The motors used in cordless impact drivers are called DC motors and are either brushed or brushless.
Brushed motors
Inside a brushed motor is an electromagnetic field, with a current flowing through it. To keep the motor turning, the current must be constantly reversed.
The brushes inside the motor are what cause the current to reverse, keeping the motor turning.
ADVANTAGES
DISADVANTAGES
Less expensive to purchase than brushless motors
If the brushes are replaceable, these motors have an extensive operational life
Can operate in colder temperatures due to the lack of electronics
Noisier than brushless motors
As speed increases, brush fiction causes torque to decrease
Usually require periodic maintenance if brushes need to be cleaned and replaced throughout the motor’s lifetime
Less efficient heat dissipation compared to brushless motors
Brushless motors
As motor technology has advanced, a new type of motor has been designed that doesn’t have brushes.
The motor is kept turning using a specially-designed controller called a Hall Effect Sensor.
Brushless motors have several advantages over brushed models and are proving a popular choice for use in cordless power tools.
ADVANTAGES
DISADVANTAGES
Require little or no maintenance due to the lack of brushes
Models with brushless motors tend to have more compact designs
No friction on the brushes so brushless motors can deliver higher levels of torque and speed simultaneously
Better heat dissipation
More efficient as there is no power loss across brushes
Quieter than brushed motors
More expensive as a specially-designed controller is required to keep the motor running
To brush, or not to brush?
Brushless motors are favoured amongst users for the many advantages they offer over brushed motors.
Though they are more expensive initially, a model with a brushless motor should serve you well in the long run.