| DeafSmith |
06-19-2012 04:25 PM |
Quote:
Originally Posted by dbn_brewer
(Post 4183364)
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?
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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.
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