| 摘要 |
A transformer primary circuit breaker is disclosed having a primary switch for opening and closing the transformer primary circuit, an operating handle (50) mounted exteriorly of the transformer for opening and closing the primary switch, a trip mechanism (16) operatively connected to open the primary switch under fault current conditions, the trip mechanism (16) including a conductive metallic sensor element (34) connected in the primary circuit and having a predetermined Curie temperature and a magnet (28) mounted for movement into engagement with the sensor element (34) and biased to open the primary switch when the temperature of the sensor element (34) approaches the Curie temperature. A shunt circuit (18) is connected to the primary circuit in parallel with the sensor element (34). The shunt circuit has a normally closed switch (46) and a resistance element (44) for limiting the current passing through the shunt circuit (18). A tab (76) is mounted on the operating handle (50) for opening the shunt circuit switch (46) and a spring is mounted in the operating handle (50) for limiting the motion of the operating handle (50) to thereby close the shunt switch (46), whereby a portion of the primary current will flow through the shunt circuit (18) when the switch (46) is closed. A bimetal switch (77) can be included in the shunt circuit (18) to open the shunt circuit (18) at predetermined oil temperatures or excessive currents. |
