# Can a sine wave input be equivalent to a direct current signal?

I want to control the temperature of an electric oven. To do this, I must find its mathematical model, or transfer function.

To control the temperature of the oven I use PWM, which goes into a circuit with optocoupler and TRIAC. In this way, the input voltage to the resistors has the following waveform: On the other hand, I have a temperature vs. time curve with the PWM at maximum power (100%). With this curve I can identify the model using the ident or procest (MATLAB) commands. When the PWM is at 100%, the input voltage to the resistors is 220 V AC and 60 Hz; so, the input is 311.127 × sin(377t)

Can this input be considered equivalent to its root mean square voltage, that is, to 220 V in direct current? It seems so to me, due to how high the frequency is (60 Hz).

If I consider the input waves as DC signals, it would be easier to simulate and tune a PID control.

• what kind of oven? Feb 13 at 4:09
• As the "time constant" is vey long, you should use, at start on, "anticipative" control. Some delay is also present, about 200 s (?). Feb 13 at 10:07
• What are the units for the graph timebase? Feb 13 at 10:37