Can anybody explain why Seimens Power contactors have nomenclature of 3TF35, 3TF47 ?
Siemens have a particular way of providing part numbers for all of their equipment, not just contactors. This was known as the MLFB code which was a German acronym (translated into English I think that this meant Machine Readable Factory Code). Each letter and number in the code had a meaning. If you Google Siemens and MLFB you may pull up the legend.
From memory I think that
3 = switcing device
TF referred to a articular range of contactors
35 (47) etc = the frame or block size of the contactor
There would then be a sequence of numbers and letters which defined the auxiliary contacts and the coil voltage.
this is the code for a component or a device. 3 is for three pole, TF is the type of contactor and 35 & 47 is the current carrying capacity of the conteactor, or in other words we should be say it that 35 & 47 is that ratting witch we operates for the load for 35 Amps. and 47 Amps.