Earth wire connected between primary and secondary of isolated offline SMPS

[ocset]

We are noticing in many isolated offline SMPS’S , that there is an insulated earth connection wire connected between primary and secondary…it connects to output ground. Would you agree that this is for the purpose of preventing the SMPS output from floating up to high voltage levels with respect to Earth ground?

[ArthurDent]

Yes, but not to any current carrying primary wire. Only to the ground (earth) wire that comes from the wall outlet.

[Gyro]

An odd question treez. 

Yes, many SMPSs have grounded outputs. It provide a solid ground reference for whatever the SMPS is powering, for safely, static discharge protection, preventing Y cap leakage etc.

[Edit: I'd probably go as far as to say that most 3 pin input SMPSs provide a grounded output]

[Giaime]

I think it's odd instead. Most SMPS I've seen are SELV type output, so they provide a basic insulation w.r.t. PE.
Many SMPS have a PE wire from primary side to secondary side, but that's just to connect to PE the output Y caps, for noise reduction.

[lordvader88]

I thought they usually have a blue, high voltage cap from pri to sec gnd. But I've only really worked on computer PSUs and little wallpack types.