OK ... Which Resistor to Use?

[MrM1]

Ok, so back here I built a precharge resistor setup with push button start for my Schneider SW inverter. I used a 100w 50 ohm resistor. But it seems improperly sized as the inverter goes into a surge and blinks on and off if I hold the button more than a second or 2. The SW is trying to start but seems like it's throwing a low power fault and just kicks on and off.

I don't want to trulstartin or run the inverter through the resistor, but I feel the 50 ohm resistor is not changing the inverter caps up enough in a 1-2 second push.

So ...

I have on hand 4 differ resistors, all 100w. Which might be the best option / choice for the SW pre charge resistor?
50 ohm
10 ohms
4 ohms
0.25 ohms

@Hedges I believe you like long rolls of wire but that is not practical for my setup ?? Ideas?

Thanks
Mike

 

[Quattrohead]

For a proper technical answer you need to know the total value of the capacitors in the inverter.
If you want to be slightly more cautious use the 10 and 4 in series, but if feeling slightly lazy go with the 10.

 

[MrM1]

I'll probably go lazy.

 

[MrM1]

Wondering what would be the different effects of the 4 above or 2 in series

 

[Roswell Bob]

I expect your power supply is booting up and causing blinking. Try the 4 ohm resistor. Power supply should come up and stay up. Then it is time to short out the resistor. If you have an auxillary power supply output on your inverter you could use this to pull in a relay and short charge resistor out. (Edit - I use a 0.3ohm resistor)

 

[efficientPV]

The question is, do you have a load connected on the inverter. The resistor should be sized for the idle current of the inverter so that voltage drop doesn't go below the minimum operating voltage. So what if it blinks. The capacitors are charged sufficiently at that point.

 

[Roswell Bob]

The question is, do you have a load connected on the inverter. The resistor should be sized for the idle current of the inverter so that voltage drop doesn't go below the minimum operating voltage. So what if it blinks. The capacitors are charged sufficiently at that point.

Yes, the resistor should be sized for the 20 or 30 watts or so that the power supply will draw before the inverter turns on. If the resistor is too large in value the power supply will blink - as the bus voltage decays. In other words the reason the power supply blinks is likely caused by the inverter caps going into a charging/discharging kind of mode.