Need guidance in designing an LC low pass filter for 10 kW autotransformer-based power supply

Autotransformer voltage tapping points are 220, 270, 320, 370, 420, 470, 520, 570, 620, 670 & 720 volts. The current rating is 16.5 A.

Power supply requirements are maximum 700 V output, minimum 200 V output, at constant 16.5 A current.

Can someone guide me in designing a second order inductor/capacitor low pass filter for the above power supply, especially L1, C1 values required?

Edit: With L=120mH C=200uF or 220uF, I got the following results (attached)Fig2

Answers 1

  • If there is overvoltage (> 720 Vac, no Safety) in this case, another bridge should be needed.

    With an inductor at the head, we cannot obtain the desired voltage of 700V DC (655 max, figure 1).

    And if the value of the choke decreases, we go back to rectifier on capacity (figure 2), and there will be very high current peaks.

    EDIT 2 : It should be interesting exploring another way.

    Here a schematic which is a PFC circuitry. Good point of starting. Made with a number of MOSFETs (15) which can be replaced with 1 modern SiC device.

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    EDIT : SAFETY ... APPLY all Safety Rules which are ESSENTIAL when working with such voltages and currents. I don't assume anything. This is only for EDUCATION.

    A complete operational "device" must measure or calculate all values of currents, voltages, powers, temperatures ... in Real Time and switch off immediately all, if not ok... except fans :-) .

    For testing such "devices" or "boards" ... begin ALWAYS with lowest voltages, if possible . Be very care full choosing all components (diodes, L, C1) with peak (if any) and RMS values ...

    Do simulation also when switching on power.

    End point : try to always switch ON power systems at 0 V, with "smart switches" (triacs or others systems). Something as this :, (point 3, page 3 : Full conduction mode voltage, some have input for 220 V directly). One can adjust on device the "initial phase angle controller" with potentiometer. Don't use "phase control" with transformer without simulation.

    case of Inductor

    case of Capacitor

    Mix of the 2

    Example of results simulation. Swith ON at Vsin = Vmax (phase = 90 degree)

    enter image description here

    enter image description here

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