The Grab differential Limit Switch is driven by holding and closing winches and used in auxiliary circuits for single lever grab control.It is used for stopping the closing motor after closing or opening, regardless of the height of the grab and starting the holding motor after closing,for transition to the hoisting actions as well as for stopping the hoisting actions as well as for stopping the holding and closing motors at the hoisting and lowest grab position.
The switch contain six heavy duty cam operated switch elements which, are used as auxiliary circuit limit switches (see switching sequence diagram). The dimensional drawing shows that the switch has two shafts which must be driven by the holding and closing winches. The contacts of limit switches are 40 Amps rated at 500 V.A.C.
Mode of Operation
The switches N5,N6 are limit switches for the highest and lowest grab positions. The ‘Grab closed’ and ‘Grab open’ limit positions are monitored by the switches N1 and N4, whereas N2 and N3 initiate the switching operations for single lever grab control.