KeepIS
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Joined: 13/10/2014
Location: AustraliaPosts: 1373 |
| Posted: 01:44am 05 May 2024 |
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I wanted to clarify something concerning the over-voltage DC input setting, and the AC OC (over current) setting.
The AC OC is the hardware OC detection and locking Reset button with OC LED employed in the Controller. Once tripped, this requires the OC Reset button to be pressed, or the DC input to be removed in order to restart the Inverter.
Both of these settings require a Kilovac or similar gas filled hermetically sealed high voltage high current (> 500A) DC relay to really be effective.
The Kilovac is required for the Auto start wiring model, and this is the only startup method that I would ever employ in a big Inverter, and/or high power battery and high power solar charger array.
A Kilovac with economizer draws around 30mA @ 48v when energized.
Once you see the absolute carnage that a high power battery bank can cause just in the inverter itself, even when correctly fused, is why I could/would never leave an Inverter unattended without this extra safety feature. It's mandatory IMHO.
Do you need it every time a FET or fault happens - maybe not - so roll the dice.
In the event of any fault condition, allowing the Controller to instantly remove all DC input to the Inverter is a must have - but this might be just me! But in the end, it's your decision, your home, shed and equipment.
EDIT: The 50 ohm Pre-Charge resistor has been mentioned before, this is still in line if the Kilovac has tripped off and the inverter on/off switch is still in the ON position, as happens after a fault condition and your not there to turn it off.
If the inverter is shorted then a 20 watt resistor will burn out, which is why you make sure it's mounted correctly. From the standpoint of an over voltage trip, any current above 500ma will drop the input voltage by 25v or more as the current increases.
The FETs will be protected as the Inverter SPWM is off, and even if the voltage is still over voltage, only a small amount of current is enough to pull the voltage down to zero through the Pre-charge resistor. However with no current and no voltage drop, your problem becomes the Cap bank voltage rating and the rating of the 75v to 12v regulator.
The following will take care of that, and an inverter OV event is nothing compared to a Battery over volt condition and destruction. This is why we need another means to protect it, and in turn, also protect the inverter long term.
I intend to fit another Kilovac in line between the Charge controllers and the 4 Battery bank BMS devices I have. I've mentioned before why you can't rely 100% on the BMS designs.
So this is a last line of defense if a BMS shorts and the current is not enough to take out circuit breakers or Fuses - or the BMS do switch off but the non running inverter is still over voltage via the pre-charge resistor.
A small, independently latched solar charger over-voltage sense circuit, powered from a 30v to 200vac plug pack, or similar DC to DC supply rated at around 4A (kilovac pull in current) to match the kilovac operating voltage - only 1.5 watts of holding power required.
So the Inverter protects itself from the batteries (high current or fault), and both batteries and inverter are protected from a solar charger over voltage event via a last line defense of another Kilovac.
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Edited 2024-05-05 14:40 by KeepIS
It's all too hard.
Mike. |
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