3 phase to 3 phase dry autotransformer

both the input side and output side of a 3-phase transformer system can be grounded, but it depends on the transformer type and how the system is designed.

For a typical 3-phase 240V → 380V transformer:

• The transformer frame/enclosure should be grounded.
• The input side usually has an equipment grounding conductor.
• The output side can also have a grounded point (usually neutral or one corner), depending on configuration.

Equipment Ground

Used for safety:

• transformer case
• enclosure
• conduit
• machine chassis

This SHOULD be grounded.

Grounded Conductor / Neutral

One point in the electrical system intentionally bonded to ground.

• Input: 3-phase → terminals A B C
• Ground: PE
• Output: 3-phase + neutral → terminals a b c n

208V Supply          Transformer Input
-----------          -----------------
L1  ----------------->  A
L2  ----------------->  B
L3  ----------------->  C
Ground -------------->  PE

Important:

• Do NOT connect neutral to A/B/C.
• PE is protective earth/ground only.

OUTPUT SIDE (380V 3-phase)

Transformer outputs:

Transformer Output      Machine
------------------      -------
a --------------------> L1
b --------------------> L2
c --------------------> L3
n --------------------> Neutral (if needed)

208V Supply Side              Transformer
----------------              -----------
L1 -------------------------> A
L2 -------------------------> B
L3 -------------------------> C
Ground (EGC) ---------------> PE