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Page 139

| Figure 8-9 Butt contacts. |

| Butt Contacts.. |

| Butt contacts (Fig. 8-9) consist of two solid elements with flat or curved faces that butt together when a circuit is closed. (Silver facings will reduce the contact resistance and thus lead to less heating, pitting, and wear.) A spring held tight by a latch or other restraining device holds the breaker closed. The moving contact butts solidly against the stationary contact. When the breaker trips, the latch is released, and the spring throws the contacts apart rapidly. |

| Wedge Contacts |

| Wedge contacts (Fig. 8-10) are probably the most frequently used contacts for circuit breakers. The wedge is squeezed between spring jaws when the breaker is closed, providing a good area for contact pressure. Forcing the wedge between the spring jaws also produces a wiping motion that maintains a clean surface on both of them. Arcs are normally taken on the top of the blade, thus protecting the actual contact area from damage. The moving contacts are usually made of a hard copper alloy with renewable arcing tips. These tips must be of rather massive proportions in order to provide a high thermal capacity and thus minimize burning. The stationary contacts consist of |

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