Inverters

You have two parameters that you can control - frequency and duty cycle.

Let's suppose that you want 100 pulses per cycle of AC. You vary the duty cycle of the pulses from 0% to 100% and back to 0% during the 100 pulses to create one cycle of your sine wave. For 5Hz, your pulse frequency would be 500 Hz. For 10Hz, your pulse frequency would be 1000Hz.

So, don't think pulse width, think frequency and duty cycle.

sorry sir

i am getting confused, please correct me if i am wrong? when i need 10hz output frequency i should make pulse frequency higher than when i need 5hz? how about duty cycle? should it vary the same way on 5hz and 10hz or it should be different?

thanks

Assuming you have the same number of pulses per cycle of AC, then yes, you need to increase the frequency of your pulses proportional to the frequency of your AC.

If I want to create a 5 Hz sine wave, using PWM, I need to first determine how many pulses I'm going to use to approximate the sine wave. Let's say I want to use 10 pulses to create each cycle of AC. The period of a 5Hz sine wave is 200mS. So the frequency of my pulses needs to be 20mS. For a 10hz sine wave, with the same number of pulses per cycle, the frequency of the pulses needs to be 10ms.

The period of a 5Hz sine wave is 200mS. So the frequency of my pulses needs to be 20mS. For a 10hz sine wave, with the same number of pulses per cycle, the frequency of the pulses needs to be 10ms.

I think this could use a little edit:

The period of a 5Hz sine wave is 200mS. So the period of my pulses needs to be 20mS (giving a frequency of 50Hz). For a 10hz sine wave, with the same number of pulses per cycle, the period of the pulses needs to be 10ms (giving a frequency of 100HZ).

sorry sir

can u explain to me about this because it is new for me?

thanks

What Bhankii said was basically correct -- the period/frequency distinction was just a typo, I think -- which I corrected only because it could be confusing to someone new to the subject. Period is the time for one cycle (so the period in 60 Hz power is one second/60, or 16 milliseconds). Frequency is the number of cycles per second (1Hz = 1 cycle per second).

a picture is worth a thousand words

If you filter and average these two signals, what do you get?

nothing - assuming these are continuous and periodic, they both average to zero. A low pass filter is what you want.

right. AC signals average zero, scratch average

but you do get the get different frequencies.