Electrical wtf moments...

So im sure all of you who have worked on electrical systems have encountered one of those moment.
It just happened to me yesterday and wanted to hear some opinions.

I was hooking up 300W LED(made in china). I wanted to check how much amperage it was drawing before I put everything in place and for choosing wires. I hooked up multimeter with external 10A. I cant recall why i did this but i know I didn't want to go grab a shunt and wanted to make sure it blows. It came out on the meter as 15A.

So... 3 wtf moments at once right?
1. It was drawing roughly 15A. Theoretically it should draw 25A or so right? But ok, probably for longer life for LED chips?

2. I hooked up external 10A(blade, made in china), because multimeter I had was digital and was rated at 10A with cylinder fuse(made in china i believe) which I didnt have spares. Came out on the meter as 15A. How is the external fuse intact?

3. How did my multimeter get away with more amperage than it was rated? Again fuse question...lol

Anybody encountered similar things before or have an answer? Or even more skeptical situations?

 

Slow blow fuse.

Some fuses are designed to blow the INSTANT it sees over current. Others are designed to not blow instantly in case it sees a high inrush current like when starting motors etc. After the initial spike of current it levels out at its regular running current. Otherwise you have to use a higher rated fuse which could cause damage by allowing a higher current

 

Yes i thought of that too but SBF in my mind is most of the times square plastic thingy. I thought blades were regular/fast acting fuse?
Besides, the current was gradually going up from 12A and stabled around 15A, not mentioning building some heat at the connector...

 

Are you saying the multimeter is Chinese?

All of my multimeters are Fluke because I never have to question them. I know that what it reads is always accurate and if in doubt I can send away from recalibration. What good is a multimeter if you can’t trust it?

 

Yes i think it is Chinese. I dont see it anymore but i think it was harbor freight. I have had it for aboout 8yrs. It always worked for me except for the noise, brightness, and temperature. This is first time I encountered electrical problem with fuses or multimeter.

I talked to one of my friend who is an electrical engineer and he told me that overclocking(telling customer 300W when its actually 200W) or protecting their asses(For multimeter using higher rated fuse than what is said on the product) is a thing for electronics these days. For a regular bladed fuse, unless it is a Fast acting fuse/fast-blo, it may take a while or more load than rated to blow... kinda surprised fuses are not doing the job i was expecting to do!

 

"Chinese"
"300WATTS"

 

I would test your multimeter against a know load to verify it is accurate. Or head down to sears and get a fluke off the shelf. They have a few under $150that I would trust all day long.

 

Maybe on my next visit to US as i live in Japan!lmao

 

I am sure the Japanese have some multimeter’s better than HF.