Inverter Fuse Question

[NinjaDeathMonk]

Hello everyone. I recently bought this inverter. The thing is, it uses two 10A fuses which I just blew. By my calculations, to produce 800W AC from a 36V DC source, it would need to input 24-25 amps. How can 20 amps worth of fuses be appropriate, specially since it claims it can handle a 1600W surge? Thanks.

 

[krby]

Yup, 20A fuses on the DC side won't do it. Is it possible the 10A fuses are meant for the AC side? In theory, you could upgrade the DC side fuses, but that is dangerous unless you are sure all the components inside and including the battery cables, terminals, etc are capable of the higher current. I wouldn't do it. I'd contact the seller.

 

[NinjaDeathMonk]

Is it possible the 10A fuses are meant for the AC side?

They are automotive-style fuses and I don't know if they can be use on AC. That said, the fuses are right in between the wires coming from the DC source, and on the opposite end of the AC plugs. Additionally, they blew when pulling around 25 amps and pushing 7-8 amps AC. So, pretty safe to say they are DC fuses.

I'd contact the seller.

I'll do that and post back. Thanks.

 

[NinjaDeathMonk]

I'm still waiting for a reply from the manufacturer. But does this reply from the eBay seller seem adequate to anyone?

New message from: reliablepower

Dear,

Good day,

I discussed with the engineer, the measurement is 36v*20A=720w. but usually when you have the 800w output, the fuse will not burnt,

there is only 10A, 15A fuse on the market, if we choose the 15A 2pcs, it will be 30A in total, it will not protect the inverter from the overload,

the fuse is for the overload protection, it is not for the full power measurement,

hope you can understand it,

kayla

So the pair of blade fuses on the inverter board need to be identical? You can't combine a 10A and a 15A? If there are two sockets, you can't use a single 25A fuse?

Edit: Also, their calculation is not accounting for the inefficiency of the inverter. Therefore it would be ( 36V x 20A ) x0.90 efficiency = 648W AC. Am I right?

 

[offgriddle]

Hello everyone. I recently bought this inverter. The thing is, it uses two 10A fuses which I just blew. By my calculations, to produce 800W AC from a 36V DC source, it would need to input 24-25 amps. How can 20 amps worth of fuses be appropriate, specially since it claims it can handle a 1600W surge? Thanks.

You know NinjaDeathMonk, (great name by the way and I am totally on board), I have at times briefly pondered the difference between AC and DC fuses and breakers, but never really dug into it. Thank you for bringing this safety critical topic to my attention. http://solarhomestead.com/difference-between-ac-and-dc-fuses/

 

[gnubie]

Cheapie fuses are notoriously random when it comes to their performance. Grab a random selection and throw a milliohm meter on them and it's more or less a lottery as to each fuse's value.

Given the random variation in cheapie fuses they may just be covering their arse with lower labelled fuses to account for them randomly having a rating greater the label Fuses don't fail straight away even on a modest over current so a short draw of 800 watts may let the fuses survive and that's what they are basing their statements about not blowing on.

It could be that the inverter doesn't have the ratings claimed too. It sure wouldn't be the first time an inverter seller &/or manufacturer has enhanced the rating of the device with nothing but a different label. This might get some people's nose out of joint but it's a fact of life with a lot of these inverters. The Powerjack range is well known for being ludicrously over spec'd on paper, 3 or even 4 times over.

This looks like a classic direct HF inverter. The 1600 watt surge rating is likely relying on a very very brief high current draw from the inverter's high voltage rail capacitors. Usually we are talking 40ms, essentially not much use.

Cartridge fuses come in sizes far greater than 15A. They use multiple fuses because it's cheap. Cheap fuses, cheap sockets, thinner copper on the PCB, you name it. It's all in the name of doing it cheaply.

Do I sound grizzled and worn? Yes, I am This sort of problem is quite common with this class of inverters and something I've seen myself more than once.

