The circuit breaker is located in the middle of the distributor, one end of the fixed contact and the bracket is sleeved on the pin shaft, and the other end is mounted on the movable bottom plate. One end of the movable contact arm is fixed with a movable contact, and the other end is also sleeved on the pin shaft. The contact arm spring makes the movable contact press the fixed contact tightly and makes the bakelite top block in the middle of the contact arm and the power-off cam touch. The contacts are made of tungsten alloy. The maximum gap when two contacts are separated is called the contact gap. The contact gap cannot be too large or too small. If it is too small, it is easy to form sparks between the contacts, which will cause the primary circuit to be de-energized; if it is too large, the contact closing time will be too short and the resulting primary current will not be large enough. To make the secondary voltage drop, the contact gap is generally specified to be 0.35-0.45mm. In order to make the gap can be adjusted, a long slot is opened on the bracket of the fixed contact, and an eccentric screw is installed inside. When adjusting, loosen the fixing screw and turn the eccentric screw to make the fixed contact rotate around the pin shaft, thereby changing the size of the gap. After adjustment, tighten the set screw.