Re: Isolator Transformer Query
In the 70's the company I worked for imported several USA made yarn spinning machines, each with multiple 3 x phase motors & dedicated control gear.
The control contactor worked on 24VAC & to facilitate this a 415V > 24V step down transformer was installed, the secondary winding of which was floating.
After a while, several transformer started to "break down" resulting in a phase voltage of 415 appearing on the control circuit. Each one was replaced with a UK match but as a precaution I tied one leg of the 24V secondary down to the machine earth & then retrospectively modified the remaining USA made ones.
Made me sleep easier at night.
Rog
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