| Electronics > Projects, Designs, and Technical Stuff |
| Useless nameplate ratings? |
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| Richard Crowley:
I have a Blackmagic Designs (BMD) Hyperdeck Studio Mini video recorder. It has a bog-standard IEC power input connector with the integrated fuse holder. The nameplate says: "100-240V 50/60Hz 0.5A" There is no power rating either on the nameplate nor on any of the published documentation. There is no indication of what fuse rating is recommended for 120V vs 240V mains voltage. I have several pieces of BMD gear working just fine here at home on 120V. But I need to take several pieces to 240V-land (Jordan) next month. The fuse is so small I don't even know if I can read the rating stamped on the end cap (if there is one)? I have tried to submit this post 6 times. But every time I try to upload the photos, the post just disappears into the bit-bucket. Even when I try to edit this post to attach photos, they disappear into the ether. Is something wrong with the system here? |
| Ian.M:
So what's wrong with that? It gives the permissible input voltage range, and that it needs AC and wont draw more than 0.5A, even right down at 100V. A fuse is too slow to save the semiconductors in a SMPSU if anything goes bad, so a 0.5A 250V T characteristic fuse should be suitable to prevent it burning out the cord or any internal wiring 'Weller style'. A faster lower current fuse would not be likely to reduce the damage if a fault occurs, but would increase the risk of nuisance blowing due to the power-on inrush current surge. |
| Richard Crowley:
OK, so if 0.5A is rated for 100V, then at 240V it is 2x over-rated and offers little or no protection. Not very reassuring for thousands of $$$ worth of gear when you are thousands of miles away from home (and no technical support). |
| soldar:
The fuse is not there to protect your equipment. It is there to protect the electric wiring and to prevent starting a fire. The fure is not there to prevent blowing a semiconductor. On the contrary, the semiconductor will blow first, thus protecting the fuse. There is no point in changing the fuse or even thinking about this. |
| DaJMasta:
Maybe so, but at that current level... are there that many faults that will trip the 500mA fuse at 120V input and could damage the hardware that wouldn't trip the 500mA fuse at 240V? If you're relying on the fuse for more than simple short protection, maybe, but in that case you probably shouldn't be relying on just a fuse, right? It's a bit lazy, but it probably makes no difference in the vast majority of the failure modes where a fuse could protect against damage. |
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