Suspecting that inefficent continuous outputs are used to get a reasonable sine wave from an inverter, I propose that a different system be used. A Mode C common base output with a primary hi frequency power connection to the collector and a 50hz lower bias signal to the base which pulses the transistor into saturation only at the peak of the base input signal. Filter capacitors to cover up the gaps in the power output. The hetrodyning of the signals produces an 50Hz output in close, short pulses from a saturated transistor, which is acting a a switch. This is much more efficient than using trasistors a variable resistors. Thus the energy lost in producing a 50hz sine wave by continuous means is eliminated, and an efficient smps can be used to produce 50hz from much more efficient frequncies. A quality sine wave is more easily produced also, dependent mainly on the frequncy of the primaru power signal. I recognise the greater cost, but the efficiencies gained are worthwile, particularly in harsh environments.

 

I see no significant advantage of that over the more common method of using a Class D (switching) amplifier with PWM to generate a sinewave, which is also quite efficient.

 

pardon my ignorance, I didn't know they did that. Pls what is class D?

 

Class "D" is, just like described, using on/off switching, usually with pulse width control, and all at a much higher frequency. The best part is that in addition to being quite efficient it can also be done without the use of microcontrollers or other programmable logic things. Also, because the PWM portion is done at a much higher frequency, the filtering to turn it into the desired waveform is quite straightforward and not so horribly complex.