inverters 70-400 vdc

ws9876 Solar Expert Posts: 440 ✭✭✭
do these type of inverters have several transformers on board that change the input to
a static volts like 48..?? if so what component is used to determine which one is used??

or do they have big zener diodes to make a steady voltage..


  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: inverters 70-400 vdc

    They are all switching power supplies.

    High input DC voltage typically have a high frequency flyback transformer. Low voltage input like MX60 or others that connect to batteries typically have nothing but a switching buck inductor. There is a new Xantrex charge controller coming out that allows input to 600 vdc to 48v or 24v battery charging.

    GT inverters typically have high voltage transformers. Some have several taps on HV DC primary side that provide for 'gear shifts' allowing more optimum efficiencies over a wider input voltage range.

    Generally, as the input to output voltage ratio increases the duty cycle of the switching reduces. This creates higher peak currents in the switching inductor and MOSFET switch which reduces conversion efficiency. A flyback transformer with primary to secondary turns ratio improves (increases) the conduction duty cycle.

    A flyback transformer is a coupled inductor. Energy is stored up in core during charging on input inductor then coupled to output winding on discharge cycle.

    A regular power transformer is a power converter. Little energy is stored in core in contrast to a flyback transformer. Current flows in primary and secondary at the same time, coupled through the transformer core with V-I ratio based on transformer primary to secondary turns ratio. A push-pull high frequency transformer can regulate output voltage by reducing its conduction period for each half cycle. This effectively 'turns-off' the transformer for some portion of the switching cycle. This gives higher output ripple voltage that requires additional filtering on output. These types of switching converters are used in most low cost portable DC-AC inverters, like Power-to-Go inverters.

    There can be a combination of types in one unit. For example, a push-pull switching transformer operating unregulated at 50-50% duty cycle allows for smallest transformer core and operates at good efficiency. Regulation is performed by a buck switcher inductor feeding the input to second stage push-pull transformer. The second stage push-pull switching transformer does a fixed conversion from about 300 vdc to 48 vdc battery output. The buck converter allows input to range from 300vdc to 600 vdc always outputting the lower 300 vdc to input of secondary push-pull switcher.

    All solar charge controllers must have a large storage capacitor to smooth out any switching power supply current ripple as seen by PV panel load. PV must have a smooth DC current load to achieve maximum efficiency at their maximum power point voltage.