step down transformer earth ? 3

[DTSFA]

if a step down transformer, 230v/27v ac is used to feed electronics, should the secondary be earthed at one side of the secondary ?

( to help deal with surges, transients, etc )

( obviously the 27v ac is bridge rectified on PCB to 24v dc regulated supply )

thanks

 

[ScottyUK]

Not necessarily. In many cases it would be desirable to have a floating secondary supply. If you have serious problems with mains-borne noise coupling through the transformer then you might want to consider an earthed interwinding screen instead.

 

[mikekilroy]

often time too, 24vdc has its common tied to ground. If this happens with your grounded ac side you will have an instant short of course that blows diodes or fuses.

 

[DRWeig]

Good one, mikekilroy.

I'm a long-time controls guy. We never ground low-voltage transformer secondaries unless we stumble across a really good reason to do so in a particular situation. Ungrounded (floating) is the default. In addition to the 24 VDC power supply troubles (very frequent), circulating currents in the ground bus can lead to the pulling out of one's hair.

Good on ya,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[nicole10g]

IMO the secondary side of the transformer should not be grounded to provide isolation to the main, else the chassis will be considered hot.

If transient noise is a concern, then an isolation capacitor can be put across the primary and the secondary of the transformer.