DC Drive as Regenerative Bus Supply

Look up power line Var Controllers. SCr's used to control saturable reactors and these in parallel with capacitors. Note that the capacitors are not switched and it appears that SCR's are not well suited to switching capacitors.

Don Kelly @shawcross.ca remove the X to answer

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I am not exactly sure what you are asking.

I have designed and built phase controlled capacitor charging supplies. With simple phase control, you still have a lagging power factor, especially when capacitors are near zero voltage.

I have also designed and build relatively high frequency chopper supplies for charging capacitors when suitable transistors became available.

The trick was to charge capacitors at the voltage they were charged to without resorting to resistors to equalize the voltages. This was accomplished using "free wheeling" diodes so that energy was temporarily stored in inductors.

There are other techniques also available for charging capacitors efficiently.

Bill

-- Ferme le Bush

Thanks. Basically here's what I'm looking for:

I want to charge a DC capacitor bus which will provide power to AC inverter or DC chopper servo motor drives. These drives not only draw power from the bus, but when the motors go into generation mode (decelerating a high inertia load, for example) they will charge the bus capacitors, raising the voltage of the bus. I need a rectifier bridge capable of not only charging the capacitors but also of discharging them back onto the AC line. Regenerative DC drives basically have two rectifier bridges, one for the positive current direction and the other for the negative, which can slow a DC motor down by in effect turning it into a generator using the reverse (negative) bridge. The power generated is put back onto the AC line in a controlled manner by the firing of the reverse SCR bridge.

I wanted to know if this same, readily available device, could be used with a capacitive DC bus instead of a DC motor and acheive the desired effect. If so, what arrangement of flyback diods, inductors, etc. would I need to connect to a DC drive to make it operate properly, as it is designed (I guess) for a motor.

I have seen similar devices designed for capacitor banks, but they are usually high powered and expensive.

Here's something similar. See page 148 of