DC Fuse Block Class T on Output of AC Inverter (Blue Sea, Go Power)

mnittler
mnittler Solar Expert Posts: 63 ✭✭✭
in General Solar Power Topics #1
I have a 10kw AC Wind Turbine connected to a 12kw grid tied inverter (Inverter can output 14kw max).  Of course the inverter converts the AC wind turbine voltage to DC and then back to AC and is also fused on the input side of the inverter.  The 240vac split phase output (U.S.) of the inverter has a Class T fuse block (I think it is a Bussman T30100-2CR fuse block) and 80 amp JJN fuses on both legs of the output of the inverter inside the inverter housing. One of the tabs broke off of one of the fuse blocks while connecting/disconnecting the #4 gauge output wire. This #4 wire output then goes to a 30 amp double pole Square D Breaker in the Square D 100 amp breaker panel about 6 feet away.

My question is: Can I substitute something like a Blue Sea or GoPower Class T DC single fuse block that is rated 160VDC and 200 amps and use the original 80 amp Class T fuse in the DC fuse holder? 

The voltage per leg is only 120vac to ground. The DC fuse block appears to be about 10 times better built than the original Bussman fuse block.  (Anyway one would never break off one of the tabs on the DC Class T fuse Block) On the DC fuse block the Class T fuse is bolted in instead of pressed in between compression clips. The original Class T JJN fuse already has the holes in the correct place on the tabs for the DC fuse block bolt pattern.

I am assuming that they are trying to protect the output of the inverter from a short circuit with a fuse which might be faster than the 30 amp breaker? Maybe just belts and suspenders since there are fuses at the bottom of the wind turbine tower, fuses on the inlet side of the inverter, 80 amp fuses on the outlet of the inverter, which connects to a 30 amp breaker, which connects to a 100 amp fused disconnect, which connects to a 200 amp fused entrance rated disconnect, which then connects to the utility.
19.76kw Solar/GT Enphase IQ7+ MicroInverters
 5.40kw Solar/GT ABB/Aurora 300 MicroInverters (AC coupled to Schneider/Xantrex XW6048 output)
 6.00kw Solar/Hybrid Xantrex XW6048 Inverter w/2 strings Trojan L-16E-AC Batteries (48VDC)
18kw Kohler Propane Generator

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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
    A DC fuse holder is really no different than an AC fuse holder. The difference is in the rating of the fuses themselves in terms of the safe interrupting voltage. Any fuse or breaker will have a harder time interrupting DC than AC, since when the current of the AC arc passes through zero it is easier to keep the arc from restriking once the voltage starts to rise again. A DC interrupter must actively try to extinguish the arc by lengthening it to the point where the voltage is inadequate to sustain it, exploding it, or putting material in the way.
    In short, as long as the fuse fits, go ahead.
    Now cheap automotive DC fuse blocks are a different story, since the fuse holder itself does not have to withstand more than ~15V and it is not at great risk of melting from a sustained arc.
    When used with higher voltage AC or particularly DC they may not survive and may even catch fire themselves.
    SMA SB 3000, old BP panels.
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  • mnittler
    mnittler Solar Expert Posts: 63 ✭✭✭
    #3
    Well, I guess that answers that.  I just wanted to see if there was any reason why the DC fuse Block would not work. 
    Thanks for the information and I can now sleep at night knowing that common sense still prevails.
    19.76kw Solar/GT Enphase IQ7+ MicroInverters
     5.40kw Solar/GT ABB/Aurora 300 MicroInverters (AC coupled to Schneider/Xantrex XW6048 output)
     6.00kw Solar/Hybrid Xantrex XW6048 Inverter w/2 strings Trojan L-16E-AC Batteries (48VDC)
    18kw Kohler Propane Generator

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  • RickGarber
    RickGarber Registered Users Posts: 1 ✭
    edited October 2015 #4
    You are looking for the fuses. As the @inetdog mentioned,Actually the DC fuse holder and the AC fuse holder both are same. They have the difference in the rating as you AC and DC can make a lot difference for the safe interrupting voltage. AC is more interrupting than the DC. Since when the current of the AC arc passes through zero it is easier to keep the arc from restriking once the voltage starts to rise again. A DC interrupter must actively try to extinguish the arc by lengthening it to the point where the voltage is inadequate to sustain it, exploding it, or putting material in the way.

    pcb prototype
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