The thermal burden on the triac was relieved as follows in Figure 2. Figure 2 The revised triac drive arrangement with a relay added such that when the pushbutton is pressed, the triac turns on AC to ...

P = V O × I TRIACAVG + R S × I TRIACRMS2 (Eq. 1) where P is the triac power (W), V O is the triac knee voltage (V), I TRIACAVG is the average load current (A), R S is the triac slope resistance ...