors convert electrical energy into mechanical energy. These motors can operate using either AC or DC electrical energy. Therefore, there are two main types of motors, AC motors and DC motors.

Both types of motor produce mechanical energy for moving any mechanical load etc., but their construction, control, efficiency, and applications are very different. 

Before we get into the list of differences between AC and DC motors, let's discuss how motors work and the basics of AC and DC motors. ZCL group shares with you.


What is an AC motor?

It is a motor that converts AC electrical energy into mechanical energy.

There are two types of AC motors: asynchronous motors and synchronous motors.

In an asynchronous (induction) motor, the stator consists of multiple windings, while the rotor (squirrel-cage or wire-wound) consists of a closed circuit of conductors. Alternating current is supplied to the stator, which produces an alternating magnetic flux called the rotating magnetic field.

According to Faraday's law of induction, this flux produces an induced current in the rotor. The induced current is opposite to the magnetic field and begins to rotate in its direction. Induction motors, whether single-phase or three-phase, therefore work according to the principle of electromagnetic induction between stator and rotor.


The Comparison between AC and DC Motors

AC motors


What is a DC motor?

It is a motor that converts DC electrical energy into mechanical energy.

The basic principle of the operation of a DC motor is that "when a current-carrying conductor is placed in a magnetic field, it is subjected to a mechanical force perpendicular to the direction of the magnetic field and the current". The direction of the force is determined by Fleming's left-hand rule.

The armature of a DC motor consists of a number of conductor windings. It is placed in a housing made for a permanent magnet that generates a magnetic field. The armature carries DC power through any DC source, such as a battery. The magnetic field interacts with the current-carrying conductors of the armature. The armature is therefore subjected to mechanical forces. 

In a BLDC (brushless DC) motor, the stator consists of a number of coils which surround a rotor armature made of permanent magnets. A thyristor is used to change the direct current into three-phase alternating current and is supplied to the stator coils to produce a rotating magnetic field. In this type of motor, the input is applied to the stationary part, so there is no need for brushes or commutators. It helps to improve the performance of the motor and its efficiency.


Applications

AC motors are the most commonly used motors in domestic and industrial applications such as drills, pumps, fans, washing machines, blowers, etc. DC motors are used in applications requiring precise position control and high torque, such as lifts, cranes, conveyors, etc.

DC motors require frequent and expensive maintenance. They are therefore more expensive than AC.


AC Motors Vs DC Motors

The choice between an AC and DC motor depends heavily on the specific application's requirements, including power needs, speed control precision, maintenance considerations, environmental factors, and budget. While DC motors historically dominated applications requiring precise speed and torque control, advancements in AC drive technology (VFDs) have increasingly allowed AC motors to compete in these areas, often with the added benefits of lower maintenance and higher reliability.


FeatureAC MotorsDC Motors
Power SupplyAlternating Current (AC)
Direct Current (DC)
ConstructionGenerally simpler (especially induction motors), no brushes/commutator (except some specialized types)
Brushed types: brushes and commutator; Brushless types: electronic controller
MaintenanceLower (fewer wearing parts)
Higher (for brushed types due to brush wear); Lower for brushless
Speed ControlMore complex (requires VFDs)
Simpler (by varying voltage or electronic commutation)
Starting TorqueCan be lower (for basic induction motors)
Generally higher (especially for brushed DC)
EfficiencyHigh, especially for large industrial types
High (especially BLDC); Lower for brushed DC due to friction
CostGenerally lower for a given power rating
Higher, especially BLDC due to electronics
Durability / LifespanHigh, longer lifespan
Lower for brushed (brush wear); High for brushless
Noise & EMIGenerally quieter, less EMI
Can be noisy and generate EMI (brushed types)
ApplicationsIndustrial machinery, home appliances, fans, pumps, compressors, large-scale power
Robotics, electric vehicles, precision control, battery-powered devices, medical equipment, and small tools


ZCL takes responsibility for its customers and guarantees that it will provide products that meet the design standards and quality in strict accordance with the requirements of the contract signed with the customer. In the manufacture of our motor products, we strictly control the quality of raw materials, original components, and accessories. If you need to buy a motor, please contact us, we have a wide range of synchronous motors, asynchronous motors, permanent magnet motors etc. for sale.

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