autoclave heat control

[NetNathan]

Are they sure the elements are jumpered correctly???
I have seen star wired as delta and delta wired as star.
Also....Delta or star configuration wired as single zone.
Have you taken amperage/voltage readings of the elements to verify correct KW?

People can "swear" everything is wired correctly all they want...but....have they TRIPLE checked it?

Also what type of elements (material) are they?
Kanthol, Chromel, Silicon Carbide......?

 

[rupej]

What frequency are your SCRs being PWMed? Its possible that it is causing a vibration in the heater elements- would explain why simple ON/OFF control doesn't cause them any issues if they aren't particularly resistant to vibration.