Weird 330w inverter question
Submitted: Friday, Jan 21, 2005 at 10:55
ThreadID:
19647
Views:
3055
Replies:
11
FollowUps:
10
This Thread has been Archived
Member - Chrispy (NSW)
Hi all
I have recently wired 40 amp-capable cable directly from a heavy fuse box near my battery to the rear of the car and fitted an Arrid power socket there for my fridge, lights, etc. I tried my 330w inverter on it yesterday and "boom!" - I took out the 20 amp fuse in my fuse box as I turned it on. I know the inverter works as I have just removed it from my other car.
Given that it's a 330w jobbie, I presume that at full continuous capacity it will be drawing around 27 amps. But in this case there was no load!!!! I just plugged it in - that's all. I replaced the fuse with a 30 amp one and it did it again. I wasn't prepared to go any higher as I'd be approaching the limit of the wiring's maximum rating.....
Does anyone here know what the idle current on these things is meant to be - in approximate terms? Or, have I suddenly (literally overnight) got a bad inverter?
It used to run a 25-amp fuse in the
old car and there were never any problems.
Cheers and thanks for any advice :)
Chris
Reply By: Member - Chrispy (NSW) - Friday, Jan 21, 2005 at 11:46
Friday, Jan 21, 2005 at 11:46
Thanks guys :)
Yup - I just found a neighbour who had a multimeter that actually worked :(
I connected it up with the main switch "off" and there was a slight spark from the terminals as I connected.
Once connected it was drawing 0.00A
I turned it on (with no load) and it drew 0.25A
I connected a light with a 60-watt globe and it drew 3.94A
So... stuff-all really.
Must be the initial contact with the power-source (slight spark) that does it. What a pain!!! I wonder if I can electrically damp that with something..... ??
Oh
well. I'll just have to connect directly to the battery for this weeken using some alligator clips.
Cheers and thanks for the help!!
Chris
AnswerID:
94247
Follow Up By: MrBitchi - Friday, Jan 21, 2005 at 14:03
Friday, Jan 21, 2005 at 14:03
A digital multimeter when used as an ameter will never catch the startup current. The display response is too slow. Try replacing the fude with a solid state circuit breaker. Might handle the startup surge a bit better.
Your local Narva stockist should be able to help you out.
Narva No. 54630
Cheers,
John.
FollowupID:
353272
Reply By: hl - Friday, Jan 21, 2005 at 12:06
Friday, Jan 21, 2005 at 12:06
Hi,
Many
inverters have a rather large capacitor across the input. It can create quite a surge when you first connect it, makes no difference whether the inverter is on or off. (will also spark quite a bit if you disconnect and short the alligator clips)
A slow blow fuse should take care of it, or better still use a circuit breaker. I have a 70 amp breaker directly at the aux battery before the cables that go through the firewall. I still use individual fuse blocks for the lighter load circuits, but the 70 amp breaker should blow when all else fails or if a cable gets pinched somewhere, perhaps in a crash.
I am surprised though that it blew a 30 amp fuse.
The idle current on modified square wave units is usually much less than 1 amp, the sine wave units are less efficient and have higher idle currents.
Cheers
AnswerID:
94251
Follow Up By: Member - Chrispy (NSW) - Friday, Jan 21, 2005 at 12:14
Friday, Jan 21, 2005 at 12:14
hl - thanks for that.
Any idea what size capacitor might do the trick? I presume I could simply run it between the two screw terminals if it won't fit inside the case....... correct?
FollowupID:
353254
Follow Up By: Member - Chrispy (NSW) - Friday, Jan 21, 2005 at 12:16
Friday, Jan 21, 2005 at 12:16
PS - Do you know if slow-blow fuses come in blade format? I know the barrel types do......
FollowupID:
353256
Follow Up By: hl - Friday, Jan 21, 2005 at 13:48
Friday, Jan 21, 2005 at 13:48
Hi Crispy,
You misunderstood me. That capacitor (or a bank of them) is already there inside the inverter and it causes the surge.
To prove my point and overcome the problem temporarily, just connect your inverter directly to the battery, to charge the capacitor. Don't turn it on though, then connect it to where u wanted it. It should not blow the fuse this time if my theory is correct. I don't think the blade fuses come in slow blow.
Cheers
FollowupID:
353267
Follow Up By: Member - Chrispy (NSW) - Friday, Jan 21, 2005 at 13:54
Friday, Jan 21, 2005 at 13:54
hl
Ahhhh!! I see.
I was under the assumption that it may not have a smoothing capacitor in this one..... I would hope so, but you'd never know with the cheapies.
I'll try your theory out.
Cheers and thanks again
Chris
FollowupID:
353268