| 摘要 |
PURPOSE: To obtain a power tool in which soft start is combined with a brake operation by connecting one ends of the field winding and the brake winding with a terminal of a double-pole-double-throw switch and connecting the brake winding across a second switch. CONSTITUTION: Even if a first switch 1 is turned ON to start a power tool, starting current is suppressed because of a brake winding 5 thus presenting soft start. When a second switch 2 is subsequently turned ON to short-circuit the brake winding 5 and the motor enters into steady operation, the current peak is lowered as compared with direct starting and the reaction of the tool is suppressed. When a switch lever is released, the second switch 2 is turned OFF earlier than the first switch 1 and the brake winding 5 is connected in series with a field winding 4 thus lowering r.p.m. of the motor 3. Subsequently, the first switch is turned OFF to form a brake circuit and the excitation is effected through the brake winding 5 and the field winding 4. Consequently, rotation of the armature 3 decreases abruptly and the armature is stopped. |
