DC BRUSH COMMUTATED VS. BRUSHLESS MOTORS Ⅱ

Noise Generation
  Audible noise in brush motors comes from bearings, brushes and rotor imbalance. In brushless designs, the noise generation from brushes is eliminated and, generally, brushless designs are quieter running. Electrical noise generation from brush motors is often quite large due to the white noise produced between the brushes and the commutator interface which is not present in the brushless designs. However, the brush motor noise is often quelled

Life Expectancy
  As a general rule, brushless units last longer than brush motors. The primary limiting feature of a brush motor are its brushes and commutator. Different application specific brush materials may be available and should be discussed with the motor manufacturer prior to ordering. Typical brush life of 2000 to 5000 runtime hours is common but, should not be considered a guarantee for all applications. Brushless units typically exceed 10,000 hours and are limited by bearing life and environmental conditions.

Cost
  More often than not, the cost of a product is the deciding factor as to which one of these technologies is chosen. The initial cost of a brushless motor design tends to be higher than a brush motor. Add to this the cost of the external commutation controls, then the brushless motor price becomes significantly higher unless the application requires
a four quadrant servo controller anyway. However, when operating life becomes an important factor, such as in high duty cycle applications, the long range cost of having to replace a brush motor can be considerable. In addition to the cost of the motor, technician expenses and lost revenue from machine downtime should be accounted for in the
selection process.