Speedage limit switches are used for heavy-duty eot cranes, wagon shunting devices, etc., to prevent over travel or traverse on power and control circuit up to 500v ac 50 cycles/second and 40 a continuous current. When used as shunt limit switch the maximium permissible frequency of operation is 1000 operations per hour. When used as series limit switch the maximum permissible frequency of operation at rated curent is 720 operations per hour. The switch normally remains closed and cuts off power to stop the motor. It operates when it reaches a pre-determined position when the lever is moved over a projecting member fixed on the girder. The series limit switch is fitted with 4 sets of contacts, which cut off 2 phases of the motor in either direction and is suitable for 500 v 50 c/s ac supply system. The contacts are automatically reset when the lever returns to zero position due to spring action. Construction: the housing is made of sheet steel suitably reinforced to give exceptional rigidity. The camshaft is mounted in the housing on moulded bushes [bearings] of synthetic material fixed to the front and rear walls. These bearings do not require any lubrication. The switches are also made in ip-54 enclosure.
