How does a sine choke exactly function? In most high power inverter systems, the primary side of the output transformer is always driven by a PWM signal. The secondary output which is sent to a load should also come out to be PWM. How does a pure sine wave inverter exactly convert this PWM into a pure sine wave? What if we fed SPWM directly to the primary of the ferrite transformer, how to filter the secondary output to get pure sine wave?

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    \$\begingroup\$ Please provide more references to "sine choke", "SPWM" etc. and also note that a pure sinewave is an impossibility. \$\endgroup\$ – Andy aka Jul 13 '16 at 7:21
  • \$\begingroup\$ The sine wave from an inverter does not come from the output filter, it comes from a look-up table with a stored sine wave which the regulator will track/have feedback to. \$\endgroup\$ – winny Jul 13 '16 at 7:47
  • \$\begingroup\$ You can convert a PWM's sine wave signal into a (reasonably) pure sine wave just by low-pass filtering it to remove the PWM frequency. The PWM may be 10's of kilohertz, but the desired frequency is only 50, 60 or perhaps 400Hz. So a low-pass filter is quite possible. \$\endgroup\$ – Simon B Jul 13 '16 at 13:29
  • \$\begingroup\$ @Andyaka SPWM is presumably sinusoidal PWM, which is a good way of getting rid of low harmonics from the PWM which are hard to filter away. \$\endgroup\$ – Tom Carpenter Jul 13 '16 at 14:51

There are two possibilities:
1. HV DC, H Bridge (low current) -> PWM, LC filter removes switching HF and what remains is a sine wave.
2. Low voltage DC, H Bridge (high current)-> PWM, LC filter (high current), transformer iron core 50/60Hz; on secondary you get sine wave.
3. Low voltage DC, push-pull converter with ferrite transformer, HV DC output, same as point 1.

The ferrite choke is a part of LC filter for elimination the HF transistir switching frequency.

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