been fault finding today at work and after some opinions as installations my norm.
the machine is a set of 3 phase rotators driven by motors.
its the usual set up. 2 contacters (fwd and rev), a transformer for the 24v supply, pendant and a circuit board for the speed control.
the operator was using the rolls, when he pressed stop there was a large bang in the panel.
found 2 fuses had blown. these fuses were the same phases that supplied the 415v primary for the transformer as well as the contacters.
IR test on the circuit through the contacters and up to the pcb is ok.
when fuses replaced and tested got 415v at the primary but nothing at the secondary. when i looked at the transformer primary windings they are all blown away and melted where they leave the terminals.
this led me to believe that the windings in the transformer had failed and brought the phases together. but the transformer its stated should be protected by a 6A fuse (it was actually a 32A fuse!).
this got me thinking that maybe the windings failure was maybe an affect of another fault.
what do people think? has anyone any experience of a transformer failing like this?
the machine is a set of 3 phase rotators driven by motors.
its the usual set up. 2 contacters (fwd and rev), a transformer for the 24v supply, pendant and a circuit board for the speed control.
the operator was using the rolls, when he pressed stop there was a large bang in the panel.
found 2 fuses had blown. these fuses were the same phases that supplied the 415v primary for the transformer as well as the contacters.
IR test on the circuit through the contacters and up to the pcb is ok.
when fuses replaced and tested got 415v at the primary but nothing at the secondary. when i looked at the transformer primary windings they are all blown away and melted where they leave the terminals.
this led me to believe that the windings in the transformer had failed and brought the phases together. but the transformer its stated should be protected by a 6A fuse (it was actually a 32A fuse!).
this got me thinking that maybe the windings failure was maybe an affect of another fault.
what do people think? has anyone any experience of a transformer failing like this?