Differences of AC Motor and DC Motor

Today, we’d like to share you with the differences of AC motor and DC motor as they are the most common in our life.

The same
Both motors work by basically positive and negative current chasing itself in a circle which never catches up to itself so the motors turn, and then converting electrical energy into mechanical energy.

If you’re familiar with AC and DC motor, you may find that their power, construct and control are different.

DC motorbrushed DC electric motor

AC or alternating current motors are powered from alternating current while DC or direct current motors are powered from direct current, such as batteries, D.C. power supplies or an AC-to-DC power converter. The DC motor includes a brushes and a commutator while AC induction motors do not use brushes. For the difference of speed control, DC motor is controlled by varying the armature winding’s current while the speed of an A.C. motor is controlled by varying the frequency.

Advantages and disadvantages
AC brushless motor  is more efficient than DC motor. In AC, polyphase or three phase motors this becomes more efficient because you need lower current to do the same thing a DC motor does which requires more voltage to push it. Thus, AC motors are better suited for high speed operation (over 2500 rpm) since there are no brushes, and commutation is not a problem.

Speed control
DC motors with a better speed control than AC. Thus, DC motors are often use in rock crushers, car crushers, etc. A lot of your home appliances ironically run on DC motors too. In additional, there are various methods to control the speed of a DC motor, such as field flux control, armature control method, and voltage control method.

Maintenance and life
AC motors require virtually no maintenance and are preferred for applications where the motor is mounted in an area not easily reached for servicing or replacement. So they are very rugged and have long life expectancies. On the contrary, DC motors need more maintenance, limit the speed and usually reduce the life expectancy.

DC motors are easy to build as they are less complex with a single power conversion from AC to DC and very cost effective for most horsepower ratings.

The Most Important Factors You Should Consider When Choosing Brushless Motor

How to choose a proper motor for your RC plane, helicopter or RC car? An instruction can tell you a particular motor to get but what if you had none or were designing a plane how would you choose? There are always a ton of threads about motors and ESCs and they are all usually variants on the same questions. Even though, we still want to share some choosing tips for new beginners.

A brushed system needs a lot of maintenance, but offers more flexibility because you can change motors depending on track conditions (how much torque you need). A brushless system on the other hand, needs almost no maintenance.

Brushless speed ratings
If you want to choose brushless electric motors for your car, the first thing to consider is how fast you realistically want the car to go. But there are two important factors you need to consider are your abilities and budget. For example, you may want your cars going 50mph, but there are only a few of us who have enough driving experience to go that fast without hitting straight into a wall.

This is similar to airplane; too much RPM will require a small prop which may not allow for enough thrust for the boat to get on plane. If a high RPM setup runs too large of a prop, excessive heat will be the result.

There is no standard for measuring the speed of the brushless motor. Some manufacturers measure the speed by turns, others use a KV rating. These terms are important to you because they will help you choose your motor’s speed.

In short, the fewer the turns on a brushless motor, the faster will be the acceleration (or spin of the armature). For a KV measurement, the higher the KV number, the faster it will accelerate.

The basics on turns and winds are as follows:
Lower Turn = Higher Top End/Less Torque
Higher Turn = Lower Top End/More Torque

If you just want to learn and play for fun, then you may choose the lower KV rating motor. On the contrary, you are getting a brushless motor for a racing, and then the fewest turns or the highest KV rating is the best choice.

Sensored or Sensorless
Brushless motors must be run from a speed controller, and there are two types brushless motor: sensored and sensorless system. The first one gives the feeling of the vehicle responding accurately to even the smallest changes of speed. These motors are highly prized by experienced racers who are always looking for an edge in the competition. A sensorless brushless motor doesn’t know how to tell whether it’s at the 12 or 6 o’clock position, so the speed control has to make its best guess to what is the correct pulse to send to make the motor go forward or reverse when the transmitter trigger is pulled or pushed.

Brushless combo Leopard 60A ESC combo

If you want to get an affordable brushless motor, you may consider the LEOPARD 60A ESC combo, it is sale under 58.90 pounds and include a brushless motor, an electronic speed controller and program card. Thus, you don’t need to consider whether the ESC is sensored or sensorless, as well as the budget.

RC Hobby Mysteries: What is Brushless Motor?

Have you ever wondered what the mysteries of brushless motors are? How does it work? Why it becomes more and more popular though it was much more expensive than brushed motor? Well come with us on a voyage of discovery.

First, we need to learn about what’s brushed motor and brushless motor.

What’s brushed motor?
Brushed motor is also known as a brushed DC electric motor. It is an internally commutated electric motor designed to be run from a direct current power source. Brushed DC motors have been in commercial use since 1886. So it has a very long history. They can be varied in speed by changing the operating voltage or the strength of the magnetic field.

In a brushed motor, an electromagnet is mounted on a spinning arm, called an armature or rotor. The armature sits between two magnets set in a horseshoe configuration, collectively called the stator. When power is fed to the electromagnet, the arm moves, aligning the north and south poles of the electromagnet with the opposing poles of the stator.

What’s brushless motor?
So you may have a basic knowledge of brushed motor. Then we have a glance of brushless motor. Just as the name implies, there is no brush.

brushless DC motor

The brushless motor turns this design inside out. Magnets are placed on the armature and are surrounded by one or more electromagnets. The current switch is controlled by computer, turning electromagnets off and on by switching the current; the computer can also factor in the motor’s current speed to optimize efficiency, all without the need for brushes.

How it works?
A DC Brushless Motor uses a permanent magnet external rotor, three phases of driving coils, one or more Hall Effect devices to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors, they act as three-phase synchronous motors containing their own variable frequency drive electronics.

Brushless DC motors have been used in many applications, particularly devices such as computer hard drives, CD/DVD players and radio control models. Brushless motors are a popular motor choice for model aircraft including helicopters. Also, the brushless motor is also popular among remote control (RC) racing enthusiasts. As it boasts better performance and suffers less wear than brushed motors of similar size; they can provide a great amount of power to RC racers.

See also How to Build a Brushless DC Motor?

If you have any confuse of brushless motor, feel free to contact us.