brushcommutated

Brushcommutated refers to a type of electric motor in which the reversal of current in the rotor windings is accomplished by physical contacts known as brushes and a rotating commutator. This term is commonly used for brushed direct-current (DC) motors and, in some cases, universal motors that can run on alternating current.

In a brushcommutated motor, the rotor carries a segmented copper commutator to which the armature windings are connected. Stationary brushes press against the commutator, maintaining electrical contact as it turns. As the rotor rotates, the commutator switches the connection of each winding at the correct moment, reversing the current and keeping torque oriented in the same direction. The motor is typically powered from a DC source, though universal motors can operate on AC while still using brushes and a commutator.

Performance characteristics include high starting torque and good torque controllability at low to moderate speeds. Speed is influenced by load and supply voltage, and can be adjusted with voltage control or pulse-width modulation. The armature current largely determines torque, while speed tends to approach a no-load value when lightly loaded. However, brushcommutated designs face limitations such as brush wear, arcing at the commutator, and maintenance needs. Efficiency can be reduced by contact resistance, brush degradation, and heat from friction.

Common applications are in power tools, household appliances, and automotive starters, where robustness and straightforward control are advantageous. In many newer designs, brushcommutated motors are being complemented or replaced by brushless alternatives to improve efficiency and reduce maintenance.