Which side of a transformer secondary to be ground referenced?

[musicgold]

Homework Statement

Not a homework question. I wish to know how do I decide which side of the secondary of an isolation transformer can be grounded.

Relevant Equations

At the 6.20 mark in the video below, the instructor says that if a system needs grounded pilot voltage, it is common to ground the X2 terminal of the secondary.

The video is located here. My question, if the secondary side is isolated and the control circuit has no connection to the primary side, why do I have to ground X2 only? This a floating AC system, so why does it matter which side is used as the reference? What will happen if I grounded the X1 terminal?

 

[DaveE]

Sorry, I didn't watch the video, but from your schematic, there's no way to decide which side should be grounded. It is an arbitrary choice at this level of detail.

 

[Baluncore]

Ground the X2 side, because X1 has a fuse.
You do not want a blown fuse to disconnect the ground.

 

[Tom.G]

From:

(https://abbott-tech.com/ is a major supplier of both Military and Industrial, harsh environment, power supplies)

Step 6- Terminate the low-voltage side of the transformer following the manufacturer’s instructions and schematics for different types of transformers. For small control transformers, there will be X1 and X2 terminals only where X1 is the power side and X2 the grounding and a side of the low voltage.

Cheers,
Tom

 

[Baluncore]

And step 7 answers the OP's question.

Step 7- Terminate the control transformer for X1 and X2 where X1 goes straight to control circuit after it passes through a fuse usually rated for the circuit. X2 is terminated to the neutral side of the control circuit and is also used for grounding safety. Therefore, X2 terminal of the small control transformer must be wound together to a grounding structure of the circuit.