They claim CE and EMC certification. Great! That sounds really good until you realise (from the EU web site about CE) it might as well actually mean China Export.

Please note that a CE marking does not indicate that a product have been approved as safe by the EU or by another authority. It does not indicate the origin of a product either.

*various edits have been made to this post*

 

[Rider]

This looks like a classic direct HF inverter. The 1600 watt surge rating is likely relying on a very very brief high current draw from the inverter's high voltage rail capacitors. Usually we are talking 40ms, essentially not much use.

FWIW, my 1000w inverter has a surge rating of 2000w. As per the vendor, the 2000w rating is for 20ms.

 

[offgriddle]

Cheapie fuses are notoriously random when it comes to their performance. Grab a random selection and throw a milliohm meter on them and it's more or less a lottery as to each fuse's value.

Given the random variation in cheapie fuses they may just be covering their arse with lower labelled fuses to account for them randomly having a rating greater the label Fuses don't fail straight away even on a modest over current so a short draw of 800 watts may let the fuses survive and that's what they are basing their statements about not blowing on.

It could be that the inverter doesn't have the ratings claimed too. It sure wouldn't be the first time an inverter seller &/or manufacturer has enhanced the rating of the device with nothing but a different label. This might get some people's nose out of joint but it's a fact of life with a lot of these inverters. The Powerjack range is well known for being ludicrously over spec'd on paper, 3 or even 4 times over.

This looks like a classic direct HF inverter. The 1600 watt surge rating is likely relying on a very very brief high current draw from the inverter's high voltage rail capacitors. Usually we are talking 40ms, essentially not much use.

Cartridge fuses come in sizes far greater than 15A. They use multiple fuses because it's cheap. Cheap fuses, cheap sockets, thinner copper on the PCB, you name it. It's all in the name of doing it cheaply.

Do I sound grizzled and worn? Yes, I am This sort of problem is quite common with this class of inverters and something I've seen myself more than once.

*various edits have been made to this post*
[/QUOTE For a couple of decades the
Buss fuse corporation was my constant companion. Nowadays, there is a better chance than not that the great Bussman fuse corporation has subbed it's manufacturing out to the eco wrecking junk producing slaves of the Pacific rim, but, hopefully Buss is present in the slave factories to assure that quality standards be met instead of wholly discarded. http://www1.cooperbussmann.com/6/AutomotiveandHardwareCatalog.html

 

[gnubie]

There are a million and one rip off bussmann fuse sellers. Sometimes fakes even make it into the normal good supply chain such as Farnell and other stockists because someone has slipped in a carton of fakes at some stage between manufacturing and delivery. The real fuses are still great.

 

[offgriddle]

There are a million and one rip off bussmann fuse sellers. Sometimes fakes even make it into the normal good supply chain such as Farnell and other stockists because someone has slipped in a carton of fakes at some stage between manufacturing and delivery. The real fuses are still great.

Maddening for sure, buyer beware.

 

[NinjaDeathMonk]

Cartridge fuses come in sizes far greater than 15A. They use multiple fuses because it's cheap. Cheap fuses, cheap sockets, thinner copper on the PCB, you name it. It's all in the name of doing it cheaply.

So the pair of blade fuses on the inverter board need to be identical? You can't combine a 10A and a 15A? If there are two sockets, you can't use a single 25A fuse?

 

[gnubie]

You can't use a single fuse as the fuse sockets probably aren't rated to handle it all, and probably the tracks on the PCB too.

If you put a 10A and 15A fuse in parallel, and assuming everything else is equal, they will share the current 2:3 but given the variation in fuses they are bound to not be all that precisely matched so exactly what the split will be is a good question. A low ohms multimeter would give you an idea of the ratio.

Without knowing the inside of your inverter I can't say if the fuse holder will be happy with 15 amps, and the same goes for the PCB track to that holder. If they put 10 amp fuses in there the device really might not be intended to draw more than 20 amps. Changing the fusing without understanding the device could result in damage.