When the Circuit breaker DC motor rotates, when the armature winding element passes from one branch to the other through the brush, the direction of the current in the element changes. We refer to the change of the current direction in the element as the commutation. In order to improve the commutation of the DC motor of the circuit breaker, the commutating pole is added, but the commutating pole must be correctly selected.
For circuit breaker DC motors, the commutating pole polarity should be opposite to the next main pole that follows the armature steering, while the generator should be the same; the commutating winding must be in series with the armature winding; the commutating pole magnetic circuit Should not be saturated. In addition, the brush should be chosen reasonably. It is required that the contact resistance between the brush and the commutator surface should be as large as possible, and the brush wear resistance should be good. Electrochemical graphite brushes are generally used in DC motors, and metal graphite brushes are generally used for low-voltage and high-current motors. A split brush can be used for motors that are particularly difficult to commutate.
The reversal of the DC motor of the circuit breaker can be realized in two ways. One is to reverse the voltage across the armature and change the direction of the armature current; the other is to change the polarity of the field winding, that is, to change the main magnetic field. direction. In actual operation, since the number of turns of the field winding of the DC motor of the circuit breaker is large and the inductance is large, the DC motor requiring frequent reverse rotation should be reversed by changing the direction of the armature current.