Hi All,

We will be using circuit breakers in front of G120 PM240-2 VFD's.

My question: Is there any value in also putting in fuses ?

(Reason for question is that when looking at some other manufacturers they show example circuits with both circuit breakers and fuses in the same circuit - but I don't see this in the Siemens installation manuals)

BobZA

[snip]

but I don't see this in the Siemens installation manuals)

Please refer below manuls for detail information.

SINAMICS G120 Power Module PM240-2 - Hardware installation manual

SINAMICS Protective Devices for Power Modules PM240-2 - Product information

SINAMICS G120/S120 Power Module, PM240-2/PM240P-2, FSD, FSE, FSF, FSG - Compact operating instrunction 

If you have electronically controlled circuit breakers with leading trip indicator aux contacts available for sending a pending upstream trip indicator to the drive so it can disable pulses before it loses power, a fuse is not necessary unless you need to protect the wiring between the source and the circuit breaker, or want to right-size the wiring to the circuit breaker rather than feeding wiring rated at the next upstream protective device.

If the breaker is a standard circuit breaker used for circuit isolation and more like a motor starter type of thing, then most certainly, the proper fusing according to the manual is important.

I have 3 different types of installations for G120 / S120 drives.

Fuse -> Drive
Fuse -> Breaker / MSP -> Drive
Fast electronic breaker with leading edge trip aux contact -> Drive

BobZA

Thank you for the reply. I do indeed have the manuals ... but as I said this is not covered in the manuals ... and that is the reason for my question ...