Originally Posted by dbn_brewer
So can I just connect my PWM to my kettle just like a switch? Would any PWM be compatible with a 5.5kw element or do I need to put a specific element with a specific PWM in order for is to work?
The PWM circuit turns the Solid State Relay (SSR) on and off. The SSR switches the power to the element accordingly. The rheostat control in the PWM circuit controls the % of time the SSR is switched on and power applied to the element. So the rheostat acts like a temperature control knob on a stove. The SSR needs to be rated to carry the current drawn by the element (with a healthy margin above that, for reliability). A 5.5 kW element at 220 volts will draw 25 amps, so probably a 40 amp SSR would work. The PWM circuit which drives the SSR needs to be able to drive the SSR and needs to run at a slow frequency compared to your line frequency (50 Hz in SA?).
I don't use an element in a kettle or PWM circuit, but there should be specific recommendations and circuit diagrams somewhere on HBT. I know I have seen at least one schematic for a PWM using a 555 timer chip.