Transformer Query

[wreck-it-steve]

Hi,

I was looking in a control panel today at work and saw that the secondary side of a 230/110v (55v, 0v, 55v) transformer had its 0v attached to the body of the transformer. Why would this be done?

Thanks

 

[ericmark]

Often in error. Control panels normally would have 0 - 110 volt and a single fuse on the line wire. Since 55-0-55 volt are used for power tools they are mass produced and therefore cheaper. In one place I worked the orignal had burn out and was replaced with the 55-0-55 version with internal link to frame of transformer. The orignal only had one fuse on the line wire. Clearly changing transformer two fuses should have been used one on each of the line outputs but this had been omitted. The fault when the old neutral was through a fault earthed resulted in the old neutral now line wire burning and taking with it many other wires in same conduit. Result machine needed complete re-wire.

Now I look more carefully at machines with 110 control circuit to ensure this is not repeated.