What is the Difference Between Brushed and Brushless DC Motors?
Parvalux has been making electric motors for more than 70 years and this short blog sets out to explain the essential differences between brushed and brushless DC electric motors.
What is a brushed DC electric motor?
A brushed DC motor has permanent magnets inside its outer body with a rotating armature inside. The permanent magnets are stationary and are called the ‘stator’. The rotating armature contains an electromagnet and is called the ‘rotor’.
In a brushed DC motor, the rotor spins 180-degrees when an electric current is applied to the armature. In order to travel beyond the initial 180 degrees, the poles of the electromagnet must flip. Carbon brushes contact the stator as the rotor spins, flipping the magnetic field and enabling the rotor to spin 360-degrees.
- High starting torque: For applications that need to get up to speed really quickly, a high-torque brushed electric motor is the choice for you. For example, in applications such as caravan movers, a high starting torque is essential.
- Low cost: Brushed DC motors are relatively inexpensive to produce and purchase compared to brushless DC motors.
- Suited to industrial environments: Due to their high starting torque, brushed motors are also a popular choice in industrial environments.
- Risk of increased maintenance: Due to the effects of friction on a motor’s carbon brushes, they will naturally wear over time. As a result, brushed electric motors are more likely to require some sort of maintenance in the form of brush cleaning or replacement.
- Lower speed: Despite a high starting torque, brushed motors are not as capable of maintaining high-level speeds. This is because running a brushed motor at a consistent high speed can cause it to get warm.
What is a brushless DC motor?
Like a brushed motor, a brushless motor works by alternating the polarity of windings inside the motor. It is essentially an inside out brushed motor, which eliminates the need for brushes. In a brushless DC motor, the permanent magnets are fitted to the rotor, with the electromagnets on the stator. An electronic speed controller (ESC) regulates or ‘commutates’ the charge to the electromagnets in the stator, to enable the rotor to travel through 360-degrees.
- Long lifespan: Brushless DC motors don’t have brushes, which means they require less maintenance than their brushed counterparts.
- Efficiency: The lack of brushes means that no speed is lost, making brushless DC motors a little more efficient, typically 85-90% compared with their brushed counterparts at a typical 75-80% efficiency.
- Quiet operation: Due to the lack of brushes, brushless motors run extremely quietly and have particularly smooth operation. This is especially useful for applications that require such properties, such as patient hoists.
- Requires a controller: Brushless DC motors need to be wired to an electronic speed control (ESC), to enable current to flow to the electromagnets.
- Cost: Due to the requirement for a controller, brushless DC motors can be more expensive.