When the current of the DC motor of the circuit breaker reaches several hundred amperes, the arc between the fractures will only be extinguished at the current zero crossing point, and the DC current does not have a zero crossing point and therefore cannot be extinguished. In this case, only a special DC circuit breaker must be used. If the arc lasts longer than 20ms, it can be called an explosion.
The high-voltage high-current AC circuit breaker extinguishes the arc between the contacts at the zero-crossing point of the sinusoidal current; the DC switch also uses this principle to connect large capacitors in parallel between the fractures. In the case of a DC breaker breaking, the reverse discharge of the capacitor is used to cause a sudden reverse of the current, and the arc is extinguished at the forced zero crossing of the current reversal.
The steps for removing the DC motor of the circuit breaker are as follows
1. Remove the wiring from the motor.
2. Remove the end cap screws and bearing cap screws of the commutator and remove the bearing cover.
3. Open the venting window of the end cap, remove the brush from the brush holder, and remove the connecting wire attached to the brush bar.
4. When removing the end cover of the commutator, put a wooden wedge on the edge of the end cover, and evenly tap the edge of the end cover with a hammer, gradually remove the end cover from the base and the bearing outer ring, and take out the brush holder.
5. Wrap the commutator to avoid soiling and bumping.
6. Remove the end cap screws from the extended end of the shaft and carefully pull out the armature of the end cap from the stator to avoid scratching the windings.