Inverter pre-charge resistor size?

FilterGuy · Jan 11, 2024

Inverter Disconnect Switch with Precharge

To get the paper, click on the orange button at the top of this page. This circuit is designed as a disconnect switch that allows the user to pre-charge the inverter capacitors before turning the switch completely on. 26 June 2020 update: At...

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yoopNreb · Mar 15, 2024

FilterGuy said:
The resistance value can be almost anything below 100 ohms.

The main thing the precharge is trying to do is keep the initial surge into the capacitors to a reasonable level. A 1-ohm resister on a 48V system will have a starting surge of around 50A that will very rapidly taper to zero. I like to keep the current closer to 2 Amps so I use 25-30 Ohms. This will taper down slowly, but still charge the capacitors in less than a second.

If the resistance gets too high, the time it takes to charge the capacitor starts to become a factor.... that is why I would not recommend anything over 100 ohms.

I have a 24v system with a 2500w inverter and a 100w 100ohm resistor. Will this work?

Xiaoyztan Aluminum Housing Wire-wound Braking Resistor Unit with Soldering Ring Lugs High Power Inverter Servo Resistor (100W 100 ohm) https://a.co/d/7ypR349

FilterGuy · Mar 15, 2024

yoopNreb said:
I have a 24v system with a 2500w inverter and a 100w 100ohm resistor. Will this work?

Yes. It will work. However, the precharge current will only be ~ 1/4A so make sure to leave it there for a few of seconds to full charge of the capacitors.

Inverter pre-charge resistor size?

FilterGuy

Solar Engineering Consultant - EG4 and Consumers

Inverter Disconnect Switch with Precharge

yoopNreb

New Member

FilterGuy

Solar Engineering Consultant - EG4 and Consumers

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