SiC heater controlled by thyristor (Part 7)
Furnace design starts by determining the power required and selecting silicon carbide heaters that can meet that requirement. Once the silicon carbide heaters have been selected the starting voltage of the furnace can be determined. With the starting voltage known the starting current can be calculated. This will be when maximum current is drawn by the furnace. Where multiple heaters are used they can often be arranged in series to maximise starting voltage and minimise starting current. Conductors and switchgear must be specified using this higher starting current.
Adequate voltage "headroom" or reserve must remain to allow the silicon carbide heaters to age. If the starting voltage is less than half the available mains voltage the use of a transformer should be considered.